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git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup
Pull cgroup updates from Tejun Heo:
- The locking around cpuset hotplug processing has always been a bit of
mess which was worked around by making hotplug processing
asynchronous. The asynchronity isn't great and led to other issues.
We tried to make the behavior synchronous a while ago but that led to
lockdep splats. Waiman took another stab at cleaning up and making it
synchronous. The patch has been in -next for well over a month and
there haven't been any complaints, so fingers crossed.
- Tracepoints added to help understanding rstat lock contentions.
- A bunch of minor changes - doc updates, code cleanups and selftests.
* tag 'cgroup-for-6.10' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (24 commits)
cgroup/rstat: add cgroup_rstat_cpu_lock helpers and tracepoints
selftests/cgroup: Drop define _GNU_SOURCE
docs: cgroup-v1: Update page cache removal functions
selftests/cgroup: fix uninitialized variables in test_zswap.c
selftests/cgroup: cpu_hogger init: use {} instead of {NULL}
selftests/cgroup: fix clang warnings: uninitialized fd variable
selftests/cgroup: fix clang build failures for abs() calls
cgroup/cpuset: Remove outdated comment in sched_partition_write()
cgroup/cpuset: Fix incorrect top_cpuset flags
cgroup/cpuset: Avoid clearing CS_SCHED_LOAD_BALANCE twice
cgroup/cpuset: Statically initialize more members of top_cpuset
cgroup: Avoid unnecessary looping in cgroup_no_v1()
cgroup, legacy_freezer: update comment for freezer_css_offline()
docs, cgroup: add entries for pids to cgroup-v2.rst
cgroup: don't call cgroup1_pidlist_destroy_all() for v2
cgroup_freezer: update comment for freezer_css_online()
cgroup/rstat: desc member cgrp in cgroup_rstat_flush_release
cgroup/rstat: add cgroup_rstat_lock helpers and tracepoints
cgroup/pids: Remove superfluous zeroing
docs: cgroup-v1: Fix description for css_online
...
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Explicitly disallow enabling mitigations at runtime for kernels that were
built with CONFIG_CPU_MITIGATIONS=n, as some architectures may omit code
entirely if mitigations are disabled at compile time.
E.g. on x86, a large pile of Kconfigs are buried behind CPU_MITIGATIONS,
and trying to provide sane behavior for retroactively enabling mitigations
is extremely difficult, bordering on impossible. E.g. page table isolation
and call depth tracking require build-time support, BHI mitigations will
still be off without additional kernel parameters, etc.
[ bp: Touchups. ]
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20240420000556.2645001-3-seanjc@google.com
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Rename x86's to CPU_MITIGATIONS, define it in generic code, and force it
on for all architectures exception x86. A recent commit to turn
mitigations off by default if SPECULATION_MITIGATIONS=n kinda sorta
missed that "cpu_mitigations" is completely generic, whereas
SPECULATION_MITIGATIONS is x86-specific.
Rename x86's SPECULATIVE_MITIGATIONS instead of keeping both and have it
select CPU_MITIGATIONS, as having two configs for the same thing is
unnecessary and confusing. This will also allow x86 to use the knob to
manage mitigations that aren't strictly related to speculative
execution.
Use another Kconfig to communicate to common code that CPU_MITIGATIONS
is already defined instead of having x86's menu depend on the common
CPU_MITIGATIONS. This allows keeping a single point of contact for all
of x86's mitigations, and it's not clear that other architectures *want*
to allow disabling mitigations at compile-time.
Fixes: f337a6a21e2f ("x86/cpu: Actually turn off mitigations by default for SPECULATION_MITIGATIONS=n")
Closes: https://lkml.kernel.org/r/20240413115324.53303a68%40canb.auug.org.au
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Reported-by: Michael Ellerman <mpe@ellerman.id.au>
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20240420000556.2645001-2-seanjc@google.com
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Initialize cpu_mitigations to CPU_MITIGATIONS_OFF if the kernel is built
with CONFIG_SPECULATION_MITIGATIONS=n, as the help text quite clearly
states that disabling SPECULATION_MITIGATIONS is supposed to turn off all
mitigations by default.
│ If you say N, all mitigations will be disabled. You really
│ should know what you are doing to say so.
As is, the kernel still defaults to CPU_MITIGATIONS_AUTO, which results in
some mitigations being enabled in spite of SPECULATION_MITIGATIONS=n.
Fixes: f43b9876e857 ("x86/retbleed: Add fine grained Kconfig knobs")
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Daniel Sneddon <daniel.sneddon@linux.intel.com>
Cc: stable@vger.kernel.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20240409175108.1512861-2-seanjc@google.com
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Since commit 3a5a6d0c2b03("cpuset: don't nest cgroup_mutex inside
get_online_cpus()"), cpuset hotplug was done asynchronously via a work
function. This is to avoid recursive locking of cgroup_mutex.
Since then, the cgroup locking scheme has changed quite a bit. A
cpuset_mutex was introduced to protect cpuset specific operations.
The cpuset_mutex is then replaced by a cpuset_rwsem. With commit
d74b27d63a8b ("cgroup/cpuset: Change cpuset_rwsem and hotplug lock
order"), cpu_hotplug_lock is acquired before cpuset_rwsem. Later on,
cpuset_rwsem is reverted back to cpuset_mutex. All these locking changes
allow the hotplug code to call into cpuset core directly.
The following commits were also merged due to the asynchronous nature
of cpuset hotplug processing.
- commit b22afcdf04c9 ("cpu/hotplug: Cure the cpusets trainwreck")
- commit 50e76632339d ("sched/cpuset/pm: Fix cpuset vs. suspend-resume
bugs")
- commit 28b89b9e6f7b ("cpuset: handle race between CPU hotplug and
cpuset_hotplug_work")
Clean up all these bandages by making cpuset hotplug
processing synchronous again with the exception that the call to
cgroup_transfer_tasks() to transfer tasks out of an empty cgroup v1
cpuset, if necessary, will still be done via a work function due to the
existing cgroup_mutex -> cpu_hotplug_lock dependency. It is possible
to reverse that dependency, but that will require updating a number of
different cgroup controllers. This special hotplug code path should be
rarely taken anyway.
As all the cpuset states will be updated by the end of the hotplug
operation, we can revert most the above commits except commit
50e76632339d ("sched/cpuset/pm: Fix cpuset vs. suspend-resume bugs")
which is partially reverted. Also removing some cpus_read_lock trylock
attempts in the cpuset partition code as they are no longer necessary
since the cpu_hotplug_lock is now held for the whole duration of the
cpuset hotplug code path.
Signed-off-by: Waiman Long <longman@redhat.com>
Tested-by: Valentin Schneider <vschneid@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 APIC updates from Thomas Gleixner:
"Rework of APIC enumeration and topology evaluation.
The current implementation has a couple of shortcomings:
- It fails to handle hybrid systems correctly.
- The APIC registration code which handles CPU number assignents is
in the middle of the APIC code and detached from the topology
evaluation.
- The various mechanisms which enumerate APICs, ACPI, MPPARSE and
guest specific ones, tweak global variables as they see fit or in
case of XENPV just hack around the generic mechanisms completely.
- The CPUID topology evaluation code is sprinkled all over the vendor
code and reevaluates global variables on every hotplug operation.
- There is no way to analyze topology on the boot CPU before bringing
up the APs. This causes problems for infrastructure like PERF which
needs to size certain aspects upfront or could be simplified if
that would be possible.
- The APIC admission and CPU number association logic is
incomprehensible and overly complex and needs to be kept around
after boot instead of completing this right after the APIC
enumeration.
This update addresses these shortcomings with the following changes:
- Rework the CPUID evaluation code so it is common for all vendors
and provides information about the APIC ID segments in a uniform
way independent of the number of segments (Thread, Core, Module,
..., Die, Package) so that this information can be computed instead
of rewriting global variables of dubious value over and over.
- A few cleanups and simplifcations of the APIC, IO/APIC and related
interfaces to prepare for the topology evaluation changes.
- Seperation of the parser stages so the early evaluation which tries
to find the APIC address can be seperately overridden from the late
evaluation which enumerates and registers the local APIC as further
preparation for sanitizing the topology evaluation.
- A new registration and admission logic which
- encapsulates the inner workings so that parsers and guest logic
cannot longer fiddle in it
- uses the APIC ID segments to build topology bitmaps at
registration time
- provides a sane admission logic
- allows to detect the crash kernel case, where CPU0 does not run
on the real BSP, automatically. This is required to prevent
sending INIT/SIPI sequences to the real BSP which would reset
the whole machine. This was so far handled by a tedious command
line parameter, which does not even work in nested crash
scenarios.
- Associates CPU number after the enumeration completed and
prevents the late registration of APICs, which was somehow
tolerated before.
- Converting all parsers and guest enumeration mechanisms over to the
new interfaces.
This allows to get rid of all global variable tweaking from the
parsers and enumeration mechanisms and sanitizes the XEN[PV]
handling so it can use CPUID evaluation for the first time.
- Mopping up existing sins by taking the information from the APIC ID
segment bitmaps.
This evaluates hybrid systems correctly on the boot CPU and allows
for cleanups and fixes in the related drivers, e.g. PERF.
The series has been extensively tested and the minimal late fallout
due to a broken ACPI/MADT table has been addressed by tightening the
admission logic further"
* tag 'x86-apic-2024-03-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (76 commits)
x86/topology: Ignore non-present APIC IDs in a present package
x86/apic: Build the x86 topology enumeration functions on UP APIC builds too
smp: Provide 'setup_max_cpus' definition on UP too
smp: Avoid 'setup_max_cpus' namespace collision/shadowing
x86/bugs: Use fixed addressing for VERW operand
x86/cpu/topology: Get rid of cpuinfo::x86_max_cores
x86/cpu/topology: Provide __num_[cores|threads]_per_package
x86/cpu/topology: Rename topology_max_die_per_package()
x86/cpu/topology: Rename smp_num_siblings
x86/cpu/topology: Retrieve cores per package from topology bitmaps
x86/cpu/topology: Use topology logical mapping mechanism
x86/cpu/topology: Provide logical pkg/die mapping
x86/cpu/topology: Simplify cpu_mark_primary_thread()
x86/cpu/topology: Mop up primary thread mask handling
x86/cpu/topology: Use topology bitmaps for sizing
x86/cpu/topology: Let XEN/PV use topology from CPUID/MADT
x86/xen/smp_pv: Count number of vCPUs early
x86/cpu/topology: Assign hotpluggable CPUIDs during init
x86/cpu/topology: Reject unknown APIC IDs on ACPI hotplug
x86/topology: Add a mechanism to track topology via APIC IDs
...
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer updates from Thomas Gleixner:
"A large set of updates and features for timers and timekeeping:
- The hierarchical timer pull model
When timer wheel timers are armed they are placed into the timer
wheel of a CPU which is likely to be busy at the time of expiry.
This is done to avoid wakeups on potentially idle CPUs.
This is wrong in several aspects:
1) The heuristics to select the target CPU are wrong by
definition as the chance to get the prediction right is
close to zero.
2) Due to #1 it is possible that timers are accumulated on
a single target CPU
3) The required computation in the enqueue path is just overhead
for dubious value especially under the consideration that the
vast majority of timer wheel timers are either canceled or
rearmed before they expire.
The timer pull model avoids the above by removing the target
computation on enqueue and queueing timers always on the CPU on
which they get armed.
This is achieved by having separate wheels for CPU pinned timers
and global timers which do not care about where they expire.
As long as a CPU is busy it handles both the pinned and the global
timers which are queued on the CPU local timer wheels.
When a CPU goes idle it evaluates its own timer wheels:
- If the first expiring timer is a pinned timer, then the global
timers can be ignored as the CPU will wake up before they
expire.
- If the first expiring timer is a global timer, then the expiry
time is propagated into the timer pull hierarchy and the CPU
makes sure to wake up for the first pinned timer.
The timer pull hierarchy organizes CPUs in groups of eight at the
lowest level and at the next levels groups of eight groups up to
the point where no further aggregation of groups is required, i.e.
the number of levels is log8(NR_CPUS). The magic number of eight
has been established by experimention, but can be adjusted if
needed.
In each group one busy CPU acts as the migrator. It's only one CPU
to avoid lock contention on remote timer wheels.
The migrator CPU checks in its own timer wheel handling whether
there are other CPUs in the group which have gone idle and have
global timers to expire. If there are global timers to expire, the
migrator locks the remote CPU timer wheel and handles the expiry.
Depending on the group level in the hierarchy this handling can
require to walk the hierarchy downwards to the CPU level.
Special care is taken when the last CPU goes idle. At this point
the CPU is the systemwide migrator at the top of the hierarchy and
it therefore cannot delegate to the hierarchy. It needs to arm its
own timer device to expire either at the first expiring timer in
the hierarchy or at the first CPU local timer, which ever expires
first.
This completely removes the overhead from the enqueue path, which
is e.g. for networking a true hotpath and trades it for a slightly
more complex idle path.
This has been in development for a couple of years and the final
series has been extensively tested by various teams from silicon
vendors and ran through extensive CI.
There have been slight performance improvements observed on network
centric workloads and an Intel team confirmed that this allows them
to power down a die completely on a mult-die socket for the first
time in a mostly idle scenario.
There is only one outstanding ~1.5% regression on a specific
overloaded netperf test which is currently investigated, but the
rest is either positive or neutral performance wise and positive on
the power management side.
- Fixes for the timekeeping interpolation code for cross-timestamps:
cross-timestamps are used for PTP to get snapshots from hardware
timers and interpolated them back to clock MONOTONIC. The changes
address a few corner cases in the interpolation code which got the
math and logic wrong.
- Simplifcation of the clocksource watchdog retry logic to
automatically adjust to handle larger systems correctly instead of
having more incomprehensible command line parameters.
- Treewide consolidation of the VDSO data structures.
- The usual small improvements and cleanups all over the place"
* tag 'timers-core-2024-03-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (62 commits)
timer/migration: Fix quick check reporting late expiry
tick/sched: Fix build failure for CONFIG_NO_HZ_COMMON=n
vdso/datapage: Quick fix - use asm/page-def.h for ARM64
timers: Assert no next dyntick timer look-up while CPU is offline
tick: Assume timekeeping is correctly handed over upon last offline idle call
tick: Shut down low-res tick from dying CPU
tick: Split nohz and highres features from nohz_mode
tick: Move individual bit features to debuggable mask accesses
tick: Move got_idle_tick away from common flags
tick: Assume the tick can't be stopped in NOHZ_MODE_INACTIVE mode
tick: Move broadcast cancellation up to CPUHP_AP_TICK_DYING
tick: Move tick cancellation up to CPUHP_AP_TICK_DYING
tick: Start centralizing tick related CPU hotplug operations
tick/sched: Don't clear ts::next_tick again in can_stop_idle_tick()
tick/sched: Rename tick_nohz_stop_sched_tick() to tick_nohz_full_stop_tick()
tick: Use IS_ENABLED() whenever possible
tick/sched: Remove useless oneshot ifdeffery
tick/nohz: Remove duplicate between lowres and highres handlers
tick/nohz: Remove duplicate between tick_nohz_switch_to_nohz() and tick_setup_sched_timer()
hrtimer: Select housekeeping CPU during migration
...
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bringup_nonboot_cpus() gets passed the 'setup_max_cpus'
variable in init/main.c - which is also the name of the parameter,
shadowing the name.
To reduce confusion and to allow the 'setup_max_cpus' value
to be #defined in the <linux/smp.h> header, use the 'max_cpus'
name for the function parameter name.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
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The timekeeping duty is handed over from the outgoing CPU on stop
machine, then the oneshot tick is stopped right after. Therefore it's
guaranteed that the current CPU isn't the timekeeper upon its last call
to idle.
Besides, calling tick_nohz_idle_stop_tick() while the dying CPU goes
into idle suggests that the tick is going to be stopped while it is
actually stopped already from the appropriate CPU hotplug state.
Remove the confusing call and the obsolete case handling and convert it
to a sanity check that verifies the above assumption.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240225225508.11587-16-frederic@kernel.org
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The broadcast shutdown code is executed through a random explicit call
within stop machine from the outgoing CPU.
However the tick broadcast is a midware between the tick callback and
the clocksource, therefore it makes more sense to shut it down after the
tick callback and before the clocksource drivers.
Move it instead to the common tick shutdown CPU hotplug state where
related operations can be ordered from highest to lowest level.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240225225508.11587-10-frederic@kernel.org
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During the CPU offlining process, the various timer tick features are
shut down from scattered places, sometimes from teardown callbacks on
stop machine, sometimes through explicit calls, sometimes from the
control CPU after the CPU died. The reason why these shutdown operations
are spread around is not always clear and it makes the tick lifecycle
hard to follow.
The tick should be shut down in order from highest to lowest level:
On stop machine from the dying CPU (high-level):
1) Hand-over the timekeeping duty (tick_handover_do_timer())
2) Cancel the tick implementation called by the clockevent callback
(tick_cancel_sched_timer())
3) Shutdown broadcasting (tick_offline_cpu() / tick_broadcast_offline())
On stop machine from the dying CPU (low-level):
4) Shutdown clockevents drivers (CPUHP_AP_*_TIMER_STARTING states)
From the control CPU after the CPU died (low-level):
5) Shutdown/unregister/cleanup clockevents for the dead CPU
(tick_cleanup_dead_cpu())
Instead the current order is 2, 4 (both from CPU hotplug states), then
1 and 3 through direct calls. This layout and order don't make much
sense. The operations 1, 2, 3 should be gathered together and in order.
Sort this situation with creating a new TICK shut-down CPU hotplug state
and start with introducing the timekeeping duty hand-over there. The
state must precede hrtimers migration because the tick hrtimer will be
stopped from it in a further patch.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240225225508.11587-8-frederic@kernel.org
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This syntax error was introduced by commit da92df490eea ("cpu: Mark
cpu_possible_mask as __ro_after_init").
Fixes: da92df490eea ("cpu: Mark cpu_possible_mask as __ro_after_init")
Signed-off-by: Max Kellermann <max.kellermann@ionos.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240222114727.1144588-1-max.kellermann@ionos.com
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cpu_possible_mask is by definition "cpus which could be hotplugged without
reboot". It's a property which is fixed after kernel enumerates the
hardware configuration.
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/41cd78af-92a3-4f23-8c7a-4316a04a66d8@p183
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Per filesystems/sysfs.rst, show() should only use sysfs_emit()
or sysfs_emit_at() when formatting the value to be returned to user space.
coccinelle complains that there are still a couple of functions that use
snprintf(). Convert them to sysfs_emit().
No functional change intended.
Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240116045151.3940401-40-lizhijian@fujitsu.com
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struct cpuhp_cpu_state has an extraneous kernel-doc comment for @cpu.
There is no struct member by that name, so remove the comment to
prevent the kernel-doc warning:
kernel/cpu.c:85: warning: Excess struct member 'cpu' description in 'cpuhp_cpu_state'
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240114030615.30441-1-rdunlap@infradead.org
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git://git.kernel.org/pub/scm/linux/kernel/git/vbabka/slab
Pull slab updates from Vlastimil Babka:
- SLUB: delayed freezing of CPU partial slabs (Chengming Zhou)
Freezing is an operation involving double_cmpxchg() that makes a slab
exclusive for a particular CPU. Chengming noticed that we use it also
in situations where we are not yet installing the slab as the CPU
slab, because freezing also indicates that the slab is not on the
shared list. This results in redundant freeze/unfreeze operation and
can be avoided by marking separately the shared list presence by
reusing the PG_workingset flag.
This approach neatly avoids the issues described in 9b1ea29bc0d7
("Revert "mm, slub: consider rest of partial list if acquire_slab()
fails"") as we can now grab a slab from the shared list in a quick
and guaranteed way without the cmpxchg_double() operation that
amplifies the lock contention and can fail.
As a result, lkp has reported 34.2% improvement of
stress-ng.rawudp.ops_per_sec
- SLAB removal and SLUB cleanups (Vlastimil Babka)
The SLAB allocator has been deprecated since 6.5 and nobody has
objected so far. We agreed at LSF/MM to wait until the next LTS,
which is 6.6, so we should be good to go now.
This doesn't yet erase all traces of SLAB outside of mm/ so some dead
code, comments or documentation remain, and will be cleaned up
gradually (some series are already in the works).
Removing the choice of allocators has already allowed to simplify and
optimize the code wiring up the kmalloc APIs to the SLUB
implementation.
* tag 'slab-for-6.8' of git://git.kernel.org/pub/scm/linux/kernel/git/vbabka/slab: (34 commits)
mm/slub: free KFENCE objects in slab_free_hook()
mm/slub: handle bulk and single object freeing separately
mm/slub: introduce __kmem_cache_free_bulk() without free hooks
mm/slub: fix bulk alloc and free stats
mm/slub: optimize free fast path code layout
mm/slub: optimize alloc fastpath code layout
mm/slub: remove slab_alloc() and __kmem_cache_alloc_lru() wrappers
mm/slab: move kmalloc() functions from slab_common.c to slub.c
mm/slab: move kmalloc_slab() to mm/slab.h
mm/slab: move kfree() from slab_common.c to slub.c
mm/slab: move struct kmem_cache_node from slab.h to slub.c
mm/slab: move memcg related functions from slab.h to slub.c
mm/slab: move pre/post-alloc hooks from slab.h to slub.c
mm/slab: consolidate includes in the internal mm/slab.h
mm/slab: move the rest of slub_def.h to mm/slab.h
mm/slab: move struct kmem_cache_cpu declaration to slub.c
mm/slab: remove mm/slab.c and slab_def.h
mm/mempool/dmapool: remove CONFIG_DEBUG_SLAB ifdefs
mm/slab: remove CONFIG_SLAB code from slab common code
cpu/hotplug: remove CPUHP_SLAB_PREPARE hooks
...
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The CPUHP_SLAB_PREPARE hooks are only used by SLAB which is removed.
SLUB defines them as NULL, so we can remove those altogether.
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: David Rientjes <rientjes@google.com>
Tested-by: David Rientjes <rientjes@google.com>
Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Tested-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer fix from Borislav Petkov:
- Do the push of pending hrtimers away from a CPU which is being
offlined earlier in the offlining process in order to prevent a
deadlock
* tag 'timers_urgent_for_v6.7_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
hrtimers: Push pending hrtimers away from outgoing CPU earlier
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2b8272ff4a70 ("cpu/hotplug: Prevent self deadlock on CPU hot-unplug")
solved the straight forward CPU hotplug deadlock vs. the scheduler
bandwidth timer. Yu discovered a more involved variant where a task which
has a bandwidth timer started on the outgoing CPU holds a lock and then
gets throttled. If the lock required by one of the CPU hotplug callbacks
the hotplug operation deadlocks because the unthrottling timer event is not
handled on the dying CPU and can only be recovered once the control CPU
reaches the hotplug state which pulls the pending hrtimers from the dead
CPU.
Solve this by pushing the hrtimers away from the dying CPU in the dying
callbacks. Nothing can queue a hrtimer on the dying CPU at that point because
all other CPUs spin in stop_machine() with interrupts disabled and once the
operation is finished the CPU is marked offline.
Reported-by: Yu Liao <liaoyu15@huawei.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Liu Tie <liutie4@huawei.com>
Link: https://lore.kernel.org/r/87a5rphara.ffs@tglx
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git://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic
Pull ia64 removal and asm-generic updates from Arnd Bergmann:
- The ia64 architecture gets its well-earned retirement as planned,
now that there is one last (mostly) working release that will be
maintained as an LTS kernel.
- The architecture specific system call tables are updated for the
added map_shadow_stack() syscall and to remove references to the
long-gone sys_lookup_dcookie() syscall.
* tag 'asm-generic-6.7' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic:
hexagon: Remove unusable symbols from the ptrace.h uapi
asm-generic: Fix spelling of architecture
arch: Reserve map_shadow_stack() syscall number for all architectures
syscalls: Cleanup references to sys_lookup_dcookie()
Documentation: Drop or replace remaining mentions of IA64
lib/raid6: Drop IA64 support
Documentation: Drop IA64 from feature descriptions
kernel: Drop IA64 support from sig_fault handlers
arch: Remove Itanium (IA-64) architecture
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git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks
Pull RCU updates from Frederic Weisbecker:
- RCU torture, locktorture and generic torture infrastructure updates
that include various fixes, cleanups and consolidations.
Among the user visible things, ftrace dumps can now be found into
their own file, and module parameters get better documented and
reported on dumps.
- Generic and misc fixes all over the place. Some highlights:
* Hotplug handling has seen some light cleanups and comments
* An RCU barrier can now be triggered through sysfs to serialize
memory stress testing and avoid OOM
* Object information is now dumped in case of invalid callback
invocation
* Also various SRCU issues, too hard to trigger to deserve urgent
pull requests, have been fixed
- RCU documentation updates
- RCU reference scalability test minor fixes and doc improvements.
- RCU tasks minor fixes
- Stall detection updates. Introduce RCU CPU Stall notifiers that
allows a subsystem to provide informations to help debugging. Also
cure some false positive stalls.
* tag 'rcu-next-v6.7' of git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks: (56 commits)
srcu: Only accelerate on enqueue time
locktorture: Check the correct variable for allocation failure
srcu: Fix callbacks acceleration mishandling
rcu: Comment why callbacks migration can't wait for CPUHP_RCUTREE_PREP
rcu: Standardize explicit CPU-hotplug calls
rcu: Conditionally build CPU-hotplug teardown callbacks
rcu: Remove references to rcu_migrate_callbacks() from diagrams
rcu: Assume rcu_report_dead() is always called locally
rcu: Assume IRQS disabled from rcu_report_dead()
rcu: Use rcu_segcblist_segempty() instead of open coding it
rcu: kmemleak: Ignore kmemleak false positives when RCU-freeing objects
srcu: Fix srcu_struct node grpmask overflow on 64-bit systems
torture: Convert parse-console.sh to mktemp
rcutorture: Traverse possible cpu to set maxcpu in rcu_nocb_toggle()
rcutorture: Replace schedule_timeout*() 1-jiffy waits with HZ/20
torture: Add kvm.sh --debug-info argument
locktorture: Rename readers_bind/writers_bind to bind_readers/bind_writers
doc: Catch-up update for locktorture module parameters
locktorture: Add call_rcu_chains module parameter
locktorture: Add new module parameters to lock_torture_print_module_parms()
...
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 core updates from Thomas Gleixner:
- Limit the hardcoded topology quirk for Hygon CPUs to those which have
a model ID less than 4.
The newer models have the topology CPUID leaf 0xB correctly
implemented and are not affected.
- Make SMT control more robust against enumeration failures
SMT control was added to allow controlling SMT at boottime or
runtime. The primary purpose was to provide a simple mechanism to
disable SMT in the light of speculation attack vectors.
It turned out that the code is sensible to enumeration failures and
worked only by chance for XEN/PV. XEN/PV has no real APIC enumeration
which means the primary thread mask is not set up correctly. By
chance a XEN/PV boot ends up with smp_num_siblings == 2, which makes
the hotplug control stay at its default value "enabled". So the mask
is never evaluated.
The ongoing rework of the topology evaluation caused XEN/PV to end up
with smp_num_siblings == 1, which sets the SMT control to "not
supported" and the empty primary thread mask causes the hotplug core
to deny the bringup of the APS.
Make the decision logic more robust and take 'not supported' and 'not
implemented' into account for the decision whether a CPU should be
booted or not.
- Fake primary thread mask for XEN/PV
Pretend that all XEN/PV vCPUs are primary threads, which makes the
usage of the primary thread mask valid on XEN/PV. That is consistent
with because all of the topology information on XEN/PV is fake or
even non-existent.
- Encapsulate topology information in cpuinfo_x86
Move the randomly scattered topology data into a separate data
structure for readability and as a preparatory step for the topology
evaluation overhaul.
- Consolidate APIC ID data type to u32
It's fixed width hardware data and not randomly u16, int, unsigned
long or whatever developers decided to use.
- Cure the abuse of cpuinfo for persisting logical IDs.
Per CPU cpuinfo is used to persist the logical package and die IDs.
That's really not the right place simply because cpuinfo is subject
to be reinitialized when a CPU goes through an offline/online cycle.
Use separate per CPU data for the persisting to enable the further
topology management rework. It will be removed once the new topology
management is in place.
- Provide a debug interface for inspecting topology information
Useful in general and extremly helpful for validating the topology
management rework in terms of correctness or "bug" compatibility.
* tag 'x86-core-2023-10-29-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (23 commits)
x86/apic, x86/hyperv: Use u32 in hv_snp_boot_ap() too
x86/cpu: Provide debug interface
x86/cpu/topology: Cure the abuse of cpuinfo for persisting logical ids
x86/apic: Use u32 for wakeup_secondary_cpu[_64]()
x86/apic: Use u32 for [gs]et_apic_id()
x86/apic: Use u32 for phys_pkg_id()
x86/apic: Use u32 for cpu_present_to_apicid()
x86/apic: Use u32 for check_apicid_used()
x86/apic: Use u32 for APIC IDs in global data
x86/apic: Use BAD_APICID consistently
x86/cpu: Move cpu_l[l2]c_id into topology info
x86/cpu: Move logical package and die IDs into topology info
x86/cpu: Remove pointless evaluation of x86_coreid_bits
x86/cpu: Move cu_id into topology info
x86/cpu: Move cpu_core_id into topology info
hwmon: (fam15h_power) Use topology_core_id()
scsi: lpfc: Use topology_core_id()
x86/cpu: Move cpu_die_id into topology info
x86/cpu: Move phys_proc_id into topology info
x86/cpu: Encapsulate topology information in cpuinfo_x86
...
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If a system has isolated CPUs via the "isolcpus=" command line parameter,
then an attempt to offline the last housekeeping CPU will result in a
WARN_ON() when rebuilding the scheduler domains and a subsequent panic due
to and unhandled empty CPU mas in partition_sched_domains_locked().
cpuset_hotplug_workfn()
rebuild_sched_domains_locked()
ndoms = generate_sched_domains(&doms, &attr);
cpumask_and(doms[0], top_cpuset.effective_cpus, housekeeping_cpumask(HK_FLAG_DOMAIN));
Thus results in an empty CPU mask which triggers the warning and then the
subsequent crash:
WARNING: CPU: 4 PID: 80 at kernel/sched/topology.c:2366 build_sched_domains+0x120c/0x1408
Call trace:
build_sched_domains+0x120c/0x1408
partition_sched_domains_locked+0x234/0x880
rebuild_sched_domains_locked+0x37c/0x798
rebuild_sched_domains+0x30/0x58
cpuset_hotplug_workfn+0x2a8/0x930
Unable to handle kernel paging request at virtual address fffe80027ab37080
partition_sched_domains_locked+0x318/0x880
rebuild_sched_domains_locked+0x37c/0x798
Aside of the resulting crash, it does not make any sense to offline the last
last housekeeping CPU.
Prevent this by masking out the non-housekeeping CPUs when selecting a
target CPU for initiating the CPU unplug operation via the work queue.
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ran Xiaokai <ran.xiaokai@zte.com.cn>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/202310171709530660462@zte.com.cn
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The SMT control mechanism got added as speculation attack vector
mitigation. The implemented logic relies on the primary thread mask to
be set up properly.
This turns out to be an issue with XEN/PV guests because their CPU hotplug
mechanics do not enumerate APICs and therefore the mask is never correctly
populated.
This went unnoticed so far because by chance XEN/PV ends up with
smp_num_siblings == 2. So smt_hotplug_control stays at its default value
CPU_SMT_ENABLED and the primary thread mask is never evaluated in the
context of CPU hotplug.
This stopped "working" with the upcoming overhaul of the topology
evaluation which legitimately provides a fake topology for XEN/PV. That
sets smp_num_siblings to 1, which causes the core CPU hot-plug core to
refuse to bring up the APs.
This happens because smt_hotplug_control is set to CPU_SMT_NOT_SUPPORTED
which causes cpu_smt_allowed() to evaluate the unpopulated primary thread
mask with the conclusion that all non-boot CPUs are not valid to be
plugged.
Make cpu_smt_allowed() more robust and take CPU_SMT_NOT_SUPPORTED and
CPU_SMT_NOT_IMPLEMENTED into account. Rename it to cpu_bootable() while at
it as that makes it more clear what the function is about.
The primary mask issue on x86 XEN/PV needs to be addressed separately as
there are users outside of the CPU hotplug code too.
Fixes: 05736e4ac13c ("cpu/hotplug: Provide knobs to control SMT")
Reported-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Juergen Gross <jgross@suse.com>
Tested-by: Sohil Mehta <sohil.mehta@intel.com>
Tested-by: Michael Kelley <mikelley@microsoft.com>
Tested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Zhang Rui <rui.zhang@intel.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20230814085112.149440843@linutronix.de
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The callbacks migration is performed through an explicit call from
the hotplug control CPU right after the death of the target CPU and
before proceeding with the CPUHP_ teardown functions.
This is unusual but necessary and yet uncommented. Summarize the reason
as explained in the changelog of:
a58163d8ca2c (rcu: Migrate callbacks earlier in the CPU-offline timeline)
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
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rcu_report_dead() and rcutree_migrate_callbacks() have their headers in
rcupdate.h while those are pure rcutree calls, like the other CPU-hotplug
functions.
Also rcu_cpu_starting() and rcu_report_dead() have different naming
conventions while they mirror each other's effects.
Fix the headers and propose a naming that relates both functions and
aligns with the prefix of other rcutree CPU-hotplug functions.
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
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rcu_report_dead() has to be called locally by the CPU that is going to
exit the RCU state machine. Passing a cpu argument here is error-prone
and leaves the possibility for a racy remote call.
Use local access instead.
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
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The Itanium architecture is obsolete, and an informal survey [0] reveals
that any residual use of Itanium hardware in production is mostly HP-UX
or OpenVMS based. The use of Linux on Itanium appears to be limited to
enthusiasts that occasionally boot a fresh Linux kernel to see whether
things are still working as intended, and perhaps to churn out some
distro packages that are rarely used in practice.
None of the original companies behind Itanium still produce or support
any hardware or software for the architecture, and it is listed as
'Orphaned' in the MAINTAINERS file, as apparently, none of the engineers
that contributed on behalf of those companies (nor anyone else, for that
matter) have been willing to support or maintain the architecture
upstream or even be responsible for applying the odd fix. The Intel
firmware team removed all IA-64 support from the Tianocore/EDK2
reference implementation of EFI in 2018. (Itanium is the original
architecture for which EFI was developed, and the way Linux supports it
deviates significantly from other architectures.) Some distros, such as
Debian and Gentoo, still maintain [unofficial] ia64 ports, but many have
dropped support years ago.
While the argument is being made [1] that there is a 'for the common
good' angle to being able to build and run existing projects such as the
Grid Community Toolkit [2] on Itanium for interoperability testing, the
fact remains that none of those projects are known to be deployed on
Linux/ia64, and very few people actually have access to such a system in
the first place. Even if there were ways imaginable in which Linux/ia64
could be put to good use today, what matters is whether anyone is
actually doing that, and this does not appear to be the case.
There are no emulators widely available, and so boot testing Itanium is
generally infeasible for ordinary contributors. GCC still supports IA-64
but its compile farm [3] no longer has any IA-64 machines. GLIBC would
like to get rid of IA-64 [4] too because it would permit some overdue
code cleanups. In summary, the benefits to the ecosystem of having IA-64
be part of it are mostly theoretical, whereas the maintenance overhead
of keeping it supported is real.
So let's rip off the band aid, and remove the IA-64 arch code entirely.
This follows the timeline proposed by the Debian/ia64 maintainer [5],
which removes support in a controlled manner, leaving IA-64 in a known
good state in the most recent LTS release. Other projects will follow
once the kernel support is removed.
[0] https://lore.kernel.org/all/CAMj1kXFCMh_578jniKpUtx_j8ByHnt=s7S+yQ+vGbKt9ud7+kQ@mail.gmail.com/
[1] https://lore.kernel.org/all/0075883c-7c51-00f5-2c2d-5119c1820410@web.de/
[2] https://gridcf.org/gct-docs/latest/index.html
[3] https://cfarm.tetaneutral.net/machines/list/
[4] https://lore.kernel.org/all/87bkiilpc4.fsf@mid.deneb.enyo.de/
[5] https://lore.kernel.org/all/ff58a3e76e5102c94bb5946d99187b358def688a.camel@physik.fu-berlin.de/
Acked-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
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Xiongfeng reported and debugged a self deadlock of the task which initiates
and controls a CPU hot-unplug operation vs. the CFS bandwidth timer.
CPU1 CPU2
T1 sets cfs_quota
starts hrtimer cfs_bandwidth 'period_timer'
T1 is migrated to CPU2
T1 initiates offlining of CPU1
Hotplug operation starts
...
'period_timer' expires and is re-enqueued on CPU1
...
take_cpu_down()
CPU1 shuts down and does not handle timers
anymore. They have to be migrated in the
post dead hotplug steps by the control task.
T1 runs the post dead offline operation
T1 is scheduled out
T1 waits for 'period_timer' to expire
T1 waits there forever if it is scheduled out before it can execute the hrtimer
offline callback hrtimers_dead_cpu().
Cure this by delegating the hotplug control operation to a worker thread on
an online CPU. This takes the initiating user space task, which might be
affected by the bandwidth timer, completely out of the picture.
Reported-by: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Yu Liao <liaoyu15@huawei.com>
Acked-by: Vincent Guittot <vincent.guittot@linaro.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/lkml/8e785777-03aa-99e1-d20e-e956f5685be6@huawei.com
Link: https://lore.kernel.org/r/87h6oqdq0i.ffs@tglx
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Commit e1572f1d08be ("cpu/SMT: create and export cpu_smt_possible()")
introduces cpu_smt_possible() to represent if SMT is theoretically
possible. It returns true when SMT is supported and not forcefully
disabled ('nosmt=force'). But the comment of it says "Returns true if
SMT is not supported of forcefully (irreversibly) disabled", which is
wrong. Fix that comment accordingly.
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Link: https://lore.kernel.org/r/20230728155313.44170-1-rui.zhang@intel.com
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Add support to the /sys/devices/system/cpu/smt/control interface for
enabling a specified number of SMT threads per core, including partial
SMT states where not all threads are brought online.
The current interface accepts "on" and "off", to enable either 1 or all
SMT threads per core.
This commit allows writing an integer, between 1 and the number of SMT
threads supported by the machine. Writing 1 is a synonym for "off", 2 or
more enables SMT with the specified number of threads.
When reading the file, if all threads are online "on" is returned, to
avoid changing behaviour for existing users. If some other number of
threads is online then the integer value is returned.
Architectures like x86 only supporting 1 thread or all threads, should not
define CONFIG_SMT_NUM_THREADS_DYNAMIC. Architecture supporting partial SMT
states, like PowerPC, should define it.
[ ldufour: Slightly reword the commit's description ]
[ ldufour: Remove switch() in __store_smt_control() ]
[ ldufour: Rix build issue in control_show() ]
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Zhang Rui <rui.zhang@intel.com>
Link: https://lore.kernel.org/r/20230705145143.40545-8-ldufour@linux.ibm.com
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Some architectures allows partial SMT states, i.e. when not all SMT threads
are brought online.
To support that, add an architecture helper which checks whether a given
CPU is allowed to be brought online depending on how many SMT threads are
currently enabled. Since this is only applicable to architecture supporting
partial SMT, only these architectures should select the new configuration
variable CONFIG_SMT_NUM_THREADS_DYNAMIC. For the other architectures, not
supporting the partial SMT states, there is no need to define
topology_cpu_smt_allowed(), the generic code assumed that all the threads
are allowed or only the primary ones.
Call the helper from cpu_smt_enable(), and cpu_smt_allowed() when SMT is
enabled, to check if the particular thread should be onlined. Notably,
also call it from cpu_smt_disable() if CPU_SMT_ENABLED, to allow
offlining some threads to move from a higher to lower number of threads
online.
[ ldufour: Slightly reword the commit's description ]
[ ldufour: Introduce CONFIG_SMT_NUM_THREADS_DYNAMIC ]
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Zhang Rui <rui.zhang@intel.com>
Link: https://lore.kernel.org/r/20230705145143.40545-7-ldufour@linux.ibm.com
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Since the maximum number of threads is now passed to cpu_smt_set_num_threads(),
checking that value is enough to know whether SMT is supported.
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Zhang Rui <rui.zhang@intel.com>
Link: https://lore.kernel.org/r/20230705145143.40545-6-ldufour@linux.ibm.com
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Some architectures allow partial SMT states at boot time, ie. when not all
SMT threads are brought online.
To support that the SMT code needs to know the maximum number of SMT
threads, and also the currently configured number.
The architecture code knows the max number of threads, so have the
architecture code pass that value to cpu_smt_set_num_threads(). Note that
although topology_max_smt_threads() exists, it is not configured early
enough to be used here. As architecture, like PowerPC, allows the threads
number to be set through the kernel command line, also pass that value.
[ ldufour: Slightly reword the commit message ]
[ ldufour: Rename cpu_smt_check_topology and add a num_threads argument ]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Zhang Rui <rui.zhang@intel.com>
Link: https://lore.kernel.org/r/20230705145143.40545-5-ldufour@linux.ibm.com
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Move the simple exit cases, i.e. those which don't depend on the value
written, earlier in the function. That makes it clearer that regardless of
the input those states cannot be transitioned out of.
That does have a user-visible effect, in that the error returned will
now always be EPERM/ENODEV for those states, regardless of the value
written. Previously writing an invalid value would return EINVAL even
when in those states.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Zhang Rui <rui.zhang@intel.com>
Link: https://lore.kernel.org/r/20230705145143.40545-4-ldufour@linux.ibm.com
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In order to export the cpuhp_smt_control enum as part of the interface
between generic and architecture code, the architecture code needs to
include asm/topology.h.
But that leads to circular header dependencies. So split the enum and
related declarations into a separate header.
[ ldufour: Reworded the commit's description ]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Zhang Rui <rui.zhang@intel.com>
Link: https://lore.kernel.org/r/20230705145143.40545-3-ldufour@linux.ibm.com
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The commit 18415f33e2ac ("cpu/hotplug: Allow "parallel" bringup up to
CPUHP_BP_KICK_AP_STATE") introduce a dependancy against a global variable
cpu_primary_thread_mask exported by the X86 code. This variable is only
used when CONFIG_HOTPLUG_PARALLEL is set.
Since cpuhp_get_primary_thread_mask() and cpuhp_smt_aware() are only used
when CONFIG_HOTPLUG_PARALLEL is set, don't define them when it is not set.
No functional change.
Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Zhang Rui <rui.zhang@intel.com>
Link: https://lore.kernel.org/r/20230705145143.40545-2-ldufour@linux.ibm.com
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cpuhp_bringup_mask() iterates over a cpumask and starts all present CPUs up
to a caller provided upper limit.
The limit variable is decremented and checked for 0 before invoking
cpu_up(), which is obviously off by one and prevents the bringup of the
last CPU when the limit is equal to the number of present CPUs.
Move the decrement and check after the cpu_up() invocation.
Fixes: 18415f33e2ac ("cpu/hotplug: Allow "parallel" bringup up to CPUHP_BP_KICK_AP_STATE")
Reported-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/87wn10ufj9.ffs@tglx
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There is often significant latency in the early stages of CPU bringup, and
time is wasted by waking each CPU (e.g. with SIPI/INIT/INIT on x86) and
then waiting for it to respond before moving on to the next.
Allow a platform to enable parallel setup which brings all to be onlined
CPUs up to the CPUHP_BP_KICK_AP state. While this state advancement on the
control CPU (BP) is single-threaded the important part is the last state
CPUHP_BP_KICK_AP which wakes the to be onlined CPUs up.
This allows the CPUs to run up to the first sychronization point
cpuhp_ap_sync_alive() where they wait for the control CPU to release them
one by one for the full onlining procedure.
This parallelism depends on the CPU hotplug core sync mechanism which
ensures that the parallel brought up CPUs wait for release before touching
any state which would make the CPU visible to anything outside the hotplug
control mechanism.
To handle the SMT constraints of X86 correctly the bringup happens in two
iterations when CONFIG_HOTPLUG_SMT is enabled. The control CPU brings up
the primary SMT threads of each core first, which can load the microcode
without the need to rendevouz with the thread siblings. Once that's
completed it brings up the secondary SMT threads.
Co-developed-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Michael Kelley <mikelley@microsoft.com>
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Tested-by: Helge Deller <deller@gmx.de> # parisc
Tested-by: Guilherme G. Piccoli <gpiccoli@igalia.com> # Steam Deck
Link: https://lore.kernel.org/r/20230512205257.240231377@linutronix.de
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The bring up logic of a to be onlined CPU consists of several parts, which
are considered to be a single hotplug state:
1) Control CPU issues the wake-up
2) To be onlined CPU starts up, does the minimal initialization,
reports to be alive and waits for release into the complete bring-up.
3) Control CPU waits for the alive report and releases the upcoming CPU
for the complete bring-up.
Allow to split this into two states:
1) Control CPU issues the wake-up
After that the to be onlined CPU starts up, does the minimal
initialization, reports to be alive and waits for release into the
full bring-up. As this can run after the control CPU dropped the
hotplug locks the code which is executed on the AP before it reports
alive has to be carefully audited to not violate any of the hotplug
constraints, especially not modifying any of the various cpumasks.
This is really only meant to avoid waiting for the AP to react on the
wake-up. Of course an architecture can move strict CPU related setup
functionality, e.g. microcode loading, with care before the
synchronization point to save further pointless waiting time.
2) Control CPU waits for the alive report and releases the upcoming CPU
for the complete bring-up.
This allows that the two states can be split up to run all to be onlined
CPUs up to state #1 on the control CPU and then at a later point run state
#2. This spares some of the latencies of the full serialized per CPU
bringup by avoiding the per CPU wakeup/wait serialization. The assumption
is that the first AP already waits when the last AP has been woken up. This
obvioulsy depends on the hardware latencies and depending on the timings
this might still not completely eliminate all wait scenarios.
This split is just a preparatory step for enabling the parallel bringup
later. The boot time bringup is still fully serialized. It has a separate
config switch so that architectures which want to support parallel bringup
can test the split of the CPUHP_BRINGUG step separately.
To enable this the architecture must support the CPU hotplug core sync
mechanism and has to be audited that there are no implicit hotplug state
dependencies which require a fully serialized bringup.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Michael Kelley <mikelley@microsoft.com>
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Tested-by: Helge Deller <deller@gmx.de> # parisc
Tested-by: Guilherme G. Piccoli <gpiccoli@igalia.com> # Steam Deck
Link: https://lore.kernel.org/r/20230512205257.080801387@linutronix.de
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Commit dce1ca0525bf ("sched/scs: Reset task stack state in bringup_cpu()")
ensured that the shadow call stack and KASAN poisoning were removed from
a CPU's stack each time that CPU is brought up, not just once.
This is not incorrect. However, with parallel bringup the idle thread setup
will happen at a different step. As a consequence the cleanup in
bringup_cpu() would be too late.
Move the SCS/KASAN cleanup to the generic _cpu_up() function instead,
which already ensures that the new CPU's stack is available, purely to
allow for early failure. This occurs when the CPU to be brought up is
in the CPUHP_OFFLINE state, which should correctly do the cleanup any
time the CPU has been taken down to the point where such is needed.
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Michael Kelley <mikelley@microsoft.com>
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Tested-by: Helge Deller <deller@gmx.de> # parisc
Tested-by: Guilherme G. Piccoli <gpiccoli@igalia.com> # Steam Deck
Link: https://lore.kernel.org/r/20230512205257.027075560@linutronix.de
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The CPU state tracking and synchronization mechanism in smpboot.c is
completely independent of the hotplug code and all logic around it is
implemented in architecture specific code.
Except for the state reporting of the AP there is absolutely nothing
architecture specific and the sychronization and decision functions can be
moved into the generic hotplug core code.
Provide an integrated variant and add the core synchronization and decision
points. This comes in two flavours:
1) DEAD state synchronization
Updated by the architecture code once the AP reaches the point where
it is ready to be torn down by the control CPU, e.g. by removing power
or clocks or tear down via the hypervisor.
The control CPU waits for this state to be reached with a timeout. If
the state is reached an architecture specific cleanup function is
invoked.
2) Full state synchronization
This extends #1 with AP alive synchronization. This is new
functionality, which allows to replace architecture specific wait
mechanims, e.g. cpumasks, completely.
It also prevents that an AP which is in a limbo state can be brought
up again. This can happen when an AP failed to report dead state
during a previous off-line operation.
The dead synchronization is what most architectures use. Only x86 makes a
bringup decision based on that state at the moment.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Michael Kelley <mikelley@microsoft.com>
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Tested-by: Helge Deller <deller@gmx.de> # parisc
Tested-by: Guilherme G. Piccoli <gpiccoli@igalia.com> # Steam Deck
Link: https://lore.kernel.org/r/20230512205256.476305035@linutronix.de
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There is no harm to hold sparse_irq lock until the upcoming CPU completes
in cpuhp_online_idle(). This allows to remove cpu_online() synchronization
from architecture code.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Michael Kelley <mikelley@microsoft.com>
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Tested-by: Helge Deller <deller@gmx.de> # parisc
Tested-by: Guilherme G. Piccoli <gpiccoli@igalia.com> # Steam Deck
Link: https://lore.kernel.org/r/20230512205256.263722880@linutronix.de
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No point in keeping them around.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Michael Kelley <mikelley@microsoft.com>
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Tested-by: Helge Deller <deller@gmx.de> # parisc
Tested-by: Guilherme G. Piccoli <gpiccoli@igalia.com> # Steam Deck
Link: https://lore.kernel.org/r/20230512205255.551974164@linutronix.de
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git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Pull MM updates from Andrew Morton:
- Nick Piggin's "shoot lazy tlbs" series, to improve the peformance of
switching from a user process to a kernel thread.
- More folio conversions from Kefeng Wang, Zhang Peng and Pankaj
Raghav.
- zsmalloc performance improvements from Sergey Senozhatsky.
- Yue Zhao has found and fixed some data race issues around the
alteration of memcg userspace tunables.
- VFS rationalizations from Christoph Hellwig:
- removal of most of the callers of write_one_page()
- make __filemap_get_folio()'s return value more useful
- Luis Chamberlain has changed tmpfs so it no longer requires swap
backing. Use `mount -o noswap'.
- Qi Zheng has made the slab shrinkers operate locklessly, providing
some scalability benefits.
- Keith Busch has improved dmapool's performance, making part of its
operations O(1) rather than O(n).
- Peter Xu adds the UFFD_FEATURE_WP_UNPOPULATED feature to userfaultd,
permitting userspace to wr-protect anon memory unpopulated ptes.
- Kirill Shutemov has changed MAX_ORDER's meaning to be inclusive
rather than exclusive, and has fixed a bunch of errors which were
caused by its unintuitive meaning.
- Axel Rasmussen give userfaultfd the UFFDIO_CONTINUE_MODE_WP feature,
which causes minor faults to install a write-protected pte.
- Vlastimil Babka has done some maintenance work on vma_merge():
cleanups to the kernel code and improvements to our userspace test
harness.
- Cleanups to do_fault_around() by Lorenzo Stoakes.
- Mike Rapoport has moved a lot of initialization code out of various
mm/ files and into mm/mm_init.c.
- Lorenzo Stoakes removd vmf_insert_mixed_prot(), which was added for
DRM, but DRM doesn't use it any more.
- Lorenzo has also coverted read_kcore() and vread() to use iterators
and has thereby removed the use of bounce buffers in some cases.
- Lorenzo has also contributed further cleanups of vma_merge().
- Chaitanya Prakash provides some fixes to the mmap selftesting code.
- Matthew Wilcox changes xfs and afs so they no longer take sleeping
locks in ->map_page(), a step towards RCUification of pagefaults.
- Suren Baghdasaryan has improved mmap_lock scalability by switching to
per-VMA locking.
- Frederic Weisbecker has reworked the percpu cache draining so that it
no longer causes latency glitches on cpu isolated workloads.
- Mike Rapoport cleans up and corrects the ARCH_FORCE_MAX_ORDER Kconfig
logic.
- Liu Shixin has changed zswap's initialization so we no longer waste a
chunk of memory if zswap is not being used.
- Yosry Ahmed has improved the performance of memcg statistics
flushing.
- David Stevens has fixed several issues involving khugepaged,
userfaultfd and shmem.
- Christoph Hellwig has provided some cleanup work to zram's IO-related
code paths.
- David Hildenbrand has fixed up some issues in the selftest code's
testing of our pte state changing.
- Pankaj Raghav has made page_endio() unneeded and has removed it.
- Peter Xu contributed some rationalizations of the userfaultfd
selftests.
- Yosry Ahmed has fixed an issue around memcg's page recalim
accounting.
- Chaitanya Prakash has fixed some arm-related issues in the
selftests/mm code.
- Longlong Xia has improved the way in which KSM handles hwpoisoned
pages.
- Peter Xu fixes a few issues with uffd-wp at fork() time.
- Stefan Roesch has changed KSM so that it may now be used on a
per-process and per-cgroup basis.
* tag 'mm-stable-2023-04-27-15-30' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (369 commits)
mm,unmap: avoid flushing TLB in batch if PTE is inaccessible
shmem: restrict noswap option to initial user namespace
mm/khugepaged: fix conflicting mods to collapse_file()
sparse: remove unnecessary 0 values from rc
mm: move 'mmap_min_addr' logic from callers into vm_unmapped_area()
hugetlb: pte_alloc_huge() to replace huge pte_alloc_map()
maple_tree: fix allocation in mas_sparse_area()
mm: do not increment pgfault stats when page fault handler retries
zsmalloc: allow only one active pool compaction context
selftests/mm: add new selftests for KSM
mm: add new KSM process and sysfs knobs
mm: add new api to enable ksm per process
mm: shrinkers: fix debugfs file permissions
mm: don't check VMA write permissions if the PTE/PMD indicates write permissions
migrate_pages_batch: fix statistics for longterm pin retry
userfaultfd: use helper function range_in_vma()
lib/show_mem.c: use for_each_populated_zone() simplify code
mm: correct arg in reclaim_pages()/reclaim_clean_pages_from_list()
fs/buffer: convert create_page_buffers to folio_create_buffers
fs/buffer: add folio_create_empty_buffers helper
...
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Add explicit _lazy_tlb annotated functions for lazy tlb mm refcounting.
This makes the lazy tlb mm references more obvious, and allows the
refcounting scheme to be modified in later changes. There is no
functional change with this patch.
Link: https://lkml.kernel.org/r/20230203071837.1136453-3-npiggin@gmail.com
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Direct access to the struct bus_type dev_root pointer is going away soon
so replace that with a call to bus_get_dev_root() instead, which is what
it is there for.
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Valentin Schneider <vschneid@redhat.com>
Cc: Phil Auld <pauld@redhat.com>
Cc: Steven Price <steven.price@arm.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Vincent Donnefort <vdonnefort@google.com>
Cc: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Link: https://lore.kernel.org/r/20230313182918.1312597-7-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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The DYING/STARTING callbacks are not expected to fail. However, as reported
by Derek, buggy drivers such as tboot are still free to return errors
within those sections, which halts the hot(un)plug and leaves the CPU in an
unrecoverable state.
As there is no rollback possible, only log the failures and proceed with
the following steps.
This restores the hotplug behaviour prior to commit 453e41085183
("cpu/hotplug: Add cpuhp_invoke_callback_range()")
Fixes: 453e41085183 ("cpu/hotplug: Add cpuhp_invoke_callback_range()")
Reported-by: Derek Dolney <z23@posteo.net>
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Derek Dolney <z23@posteo.net>
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=215867
Link: https://lore.kernel.org/r/20220927101259.1149636-1-vdonnefort@google.com
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Since the boot cpu does not go through the hotplug process it ends
up with state == CPUHP_ONLINE but target == CPUHP_OFFLINE.
So set the target to match in boot_cpu_hotplug_init().
Signed-off-by: Phil Auld <pauld@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Link: https://lore.kernel.org/r/20221117162329.3164999-3-pauld@redhat.com
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Writing the current state back in hotplug/target calls cpu_down()
which will set cpu dying even when it isn't and then nothing will
ever clear it. A stress test that reads values and writes them back
for all cpu device files in sysfs will trigger the BUG() in
select_fallback_rq once all cpus are marked as dying.
kernel/cpu.c::target_store()
...
if (st->state < target)
ret = cpu_up(dev->id, target);
else
ret = cpu_down(dev->id, target);
cpu_down() -> cpu_set_state()
bool bringup = st->state < target;
...
if (cpu_dying(cpu) != !bringup)
set_cpu_dying(cpu, !bringup);
Fix this by letting state==target fall through in the target_store()
conditional. Also make sure st->target == target in that case.
Fixes: 757c989b9994 ("cpu/hotplug: Make target state writeable")
Signed-off-by: Phil Auld <pauld@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Link: https://lore.kernel.org/r/20221117162329.3164999-2-pauld@redhat.com
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull Intel TDX support from Borislav Petkov:
"Intel Trust Domain Extensions (TDX) support.
This is the Intel version of a confidential computing solution called
Trust Domain Extensions (TDX). This series adds support to run the
kernel as part of a TDX guest. It provides similar guest protections
to AMD's SEV-SNP like guest memory and register state encryption,
memory integrity protection and a lot more.
Design-wise, it differs from AMD's solution considerably: it uses a
software module which runs in a special CPU mode called (Secure
Arbitration Mode) SEAM. As the name suggests, this module serves as
sort of an arbiter which the confidential guest calls for services it
needs during its lifetime.
Just like AMD's SNP set, this series reworks and streamlines certain
parts of x86 arch code so that this feature can be properly
accomodated"
* tag 'x86_tdx_for_v5.19_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (34 commits)
x86/tdx: Fix RETs in TDX asm
x86/tdx: Annotate a noreturn function
x86/mm: Fix spacing within memory encryption features message
x86/kaslr: Fix build warning in KASLR code in boot stub
Documentation/x86: Document TDX kernel architecture
ACPICA: Avoid cache flush inside virtual machines
x86/tdx/ioapic: Add shared bit for IOAPIC base address
x86/mm: Make DMA memory shared for TD guest
x86/mm/cpa: Add support for TDX shared memory
x86/tdx: Make pages shared in ioremap()
x86/topology: Disable CPU online/offline control for TDX guests
x86/boot: Avoid #VE during boot for TDX platforms
x86/boot: Set CR0.NE early and keep it set during the boot
x86/acpi/x86/boot: Add multiprocessor wake-up support
x86/boot: Add a trampoline for booting APs via firmware handoff
x86/tdx: Wire up KVM hypercalls
x86/tdx: Port I/O: Add early boot support
x86/tdx: Port I/O: Add runtime hypercalls
x86/boot: Port I/O: Add decompression-time support for TDX
x86/boot: Port I/O: Allow to hook up alternative helpers
...
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Rather than waiting until a CPU is first brought online, do the
initialisation of the cpuhp_cpu_state structure for each CPU during the
__init phase. This saves a (small) amount of non-__init memory and
avoids potential confusion about when the cpuhp_cpu_state struct is
valid.
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Steven Price <steven.price@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20220411152233.474129-3-steven.price@arm.com
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Currently the setting of the 'cpu' member of struct cpuhp_cpu_state in
cpuhp_create() is too late as it is used earlier in _cpu_up().
If kzalloc_node() in __smpboot_create_thread() fails then the rollback will
be done with st->cpu==0 causing CPU0 to be erroneously set to be dying,
causing the scheduler to get mightily confused and throw its toys out of
the pram.
However the cpu number is actually available directly, so simply remove
the 'cpu' member and avoid the problem in the first place.
Fixes: 2ea46c6fc945 ("cpumask/hotplug: Fix cpu_dying() state tracking")
Signed-off-by: Steven Price <steven.price@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20220411152233.474129-2-steven.price@arm.com
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Unlike regular VMs, TDX guests use the firmware hand-off wakeup method
to wake up the APs during the boot process. This wakeup model uses a
mailbox to communicate with firmware to bring up the APs. As per the
design, this mailbox can only be used once for the given AP, which means
after the APs are booted, the same mailbox cannot be used to
offline/online the given AP. More details about this requirement can be
found in Intel TDX Virtual Firmware Design Guide, sec titled "AP
initialization in OS" and in sec titled "Hotplug Device".
Since the architecture does not support any method of offlining the
CPUs, disable CPU hotplug support in the kernel.
Since this hotplug disable feature can be re-used by other VM guests,
add a new CC attribute CC_ATTR_HOTPLUG_DISABLED and use it to disable
the hotplug support.
Attempt to offline CPU will fail with -EOPNOTSUPP.
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20220405232939.73860-25-kirill.shutemov@linux.intel.com
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler updates from Ingo Molnar:
- Cleanups for SCHED_DEADLINE
- Tracing updates/fixes
- CPU Accounting fixes
- First wave of changes to optimize the overhead of the scheduler
build, from the fast-headers tree - including placeholder *_api.h
headers for later header split-ups.
- Preempt-dynamic using static_branch() for ARM64
- Isolation housekeeping mask rework; preperatory for further changes
- NUMA-balancing: deal with CPU-less nodes
- NUMA-balancing: tune systems that have multiple LLC cache domains per
node (eg. AMD)
- Updates to RSEQ UAPI in preparation for glibc usage
- Lots of RSEQ/selftests, for same
- Add Suren as PSI co-maintainer
* tag 'sched-core-2022-03-22' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (81 commits)
sched/headers: ARM needs asm/paravirt_api_clock.h too
sched/numa: Fix boot crash on arm64 systems
headers/prep: Fix header to build standalone: <linux/psi.h>
sched/headers: Only include <linux/entry-common.h> when CONFIG_GENERIC_ENTRY=y
cgroup: Fix suspicious rcu_dereference_check() usage warning
sched/preempt: Tell about PREEMPT_DYNAMIC on kernel headers
sched/topology: Remove redundant variable and fix incorrect type in build_sched_domains
sched/deadline,rt: Remove unused parameter from pick_next_[rt|dl]_entity()
sched/deadline,rt: Remove unused functions for !CONFIG_SMP
sched/deadline: Use __node_2_[pdl|dle]() and rb_first_cached() consistently
sched/deadline: Merge dl_task_can_attach() and dl_cpu_busy()
sched/deadline: Move bandwidth mgmt and reclaim functions into sched class source file
sched/deadline: Remove unused def_dl_bandwidth
sched/tracing: Report TASK_RTLOCK_WAIT tasks as TASK_UNINTERRUPTIBLE
sched/tracing: Don't re-read p->state when emitting sched_switch event
sched/rt: Plug rt_mutex_setprio() vs push_rt_task() race
sched/cpuacct: Remove redundant RCU read lock
sched/cpuacct: Optimize away RCU read lock
sched/cpuacct: Fix charge percpu cpuusage
sched/headers: Reorganize, clean up and optimize kernel/sched/sched.h dependencies
...
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For the irq randomness fast pool, rather than having to use expensive
atomics, which were visibly the most expensive thing in the entire irq
handler, simply take care of the extreme edge case of resetting count to
zero in the cpuhp online handler, just after workqueues have been
reenabled. This simplifies the code a bit and lets us use vanilla
variables rather than atomics, and performance should be improved.
As well, very early on when the CPU comes up, while interrupts are still
disabled, we clear out the per-cpu crng and its batches, so that it
always starts with fresh randomness.
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Sultan Alsawaf <sultan@kerneltoast.com>
Cc: Dominik Brodowski <linux@dominikbrodowski.net>
Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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Refer to housekeeping APIs using single feature types instead of flags.
This prevents from passing multiple isolation features at once to
housekeeping interfaces, which soon won't be possible anymore as each
isolation features will have their own cpumask.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Juri Lelli <juri.lelli@redhat.com>
Reviewed-by: Phil Auld <pauld@redhat.com>
Link: https://lore.kernel.org/r/20220207155910.527133-5-frederic@kernel.org
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To hot unplug a CPU, the idle task on that CPU calls a few layers of C
code before finally leaving the kernel. When KASAN is in use, poisoned
shadow is left around for each of the active stack frames, and when
shadow call stacks are in use. When shadow call stacks (SCS) are in use
the task's saved SCS SP is left pointing at an arbitrary point within
the task's shadow call stack.
When a CPU is offlined than onlined back into the kernel, this stale
state can adversely affect execution. Stale KASAN shadow can alias new
stackframes and result in bogus KASAN warnings. A stale SCS SP is
effectively a memory leak, and prevents a portion of the shadow call
stack being used. Across a number of hotplug cycles the idle task's
entire shadow call stack can become unusable.
We previously fixed the KASAN issue in commit:
e1b77c92981a5222 ("sched/kasan: remove stale KASAN poison after hotplug")
... by removing any stale KASAN stack poison immediately prior to
onlining a CPU.
Subsequently in commit:
f1a0a376ca0c4ef1 ("sched/core: Initialize the idle task with preemption disabled")
... the refactoring left the KASAN and SCS cleanup in one-time idle
thread initialization code rather than something invoked prior to each
CPU being onlined, breaking both as above.
We fixed SCS (but not KASAN) in commit:
63acd42c0d4942f7 ("sched/scs: Reset the shadow stack when idle_task_exit")
... but as this runs in the context of the idle task being offlined it's
potentially fragile.
To fix these consistently and more robustly, reset the SCS SP and KASAN
shadow of a CPU's idle task immediately before we online that CPU in
bringup_cpu(). This ensures the idle task always has a consistent state
when it is running, and removes the need to so so when exiting an idle
task.
Whenever any thread is created, dup_task_struct() will give the task a
stack which is free of KASAN shadow, and initialize the task's SCS SP,
so there's no need to specially initialize either for idle thread within
init_idle(), as this was only necessary to handle hotplug cycles.
I've tested this on arm64 with:
* gcc 11.1.0, defconfig +KASAN_INLINE, KASAN_STACK
* clang 12.0.0, defconfig +KASAN_INLINE, KASAN_STACK, SHADOW_CALL_STACK
... offlining and onlining CPUS with:
| while true; do
| for C in /sys/devices/system/cpu/cpu*/online; do
| echo 0 > $C;
| echo 1 > $C;
| done
| done
Fixes: f1a0a376ca0c4ef1 ("sched/core: Initialize the idle task with preemption disabled")
Reported-by: Qian Cai <quic_qiancai@quicinc.com>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Tested-by: Qian Cai <quic_qiancai@quicinc.com>
Link: https://lore.kernel.org/lkml/20211115113310.35693-1-mark.rutland@arm.com/
|
|
CPU hotplug callbacks can fail and cause a rollback to the previous
state. These failures are silent and therefore hard to debug.
Add pr_debug() to the up and down paths which provide information about the
error code, the CPU and the failed state. The debug printks can be enabled
via kernel command line or sysfs.
[ tglx: Adopt to current mainline, massage printk and changelog ]
Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Qais Yousef <qais.yousef@arm.com>
Link: https://lore.kernel.org/r/20210409055316.1709-1-dongli.zhang@oracle.com
|
|
Use DEVICE_ATTR_*() helper instead of plain DEVICE_ATTR,
which makes the code a bit shorter and easier to read.
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210527141105.2312-1-yuehaibing@huawei.com
|
|
kernel/cpu.c:57: warning: cannot understand function prototype: 'struct cpuhp_cpu_state '
kernel/cpu.c:115: warning: cannot understand function prototype: 'struct cpuhp_step '
kernel/cpu.c:146: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
* cpuhp_invoke_callback _ Invoke the callbacks for a given state
kernel/cpu.c:75: warning: Function parameter or member 'fail' not described in 'cpuhp_cpu_state'
kernel/cpu.c:75: warning: Function parameter or member 'cpu' not described in 'cpuhp_cpu_state'
kernel/cpu.c:75: warning: Function parameter or member 'node' not described in 'cpuhp_cpu_state'
kernel/cpu.c:75: warning: Function parameter or member 'last' not described in 'cpuhp_cpu_state'
kernel/cpu.c:130: warning: Function parameter or member 'list' not described in 'cpuhp_step'
kernel/cpu.c:130: warning: Function parameter or member 'multi_instance' not described in 'cpuhp_step'
kernel/cpu.c:158: warning: No description found for return value of 'cpuhp_invoke_callback'
kernel/cpu.c:1188: warning: No description found for return value of 'cpu_device_down'
kernel/cpu.c:1400: warning: No description found for return value of 'cpu_device_up'
kernel/cpu.c:1425: warning: No description found for return value of 'bringup_hibernate_cpu'
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210809223825.24512-1-rdunlap@infradead.org
|
|
Fixes the following W=1 kernel build warning(s):
kernel/cpu.c:1949: warning: Function parameter or member
'name' not described in '__cpuhp_setup_state_cpuslocked'
Signed-off-by: Baokun Li <libaokun1@huawei.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210605063003.681049-1-libaokun1@huawei.com
|
|
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull CPU hotplug fix from Thomas Gleixner:
"A fix for the CPU hotplug and cpusets interaction:
cpusets delegate the hotplug work to a workqueue to prevent a lock
order inversion vs. the CPU hotplug lock. The work is not flushed
before the hotplug operation returns which creates user visible
inconsistent state. Prevent this by flushing the work after dropping
CPU hotplug lock and before releasing the outer mutex which serializes
the CPU hotplug related sysfs interface operations"
* tag 'smp-urgent-2021-06-29' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
cpu/hotplug: Cure the cpusets trainwreck
|
|
Alexey and Joshua tried to solve a cpusets related hotplug problem which is
user space visible and results in unexpected behaviour for some time after
a CPU has been plugged in and the corresponding uevent was delivered.
cpusets delegate the hotplug work (rebuilding cpumasks etc.) to a
workqueue. This is done because the cpusets code has already a lock
nesting of cgroups_mutex -> cpu_hotplug_lock. A synchronous callback or
waiting for the work to finish with cpu_hotplug_lock held can and will
deadlock because that results in the reverse lock order.
As a consequence the uevent can be delivered before cpusets have consistent
state which means that a user space invocation of sched_setaffinity() to
move a task to the plugged CPU fails up to the point where the scheduled
work has been processed.
The same is true for CPU unplug, but that does not create user observable
failure (yet).
It's still inconsistent to claim that an operation is finished before it
actually is and that's the real issue at hand. uevents just make it
reliably observable.
Obviously the problem should be fixed in cpusets/cgroups, but untangling
that is pretty much impossible because according to the changelog of the
commit which introduced this 8 years ago:
3a5a6d0c2b03("cpuset: don't nest cgroup_mutex inside get_online_cpus()")
the lock order cgroups_mutex -> cpu_hotplug_lock is a design decision and
the whole code is built around that.
So bite the bullet and invoke the relevant cpuset function, which waits for
the work to finish, in _cpu_up/down() after dropping cpu_hotplug_lock and
only when tasks are not frozen by suspend/hibernate because that would
obviously wait forever.
Waiting there with cpu_add_remove_lock, which is protecting the present
and possible CPU maps, held is not a problem at all because neither work
queues nor cpusets/cgroups have any lockchains related to that lock.
Waiting in the hotplug machinery is not problematic either because there
are already state callbacks which wait for hardware queues to drain. It
makes the operations slightly slower, but hotplug is slow anyway.
This ensures that state is consistent before returning from a hotplug
up/down operation. It's still inconsistent during the operation, but that's
a different story.
Add a large comment which explains why this is done and why this is not a
dump ground for the hack of the day to work around half thought out locking
schemes. Document also the implications vs. hotplug operations and
serialization or the lack of it.
Thanks to Alexy and Joshua for analyzing why this temporary
sched_setaffinity() failure happened.
Fixes: 3a5a6d0c2b03("cpuset: don't nest cgroup_mutex inside get_online_cpus()")
Reported-by: Alexey Klimov <aklimov@redhat.com>
Reported-by: Joshua Baker <jobaker@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Alexey Klimov <aklimov@redhat.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/87tuowcnv3.ffs@nanos.tec.linutronix.de
|
|
It is unnecessary to invoke per_cpu_ptr() everytime to access cpuhp_state.
Use the available pointer instead.
Signed-off-by: Yuan ZhaoXiong <yuanzhaoxiong@baidu.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lore.kernel.org/r/1621776690-13264-1-git-send-email-yuanzhaoxiong@baidu.com
|
|
Vincent reported that for states with a NULL startup/teardown function
we do not call cpuhp_invoke_callback() (because there is none) and as
such we'll not update the cpu_dying() state.
The stale cpu_dying() can eventually lead to triggering BUG().
Rectify this by updating cpu_dying() in the exact same places the
hotplug machinery tracks its directional state, namely
cpuhp_set_state() and cpuhp_reset_state().
Reported-by: Vincent Donnefort <vincent.donnefort@arm.com>
Suggested-by: Vincent Donnefort <vincent.donnefort@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Donnefort <vincent.donnefort@arm.com>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/YH7r+AoQEReSvxBI@hirez.programming.kicks-ass.net
|
|
Introduce a cpumask that indicates (for each CPU) what direction the
CPU hotplug is currently going. Notably, it tracks rollbacks. Eg. when
an up fails and we do a roll-back down, it will accurately reflect the
direction.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210310150109.151441252@infradead.org
|
|
Factorizing and unifying cpuhp callback range invocations, especially for
the hotunplug path, where two different ways of decrementing were used. The
first one, decrements before the callback is called:
cpuhp_thread_fun()
state = st->state;
st->state--;
cpuhp_invoke_callback(state);
The second one, after:
take_down_cpu()|cpuhp_down_callbacks()
cpuhp_invoke_callback(st->state);
st->state--;
This is problematic for rolling back the steps in case of error, as
depending on the decrement, the rollback will start from N or N-1. It also
makes tracing inconsistent, between steps run in the cpuhp thread and
the others.
Additionally, avoid useless cpuhp_thread_fun() loops by skipping empty
steps.
Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20210216103506.416286-4-vincent.donnefort@arm.com
|
|
The atomic states (between CPUHP_AP_IDLE_DEAD and CPUHP_AP_ONLINE) are
triggered by the CPUHP_BRINGUP_CPU step. If the latter fails, no atomic
state can be rolled back.
DEAD callbacks too can't fail and disallow recovery. As a consequence,
during hotunplug, the fail injection interface should prohibit all states
from CPUHP_BRINGUP_CPU to CPUHP_ONLINE.
Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20210216103506.416286-3-vincent.donnefort@arm.com
|
|
Currently, the only way of resetting the fail injection is to trigger a
hotplug, hotunplug or both. This is rather annoying for testing
and, as the default value for this file is -1, it seems pretty natural to
let a user write it.
Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20210216103506.416286-2-vincent.donnefort@arm.com
|
|
This commit adds a lockdep_is_cpus_held() function to verify that the
proper locks are held and that various operations are running in the
correct context.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Neeraj Upadhyay <neeraju@codeaurora.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
|
|
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler updates from Thomas Gleixner:
- migrate_disable/enable() support which originates from the RT tree
and is now a prerequisite for the new preemptible kmap_local() API
which aims to replace kmap_atomic().
- A fair amount of topology and NUMA related improvements
- Improvements for the frequency invariant calculations
- Enhanced robustness for the global CPU priority tracking and decision
making
- The usual small fixes and enhancements all over the place
* tag 'sched-core-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (61 commits)
sched/fair: Trivial correction of the newidle_balance() comment
sched/fair: Clear SMT siblings after determining the core is not idle
sched: Fix kernel-doc markup
x86: Print ratio freq_max/freq_base used in frequency invariance calculations
x86, sched: Use midpoint of max_boost and max_P for frequency invariance on AMD EPYC
x86, sched: Calculate frequency invariance for AMD systems
irq_work: Optimize irq_work_single()
smp: Cleanup smp_call_function*()
irq_work: Cleanup
sched: Limit the amount of NUMA imbalance that can exist at fork time
sched/numa: Allow a floating imbalance between NUMA nodes
sched: Avoid unnecessary calculation of load imbalance at clone time
sched/numa: Rename nr_running and break out the magic number
sched: Make migrate_disable/enable() independent of RT
sched/topology: Condition EAS enablement on FIE support
arm64: Rebuild sched domains on invariance status changes
sched/topology,schedutil: Wrap sched domains rebuild
sched/uclamp: Allow to reset a task uclamp constraint value
sched/core: Fix typos in comments
Documentation: scheduler: fix information on arch SD flags, sched_domain and sched_debug
...
|
|
powerpc/64s keeps a counter in the mm which counts bits set in
mm_cpumask as well as other things. This means it can't use generic code
to clear bits out of the mask and doesn't adjust the arch specific
counter.
Add an arch override that allows powerpc/64s to use
clear_tasks_mm_cpumask().
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201126102530.691335-4-npiggin@gmail.com
|
|
With the new mechanism which kicks tasks off the outgoing CPU at the end of
schedule() the situation on an outgoing CPU right before the stopper thread
brings it down completely is:
- All user tasks and all unbound kernel threads have either been migrated
away or are not running and the next wakeup will move them to a online CPU.
- All per CPU kernel threads, except cpu hotplug thread and the stopper
thread have either been unbound or parked by the responsible CPU hotplug
callback.
That means that at the last step before the stopper thread is invoked the
cpu hotplug thread is the last legitimate running task on the outgoing
CPU.
Add a final wait step right before the stopper thread is kicked which
ensures that any still running tasks on the way to park or on the way to
kick themself of the CPU are either sleeping or gone.
This allows to remove the migrate_tasks() crutch in sched_cpu_dying(). If
sched_cpu_dying() detects that there is still another running task aside of
the stopper thread then it will explode with the appropriate fireworks.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Reviewed-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Link: https://lkml.kernel.org/r/20201023102346.547163969@infradead.org
|
|
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler updates from Ingo Molnar:
"The changes in this cycle are:
- Optimize the task wakeup CPU selection logic, to improve
scalability and reduce wakeup latency spikes
- PELT enhancements
- CFS bandwidth handling fixes
- Optimize the wakeup path by remove rq->wake_list and replacing it
with ->ttwu_pending
- Optimize IPI cross-calls by making flush_smp_call_function_queue()
process sync callbacks first.
- Misc fixes and enhancements"
* tag 'sched-core-2020-06-02' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (36 commits)
irq_work: Define irq_work_single() on !CONFIG_IRQ_WORK too
sched/headers: Split out open-coded prototypes into kernel/sched/smp.h
sched: Replace rq::wake_list
sched: Add rq::ttwu_pending
irq_work, smp: Allow irq_work on call_single_queue
smp: Optimize send_call_function_single_ipi()
smp: Move irq_work_run() out of flush_smp_call_function_queue()
smp: Optimize flush_smp_call_function_queue()
sched: Fix smp_call_function_single_async() usage for ILB
sched/core: Offload wakee task activation if it the wakee is descheduling
sched/core: Optimize ttwu() spinning on p->on_cpu
sched: Defend cfs and rt bandwidth quota against overflow
sched/cpuacct: Fix charge cpuacct.usage_sys
sched/fair: Replace zero-length array with flexible-array
sched/pelt: Sync util/runnable_sum with PELT window when propagating
sched/cpuacct: Use __this_cpu_add() instead of this_cpu_ptr()
sched/fair: Optimize enqueue_task_fair()
sched: Make scheduler_ipi inline
sched: Clean up scheduler_ipi()
sched/core: Simplify sched_init()
...
|
|
The refactored function is no longer required as the codepaths that call
freeze_secondary_cpus() are all suspend/resume related now.
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Link: https://lkml.kernel.org/r/20200430114004.17477-2-qais.yousef@arm.com
|
|
The single user could have called freeze_secondary_cpus() directly.
Since this function was a source of confusion, remove it as it's
just a pointless wrapper.
While at it, rename enable_nonboot_cpus() to thaw_secondary_cpus() to
preserve the naming symmetry.
Done automatically via:
git grep -l enable_nonboot_cpus | xargs sed -i 's/enable_nonboot_cpus/thaw_secondary_cpus/g'
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Link: https://lkml.kernel.org/r/20200430114004.17477-1-qais.yousef@arm.com
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|
In the CPU-offline process, it calls mmdrop() after idle entry and the
subsequent call to cpuhp_report_idle_dead(). Once execution passes the
call to rcu_report_dead(), RCU is ignoring the CPU, which results in
lockdep complaining when mmdrop() uses RCU from either memcg or
debugobjects below.
Fix it by cleaning up the active_mm state from BP instead. Every arch
which has CONFIG_HOTPLUG_CPU should have already called idle_task_exit()
from AP. The only exception is parisc because it switches them to
&init_mm unconditionally (see smp_boot_one_cpu() and smp_cpu_init()),
but the patch will still work there because it calls mmgrab(&init_mm) in
smp_cpu_init() and then should call mmdrop(&init_mm) in finish_cpu().
WARNING: suspicious RCU usage
-----------------------------
kernel/workqueue.c:710 RCU or wq_pool_mutex should be held!
other info that might help us debug this:
RCU used illegally from offline CPU!
Call Trace:
dump_stack+0xf4/0x164 (unreliable)
lockdep_rcu_suspicious+0x140/0x164
get_work_pool+0x110/0x150
__queue_work+0x1bc/0xca0
queue_work_on+0x114/0x120
css_release+0x9c/0xc0
percpu_ref_put_many+0x204/0x230
free_pcp_prepare+0x264/0x570
free_unref_page+0x38/0xf0
__mmdrop+0x21c/0x2c0
idle_task_exit+0x170/0x1b0
pnv_smp_cpu_kill_self+0x38/0x2e0
cpu_die+0x48/0x64
arch_cpu_idle_dead+0x30/0x50
do_idle+0x2f4/0x470
cpu_startup_entry+0x38/0x40
start_secondary+0x7a8/0xa80
start_secondary_resume+0x10/0x14
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Qian Cai <cai@lca.pw>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Link: https://lkml.kernel.org/r/20200401214033.8448-1-cai@lca.pw
|
|
Signed-off-by: Ethon Paul <ethp@qq.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200417164008.6541-1-ethp@qq.com
|
|
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull core SMP updates from Thomas Gleixner:
"CPU (hotplug) updates:
- Support for locked CSD objects in smp_call_function_single_async()
which allows to simplify callsites in the scheduler core and MIPS
- Treewide consolidation of CPU hotplug functions which ensures the
consistency between the sysfs interface and kernel state. The low
level functions cpu_up/down() are now confined to the core code and
not longer accessible from random code"
* tag 'smp-core-2020-03-30' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (22 commits)
cpu/hotplug: Ignore pm_wakeup_pending() for disable_nonboot_cpus()
cpu/hotplug: Hide cpu_up/down()
cpu/hotplug: Move bringup of secondary CPUs out of smp_init()
torture: Replace cpu_up/down() with add/remove_cpu()
firmware: psci: Replace cpu_up/down() with add/remove_cpu()
xen/cpuhotplug: Replace cpu_up/down() with device_online/offline()
parisc: Replace cpu_up/down() with add/remove_cpu()
sparc: Replace cpu_up/down() with add/remove_cpu()
powerpc: Replace cpu_up/down() with add/remove_cpu()
x86/smp: Replace cpu_up/down() with add/remove_cpu()
arm64: hibernate: Use bringup_hibernate_cpu()
cpu/hotplug: Provide bringup_hibernate_cpu()
arm64: Use reboot_cpu instead of hardconding it to 0
arm64: Don't use disable_nonboot_cpus()
ARM: Use reboot_cpu instead of hardcoding it to 0
ARM: Don't use disable_nonboot_cpus()
ia64: Replace cpu_down() with smp_shutdown_nonboot_cpus()
cpu/hotplug: Create a new function to shutdown nonboot cpus
cpu/hotplug: Add new {add,remove}_cpu() functions
sched/core: Remove rq.hrtick_csd_pending
...
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|
A recent change to freeze_secondary_cpus() which added an early abort if a
wakeup is pending missed the fact that the function is also invoked for
shutdown, reboot and kexec via disable_nonboot_cpus().
In case of disable_nonboot_cpus() the wakeup event needs to be ignored as
the purpose is to terminate the currently running kernel.
Add a 'suspend' argument which is only set when the freeze is in context of
a suspend operation. If not set then an eventually pending wakeup event is
ignored.
Fixes: a66d955e910a ("cpu/hotplug: Abort disabling secondary CPUs if wakeup is pending")
Reported-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Pavankumar Kondeti <pkondeti@codeaurora.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/874kuaxdiz.fsf@nanos.tec.linutronix.de
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Use separate functions for the device core to bring a CPU up and down.
Users outside the device core must use add/remove_cpu() which will take
care of extra housekeeping work like keeping sysfs in sync.
Make cpu_up/down() static and replace the extra layer of indirection.
[ tglx: Removed the extra wrapper functions and adjusted function names ]
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200323135110.30522-18-qais.yousef@arm.com
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This is the last direct user of cpu_up() before it can become an internal
implementation detail of the cpu subsystem.
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200323135110.30522-17-qais.yousef@arm.com
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arm64 uses cpu_up() in the resume from hibernation code to ensure that the
CPU on which the system hibernated is online. Provide a core function for
this.
[ tglx: Split out from the combo arm64 patch ]
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lkml.kernel.org/r/20200323135110.30522-9-qais.yousef@arm.com
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This function will be used later in machine_shutdown() for some
architectures.
disable_nonboot_cpus() is not safe to use when doing machine_down(),
because it relies on freeze_secondary_cpus() which in turn is a
suspend/resume related freeze and could abort if the logic detects any
pending activities that can prevent finishing the offlining process.
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200323135110.30522-3-qais.yousef@arm.com
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The new functions use device_{online,offline}() which are userspace safe.
This is in preparation to move cpu_{up, down} kernel users to use a safer
interface that is not racy with userspace.
Suggested-by: "Paul E. McKenney" <paulmck@kernel.org>
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Link: https://lkml.kernel.org/r/20200323135110.30522-2-qais.yousef@arm.com
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As preparation for replacing the embedded rwsem, give percpu-rwsem its
own lockdep_map.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Davidlohr Bueso <dbueso@suse.de>
Acked-by: Will Deacon <will@kernel.org>
Acked-by: Waiman Long <longman@redhat.com>
Tested-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lkml.kernel.org/r/20200131151539.927625541@infradead.org
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler updates from Ingo Molnar:
"These were the main changes in this cycle:
- More -rt motivated separation of CONFIG_PREEMPT and
CONFIG_PREEMPTION.
- Add more low level scheduling topology sanity checks and warnings
to filter out nonsensical topologies that break scheduling.
- Extend uclamp constraints to influence wakeup CPU placement
- Make the RT scheduler more aware of asymmetric topologies and CPU
capacities, via uclamp metrics, if CONFIG_UCLAMP_TASK=y
- Make idle CPU selection more consistent
- Various fixes, smaller cleanups, updates and enhancements - please
see the git log for details"
* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (58 commits)
sched/fair: Define sched_idle_cpu() only for SMP configurations
sched/topology: Assert non-NUMA topology masks don't (partially) overlap
idle: fix spelling mistake "iterrupts" -> "interrupts"
sched/fair: Remove redundant call to cpufreq_update_util()
sched/psi: create /proc/pressure and /proc/pressure/{io|memory|cpu} only when psi enabled
sched/fair: Fix sgc->{min,max}_capacity calculation for SD_OVERLAP
sched/fair: calculate delta runnable load only when it's needed
sched/cputime: move rq parameter in irqtime_account_process_tick
stop_machine: Make stop_cpus() static
sched/debug: Reset watchdog on all CPUs while processing sysrq-t
sched/core: Fix size of rq::uclamp initialization
sched/uclamp: Fix a bug in propagating uclamp value in new cgroups
sched/fair: Load balance aggressively for SCHED_IDLE CPUs
sched/fair : Improve update_sd_pick_busiest for spare capacity case
watchdog: Remove soft_lockup_hrtimer_cnt and related code
sched/rt: Make RT capacity-aware
sched/fair: Make EAS wakeup placement consider uclamp restrictions
sched/fair: Make task_fits_capacity() consider uclamp restrictions
sched/uclamp: Rename uclamp_util_with() into uclamp_rq_util_with()
sched/uclamp: Make uclamp util helpers use and return UL values
...
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When CONFIG_SYSFS is disabled, but CONFIG_HOTPLUG_SMT is enabled,
the kernel fails to link:
arch/x86/power/cpu.o: In function `hibernate_resume_nonboot_cpu_disable':
(.text+0x38d): undefined reference to `cpuhp_smt_enable'
arch/x86/power/hibernate.o: In function `arch_resume_nosmt':
hibernate.c:(.text+0x291): undefined reference to `cpuhp_smt_enable'
hibernate.c:(.text+0x29c): undefined reference to `cpuhp_smt_disable'
Move the exported functions out of the #ifdef section into its
own with the correct conditions.
The patch that caused this is marked for stable backports, so
this one may need to be backported as well.
Fixes: ec527c318036 ("x86/power: Fix 'nosmt' vs hibernation triple fault during resume")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Jiri Kosina <jkosina@suse.cz>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20191210195614.786555-1-arnd@arndb.de
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Paul reported a very sporadic, rcutorture induced, workqueue failure.
When the planets align, the workqueue rescuer's self-migrate fails and
then triggers a WARN for running a work on the wrong CPU.
Tejun then figured that set_cpus_allowed_ptr()'s stop_one_cpu() call
could be ignored! When stopper->enabled is false, stop_machine will
insta complete the work, without actually doing the work. Worse, it
will not WARN about this (we really should fix this).
It turns out there is a small window where a freshly online'ed CPU is
marked 'online' but doesn't yet have the stopper task running:
BP AP
bringup_cpu()
__cpu_up(cpu, idle) --> start_secondary()
...
cpu_startup_entry()
bringup_wait_for_ap()
wait_for_ap_thread() <-- cpuhp_online_idle()
while (1)
do_idle()
... available to run kthreads ...
stop_machine_unpark()
stopper->enable = true;
Close this by moving the stop_machine_unpark() into
cpuhp_online_idle(), such that the stopper thread is ready before we
start the idle loop and schedule.
Reported-by: "Paul E. McKenney" <paulmck@kernel.org>
Debugged-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: "Paul E. McKenney" <paulmck@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking updates from Ingo Molnar:
"The main changes in this cycle were:
- A comprehensive rewrite of the robust/PI futex code's exit handling
to fix various exit races. (Thomas Gleixner et al)
- Rework the generic REFCOUNT_FULL implementation using
atomic_fetch_* operations so that the performance impact of the
cmpxchg() loops is mitigated for common refcount operations.
With these performance improvements the generic implementation of
refcount_t should be good enough for everybody - and this got
confirmed by performance testing, so remove ARCH_HAS_REFCOUNT and
REFCOUNT_FULL entirely, leaving the generic implementation enabled
unconditionally. (Will Deacon)
- Other misc changes, fixes, cleanups"
* 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (27 commits)
lkdtm: Remove references to CONFIG_REFCOUNT_FULL
locking/refcount: Remove unused 'refcount_error_report()' function
locking/refcount: Consolidate implementations of refcount_t
locking/refcount: Consolidate REFCOUNT_{MAX,SATURATED} definitions
locking/refcount: Move saturation warnings out of line
locking/refcount: Improve performance of generic REFCOUNT_FULL code
locking/refcount: Move the bulk of the REFCOUNT_FULL implementation into the <linux/refcount.h> header
locking/refcount: Remove unused refcount_*_checked() variants
locking/refcount: Ensure integer operands are treated as signed
locking/refcount: Define constants for saturation and max refcount values
futex: Prevent exit livelock
futex: Provide distinct return value when owner is exiting
futex: Add mutex around futex exit
futex: Provide state handling for exec() as well
futex: Sanitize exit state handling
futex: Mark the begin of futex exit explicitly
futex: Set task::futex_state to DEAD right after handling futex exit
futex: Split futex_mm_release() for exit/exec
exit/exec: Seperate mm_release()
futex: Replace PF_EXITPIDONE with a state
...
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A kernel module may need to check the value of the "mitigations=" kernel
command line parameter as part of its setup when the module needs
to perform software mitigations for a CPU flaw.
Uninline and export the helper functions surrounding the cpu_mitigations
enum to allow for their usage from a module.
Lastly, privatize the enum and cpu_mitigations variable since the value of
cpu_mitigations can be checked with the exported helper functions.
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Since the following commit:
b4adfe8e05f1 ("locking/lockdep: Remove unused argument in __lock_release")
@nested is no longer used in lock_release(), so remove it from all
lock_release() calls and friends.
Signed-off-by: Qian Cai <cai@lca.pw>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Will Deacon <will@kernel.org>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: airlied@linux.ie
Cc: akpm@linux-foundation.org
Cc: alexander.levin@microsoft.com
Cc: daniel@iogearbox.net
Cc: davem@davemloft.net
Cc: dri-devel@lists.freedesktop.org
Cc: duyuyang@gmail.com
Cc: gregkh@linuxfoundation.org
Cc: hannes@cmpxchg.org
Cc: intel-gfx@lists.freedesktop.org
Cc: jack@suse.com
Cc: jlbec@evilplan.or
Cc: joonas.lahtinen@linux.intel.com
Cc: joseph.qi@linux.alibaba.com
Cc: jslaby@suse.com
Cc: juri.lelli@redhat.com
Cc: maarten.lankhorst@linux.intel.com
Cc: mark@fasheh.com
Cc: mhocko@kernel.org
Cc: mripard@kernel.org
Cc: ocfs2-devel@oss.oracle.com
Cc: rodrigo.vivi@intel.com
Cc: sean@poorly.run
Cc: st@kernel.org
Cc: tj@kernel.org
Cc: tytso@mit.edu
Cc: vdavydov.dev@gmail.com
Cc: vincent.guittot@linaro.org
Cc: viro@zeniv.linux.org.uk
Link: https://lkml.kernel.org/r/1568909380-32199-1-git-send-email-cai@lca.pw
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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KVM needs to know if SMT is theoretically possible, this means it is
supported and not forcefully disabled ('nosmt=force'). Create and
export cpu_smt_possible() answering this question.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Re-evaluating the bitmap wheight of the online cpus bitmap in every
invocation of num_online_cpus() over and over is a pretty useless
exercise. Especially when num_online_cpus() is used in code paths
like the IPI delivery of x86 or the membarrier code.
Cache the number of online CPUs in the core and just return the cached
variable. The accessor function provides only a snapshot when used without
protection against concurrent CPU hotplug.
The storage needs to use an atomic_t because the kexec and reboot code
(ab)use set_cpu_online() in their 'shutdown' handlers without any form of
serialization as pointed out by Mathieu. Regular CPU hotplug usage is
properly serialized.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1907091622590.1634@nanos.tec.linutronix.de
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The booted once information which is required to deal with the MCE
broadcast issue on X86 correctly is stored in the per cpu hotplug state,
which is perfectly fine for the intended purpose.
X86 needs that information for supporting NMI broadcasting via shortcuts,
but retrieving it from per cpu data is cumbersome.
Move it to a cpumask so the information can be checked against the
cpu_present_mask quickly.
No functional change intended.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20190722105219.818822855@linutronix.de
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull SMP/hotplug updates from Thomas Gleixner:
"A small set of updates for SMP and CPU hotplug:
- Abort disabling secondary CPUs in the freezer when a wakeup is
pending instead of evaluating it only after all CPUs have been
offlined.
- Remove the shared annotation for the strict per CPU cfd_data in the
smp function call core code.
- Remove the return values of smp_call_function() and on_each_cpu()
as they are unconditionally 0. Fixup the few callers which actually
bothered to check the return value"
* 'smp-hotplug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
smp: Remove smp_call_function() and on_each_cpu() return values
smp: Do not mark call_function_data as shared
cpu/hotplug: Abort disabling secondary CPUs if wakeup is pending
cpu/hotplug: Fix notify_cpu_starting() reference in bringup_wait_for_ap()
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Setting invalid value to /sys/devices/system/cpu/cpuX/hotplug/fail
can control `struct cpuhp_step *sp` address, results in the following
global-out-of-bounds read.
Reproducer:
# echo -2 > /sys/devices/system/cpu/cpu0/hotplug/fail
KASAN report:
BUG: KASAN: global-out-of-bounds in write_cpuhp_fail+0x2cd/0x2e0
Read of size 8 at addr ffffffff89734438 by task bash/1941
CPU: 0 PID: 1941 Comm: bash Not tainted 5.2.0-rc6+ #31
Call Trace:
write_cpuhp_fail+0x2cd/0x2e0
dev_attr_store+0x58/0x80
sysfs_kf_write+0x13d/0x1a0
kernfs_fop_write+0x2bc/0x460
vfs_write+0x1e1/0x560
ksys_write+0x126/0x250
do_syscall_64+0xc1/0x390
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7f05e4f4c970
The buggy address belongs to the variable:
cpu_hotplug_lock+0x98/0xa0
Memory state around the buggy address:
ffffffff89734300: fa fa fa fa 00 00 00 00 00 00 00 00 00 00 00 00
ffffffff89734380: fa fa fa fa 00 00 00 00 00 00 00 00 00 00 00 00
>ffffffff89734400: 00 00 00 00 fa fa fa fa 00 00 00 00 fa fa fa fa
^
ffffffff89734480: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffffffff89734500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
Add a sanity check for the value written from user space.
Fixes: 1db49484f21ed ("smp/hotplug: Hotplug state fail injection")
Signed-off-by: Eiichi Tsukata <devel@etsukata.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: peterz@infradead.org
Link: https://lkml.kernel.org/r/20190627024732.31672-1-devel@etsukata.com
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Currently, if the user specifies an unsupported mitigation strategy on the
kernel command line, it will be ignored silently. The code will fall back
to the default strategy, possibly leaving the system more vulnerable than
expected.
This may happen due to e.g. a simple typo, or, for a stable kernel release,
because not all mitigation strategies have been backported.
Inform the user by printing a message.
Fixes: 98af8452945c5565 ("cpu/speculation: Add 'mitigations=' cmdline option")
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ben Hutchings <ben@decadent.org.uk>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20190516070935.22546-1-geert@linux-m68k.org
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When "deep" suspend is enabled, all CPUs except the primary CPU are frozen
via CPU hotplug one by one. After all secondary CPUs are unplugged the
wakeup pending condition is evaluated and if pending the suspend operation
is aborted and the secondary CPUs are brought up again.
CPU hotplug is a slow operation, so it makes sense to check for wakeup
pending in the freezer loop before bringing down the next CPU. This
improves the system suspend abort latency significantly.
[ tglx: Massaged changelog and improved printk message ]
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Len Brown <len.brown@intel.com>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: iri Kosina <jkosina@suse.cz>
Cc: Mukesh Ojha <mojha@codeaurora.org>
Cc: linux-pm@vger.kernel.org
Link: https://lkml.kernel.org/r/1559536263-16472-1-git-send-email-pkondeti@codeaurora.org
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As explained in
0cc3cd21657b ("cpu/hotplug: Boot HT siblings at least once")
we always, no matter what, have to bring up x86 HT siblings during boot at
least once in order to avoid first MCE bringing the system to its knees.
That means that whenever 'nosmt' is supplied on the kernel command-line,
all the HT siblings are as a result sitting in mwait or cpudile after
going through the online-offline cycle at least once.
This causes a serious issue though when a kernel, which saw 'nosmt' on its
commandline, is going to perform resume from hibernation: if the resume
from the hibernated image is successful, cr3 is flipped in order to point
to the address space of the kernel that is being resumed, which in turn
means that all the HT siblings are all of a sudden mwaiting on address
which is no longer valid.
That results in triple fault shortly after cr3 is switched, and machine
reboots.
Fix this by always waking up all the SMT siblings before initiating the
'restore from hibernation' process; this guarantees that all the HT
siblings will be properly carried over to the resumed kernel waiting in
resume_play_dead(), and acted upon accordingly afterwards, based on the
target kernel configuration.
Symmetricaly, the resumed kernel has to push the SMT siblings to mwait
again in case it has SMT disabled; this means it has to online all
the siblings when resuming (so that they come out of hlt) and offline
them again to let them reach mwait.
Cc: 4.19+ <stable@vger.kernel.org> # v4.19+
Debugged-by: Thomas Gleixner <tglx@linutronix.de>
Fixes: 0cc3cd21657b ("cpu/hotplug: Boot HT siblings at least once")
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Acked-by: Pavel Machek <pavel@ucw.cz>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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|
bringup_wait_for_ap() comment references cpu_notify_starting(), but the
function is actually called notify_cpu_starting(). Fix that.
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lkml.kernel.org/r/nycvar.YFH.7.76.1905282128100.1962@cbobk.fhfr.pm
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|
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer updates from Ingo Molnar:
"This cycle had the following changes:
- Timer tracing improvements (Anna-Maria Gleixner)
- Continued tasklet reduction work: remove the hrtimer_tasklet
(Thomas Gleixner)
- Fix CPU hotplug remove race in the tick-broadcast mask handling
code (Thomas Gleixner)
- Force upper bound for setting CLOCK_REALTIME, to fix ABI
inconsistencies with handling values that are close to the maximum
supported and the vagueness of when uptime related wraparound might
occur. Make the consistent maximum the year 2232 across all
relevant ABIs and APIs. (Thomas Gleixner)
- various cleanups and smaller fixes"
* 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
tick: Fix typos in comments
tick/broadcast: Fix warning about undefined tick_broadcast_oneshot_offline()
timekeeping: Force upper bound for setting CLOCK_REALTIME
timer/trace: Improve timer tracing
timer/trace: Replace deprecated vsprintf pointer extension %pf by %ps
timer: Move trace point to get proper index
tick/sched: Update tick_sched struct documentation
tick: Remove outgoing CPU from broadcast masks
timekeeping: Consistently use unsigned int for seqcount snapshot
softirq: Remove tasklet_hrtimer
xfrm: Replace hrtimer tasklet with softirq hrtimer
mac80211_hwsim: Replace hrtimer tasklet with softirq hrtimer
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull CPU hotplug updates from Ingo Molnar:
"Two changes in this cycle:
- Make the /sys/devices/system/cpu/smt/* files available on all
arches, so user space has a consistent way to detect whether SMT is
enabled.
- Sparse annotation fix"
* 'smp-hotplug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
smpboot: Place the __percpu annotation correctly
cpu/hotplug: Create SMT sysfs interface for all arches
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler updates from Ingo Molnar:
"The main changes in this cycle were:
- Make nohz housekeeping processing more permissive and less
intrusive to isolated CPUs
- Decouple CPU-bound workqueue acconting from the scheduler and move
it into the workqueue code.
- Optimize topology building
- Better handle quota and period overflows
- Add more RCU annotations
- Comment updates, misc cleanups"
* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (25 commits)
nohz_full: Allow the boot CPU to be nohz_full
sched/isolation: Require a present CPU in housekeeping mask
kernel/cpu: Allow non-zero CPU to be primary for suspend / kexec freeze
power/suspend: Add function to disable secondaries for suspend
sched/core: Allow the remote scheduler tick to be started on CPU0
sched/nohz: Run NOHZ idle load balancer on HK_FLAG_MISC CPUs
sched/debug: Fix spelling mistake "logaritmic" -> "logarithmic"
sched/topology: Update init_sched_domains() comment
cgroup/cpuset: Update stale generate_sched_domains() comments
sched/core: Check quota and period overflow at usec to nsec conversion
sched/core: Handle overflow in cpu_shares_write_u64
sched/rt: Check integer overflow at usec to nsec conversion
sched/core: Fix typo in comment
sched/core: Make some functions static
sched/core: Unify p->on_rq updates
sched/core: Remove ttwu_activate()
sched/core, workqueues: Distangle worker accounting from rq lock
sched/fair: Remove unneeded prototype of capacity_of()
sched/topology: Skip duplicate group rewrites in build_sched_groups()
sched/topology: Fix build_sched_groups() comment
...
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull speculation mitigation update from Ingo Molnar:
"This adds the "mitigations=" bootline option, which offers a
cross-arch set of options that will work on x86, PowerPC and s390 that
will map to the arch specific option internally"
* 'core-speculation-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
s390/speculation: Support 'mitigations=' cmdline option
powerpc/speculation: Support 'mitigations=' cmdline option
x86/speculation: Support 'mitigations=' cmdline option
cpu/speculation: Add 'mitigations=' cmdline option
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This patch provides an arch option, ARCH_SUSPEND_NONZERO_CPU, to
opt-in to allowing suspend to occur on one of the housekeeping CPUs
rather than hardcoded CPU0.
This will allow CPU0 to be a nohz_full CPU with a later change.
It may be possible for platforms with hardware/firmware restrictions
on suspend/wake effectively support this by handing off the final
stage to CPU0 when kernel housekeeping is no longer required. Another
option is to make housekeeping / nohz_full mask dynamic at runtime,
but the complexity could not be justified at this time.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rafael J . Wysocki <rafael.j.wysocki@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linuxppc-dev@lists.ozlabs.org
Link: https://lkml.kernel.org/r/20190411033448.20842-4-npiggin@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Keeping track of the number of mitigations for all the CPU speculation
bugs has become overwhelming for many users. It's getting more and more
complicated to decide which mitigations are needed for a given
architecture. Complicating matters is the fact that each arch tends to
have its own custom way to mitigate the same vulnerability.
Most users fall into a few basic categories:
a) they want all mitigations off;
b) they want all reasonable mitigations on, with SMT enabled even if
it's vulnerable; or
c) they want all reasonable mitigations on, with SMT disabled if
vulnerable.
Define a set of curated, arch-independent options, each of which is an
aggregation of existing options:
- mitigations=off: Disable all mitigations.
- mitigations=auto: [default] Enable all the default mitigations, but
leave SMT enabled, even if it's vulnerable.
- mitigations=auto,nosmt: Enable all the default mitigations, disabling
SMT if needed by a mitigation.
Currently, these options are placeholders which don't actually do
anything. They will be fleshed out in upcoming patches.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Jiri Kosina <jkosina@suse.cz> (on x86)
Reviewed-by: Jiri Kosina <jkosina@suse.cz>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H . Peter Anvin" <hpa@zytor.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Waiman Long <longman@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Jon Masters <jcm@redhat.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: linux-s390@vger.kernel.org
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-arch@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Tyler Hicks <tyhicks@canonical.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Steven Price <steven.price@arm.com>
Cc: Phil Auld <pauld@redhat.com>
Link: https://lkml.kernel.org/r/b07a8ef9b7c5055c3a4637c87d07c296d5016fe0.1555085500.git.jpoimboe@redhat.com
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Make the /sys/devices/system/cpu/smt/* files available on all arches, so
user space has a consistent way to detect whether SMT is enabled.
The 'control' file now shows 'notimplemented' for architectures which
don't yet have CONFIG_HOTPLUG_SMT.
[ tglx: Make notimplemented a real state ]
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Waiman Long <longman@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Jiri Kosina <jikos@kernel.org>
Link: https://lkml.kernel.org/r/469c2b98055f2c41e75748e06447d592a64080c9.1553635520.git.jpoimboe@redhat.com
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Tianyu reported a crash in a CPU hotplug teardown callback when booting a
kernel which has CONFIG_HOTPLUG_CPU disabled with the 'nosmt' boot
parameter.
It turns out that the SMP=y CONFIG_HOTPLUG_CPU=n case has been broken
forever in case that a bringup callback fails. Unfortunately this issue was
not recognized when the CPU hotplug code was reworked, so the shortcoming
just stayed in place.
When a bringup callback fails, the CPU hotplug code rolls back the
operation and takes the CPU offline.
The 'nosmt' command line argument uses a bringup failure to abort the
bringup of SMT sibling CPUs. This partial bringup is required due to the
MCE misdesign on Intel CPUs.
With CONFIG_HOTPLUG_CPU=y the rollback works perfectly fine, but
CONFIG_HOTPLUG_CPU=n lacks essential mechanisms to exercise the low level
teardown of a CPU including the synchronizations in various facilities like
RCU, NOHZ and others.
As a consequence the teardown callbacks which must be executed on the
outgoing CPU within stop machine with interrupts disabled are executed on
the control CPU in interrupt enabled and preemptible context causing the
kernel to crash and burn. The pre state machine code has a different
failure mode which is more subtle and resulting in a less obvious use after
free crash because the control side frees resources which are still in use
by the undead CPU.
But this is not a x86 only problem. Any architecture which supports the
SMP=y HOTPLUG_CPU=n combination suffers from the same issue. It's just less
likely to be triggered because in 99.99999% of the cases all bringup
callbacks succeed.
The easy solution of making HOTPLUG_CPU mandatory for SMP is not working on
all architectures as the following architectures have either no hotplug
support at all or not all subarchitectures support it:
alpha, arc, hexagon, openrisc, riscv, sparc (32bit), mips (partial).
Crashing the kernel in such a situation is not an acceptable state
either.
Implement a minimal rollback variant by limiting the teardown to the point
where all regular teardown callbacks have been invoked and leave the CPU in
the 'dead' idle state. This has the following consequences:
- the CPU is brought down to the point where the stop_machine takedown
would happen.
- the CPU stays there forever and is idle
- The CPU is cleared in the CPU active mask, but not in the CPU online
mask which is a legit state.
- Interrupts are not forced away from the CPU
- All facilities which only look at online mask would still see it, but
that is the case during normal hotplug/unplug operations as well. It's
just a (way) longer time frame.
This will expose issues, which haven't been exposed before or only seldom,
because now the normally transient state of being non active but online is
a permanent state. In testing this exposed already an issue vs. work queues
where the vmstat code schedules work on the almost dead CPU which ends up
in an unbound workqueue and triggers 'preemtible context' warnings. This is
not a problem of this change, it merily exposes an already existing issue.
Still this is better than crashing fully without a chance to debug it.
This is mainly thought as workaround for those architectures which do not
support HOTPLUG_CPU. All others should enforce HOTPLUG_CPU for SMP.
Fixes: 2e1a3483ce74 ("cpu/hotplug: Split out the state walk into functions")
Reported-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Konrad Wilk <konrad.wilk@oracle.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Mukesh Ojha <mojha@codeaurora.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Rik van Riel <riel@surriel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Micheal Kelley <michael.h.kelley@microsoft.com>
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20190326163811.503390616@linutronix.de
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Valentin reported that unplugging a CPU occasionally results in a warning
in the tick broadcast code which is triggered when an offline CPU is in the
broadcast mask.
This happens because the outgoing CPU is not removing itself from the
broadcast masks, especially not from the broadcast_force_mask. The removal
happens on the control CPU after the outgoing CPU is dead. It's a long
standing issue, but the warning is harmless.
Rework the hotplug mechanism so that the outgoing CPU removes itself from
the broadcast masks after disabling interrupts and removing itself from the
online mask.
Reported-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Valentin Schneider <valentin.schneider@arm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1903211540180.1784@nanos.tec.linutronix.de
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Signed-off-by: Ingo Molnar <mingo@kernel.org>
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With the following commit:
73d5e2b47264 ("cpu/hotplug: detect SMT disabled by BIOS")
... the hotplug code attempted to detect when SMT was disabled by BIOS,
in which case it reported SMT as permanently disabled. However, that
code broke a virt hotplug scenario, where the guest is booted with only
primary CPU threads, and a sibling is brought online later.
The problem is that there doesn't seem to be a way to reliably
distinguish between the HW "SMT disabled by BIOS" case and the virt
"sibling not yet brought online" case. So the above-mentioned commit
was a bit misguided, as it permanently disabled SMT for both cases,
preventing future virt sibling hotplugs.
Going back and reviewing the original problems which were attempted to
be solved by that commit, when SMT was disabled in BIOS:
1) /sys/devices/system/cpu/smt/control showed "on" instead of
"notsupported"; and
2) vmx_vm_init() was incorrectly showing the L1TF_MSG_SMT warning.
I'd propose that we instead consider #1 above to not actually be a
problem. Because, at least in the virt case, it's possible that SMT
wasn't disabled by BIOS and a sibling thread could be brought online
later. So it makes sense to just always default the smt control to "on"
to allow for that possibility (assuming cpuid indicates that the CPU
supports SMT).
The real problem is #2, which has a simple fix: change vmx_vm_init() to
query the actual current SMT state -- i.e., whether any siblings are
currently online -- instead of looking at the SMT "control" sysfs value.
So fix it by:
a) reverting the original "fix" and its followup fix:
73d5e2b47264 ("cpu/hotplug: detect SMT disabled by BIOS")
bc2d8d262cba ("cpu/hotplug: Fix SMT supported evaluation")
and
b) changing vmx_vm_init() to query the actual current SMT state --
instead of the sysfs control value -- to determine whether the L1TF
warning is needed. This also requires the 'sched_smt_present'
variable to exported, instead of 'cpu_smt_control'.
Fixes: 73d5e2b47264 ("cpu/hotplug: detect SMT disabled by BIOS")
Reported-by: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Joe Mario <jmario@redhat.com>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: kvm@vger.kernel.org
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/e3a85d585da28cc333ecbc1e78ee9216e6da9396.1548794349.git.jpoimboe@redhat.com
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With commit a74cfffb03b7 ("x86/speculation: Rework SMT state change"),
arch_smt_update() is invoked from each individual CPU hotplug function.
Therefore the extra arch_smt_update() call in the sysfs SMT control is
redundant.
Fixes: a74cfffb03b7 ("x86/speculation: Rework SMT state change")
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: <konrad.wilk@oracle.com>
Cc: <dwmw@amazon.co.uk>
Cc: <bp@suse.de>
Cc: <srinivas.eeda@oracle.com>
Cc: <peterz@infradead.org>
Cc: <hpa@zytor.com>
Link: https://lkml.kernel.org/r/e2e064f2-e8ef-42ca-bf4f-76b612964752@default
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Since we've had:
commit cb538267ea1e ("jump_label/lockdep: Assert we hold the hotplug lock for _cpuslocked() operations")
we've been getting some lockdep warnings during init, such as on HiKey960:
[ 0.820495] WARNING: CPU: 4 PID: 0 at kernel/cpu.c:316 lockdep_assert_cpus_held+0x3c/0x48
[ 0.820498] Modules linked in:
[ 0.820509] CPU: 4 PID: 0 Comm: swapper/4 Tainted: G S 4.20.0-rc5-00051-g4cae42a #34
[ 0.820511] Hardware name: HiKey960 (DT)
[ 0.820516] pstate: 600001c5 (nZCv dAIF -PAN -UAO)
[ 0.820520] pc : lockdep_assert_cpus_held+0x3c/0x48
[ 0.820523] lr : lockdep_assert_cpus_held+0x38/0x48
[ 0.820526] sp : ffff00000a9cbe50
[ 0.820528] x29: ffff00000a9cbe50 x28: 0000000000000000
[ 0.820533] x27: 00008000b69e5000 x26: ffff8000bff4cfe0
[ 0.820537] x25: ffff000008ba69e0 x24: 0000000000000001
[ 0.820541] x23: ffff000008fce000 x22: ffff000008ba70c8
[ 0.820545] x21: 0000000000000001 x20: 0000000000000003
[ 0.820548] x19: ffff00000a35d628 x18: ffffffffffffffff
[ 0.820552] x17: 0000000000000000 x16: 0000000000000000
[ 0.820556] x15: ffff00000958f848 x14: 455f3052464d4d34
[ 0.820559] x13: 00000000769dde98 x12: ffff8000bf3f65a8
[ 0.820564] x11: 0000000000000000 x10: ffff00000958f848
[ 0.820567] x9 : ffff000009592000 x8 : ffff00000958f848
[ 0.820571] x7 : ffff00000818ffa0 x6 : 0000000000000000
[ 0.820574] x5 : 0000000000000000 x4 : 0000000000000001
[ 0.820578] x3 : 0000000000000000 x2 : 0000000000000001
[ 0.820582] x1 : 00000000ffffffff x0 : 0000000000000000
[ 0.820587] Call trace:
[ 0.820591] lockdep_assert_cpus_held+0x3c/0x48
[ 0.820598] static_key_enable_cpuslocked+0x28/0xd0
[ 0.820606] arch_timer_check_ool_workaround+0xe8/0x228
[ 0.820610] arch_timer_starting_cpu+0xe4/0x2d8
[ 0.820615] cpuhp_invoke_callback+0xe8/0xd08
[ 0.820619] notify_cpu_starting+0x80/0xb8
[ 0.820625] secondary_start_kernel+0x118/0x1d0
We've also had a similar warning in sched_init_smp() for every
asymmetric system that would enable the sched_asym_cpucapacity static
key, although that was singled out in:
commit 40fa3780bac2 ("sched/core: Take the hotplug lock in sched_init_smp()")
Those warnings are actually harmless, since we cannot have hotplug
operations at the time they appear. Instead of starting to sprinkle
useless hotplug lock operations in the init codepaths, mute the
warnings until they start warning about real problems.
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: cai@gmx.us
Cc: daniel.lezcano@linaro.org
Cc: dietmar.eggemann@arm.com
Cc: linux-arm-kernel@lists.infradead.org
Cc: longman@redhat.com
Cc: marc.zyngier@arm.com
Cc: mark.rutland@arm.com
Link: https://lkml.kernel.org/r/1545243796-23224-2-git-send-email-valentin.schneider@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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arch_smt_update() is only called when the sysfs SMT control knob is
changed. This means that when SMT is enabled in the sysfs control knob the
system is considered to have SMT active even if all siblings are offline.
To allow finegrained control of the speculation mitigations, the actual SMT
state is more interesting than the fact that siblings could be enabled.
Rework the code, so arch_smt_update() is invoked from each individual CPU
hotplug function, and simplify the update function while at it.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Woodhouse <dwmw@amazon.co.uk>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Casey Schaufler <casey.schaufler@intel.com>
Cc: Asit Mallick <asit.k.mallick@intel.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Jon Masters <jcm@redhat.com>
Cc: Waiman Long <longman9394@gmail.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Dave Stewart <david.c.stewart@intel.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20181125185004.521974984@linutronix.de
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 pti updates from Ingo Molnar:
"The main changes:
- Make the IBPB barrier more strict and add STIBP support (Jiri
Kosina)
- Micro-optimize and clean up the entry code (Andy Lutomirski)
- ... plus misc other fixes"
* 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/speculation: Propagate information about RSB filling mitigation to sysfs
x86/speculation: Enable cross-hyperthread spectre v2 STIBP mitigation
x86/speculation: Apply IBPB more strictly to avoid cross-process data leak
x86/speculation: Add RETPOLINE_AMD support to the inline asm CALL_NOSPEC variant
x86/CPU: Fix unused variable warning when !CONFIG_IA32_EMULATION
x86/pti/64: Remove the SYSCALL64 entry trampoline
x86/entry/64: Use the TSS sp2 slot for SYSCALL/SYSRET scratch space
x86/entry/64: Document idtentry
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler updates from Ingo Molnar:
"The main changes are:
- Migrate CPU-intense 'misfit' tasks on asymmetric capacity systems,
to better utilize (much) faster 'big core' CPUs. (Morten Rasmussen,
Valentin Schneider)
- Topology handling improvements, in particular when CPU capacity
changes and related load-balancing fixes/improvements (Morten
Rasmussen)
- ... plus misc other improvements, fixes and updates"
* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (28 commits)
sched/completions/Documentation: Add recommendation for dynamic and ONSTACK completions
sched/completions/Documentation: Clean up the document some more
sched/completions/Documentation: Fix a couple of punctuation nits
cpu/SMT: State SMT is disabled even with nosmt and without "=force"
sched/core: Fix comment regarding nr_iowait_cpu() and get_iowait_load()
sched/fair: Remove setting task's se->runnable_weight during PELT update
sched/fair: Disable LB_BIAS by default
sched/pelt: Fix warning and clean up IRQ PELT config
sched/topology: Make local variables static
sched/debug: Use symbolic names for task state constants
sched/numa: Remove unused numa_stats::nr_running field
sched/numa: Remove unused code from update_numa_stats()
sched/debug: Explicitly cast sched_feat() to bool
sched/core: Disable SD_PREFER_SIBLING on asymmetric CPU capacity domains
sched/fair: Don't move tasks to lower capacity CPUs unless necessary
sched/fair: Set rq->rd->overload when misfit
sched/fair: Wrap rq->rd->overload accesses with READ/WRITE_ONCE()
sched/core: Change root_domain->overload type to int
sched/fair: Change 'prefer_sibling' type to bool
sched/fair: Kick nohz balance if rq->misfit_task_load
...
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When booting with "nosmt=force" a message is issued into dmesg to
confirm that SMT has been force-disabled but such a message is not
issued when only "nosmt" is on the kernel command line.
Fix that.
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20181004172227.10094-1-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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STIBP is a feature provided by certain Intel ucodes / CPUs. This feature
(once enabled) prevents cross-hyperthread control of decisions made by
indirect branch predictors.
Enable this feature if
- the CPU is vulnerable to spectre v2
- the CPU supports SMT and has SMT siblings online
- spectre_v2 mitigation autoselection is enabled (default)
After some previous discussion, this leaves STIBP on all the time, as wrmsr
on crossing kernel boundary is a no-no. This could perhaps later be a bit
more optimized (like disabling it in NOHZ, experiment with disabling it in
idle, etc) if needed.
Note that the synchronization of the mask manipulation via newly added
spec_ctrl_mutex is currently not strictly needed, as the only updater is
already being serialized by cpu_add_remove_lock, but let's make this a
little bit more future-proof.
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: "WoodhouseDavid" <dwmw@amazon.co.uk>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: "SchauflerCasey" <casey.schaufler@intel.com>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/nycvar.YFH.7.76.1809251438240.15880@cbobk.fhfr.pm
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Anybody trying to assert the cpu_hotplug_lock is held (lockdep_assert_cpus_held())
from AP callbacks will fail, because the lock is held by the BP.
Stick in an explicit annotation in cpuhp_thread_fun() to make this work.
Reported-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-tip-commits@vger.kernel.org
Fixes: cb538267ea1e ("jump_label/lockdep: Assert we hold the hotplug lock for _cpuslocked() operations")
Link: http://lkml.kernel.org/r/20180911095127.GT24082@hirez.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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|
When a teardown callback fails, the CPU hotplug code brings the CPU back to
the previous state. The previous state becomes the new target state. The
rollback happens in undo_cpu_down() which increments the state
unconditionally even if the state is already the same as the target.
As a consequence the next CPU hotplug operation will start at the wrong
state. This is easily to observe when __cpu_disable() fails.
Prevent the unconditional undo by checking the state vs. target before
incrementing state and fix up the consequently wrong conditional in the
unplug code which handles the failure of the final CPU take down on the
control CPU side.
Fixes: 4dddfb5faa61 ("smp/hotplug: Rewrite AP state machine core")
Reported-by: Neeraj Upadhyay <neeraju@codeaurora.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Tested-by: Sudeep Holla <sudeep.holla@arm.com>
Tested-by: Neeraj Upadhyay <neeraju@codeaurora.org>
Cc: josh@joshtriplett.org
Cc: peterz@infradead.org
Cc: jiangshanlai@gmail.com
Cc: dzickus@redhat.com
Cc: brendan.jackman@arm.com
Cc: malat@debian.org
Cc: sramana@codeaurora.org
Cc: linux-arm-msm@vger.kernel.org
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1809051419580.1416@nanos.tec.linutronix.de
----
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The smp_mb() in cpuhp_thread_fun() is misplaced. It needs to be after the
load of st->should_run to prevent reordering of the later load/stores
w.r.t. the load of st->should_run.
Fixes: 4dddfb5faa61 ("smp/hotplug: Rewrite AP state machine core")
Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infraded.org>
Cc: josh@joshtriplett.org
Cc: peterz@infradead.org
Cc: jiangshanlai@gmail.com
Cc: dzickus@redhat.com
Cc: brendan.jackman@arm.com
Cc: malat@debian.org
Cc: mojha@codeaurora.org
Cc: sramana@codeaurora.org
Cc: linux-arm-msm@vger.kernel.org
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/1536126727-11629-1-git-send-email-neeraju@codeaurora.org
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When notifiers were there, `skip_onerr` was used to avoid calling
particular step startup/teardown callbacks in the CPU up/down rollback
path, which made the hotplug asymmetric.
As notifiers are gone now after the full state machine conversion, the
`skip_onerr` field is no longer required.
Remove it from the structure and its usage.
Signed-off-by: Mukesh Ojha <mojha@codeaurora.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/1535439294-31426-1-git-send-email-mojha@codeaurora.org
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Commit 0cc3cd21657b ("cpu/hotplug: Boot HT siblings at least once")
breaks non-SMP builds.
[ I suspect the 'bool' fields should just be made to be bitfields and be
exposed regardless of configuration, but that's a separate cleanup
that I'll leave to the owners of this file for later. - Linus ]
Fixes: 0cc3cd21657b ("cpu/hotplug: Boot HT siblings at least once")
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Signed-off-by: Abel Vesa <abelvesa@linux.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm
Pull power management updates from Rafael Wysocki:
"These add a new framework for CPU idle time injection, to be used by
all of the idle injection code in the kernel in the future, fix some
issues and add a number of relatively small extensions in multiple
places.
Specifics:
- Add a new framework for CPU idle time injection (Daniel Lezcano).
- Add AVS support to the armada-37xx cpufreq driver (Gregory
CLEMENT).
- Add support for current CPU frequency reporting to the ACPI CPPC
cpufreq driver (George Cherian).
- Rework the cooling device registration in the imx6q/thermal driver
(Bastian Stender).
- Make the pcc-cpufreq driver refuse to work with dynamic scaling
governors on systems with many CPUs to avoid scalability issues
with it (Rafael Wysocki).
- Fix the intel_pstate driver to report different maximum CPU
frequencies on systems where they really are different and to
ignore the turbo active ratio if hardware-managend P-states (HWP)
are in use; make it use the match_string() helper (Xie Yisheng,
Srinivas Pandruvada).
- Fix a minor deferred probe issue in the qcom-kryo cpufreq driver
(Niklas Cassel).
- Add a tracepoint for the tracking of frequency limits changes (from
Andriod) to the cpufreq core (Ruchi Kandoi).
- Fix a circular lock dependency between CPU hotplug and sysfs
locking in the cpufreq core reported by lockdep (Waiman Long).
- Avoid excessive error reports on driver registration failures in
the ARM cpuidle driver (Sudeep Holla).
- Add a new device links flag to the driver core to make links go
away automatically on supplier driver removal (Vivek Gautam).
- Eliminate potential race condition between system-wide power
management transitions and system shutdown (Pingfan Liu).
- Add a quirk to save NVS memory on system suspend for the ASUS 1025C
laptop (Willy Tarreau).
- Make more systems use suspend-to-idle (instead of ACPI S3) by
default (Tristian Celestin).
- Get rid of stack VLA usage in the low-level hibernation code on
64-bit x86 (Kees Cook).
- Fix error handling in the hibernation core and mark an expected
fall-through switch in it (Chengguang Xu, Gustavo Silva).
- Extend the generic power domains (genpd) framework to support
attaching a device to a power domain by name (Ulf Hansson).
- Fix device reference counting and user limits initialization in the
devfreq core (Arvind Yadav, Matthias Kaehlcke).
- Fix a few issues in the rk3399_dmc devfreq driver and improve its
documentation (Enric Balletbo i Serra, Lin Huang, Nick Milner).
- Drop a redundant error message from the exynos-ppmu devfreq driver
(Markus Elfring)"
* tag 'pm-4.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm: (35 commits)
PM / reboot: Eliminate race between reboot and suspend
PM / hibernate: Mark expected switch fall-through
cpufreq: intel_pstate: Ignore turbo active ratio in HWP
cpufreq: Fix a circular lock dependency problem
cpu/hotplug: Add a cpus_read_trylock() function
x86/power/hibernate_64: Remove VLA usage
cpufreq: trace frequency limits change
cpufreq: intel_pstate: Show different max frequency with turbo 3 and HWP
cpufreq: pcc-cpufreq: Disable dynamic scaling on many-CPU systems
cpufreq: qcom-kryo: Silently error out on EPROBE_DEFER
cpufreq / CPPC: Add cpuinfo_cur_freq support for CPPC
cpufreq: armada-37xx: Add AVS support
dt-bindings: marvell: Add documentation for the Armada 3700 AVS binding
PM / devfreq: rk3399_dmc: Fix duplicated opp table on reload.
PM / devfreq: Init user limits from OPP limits, not viceversa
PM / devfreq: rk3399_dmc: fix spelling mistakes.
PM / devfreq: rk3399_dmc: do not print error when get supply and clk defer.
dt-bindings: devfreq: rk3399_dmc: move interrupts to be optional.
PM / devfreq: rk3399_dmc: remove wait for dcf irq event.
dt-bindings: clock: add rk3399 DDR3 standard speed bins.
...
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Merge L1 Terminal Fault fixes from Thomas Gleixner:
"L1TF, aka L1 Terminal Fault, is yet another speculative hardware
engineering trainwreck. It's a hardware vulnerability which allows
unprivileged speculative access to data which is available in the
Level 1 Data Cache when the page table entry controlling the virtual
address, which is used for the access, has the Present bit cleared or
other reserved bits set.
If an instruction accesses a virtual address for which the relevant
page table entry (PTE) has the Present bit cleared or other reserved
bits set, then speculative execution ignores the invalid PTE and loads
the referenced data if it is present in the Level 1 Data Cache, as if
the page referenced by the address bits in the PTE was still present
and accessible.
While this is a purely speculative mechanism and the instruction will
raise a page fault when it is retired eventually, the pure act of
loading the data and making it available to other speculative
instructions opens up the opportunity for side channel attacks to
unprivileged malicious code, similar to the Meltdown attack.
While Meltdown breaks the user space to kernel space protection, L1TF
allows to attack any physical memory address in the system and the
attack works across all protection domains. It allows an attack of SGX
and also works from inside virtual machines because the speculation
bypasses the extended page table (EPT) protection mechanism.
The assoicated CVEs are: CVE-2018-3615, CVE-2018-3620, CVE-2018-3646
The mitigations provided by this pull request include:
- Host side protection by inverting the upper address bits of a non
present page table entry so the entry points to uncacheable memory.
- Hypervisor protection by flushing L1 Data Cache on VMENTER.
- SMT (HyperThreading) control knobs, which allow to 'turn off' SMT
by offlining the sibling CPU threads. The knobs are available on
the kernel command line and at runtime via sysfs
- Control knobs for the hypervisor mitigation, related to L1D flush
and SMT control. The knobs are available on the kernel command line
and at runtime via sysfs
- Extensive documentation about L1TF including various degrees of
mitigations.
Thanks to all people who have contributed to this in various ways -
patches, review, testing, backporting - and the fruitful, sometimes
heated, but at the end constructive discussions.
There is work in progress to provide other forms of mitigations, which
might be less horrible performance wise for a particular kind of
workloads, but this is not yet ready for consumption due to their
complexity and limitations"
* 'l1tf-final' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (75 commits)
x86/microcode: Allow late microcode loading with SMT disabled
tools headers: Synchronise x86 cpufeatures.h for L1TF additions
x86/mm/kmmio: Make the tracer robust against L1TF
x86/mm/pat: Make set_memory_np() L1TF safe
x86/speculation/l1tf: Make pmd/pud_mknotpresent() invert
x86/speculation/l1tf: Invert all not present mappings
cpu/hotplug: Fix SMT supported evaluation
KVM: VMX: Tell the nested hypervisor to skip L1D flush on vmentry
x86/speculation: Use ARCH_CAPABILITIES to skip L1D flush on vmentry
x86/speculation: Simplify sysfs report of VMX L1TF vulnerability
Documentation/l1tf: Remove Yonah processors from not vulnerable list
x86/KVM/VMX: Don't set l1tf_flush_l1d from vmx_handle_external_intr()
x86/irq: Let interrupt handlers set kvm_cpu_l1tf_flush_l1d
x86: Don't include linux/irq.h from asm/hardirq.h
x86/KVM/VMX: Introduce per-host-cpu analogue of l1tf_flush_l1d
x86/irq: Demote irq_cpustat_t::__softirq_pending to u16
x86/KVM/VMX: Move the l1tf_flush_l1d test to vmx_l1d_flush()
x86/KVM/VMX: Replace 'vmx_l1d_flush_always' with 'vmx_l1d_flush_cond'
x86/KVM/VMX: Don't set l1tf_flush_l1d to true from vmx_l1d_flush()
cpu/hotplug: detect SMT disabled by BIOS
...
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull CPU hotplug update from Thomas Gleixner:
"A trivial name fix for the hotplug state machine"
* 'smp-hotplug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
cpu/hotplug: Clarify CPU hotplug step name for timers
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler updates from Thomas Gleixner:
- Cleanup and improvement of NUMA balancing
- Refactoring and improvements to the PELT (Per Entity Load Tracking)
code
- Watchdog simplification and related cleanups
- The usual pile of small incremental fixes and improvements
* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (41 commits)
watchdog: Reduce message verbosity
stop_machine: Reflow cpu_stop_queue_two_works()
sched/numa: Move task_numa_placement() closer to numa_migrate_preferred()
sched/numa: Use group_weights to identify if migration degrades locality
sched/numa: Update the scan period without holding the numa_group lock
sched/numa: Remove numa_has_capacity()
sched/numa: Modify migrate_swap() to accept additional parameters
sched/numa: Remove unused task_capacity from 'struct numa_stats'
sched/numa: Skip nodes that are at 'hoplimit'
sched/debug: Reverse the order of printing faults
sched/numa: Use task faults only if numa_group is not yet set up
sched/numa: Set preferred_node based on best_cpu
sched/numa: Simplify load_too_imbalanced()
sched/numa: Evaluate move once per node
sched/numa: Remove redundant field
sched/debug: Show the sum wait time of a task group
sched/fair: Remove #ifdefs from scale_rt_capacity()
sched/core: Remove get_cpu() from sched_fork()
sched/cpufreq: Clarify sugov_get_util()
sched/sysctl: Remove unused sched_time_avg_ms sysctl
...
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This is purely a preparatory patch for upcoming changes during the 4.19
merge window.
We have a function called "boot_cpu_state_init()" that isn't really
about the bootup cpu state: that is done much earlier by the similarly
named "boot_cpu_init()" (note lack of "state" in name).
This function initializes some hotplug CPU state, and needs to run after
the percpu data has been properly initialized. It even has a comment to
that effect.
Except it _doesn't_ actually run after the percpu data has been properly
initialized. On x86 it happens to do that, but on at least arm and
arm64, the percpu base pointers are initialized by the arch-specific
'smp_prepare_boot_cpu()' hook, which ran _after_ boot_cpu_state_init().
This had some unexpected results, and in particular we have a patch
pending for the merge window that did the obvious cleanup of using
'this_cpu_write()' in the cpu hotplug init code:
- per_cpu_ptr(&cpuhp_state, smp_processor_id())->state = CPUHP_ONLINE;
+ this_cpu_write(cpuhp_state.state, CPUHP_ONLINE);
which is obviously the right thing to do. Except because of the
ordering issue, it actually failed miserably and unexpectedly on arm64.
So this just fixes the ordering, and changes the name of the function to
be 'boot_cpu_hotplug_init()' to make it obvious that it's about cpu
hotplug state, because the core CPU state was supposed to have already
been done earlier.
Marked for stable, since the (not yet merged) patch that will show this
problem is marked for stable.
Reported-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: Mian Yousaf Kaukab <yousaf.kaukab@suse.com>
Suggested-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Josh reported that the late SMT evaluation in cpu_smt_state_init() sets
cpu_smt_control to CPU_SMT_NOT_SUPPORTED in case that 'nosmt' was supplied
on the kernel command line as it cannot differentiate between SMT disabled
by BIOS and SMT soft disable via 'nosmt'. That wreckages the state and
makes the sysfs interface unusable.
Rework this so that during bringup of the non boot CPUs the availability of
SMT is determined in cpu_smt_allowed(). If a newly booted CPU is not a
'primary' thread then set the local cpu_smt_available marker and evaluate
this explicitely right after the initial SMP bringup has finished.
SMT evaulation on x86 is a trainwreck as the firmware has all the
information _before_ booting the kernel, but there is no interface to query
it.
Fixes: 73d5e2b47264 ("cpu/hotplug: detect SMT disabled by BIOS")
Reported-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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After commit 249d4a9b3246 ("timers: Reinitialize per cpu bases on hotplug")
i.e. the introduction of state CPUHP_TIMERS_PREPARE instead of
CPUHP_TIMERS_DEAD the step name "timers:dead" is not longer accurate.
Rename it to "timers:prepare".
[ tglx: Massaged changelog ]
Signed-off-by: Mukesh Ojha <mojha@codeaurora.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: gkohli@codeaurora.org
Cc: neeraju@codeaurora.org
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Brendan Jackman <brendan.jackman@arm.com>
Cc: Mathieu Malaterre <malat@debian.org>
Link: https://lkml.kernel.org/r/1532443668-26810-1-git-send-email-mojha@codeaurora.org
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There are use cases where it can be useful to have a cpus_read_trylock()
function to work around circular lock dependency problem involving
the cpu_hotplug_lock.
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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If SMT is disabled in BIOS, the CPU code doesn't properly detect it.
The /sys/devices/system/cpu/smt/control file shows 'on', and the 'l1tf'
vulnerabilities file shows SMT as vulnerable.
Fix it by forcing 'cpu_smt_control' to CPU_SMT_NOT_SUPPORTED in such a
case. Unfortunately the detection can only be done after bringing all
the CPUs online, so we have to overwrite any previous writes to the
variable.
Reported-by: Joe Mario <jmario@redhat.com>
Tested-by: Jiri Kosina <jkosina@suse.cz>
Fixes: f048c399e0f7 ("x86/topology: Provide topology_smt_supported()")
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
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The CPU_SMT_NOT_SUPPORTED state is set (if the processor does not support
SMT) when the sysfs SMT control file is initialized.
That was fine so far as this was only required to make the output of the
control file correct and to prevent writes in that case.
With the upcoming l1tf command line parameter, this needs to be set up
before the L1TF mitigation selection and command line parsing happens.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Jiri Kosina <jkosina@suse.cz>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lkml.kernel.org/r/20180713142323.121795971@linutronix.de
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The L1TF mitigation will gain a commend line parameter which allows to set
a combination of hypervisor mitigation and SMT control.
Expose cpu_smt_disable() so the command line parser can tweak SMT settings.
[ tglx: Split out of larger patch and made it preserve an already existing
force off state ]
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Jiri Kosina <jkosina@suse.cz>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lkml.kernel.org/r/20180713142323.039715135@linutronix.de
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Writing 'off' to /sys/devices/system/cpu/smt/control offlines all SMT
siblings. Writing 'on' merily enables the abilify to online them, but does
not online them automatically.
Make 'on' more useful by onlining all offline siblings.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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If the L1TF CPU bug is present we allow the KVM module to be loaded as the
major of users that use Linux and KVM have trusted guests and do not want a
broken setup.
Cloud vendors are the ones that are uncomfortable with CVE 2018-3620 and as
such they are the ones that should set nosmt to one.
Setting 'nosmt' means that the system administrator also needs to disable
SMT (Hyper-threading) in the BIOS, or via the 'nosmt' command line
parameter, or via the /sys/devices/system/cpu/smt/control. See commit
05736e4ac13c ("cpu/hotplug: Provide knobs to control SMT").
Other mitigations are to use task affinity, cpu sets, interrupt binding,
etc - anything to make sure that _only_ the same guests vCPUs are running
on sibling threads.
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Oleg suggested to replace the "watchdog/%u" threads with
cpu_stop_work. That removes one thread per CPU while at the same time
fixes softlockup vs SCHED_DEADLINE.
But more importantly, it does away with the single
smpboot_update_cpumask_percpu_thread() user, which allows
cleanups/shrinkage of the smpboot interface.
Suggested-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Due to the way Machine Check Exceptions work on X86 hyperthreads it's
required to boot up _all_ logical cores at least once in order to set the
CR4.MCE bit.
So instead of ignoring the sibling threads right away, let them boot up
once so they can configure themselves. After they came out of the initial
boot stage check whether its a "secondary" sibling and cancel the operation
which puts the CPU back into offline state.
Reported-by: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Tony Luck <tony.luck@intel.com>
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Provide a command line and a sysfs knob to control SMT.
The command line options are:
'nosmt': Enumerate secondary threads, but do not online them
'nosmt=force': Ignore secondary threads completely during enumeration
via MP table and ACPI/MADT.
The sysfs control file has the following states (read/write):
'on': SMT is enabled. Secondary threads can be freely onlined
'off': SMT is disabled. Secondary threads, even if enumerated
cannot be onlined
'forceoff': SMT is permanentely disabled. Writes to the control
file are rejected.
'notsupported': SMT is not supported by the CPU
The command line option 'nosmt' sets the sysfs control to 'off'. This
can be changed to 'on' to reenable SMT during runtime.
The command line option 'nosmt=force' sets the sysfs control to
'forceoff'. This cannot be changed during runtime.
When SMT is 'on' and the control file is changed to 'off' then all online
secondary threads are offlined and attempts to online a secondary thread
later on are rejected.
When SMT is 'off' and the control file is changed to 'on' then secondary
threads can be onlined again. The 'off' -> 'on' transition does not
automatically online the secondary threads.
When the control file is set to 'forceoff', the behaviour is the same as
setting it to 'off', but the operation is irreversible and later writes to
the control file are rejected.
When the control status is 'notsupported' then writes to the control file
are rejected.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
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Split out the inner workings of do_cpu_down() to allow reuse of that
function for the upcoming SMT disabling mechanism.
No functional change.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
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The asymmetry caused a warning to trigger if the bootup was stopped in state
CPUHP_AP_ONLINE_IDLE. The warning no longer triggers as kthread_park() can
now be invoked on already or still parked threads. But there is still no
reason to have this be asymmetric.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
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The cpuhp_is_ap_state() function is no longer called outside of the
CONFIG_SMP #ifdef section, causing a harmless warning:
kernel/cpu.c:129:13: error: 'cpuhp_is_ap_state' defined but not used [-Werror=unused-function]
This moves the function into the #ifdef to get a clean build again.
Fixes: 17a2f1ced028 ("cpu/hotplug: Merge cpuhp_bp_states and cpuhp_ap_states")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Link: https://lkml.kernel.org/r/20180315153829.3819606-1-arnd@arndb.de
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cpuhp_bp_states and cpuhp_ap_states have different set of steps without any
conflicting steps, so that they can be merged.
The original `[CPUHP_BRINGUP_CPU] = { },` is removed, because the new
cpuhp_hp_states has CPUHP_ONLINE index which is larger than
CPUHP_BRINGUP_CPU.
Signed-off-by: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Link: https://lkml.kernel.org/r/20171201135008.21633-1-jiangshanlai@gmail.com
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer fixes from Thomas Gleixner:
"A pile of fixes for long standing issues with the timer wheel and the
NOHZ code:
- Prevent timer base confusion accross the nohz switch, which can
cause unlocked access and data corruption
- Reinitialize the stale base clock on cpu hotplug to prevent subtle
side effects including rollovers on 32bit
- Prevent an interrupt storm when the timer softirq is already
pending caused by tick_nohz_stop_sched_tick()
- Move the timer start tracepoint to a place where it actually makes
sense
- Add documentation to timerqueue functions as they caused confusion
several times now"
* 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
timerqueue: Document return values of timerqueue_add/del()
timers: Invoke timer_start_debug() where it makes sense
nohz: Prevent a timer interrupt storm in tick_nohz_stop_sched_tick()
timers: Reinitialize per cpu bases on hotplug
timers: Use deferrable base independent of base::nohz_active
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The timer wheel bases are not (re)initialized on CPU hotplug. That leaves
them with a potentially stale clk and next_expiry valuem, which can cause
trouble then the CPU is plugged.
Add a prepare callback which forwards the clock, sets next_expiry to far in
the future and reset the control flags to a known state.
Set base->must_forward_clk so the first timer which is queued will try to
forward the clock to current jiffies.
Fixes: 500462a9de65 ("timers: Switch to a non-cascading wheel")
Reported-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Anna-Maria Gleixner <anna-maria@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/alpine.DEB.2.20.1712272152200.2431@nanos
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|
Fix non-fatal warnings such as:
kernel/cpu.c:95:1: warning: ‘inline’ is not at beginning of declaration [-Wold-style-declaration]
static void inline cpuhp_lock_release(bool bringup) { }
^~~~~~
Signed-off-by: Mathieu Malaterre <malat@debian.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Link: https://lkml.kernel.org/r/20171226140855.16583-1-malat@debian.org
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|
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull CPU hotplug fix from Ingo Molnar:
"A single fix moving the smp-call queue flush step to the intended
point in the state machine"
* 'smp-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
smp/hotplug: Move step CPUHP_AP_SMPCFD_DYING to the correct place
|
|
CPUHP_AP_SCHED_MIGRATE_DYING doesn't exist, it looks like this was
supposed to refer to CPUHP_AP_SCHED_STARTING's teardown callback,
i.e. sched_cpu_dying().
Signed-off-by: Brendan Jackman <brendan.jackman@arm.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Quentin Perret <quentin.perret@arm.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20171206105911.28093-1-brendan.jackman@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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|
Commit 31487f8328f2 ("smp/cfd: Convert core to hotplug state machine")
accidently put this step on the wrong place. The step should be at the
cpuhp_ap_states[] rather than the cpuhp_bp_states[].
grep smpcfd /sys/devices/system/cpu/hotplug/states
40: smpcfd:prepare
129: smpcfd:dying
"smpcfd:dying" was missing before.
So was the invocation of the function smpcfd_dying_cpu().
Fixes: 31487f8328f2 ("smp/cfd: Convert core to hotplug state machine")
Signed-off-by: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: stable@vger.kernel.org
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Link: https://lkml.kernel.org/r/20171128131954.81229-1-jiangshanlai@gmail.com
|
|
The recent rework of the cpu hotplug internals changed the usage of the per
cpu state->node field, but missed to clean it up after usage.
So subsequent hotplug operations use the stale pointer from a previous
operation and hand it into the callback functions. The callbacks then
dereference a pointer which either belongs to a different facility or
points to freed and potentially reused memory. In either case data
corruption and crashes are the obvious consequence.
Reset the node and the last pointers in the per cpu state to NULL after the
operation which set them has completed.
Fixes: 96abb968549c ("smp/hotplug: Allow external multi-instance rollback")
Reported-by: Tvrtko Ursulin <tursulin@ursulin.net>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Link: https://lkml.kernel.org/r/alpine.DEB.2.20.1710211606130.3213@nanos
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|
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull watchddog clean-up and fixes from Thomas Gleixner:
"The watchdog (hard/softlockup detector) code is pretty much broken in
its current state. The patch series addresses this by removing all
duct tape and refactoring it into a workable state.
The reasons why I ask for inclusion that late in the cycle are:
1) The code causes lockdep splats vs. hotplug locking which get
reported over and over. Unfortunately there is no easy fix.
2) The risk of breakage is minimal because it's already broken
3) As 4.14 is a long term stable kernel, I prefer to have working
watchdog code in that and the lockdep issues resolved. I wouldn't
ask you to pull if 4.14 wouldn't be a LTS kernel or if the
solution would be easy to backport.
4) The series was around before the merge window opened, but then got
delayed due to the UP failure caused by the for_each_cpu()
surprise which we discussed recently.
Changes vs. V1:
- Addressed your review points
- Addressed the warning in the powerpc code which was discovered late
- Changed two function names which made sense up to a certain point
in the series. Now they match what they do in the end.
- Fixed a 'unused variable' warning, which got not detected by the
intel robot. I triggered it when trying all possible related config
combinations manually. Randconfig testing seems not random enough.
The changes have been tested by and reviewed by Don Zickus and tested
and acked by Micheal Ellerman for powerpc"
* 'core-watchdog-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (36 commits)
watchdog/core: Put softlockup_threads_initialized under ifdef guard
watchdog/core: Rename some softlockup_* functions
powerpc/watchdog: Make use of watchdog_nmi_probe()
watchdog/core, powerpc: Lock cpus across reconfiguration
watchdog/core, powerpc: Replace watchdog_nmi_reconfigure()
watchdog/hardlockup/perf: Fix spelling mistake: "permanetely" -> "permanently"
watchdog/hardlockup/perf: Cure UP damage
watchdog/hardlockup: Clean up hotplug locking mess
watchdog/hardlockup/perf: Simplify deferred event destroy
watchdog/hardlockup/perf: Use new perf CPU enable mechanism
watchdog/hardlockup/perf: Implement CPU enable replacement
watchdog/hardlockup/perf: Implement init time detection of perf
watchdog/hardlockup/perf: Implement init time perf validation
watchdog/core: Get rid of the racy update loop
watchdog/core, powerpc: Make watchdog_nmi_reconfigure() two stage
watchdog/sysctl: Clean up sysctl variable name space
watchdog/sysctl: Get rid of the #ifdeffery
watchdog/core: Clean up header mess
watchdog/core: Further simplify sysctl handling
watchdog/core: Get rid of the thread teardown/setup dance
...
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Add a sysfs file to one-time fail a specific state. This can be used
to test the state rollback code paths.
Something like this (hotplug-up.sh):
#!/bin/bash
echo 0 > /debug/sched_debug
echo 1 > /debug/tracing/events/cpuhp/enable
ALL_STATES=`cat /sys/devices/system/cpu/hotplug/states | cut -d':' -f1`
STATES=${1:-$ALL_STATES}
for state in $STATES
do
echo 0 > /sys/devices/system/cpu/cpu1/online
echo 0 > /debug/tracing/trace
echo Fail state: $state
echo $state > /sys/devices/system/cpu/cpu1/hotplug/fail
cat /sys/devices/system/cpu/cpu1/hotplug/fail
echo 1 > /sys/devices/system/cpu/cpu1/online
cat /debug/tracing/trace > hotfail-${state}.trace
sleep 1
done
Can be used to test for all possible rollback (barring multi-instance)
scenarios on CPU-up, CPU-down is a trivial modification of the above.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: bigeasy@linutronix.de
Cc: efault@gmx.de
Cc: rostedt@goodmis.org
Cc: max.byungchul.park@gmail.com
Link: https://lkml.kernel.org/r/20170920170546.972581715@infradead.org
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With lockdep-crossrelease we get deadlock reports that span cpu-up and
cpu-down chains. Such deadlocks cannot possibly happen because cpu-up
and cpu-down are globally serialized.
takedown_cpu()
irq_lock_sparse()
wait_for_completion(&st->done)
cpuhp_thread_fun
cpuhp_up_callback
cpuhp_invoke_callback
irq_affinity_online_cpu
irq_local_spare()
irq_unlock_sparse()
complete(&st->done)
Now that we have consistent AP state, we can trivially separate the
AP completion between up and down using st->bringup.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: max.byungchul.park@gmail.com
Cc: bigeasy@linutronix.de
Cc: efault@gmx.de
Cc: rostedt@goodmis.org
Link: https://lkml.kernel.org/r/20170920170546.872472799@infradead.org
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With lockdep-crossrelease we get deadlock reports that span cpu-up and
cpu-down chains. Such deadlocks cannot possibly happen because cpu-up
and cpu-down are globally serialized.
CPU0 CPU1 CPU2
cpuhp_up_callbacks: takedown_cpu: cpuhp_thread_fun:
cpuhp_state
irq_lock_sparse()
irq_lock_sparse()
wait_for_completion()
cpuhp_state
complete()
Now that we have consistent AP state, we can trivially separate the
AP-work class between up and down using st->bringup.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: max.byungchul.park@gmail.com
Cc: bigeasy@linutronix.de
Cc: efault@gmx.de
Cc: rostedt@goodmis.org
Link: https://lkml.kernel.org/r/20170920170546.922524234@infradead.org
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While the generic callback functions have an 'int' return and thus
appear to be allowed to return error, this is not true for all states.
Specifically, what used to be STARTING/DYING are ran with IRQs
disabled from critical parts of CPU bringup/teardown and are not
allowed to fail. Add WARNs to enforce this rule.
But since some callbacks are indeed allowed to fail, we have the
situation where a state-machine rollback encounters a failure, in this
case we're stuck, we can't go forward and we can't go back. Also add a
WARN for that case.
AFAICT this is a fundamental 'problem' with no real obvious solution.
We want the 'prepare' callbacks to allow failure on either up or down.
Typically on prepare-up this would be things like -ENOMEM from
resource allocations, and the typical usage in prepare-down would be
something like -EBUSY to avoid CPUs being taken away.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: bigeasy@linutronix.de
Cc: efault@gmx.de
Cc: rostedt@goodmis.org
Cc: max.byungchul.park@gmail.com
Link: https://lkml.kernel.org/r/20170920170546.819539119@infradead.org
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There is currently no explicit state change on rollback. That is,
st->bringup, st->rollback and st->target are not consistent when doing
the rollback.
Rework the AP state handling to be more coherent. This does mean we
have to do a second AP kick-and-wait for rollback, but since rollback
is the slow path of a slowpath, this really should not matter.
Take this opportunity to simplify the AP thread function to only run a
single callback per invocation. This unifies the three single/up/down
modes is supports. The looping it used to do for up/down are achieved
by retaining should_run and relying on the main smpboot_thread_fn()
loop.
(I have most of a patch that does the same for the BP state handling,
but that's not critical and gets a little complicated because
CPUHP_BRINGUP_CPU does the AP handoff from a callback, which gets
recursive @st usage, I still have de-fugly that.)
[ tglx: Move cpuhp_down_callbacks() et al. into the HOTPLUG_CPU section to
avoid gcc complaining about unused functions. Make the HOTPLUG_CPU
one piece instead of having two consecutive ifdef sections of the
same type. ]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: bigeasy@linutronix.de
Cc: efault@gmx.de
Cc: rostedt@goodmis.org
Cc: max.byungchul.park@gmail.com
Link: https://lkml.kernel.org/r/20170920170546.769658088@infradead.org
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Currently the rollback of multi-instance states is handled inside
cpuhp_invoke_callback(). The problem is that when we want to allow an
explicit state change for rollback, we need to return from the
function without doing the rollback.
Change cpuhp_invoke_callback() to optionally return the multi-instance
state, such that rollback can be done from a subsequent call.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: bigeasy@linutronix.de
Cc: efault@gmx.de
Cc: rostedt@goodmis.org
Cc: max.byungchul.park@gmail.com
Link: https://lkml.kernel.org/r/20170920170546.720361181@infradead.org
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|
The following deadlock is possible in the watchdog hotplug code:
cpus_write_lock()
...
takedown_cpu()
smpboot_park_threads()
smpboot_park_thread()
kthread_park()
->park() := watchdog_disable()
watchdog_nmi_disable()
perf_event_release_kernel();
put_event()
_free_event()
->destroy() := hw_perf_event_destroy()
x86_release_hardware()
release_ds_buffers()
get_online_cpus()
when a per cpu watchdog perf event is destroyed which drops the last
reference to the PMU hardware. The cleanup code there invokes
get_online_cpus() which instantly deadlocks because the hotplug percpu
rwsem is write locked.
To solve this add a deferring mechanism:
cpus_write_lock()
kthread_park()
watchdog_nmi_disable(deferred)
perf_event_disable(event);
move_event_to_deferred(event);
....
cpus_write_unlock()
cleaup_deferred_events()
perf_event_release_kernel()
This is still properly serialized against concurrent hotplug via the
cpu_add_remove_lock, which is held by the task which initiated the hotplug
event.
This is also used to handle event destruction when the watchdog threads are
parked via other mechanisms than CPU hotplug.
Analyzed-by: Peter Zijlstra <peterz@infradead.org>
Reported-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Don Zickus <dzickus@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Link: http://lkml.kernel.org/r/20170912194146.884469246@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull CPU hotplug fix from Thomas Gleixner:
"A single fix to handle the removal of the first dynamic CPU hotplug
state correctly"
* 'smp-hotplug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
smp/hotplug: Handle removal correctly in cpuhp_store_callbacks()
|
|
RCU callbacks must be migrated away from an outgoing CPU, and this is
done near the end of the CPU-hotplug operation, after the outgoing CPU is
long gone. Unfortunately, this means that other CPU-hotplug callbacks
can execute while the outgoing CPU's callbacks are still immobilized
on the long-gone CPU's callback lists. If any of these CPU-hotplug
callbacks must wait, either directly or indirectly, for the invocation
of any of the immobilized RCU callbacks, the system will hang.
This commit avoids such hangs by migrating the callbacks away from the
outgoing CPU immediately upon its departure, shortly after the return
from __cpu_die() in takedown_cpu(). Thus, RCU is able to advance these
callbacks and invoke them, which allows all the after-the-fact CPU-hotplug
callbacks to wait on these RCU callbacks without risk of a hang.
While in the neighborhood, this commit also moves rcu_send_cbs_to_orphanage()
and rcu_adopt_orphan_cbs() under a pre-existing #ifdef to avoid including
dead code on the one hand and to avoid define-without-use warnings on the
other hand.
Reported-by: Jeffrey Hugo <jhugo@codeaurora.org>
Link: http://lkml.kernel.org/r/db9c91f6-1b17-6136-84f0-03c3c2581ab4@codeaurora.org
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Anna-Maria Gleixner <anna-maria@linutronix.de>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Richard Weinberger <richard@nod.at>
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|
If cpuhp_store_callbacks() is called for CPUHP_AP_ONLINE_DYN or
CPUHP_BP_PREPARE_DYN, which are the indicators for dynamically allocated
states, then cpuhp_store_callbacks() allocates a new dynamic state. The
first allocation in each range returns CPUHP_AP_ONLINE_DYN or
CPUHP_BP_PREPARE_DYN.
If cpuhp_remove_state() is invoked for one of these states, then there is
no protection against the allocation mechanism. So the removal, which
should clear the callbacks and the name, gets a new state assigned and
clears that one.
As a consequence the state which should be cleared stays initialized. A
consecutive CPU hotplug operation dereferences the state callbacks and
accesses either freed or reused memory, resulting in crashes.
Add a protection against this by checking the name argument for NULL. If
it's NULL it's a removal. If not, it's an allocation.
[ tglx: Added a comment and massaged changelog ]
Fixes: 5b7aa87e0482 ("cpu/hotplug: Implement setup/removal interface")
Signed-off-by: Ethan Barnes <ethan.barnes@sandisk.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.or>
Cc: "Srivatsa S. Bhat" <srivatsa@mit.edu>
Cc: Sebastian Siewior <bigeasy@linutronix.d>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/DM2PR04MB398242FC7776D603D9F99C894A60@DM2PR04MB398.namprd04.prod.outlook.com
|
|
The move of the unpark functions to the control thread moved the BUG_ON()
there as well. While it made some sense in the idle thread of the upcoming
CPU, it's bogus to crash the control thread on the already online CPU,
especially as the function has a return value and the callsite is prepared
to handle an error return.
Replace it with a WARN_ON_ONCE() and return a proper error code.
Fixes: 9cd4f1a4e7a8 ("smp/hotplug: Move unparking of percpu threads to the control CPU")
Rightfully-ranted-at-by: Linux Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
|
|
Vikram reported the following backtrace:
BUG: scheduling while atomic: swapper/7/0/0x00000002
CPU: 7 PID: 0 Comm: swapper/7 Not tainted 4.9.32-perf+ #680
schedule
schedule_hrtimeout_range_clock
schedule_hrtimeout
wait_task_inactive
__kthread_bind_mask
__kthread_bind
__kthread_unpark
kthread_unpark
cpuhp_online_idle
cpu_startup_entry
secondary_start_kernel
He analyzed correctly that a parked cpu hotplug thread of an offlined CPU
was still on the runqueue when the CPU came back online and tried to unpark
it. This causes the thread which invoked kthread_unpark() to call
wait_task_inactive() and subsequently schedule() with preemption disabled.
His proposed workaround was to "make sure" that a parked thread has
scheduled out when the CPU goes offline, so the situation cannot happen.
But that's still wrong because the root cause is not the fact that the
percpu thread is still on the runqueue and neither that preemption is
disabled, which could be simply solved by enabling preemption before
calling kthread_unpark().
The real issue is that the calling thread is the idle task of the upcoming
CPU, which is not supposed to call anything which might sleep. The moron,
who wrote that code, missed completely that kthread_unpark() might end up
in schedule().
The solution is simpler than expected. The thread which controls the
hotplug operation is waiting for the CPU to call complete() on the hotplug
state completion. So the idle task of the upcoming CPU can set its state to
CPUHP_AP_ONLINE_IDLE and invoke complete(). This in turn wakes the control
task on a different CPU, which then can safely do the unpark and kick the
now unparked hotplug thread of the upcoming CPU to complete the bringup to
the final target state.
Control CPU AP
bringup_cpu();
__cpu_up() ------------>
bringup_ap();
bringup_wait_for_ap()
wait_for_completion();
cpuhp_online_idle();
<------------ complete();
unpark(AP->stopper);
unpark(AP->hotplugthread);
while(1)
do_idle();
kick(AP->hotplugthread);
wait_for_completion(); hotplug_thread()
run_online_callbacks();
complete();
Fixes: 8df3e07e7f21 ("cpu/hotplug: Let upcoming cpu bring itself fully up")
Reported-by: Vikram Mulukutla <markivx@codeaurora.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Sewior <bigeasy@linutronix.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1707042218020.2131@nanos
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
|
|
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull SMP hotplug updates from Thomas Gleixner:
"This update is primarily a cleanup of the CPU hotplug locking code.
The hotplug locking mechanism is an open coded RWSEM, which allows
recursive locking. The main problem with that is the recursive nature
as it evades the full lockdep coverage and hides potential deadlocks.
The rework replaces the open coded RWSEM with a percpu RWSEM and
establishes full lockdep coverage that way.
The bulk of the changes fix up recursive locking issues and address
the now fully reported potential deadlocks all over the place. Some of
these deadlocks have been observed in the RT tree, but on mainline the
probability was low enough to hide them away."
* 'smp-hotplug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (37 commits)
cpu/hotplug: Constify attribute_group structures
powerpc: Only obtain cpu_hotplug_lock if called by rtasd
ARM/hw_breakpoint: Fix possible recursive locking for arch_hw_breakpoint_init
cpu/hotplug: Remove unused check_for_tasks() function
perf/core: Don't release cred_guard_mutex if not taken
cpuhotplug: Link lock stacks for hotplug callbacks
acpi/processor: Prevent cpu hotplug deadlock
sched: Provide is_percpu_thread() helper
cpu/hotplug: Convert hotplug locking to percpu rwsem
s390: Prevent hotplug rwsem recursion
arm: Prevent hotplug rwsem recursion
arm64: Prevent cpu hotplug rwsem recursion
kprobes: Cure hotplug lock ordering issues
jump_label: Reorder hotplug lock and jump_label_lock
perf/tracing/cpuhotplug: Fix locking order
ACPI/processor: Use cpu_hotplug_disable() instead of get_online_cpus()
PCI: Replace the racy recursion prevention
PCI: Use cpu_hotplug_disable() instead of get_online_cpus()
perf/x86/intel: Drop get_online_cpus() in intel_snb_check_microcode()
x86/perf: Drop EXPORT of perf_check_microcode
...
|
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attribute_groups are not supposed to change at runtime. All functions
working with attribute_groups provided by <linux/sysfs.h> work with const
attribute_group.
So mark the non-const structs as const:
File size before:
text data bss dec hex filename
12582 15361 20 27963 6d3b kernel/cpu.o
File size After adding 'const':
text data bss dec hex filename
12710 15265 20 27995 6d5b kernel/cpu.o
Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: anna-maria@linutronix.de
Cc: bigeasy@linutronix.de
Cc: boris.ostrovsky@oracle.com
Cc: rcochran@linutronix.de
Link: http://lkml.kernel.org/r/f9079e94e12b36d245e7adbf67d312bc5d0250c6.1498737970.git.arvind.yadav.cs@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
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If a CPU goes offline, interrupts affine to the CPU are moved away. If the
outgoing CPU is the last CPU in the affinity mask the migration code breaks
the affinity and sets it it all online cpus.
This is a problem for affinity managed interrupts as CPU hotplug is often
used for power management purposes. If the affinity is broken, the
interrupt is not longer affine to the CPUs to which it was allocated.
The affinity spreading allows to lay out multi queue devices in a way that
they are assigned to a single CPU or a group of CPUs. If the last CPU goes
offline, then the queue is not longer used, so the interrupt can be
shutdown gracefully and parked until one of the assigned CPUs comes online
again.
Add a graceful shutdown mechanism into the irq affinity breaking code path,
mark the irq as MANAGED_SHUTDOWN and leave the affinity mask unmodified.
In the online path, scan the active interrupts for managed interrupts and
if the interrupt is functional and the newly online CPU is part of the
affinity mask, restart the interrupt if it is marked MANAGED_SHUTDOWN or if
the interrupts is started up, try to add the CPU back to the effective
affinity mask.
Originally-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Keith Busch <keith.busch@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20170619235447.273417334@linutronix.de
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clang -Wunused-function found one remaining function that was
apparently meant to be removed in a recent code cleanup:
kernel/cpu.c:565:20: warning: unused function 'check_for_tasks' [-Wunused-function]
Sebastian explained: The function became unused unintentionally, but there
is already a failure check, when a task cannot be removed from the outgoing
cpu in the scheduler code, so bringing it back is not really giving any
extra value.
Fixes: 530e9b76ae8f ("cpu/hotplug: Remove obsolete cpu hotplug register/unregister functions")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Anna-Maria Gleixner <anna-maria@linutronix.de>
Link: http://lkml.kernel.org/r/20170608085544.2257132-1-arnd@arndb.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
|
|
If a custom CPU target is specified and that one is not available _or_
can't be interrupted then the code returns to userland without dropping a
lock as notices by lockdep:
|echo 133 > /sys/devices/system/cpu/cpu7/hotplug/target
| ================================================
| [ BUG: lock held when returning to user space! ]
| ------------------------------------------------
| bash/503 is leaving the kernel with locks still held!
| 1 lock held by bash/503:
| #0: (device_hotplug_lock){+.+...}, at: [<ffffffff815b5650>] lock_device_hotplug_sysfs+0x10/0x40
So release the lock then.
Fixes: 757c989b9994 ("cpu/hotplug: Make target state writeable")
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/20170602142714.3ogo25f2wbq6fjpj@linutronix.de
|
|
The CPU hotplug callbacks are not covered by lockdep versus the cpu hotplug
rwsem.
CPU0 CPU1
cpuhp_setup_state(STATE, startup, teardown);
cpus_read_lock();
invoke_callback_on_ap();
kick_hotplug_thread(ap);
wait_for_completion(); hotplug_thread_fn()
lock(m);
do_stuff();
unlock(m);
Lockdep does not know about this dependency and will not trigger on the
following code sequence:
lock(m);
cpus_read_lock();
Add a lockdep map and connect the initiators lock chain with the hotplug
thread lock chain, so potential deadlocks can be detected.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20170524081549.709375845@linutronix.de
|
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There are no more (known) nested calls to get_online_cpus() and all
observed lock ordering problems have been addressed.
Replace the magic nested 'rwsem' hackery with a percpu-rwsem.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20170524081549.447014063@linutronix.de
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takedown_cpu() is a cpu hotplug function invoking stop_machine(). The cpu
hotplug machinery holds the hotplug lock for write.
stop_machine() invokes get_online_cpus() as well. This is correct, but
prevents the conversion of the hotplug locking to a percpu rwsem.
Use stop_machine_cpuslocked() to avoid the nested call.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20170524081548.423292433@linutronix.de
|
|
Add cpuslocked() variants for the multi instance registration so this can
be called from a cpus_read_lock() protected region.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20170524081547.321782217@linutronix.de
|
|
Some call sites of cpuhp_setup/remove_state[_nocalls]() are within a
cpus_read locked region.
cpuhp_setup/remove_state[_nocalls]() call cpus_read_lock() as well, which
is possible in the current implementation but prevents converting the
hotplug locking to a percpu rwsem.
Provide locked versions of the interfaces to avoid nested calls to
cpus_read_lock().
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20170524081547.239600868@linutronix.de
|
|
The counting 'rwsem' hackery of get|put_online_cpus() is going to be
replaced by percpu rwsem.
Rename the functions to make it clear that it's locking and not some
refcount style interface. These new functions will be used for the
preparatory patches which make the code ready for the percpu rwsem
conversion.
Rename all instances in the cpu hotplug code while at it.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20170524081547.080397752@linutronix.de
|
|
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
Since commit 383776fa7527 ("locking/lockdep: Handle statically initialized
PER_CPU locks properly") we try to collapse per-cpu locks into a single
class by giving them all the same key. For this key we choose the canonical
address of the per-cpu object, which would be the offset into the per-cpu
area.
This has two problems:
- there is a case where we run !0 lock->key through static_obj() and
expect this to pass; it doesn't for canonical pointers.
- 0 is a valid canonical address.
Cure both issues by redefining the canonical address as the address of the
per-cpu variable on the boot CPU.
Since I didn't want to rely on CPU0 being the boot-cpu, or even existing at
all, track the boot CPU in a variable.
Fixes: 383776fa7527 ("locking/lockdep: Handle statically initialized PER_CPU locks properly")
Reported-by: kernel test robot <fengguang.wu@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Borislav Petkov <bp@suse.de>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: linux-mm@kvack.org
Cc: wfg@linux.intel.com
Cc: kernel test robot <fengguang.wu@intel.com>
Cc: LKP <lkp@01.org>
Link: http://lkml.kernel.org/r/20170320114108.kbvcsuepem45j5cr@hirez.programming.kicks-ass.net
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
|
|
The setup/remove_state/instance() functions in the hotplug core code are
serialized against concurrent CPU hotplug, but unfortunately not serialized
against themself.
As a consequence a concurrent invocation of these function results in
corruption of the callback machinery because two instances try to invoke
callbacks on remote cpus at the same time. This results in missing callback
invocations and initiator threads waiting forever on the completion.
The obvious solution to replace get_cpu_online() with cpu_hotplug_begin()
is not possible because at least one callsite calls into these functions
from a get_online_cpu() locked region.
Extend the protection scope of the cpuhp_state_mutex from solely protecting
the state arrays to cover the callback invocation machinery as well.
Fixes: 5b7aa87e0482 ("cpu/hotplug: Implement setup/removal interface")
Reported-and-tested-by: Bart Van Assche <Bart.VanAssche@sandisk.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: hpa@zytor.com
Cc: mingo@kernel.org
Cc: akpm@linux-foundation.org
Cc: torvalds@linux-foundation.org
Link: http://lkml.kernel.org/r/20170314150645.g4tdyoszlcbajmna@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
|
|
<linux/sched/task.h>
We are going to split <linux/sched/task.h> out of <linux/sched.h>, which
will have to be picked up from other headers and a couple of .c files.
Create a trivial placeholder <linux/sched/task.h> file that just
maps to <linux/sched.h> to make this patch obviously correct and
bisectable.
Include the new header in the files that are going to need it.
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
<linux/sched/hotplug.h>
We are going to split <linux/sched/hotplug.h> out of <linux/sched.h>, which
will have to be picked up from other headers and a couple of .c files.
Create a trivial placeholder <linux/sched/hotplug.h> file that just
maps to <linux/sched.h> to make this patch obviously correct and
bisectable.
Include the new header in the files that are going to need it.
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
<linux/sched/signal.h>
We are going to split <linux/sched/signal.h> out of <linux/sched.h>, which
will have to be picked up from other headers and a couple of .c files.
Create a trivial placeholder <linux/sched/signal.h> file that just
maps to <linux/sched.h> to make this patch obviously correct and
bisectable.
Include the new header in the files that are going to need it.
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
After the recent removal of the hotplug notifiers the variable 'hasdied' in
_cpu_down() is set but no longer read, leading to the following GCC warning
when building with 'make W=1':
kernel/cpu.c:767:7: warning: variable ‘hasdied’ set but not used [-Wunused-but-set-variable]
Fix it by removing the variable.
Fixes: 530e9b76ae8f ("cpu/hotplug: Remove obsolete cpu hotplug register/unregister functions")
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20170117143501.20893-1-tklauser@distanz.ch
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
|
|
Mathieu reported that the LTTNG modules are broken as of 4.10-rc1 due to
the removal of the cpu hotplug notifiers.
Usually I don't care much about out of tree modules, but LTTNG is widely
used in distros. There are two ways to solve that:
1) Reserve a hotplug state for LTTNG
2) Add a dynamic range for the prepare states.
While #1 is the simplest solution, #2 is the proper one as we can convert
in tree users, which do not care about ordering, to the dynamic range as
well.
Add a dynamic range which allows LTTNG to request states in the prepare
stage.
Reported-and-tested-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Sewior <bigeasy@linutronix.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1701101353010.3401@nanos
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
|
|
The attempt to prevent overwriting an active state resulted in a
disaster which effectively disables all dynamically allocated hotplug
states.
Cleanup the mess.
Fixes: dc280d936239 ("cpu/hotplug: Prevent overwriting of callbacks")
Reported-by: Markus Trippelsdorf <markus@trippelsdorf.de>
Reported-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
hotcpu_notifier(), cpu_notifier(), __hotcpu_notifier(), __cpu_notifier(),
register_hotcpu_notifier(), register_cpu_notifier(),
__register_hotcpu_notifier(), __register_cpu_notifier(),
unregister_hotcpu_notifier(), unregister_cpu_notifier(),
__unregister_hotcpu_notifier(), __unregister_cpu_notifier()
are unused now. Remove them and all related code.
Remove also the now pointless cpu notifier error injection mechanism. The
states can be executed step by step and error rollback is the same as cpu
down, so any state transition can be tested w/o requiring the notifier
error injection.
Some CPU hotplug states are kept as they are (ab)used for hotplug state
tracking.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20161221192112.005642358@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
|
|
Developers manage to overwrite states blindly without thought. That's fatal
and hard to debug. Add sanity checks to make it fail.
This requries to restructure the code so that the dynamic state allocation
happens in the same lock protected section as the actual store. Otherwise
the previous assignment of 'Reserved' to the name field would trigger the
overwrite check.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Link: http://lkml.kernel.org/r/20161221192111.675234535@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
|
|
When invoked with CPUHP_AP_ONLINE_DYN state __cpuhp_setup_state()
is expected to return positive value which is the hotplug state that
the routine assigns.
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: linux-pm@vger.kernel.org
Cc: viresh.kumar@linaro.org
Cc: bigeasy@linutronix.de
Cc: rjw@rjwysocki.net
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/1481814058-4799-2-git-send-email-boris.ostrovsky@oracle.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
|
|
Yu Zhao has noticed that __unregister_cpu_notifier only unregisters its
notifiers when HOTPLUG_CPU=y while the registration might succeed even
when HOTPLUG_CPU=n if MODULE is enabled. This means that e.g. zswap
might keep a stale notifier on the list on the manual clean up during
the pool tear down and thus corrupt the list. Resulting in the following
[ 144.964346] BUG: unable to handle kernel paging request at ffff880658a2be78
[ 144.971337] IP: [<ffffffffa290b00b>] raw_notifier_chain_register+0x1b/0x40
<snipped>
[ 145.122628] Call Trace:
[ 145.125086] [<ffffffffa28e5cf8>] __register_cpu_notifier+0x18/0x20
[ 145.131350] [<ffffffffa2a5dd73>] zswap_pool_create+0x273/0x400
[ 145.137268] [<ffffffffa2a5e0fc>] __zswap_param_set+0x1fc/0x300
[ 145.143188] [<ffffffffa2944c1d>] ? trace_hardirqs_on+0xd/0x10
[ 145.149018] [<ffffffffa2908798>] ? kernel_param_lock+0x28/0x30
[ 145.154940] [<ffffffffa2a3e8cf>] ? __might_fault+0x4f/0xa0
[ 145.160511] [<ffffffffa2a5e237>] zswap_compressor_param_set+0x17/0x20
[ 145.167035] [<ffffffffa2908d3c>] param_attr_store+0x5c/0xb0
[ 145.172694] [<ffffffffa290848d>] module_attr_store+0x1d/0x30
[ 145.178443] [<ffffffffa2b2b41f>] sysfs_kf_write+0x4f/0x70
[ 145.183925] [<ffffffffa2b2a5b9>] kernfs_fop_write+0x149/0x180
[ 145.189761] [<ffffffffa2a99248>] __vfs_write+0x18/0x40
[ 145.194982] [<ffffffffa2a9a412>] vfs_write+0xb2/0x1a0
[ 145.200122] [<ffffffffa2a9a732>] SyS_write+0x52/0xa0
[ 145.205177] [<ffffffffa2ff4d97>] entry_SYSCALL_64_fastpath+0x12/0x17
This can be even triggered manually by changing
/sys/module/zswap/parameters/compressor multiple times.
Fix this issue by making unregister APIs symmetric to the register so
there are no surprises.
Fixes: 47e627bc8c9a ("[PATCH] hotplug: Allow modules to use the cpu hotplug notifiers even if !CONFIG_HOTPLUG_CPU")
Reported-and-tested-by: Yu Zhao <yuzhao@google.com>
Signed-off-by: Michal Hocko <mhocko@suse.com>
Cc: linux-mm@kvack.org
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dan Streetman <ddstreet@ieee.org>
Link: http://lkml.kernel.org/r/20161207135438.4310-1-mhocko@kernel.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
|
|
Use distinctive name for cpu_hotplug.dep_map to avoid the actual
cpu_hotplug.lock appearing as cpu_hotplug.lock#2 in lockdep splats.
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Gautham R . Shenoy <ego@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: intel-gfx@lists.freedesktop.org
Cc: trivial@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull CPU hotplug updates from Thomas Gleixner:
"Yet another batch of cpu hotplug core updates and conversions:
- Provide core infrastructure for multi instance drivers so the
drivers do not have to keep custom lists.
- Convert custom lists to the new infrastructure. The block-mq custom
list conversion comes through the block tree and makes the diffstat
tip over to more lines removed than added.
- Handle unbalanced hotplug enable/disable calls more gracefully.
- Remove the obsolete CPU_STARTING/DYING notifier support.
- Convert another batch of notifier users.
The relayfs changes which conflicted with the conversion have been
shipped to me by Andrew.
The remaining lot is targeted for 4.10 so that we finally can remove
the rest of the notifiers"
* 'smp-hotplug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (46 commits)
cpufreq: Fix up conversion to hotplug state machine
blk/mq: Reserve hotplug states for block multiqueue
x86/apic/uv: Convert to hotplug state machine
s390/mm/pfault: Convert to hotplug state machine
mips/loongson/smp: Convert to hotplug state machine
mips/octeon/smp: Convert to hotplug state machine
fault-injection/cpu: Convert to hotplug state machine
padata: Convert to hotplug state machine
cpufreq: Convert to hotplug state machine
ACPI/processor: Convert to hotplug state machine
virtio scsi: Convert to hotplug state machine
oprofile/timer: Convert to hotplug state machine
block/softirq: Convert to hotplug state machine
lib/irq_poll: Convert to hotplug state machine
x86/microcode: Convert to hotplug state machine
sh/SH-X3 SMP: Convert to hotplug state machine
ia64/mca: Convert to hotplug state machine
ARM/OMAP/wakeupgen: Convert to hotplug state machine
ARM/shmobile: Convert to hotplug state machine
arm64/FP/SIMD: Convert to hotplug state machine
...
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull RCU updates from Ingo Molnar:
"The main changes in this cycle were:
- Expedited grace-period changes, most notably avoiding having user
threads drive expedited grace periods, using a workqueue instead.
- Miscellaneous fixes, including a performance fix for lists that was
sent with the lists modifications.
- CPU hotplug updates, most notably providing exact CPU-online
tracking for RCU. This will in turn allow removal of the checks
supporting RCU's prior heuristic that was based on the assumption
that CPUs would take no longer than one jiffy to come online.
- Torture-test updates.
- Documentation updates"
* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (22 commits)
list: Expand list_first_entry_or_null()
torture: TOROUT_STRING(): Insert a space between flag and message
rcuperf: Consistently insert space between flag and message
rcutorture: Print out barrier error as document says
torture: Add task state to writer-task stall printk()s
torture: Convert torture_shutdown() to hrtimer
rcutorture: Convert to hotplug state machine
cpu/hotplug: Get rid of CPU_STARTING reference
rcu: Provide exact CPU-online tracking for RCU
rcu: Avoid redundant quiescent-state chasing
rcu: Don't use modular infrastructure in non-modular code
sched: Make wake_up_nohz_cpu() handle CPUs going offline
rcu: Use rcu_gp_kthread_wake() to wake up grace period kthreads
rcu: Use RCU's online-CPU state for expedited IPI retry
rcu: Exclude RCU-offline CPUs from expedited grace periods
rcu: Make expedited RCU CPU stall warnings respond to controls
rcu: Stop disabling expedited RCU CPU stall warnings
rcu: Drive expedited grace periods from workqueue
rcu: Consolidate expedited grace period machinery
documentation: Record reason for rcu_head two-byte alignment
...
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Install the callbacks via the state machine.
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: linux-mm@kvack.org
Cc: rt@linutronix.de
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Lameter <cl@linux.com>
Link: http://lkml.kernel.org/r/20160823125319.abeapfjapf2kfezp@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Install the callbacks via the state machine. They are installed at run time but
relay_prepare_cpu() does not need to be invoked by the boot CPU because
relay_open() was not yet invoked and there are no pools that need to be created.
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: rt@linutronix.de
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/20160818125731.27256-3-bigeasy@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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All users are converted to state machine, remove CPU_STARTING and the
corresponding CPU_DYING.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160818125731.27256-2-bigeasy@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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We should have all names in the scheme "[subsys/]facility:state]". Fix the
core to comply.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Some compilers are unhappy with the anon union in the state array. Replace
it with a named union.
While at it align the state array initializers proper and add the missing
name tags.
Fixes: cf392d10b69e "cpu/hotplug: Add multi instance support"
Reported-by: Ingo Molnar <mingo@kernel.org>
Reported-by: Fenguang Wu <fengguang.wu@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: rt@linutronix.de
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When cpu_hotplug_enable() is called unbalanced w/o a preceeding
cpu_hotplug_disable() the code emits a warning, but happily decrements the
disabled counter. This causes the next operations to malfunction.
Prevent the decrement and just emit a warning.
Signed-off-by: Lianwei Wang <lianwei.wang@gmail.com>
Cc: peterz@infradead.org
Cc: linux-pm@vger.kernel.org
Cc: oleg@redhat.com
Link: http://lkml.kernel.org/r/1465541008-12476-1-git-send-email-lianwei.wang@gmail.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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This patch adds the ability for a given state to have multiple
instances. Until now all states have a single instance and the startup /
teardown callback use global variables.
A few drivers need to perform a the same callbacks on multiple
"instances". Currently we have three drivers in tree which all have a
global list which they iterate over. With multi instance they support
don't need their private list and the functionality has been moved into
core code. Plus we hold the hotplug lock in core so no cpus comes/goes
while instances are registered and we do rollback in error case :)
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/1471024183-12666-3-git-send-email-bigeasy@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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This is preparation for the following patch.
This rework here changes the arguments of cpuhp_invoke_callback(). It
passes now `state' and whether `startup' or `teardown' callback should
be invoked. The callback then is looked up by the function.
The following is a clanup of callers:
- cpuhp_issue_call() has one argument less
- struct cpuhp_cpu_state (which is used by the hotplug thread) gets also
its callback removed. The decision if it is a single callback
invocation moved to the `single' variable. Also a `bringup' variable
has been added to distinguish between startup and teardown callback.
- take_cpu_down() needs to start one step earlier. We always get here
via CPUHP_TEARDOWN_CPU callback. Before that change cpuhp_ap_states +
CPUHP_TEARDOWN_CPU pointed to an empty entry because TEARDOWN is saved
in bp_states for this reason. Now that we use cpuhp_get_step() to
lookup the state we must explicitly skip it in order not to invoke it
twice.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/1471024183-12666-2-git-send-email-bigeasy@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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