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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler updates from Ingo Molnar:
- Add cpufreq pressure feedback for the scheduler
- Rework misfit load-balancing wrt affinity restrictions
- Clean up and simplify the code around ::overutilized and
::overload access.
- Simplify sched_balance_newidle()
- Bump SCHEDSTAT_VERSION to 16 due to a cleanup of CPU_MAX_IDLE_TYPES
handling that changed the output.
- Rework & clean up <asm/vtime.h> interactions wrt arch_vtime_task_switch()
- Reorganize, clean up and unify most of the higher level
scheduler balancing function names around the sched_balance_*()
prefix
- Simplify the balancing flag code (sched_balance_running)
- Miscellaneous cleanups & fixes
* tag 'sched-core-2024-05-13' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (50 commits)
sched/pelt: Remove shift of thermal clock
sched/cpufreq: Rename arch_update_thermal_pressure() => arch_update_hw_pressure()
thermal/cpufreq: Remove arch_update_thermal_pressure()
sched/cpufreq: Take cpufreq feedback into account
cpufreq: Add a cpufreq pressure feedback for the scheduler
sched/fair: Fix update of rd->sg_overutilized
sched/vtime: Do not include <asm/vtime.h> header
s390/irq,nmi: Include <asm/vtime.h> header directly
s390/vtime: Remove unused __ARCH_HAS_VTIME_TASK_SWITCH leftover
sched/vtime: Get rid of generic vtime_task_switch() implementation
sched/vtime: Remove confusing arch_vtime_task_switch() declaration
sched/balancing: Simplify the sg_status bitmask and use separate ->overloaded and ->overutilized flags
sched/fair: Rename set_rd_overutilized_status() to set_rd_overutilized()
sched/fair: Rename SG_OVERLOAD to SG_OVERLOADED
sched/fair: Rename {set|get}_rd_overload() to {set|get}_rd_overloaded()
sched/fair: Rename root_domain::overload to ::overloaded
sched/fair: Use helper functions to access root_domain::overload
sched/fair: Check root_domain::overload value before update
sched/fair: Combine EAS check with root_domain::overutilized access
sched/fair: Simplify the continue_balancing logic in sched_balance_newidle()
...
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Yue Sun and xingwei lee reported a divide error bug in
wq_update_node_max_active():
divide error: 0000 [#1] PREEMPT SMP KASAN PTI
CPU: 1 PID: 21 Comm: cpuhp/1 Not tainted 6.9.0-rc5 #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
RIP: 0010:wq_update_node_max_active+0x369/0x6b0 kernel/workqueue.c:1605
Code: 24 bf 00 00 00 80 44 89 fe e8 83 27 33 00 41 83 fc ff 75 0d 41
81 ff 00 00 00 80 0f 84 68 01 00 00 e8 fb 22 33 00 44 89 f8 99 <41> f7
fc 89 c5 89 c7 44 89 ee e8 a8 24 33 00 89 ef 8b 5c 24 04 89
RSP: 0018:ffffc9000018fbb0 EFLAGS: 00010293
RAX: 00000000000000ff RBX: 0000000000000001 RCX: ffff888100ada500
RDX: 0000000000000000 RSI: 00000000000000ff RDI: 0000000080000000
RBP: 0000000000000001 R08: ffffffff815b1fcd R09: 1ffff1100364ad72
R10: dffffc0000000000 R11: ffffed100364ad73 R12: 0000000000000000
R13: 0000000000000100 R14: 0000000000000000 R15: 00000000000000ff
FS: 0000000000000000(0000) GS:ffff888135c00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fb8c06ca6f8 CR3: 000000010d6c6000 CR4: 0000000000750ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
PKRU: 55555554
Call Trace:
<TASK>
workqueue_offline_cpu+0x56f/0x600 kernel/workqueue.c:6525
cpuhp_invoke_callback+0x4e1/0x870 kernel/cpu.c:194
cpuhp_thread_fun+0x411/0x7d0 kernel/cpu.c:1092
smpboot_thread_fn+0x544/0xa10 kernel/smpboot.c:164
kthread+0x2ed/0x390 kernel/kthread.c:388
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:244
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
After analysis, it happens when all of the CPUs in a workqueue's affinity
get offine.
The problem can be easily reproduced by:
# echo 8 > /sys/devices/virtual/workqueue/<any-wq-name>/cpumask
# echo 0 > /sys/devices/system/cpu/cpu3/online
Use the default max_actives for nodes when all of the CPUs in the
workqueue's affinity get offline to fix the problem.
Reported-by: Yue Sun <samsun1006219@gmail.com>
Reported-by: xingwei lee <xrivendell7@gmail.com>
Link: https://lore.kernel.org/lkml/CAEkJfYPGS1_4JqvpSo0=FM0S1ytB8CEbyreLTtWpR900dUZymw@mail.gmail.com/
Fixes: 5797b1c18919 ("workqueue: Implement system-wide nr_active enforcement for unbound workqueues")
Cc: stable@vger.kernel.org
Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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The default nna (node_nr_active) is used when the pool isn't tied to a
specific NUMA node. This can happen in the following cases:
1. On NUMA, if per-node pwq init failure and the fallback pwq is used.
2. On NUMA, if a pool is configured to span multiple nodes.
3. On single node setups.
5797b1c18919 ("workqueue: Implement system-wide nr_active enforcement for
unbound workqueues") set the default nna->max to min_active because only #1
was being considered. For #2 and #3, using min_active means that the max
concurrency in normal operation is pushed down to min_active which is
currently 8, which can obviously lead to performance issues.
exact value nna->max is set to doesn't really matter. #2 can only happen if
the workqueue is intentionally configured to ignore NUMA boundaries and
there's no good way to distribute max_active in this case. #3 is the default
behavior on single node machines.
Let's set it the default nna->max to max_active. This fixes the artificially
lowered concurrency problem on single node machines and shouldn't hurt
anything for other cases.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Shinichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Fixes: 5797b1c18919 ("workqueue: Implement system-wide nr_active enforcement for unbound workqueues")
Link: https://lore.kernel.org/dm-devel/20240410084531.2134621-1-shinichiro.kawasaki@wdc.com/
Signed-off-by: Tejun Heo <tj@kernel.org>
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With cpu_possible_mask=0-63 and cpu_online_mask=0-7 the following
kernel oops was observed:
smp: Bringing up secondary CPUs ...
smp: Brought up 1 node, 8 CPUs
Unable to handle kernel pointer dereference in virtual kernel address space
Failing address: 0000000000000000 TEID: 0000000000000803
[..]
Call Trace:
arch_vcpu_is_preempted+0x12/0x80
select_idle_sibling+0x42/0x560
select_task_rq_fair+0x29a/0x3b0
try_to_wake_up+0x38e/0x6e0
kick_pool+0xa4/0x198
__queue_work.part.0+0x2bc/0x3a8
call_timer_fn+0x36/0x160
__run_timers+0x1e2/0x328
__run_timer_base+0x5a/0x88
run_timer_softirq+0x40/0x78
__do_softirq+0x118/0x388
irq_exit_rcu+0xc0/0xd8
do_ext_irq+0xae/0x168
ext_int_handler+0xbe/0xf0
psw_idle_exit+0x0/0xc
default_idle_call+0x3c/0x110
do_idle+0xd4/0x158
cpu_startup_entry+0x40/0x48
rest_init+0xc6/0xc8
start_kernel+0x3c4/0x5e0
startup_continue+0x3c/0x50
The crash is caused by calling arch_vcpu_is_preempted() for an offline
CPU. To avoid this, select the cpu with cpumask_any_and_distribute()
to mask __pod_cpumask with cpu_online_mask. In case no cpu is left in
the pool, skip the assignment.
tj: This doesn't fully fix the bug as CPUs can still go down between picking
the target CPU and the wake call. Fixing that likely requires adding
cpu_online() test to either the sched or s390 arch code. However, regardless
of how that is fixed, workqueue shouldn't be picking a CPU which isn't
online as that would result in unpredictable and worse behavior.
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Fixes: 8639ecebc9b1 ("workqueue: Implement non-strict affinity scope for unbound workqueues")
Cc: stable@vger.kernel.org # v6.6+
Signed-off-by: Tejun Heo <tj@kernel.org>
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This commit add missed destroy_work_on_stack() operations for
dead_work.work.
Signed-off-by: Zqiang <qiang.zhang1211@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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While reviewing users of subsys_virtual_register() I noticed that
wq_sysfs_init() ignores the @groups argument. This looks like a
historical artifact as the original wq_subsys only had one attribute to
register.
On the way to building up an @groups argument to pass to
subsys_virtual_register() a few more cleanups fell out:
* Use DEVICE_ATTR_RO() and DEVICE_ATTR_RW() for
cpumask_{isolated,requested} and cpumask respectively. Rename the
@show and @store methods accordingly.
* Co-locate the attribute definition with the methods. This required
moving wq_unbound_cpumask_show down next to wq_unbound_cpumask_store
(renamed to cpumask_show() and cpumask_store())
* Use ATTRIBUTE_GROUPS() to skip some boilerplate declarations
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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It is clearer than open code.
Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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attrs->affn_strict
Allow more pools can be shared when attrs->affn_strict.
Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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dead_work is a stack variable.
Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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on BH work items
Now that work_grab_pending() can always grab the PENDING bit without
sleeping, the only thing that prevents allowing cancel_work_sync() of a BH
work item from an atomic context is the flushing of the in-flight instance.
When we're flushing a BH work item for cancel_work_sync(), we know that the
work item is not queued and must be executing in a BH context, which means
that it's safe to busy-wait for its completion from a non-hardirq atomic
context.
This patch updates __flush_work() so that it busy-waits when flushing a BH
work item for cancel_work_sync(). might_sleep() is pushed from
start_flush_work() to its callers - when operating on a BH work item,
__cancel_work_sync() now enforces !in_hardirq() instead of might_sleep().
This allows cancel_work_sync() and disable_work() to be called from
non-hardirq atomic contexts on BH work items.
v3: In __flush_work(), test WORK_OFFQ_BH to tell whether a work item being
canceled can be busy waited instead of making start_flush_work() return
the pool. (Lai)
v2: Lai pointed out that __flush_work() was accessing pool->flags outside
the RCU critical section protecting the pool pointer. Fix it by testing
and remembering the result inside the RCU critical section.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
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Add an off-queue flag, WORK_OFFQ_BH, that indicates whether the last
workqueue the work item was on was a BH one. This will be used to test
whether a work item is BH in cancel_sync path to implement atomic
cancel_sync'ing for BH work items.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
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cancel[_delayed]_work_sync() guarantees that it can shut down
self-requeueing work items. To achieve that, it grabs and then holds
WORK_STRUCT_PENDING bit set while flushing the currently executing instance.
As the PENDING bit is set, all queueing attempts including the
self-requeueing ones fail and once the currently executing instance is
flushed, the work item should be idle as long as someone else isn't actively
queueing it.
This means that the cancel_work_sync path may hold the PENDING bit set while
flushing the target work item. This isn't a problem for the queueing path -
it can just fail which is the desired effect. It doesn't affect flush. It
doesn't matter to cancel_work either as it can just report that the work
item has successfully canceled. However, if there's another cancel_work_sync
attempt on the work item, it can't simply fail or report success and that
would breach the guarantee that it should provide. cancel_work_sync has to
wait for and grab that PENDING bit and go through the motions.
WORK_OFFQ_CANCELING and wq_cancel_waitq are what implement this
cancel_work_sync to cancel_work_sync wait mechanism. When a work item is
being canceled, WORK_OFFQ_CANCELING is also set on it and other
cancel_work_sync attempts wait on the bit to be cleared using the wait
queue.
While this works, it's an isolated wart which doesn't jive with the rest of
flush and cancel mechanisms and forces enable_work() and disable_work() to
require a sleepable context, which hampers their usability.
Now that a work item can be disabled, we can use that to block queueing
while cancel_work_sync is in progress. Instead of holding PENDING the bit,
it can temporarily disable the work item, flush and then re-enable it as
that'd achieve the same end result of blocking queueings while canceling and
thus enable canceling of self-requeueing work items.
- WORK_OFFQ_CANCELING and the surrounding mechanims are removed.
- work_grab_pending() is now simpler, no longer has to wait for a blocking
operation and thus can be called from any context.
- With work_grab_pending() simplified, no need to use try_to_grab_pending()
directly. All users are converted to use work_grab_pending().
- __cancel_work_sync() is updated to __cancel_work() with
WORK_CANCEL_DISABLE to cancel and plug racing queueing attempts. It then
flushes and re-enables the work item if necessary.
- These changes allow disable_work() and enable_work() to be called from any
context.
v2: Lai pointed out that mod_delayed_work_on() needs to check the disable
count before queueing the delayed work item. Added
clear_pending_if_disabled() call.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
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While (delayed) work items could be flushed and canceled, there was no way
to prevent them from being queued in the future. While this didn't lead to
functional deficiencies, it sometimes required a bit more effort from the
workqueue users to e.g. sequence shutdown steps with more care.
Workqueue is currently in the process of replacing tasklet which does
support disabling and enabling. The feature is used relatively widely to,
for example, temporarily suppress main path while a control plane operation
(reset or config change) is in progress.
To enable easy conversion of tasklet users and as it seems like an inherent
useful feature, this patch implements disabling and enabling of work items.
- A work item carries 16bit disable count in work->data while not queued.
The access to the count is synchronized by the PENDING bit like all other
parts of work->data.
- If the count is non-zero, the work item cannot be queued. Any attempt to
queue the work item fails and returns %false.
- disable_work[_sync](), enable_work(), disable_delayed_work[_sync]() and
enable_delayed_work() are added.
v3: enable_work() was using local_irq_enable() instead of
local_irq_restore() to undo IRQ-disable by work_grab_pending(). This is
awkward now and will become incorrect as enable_work() will later be
used from IRQ context too. (Lai)
v2: Lai noticed that queue_work_node() wasn't checking the disable count.
Fixed. queue_rcu_work() is updated to trigger warning if the inner work
item is disabled.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
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The cancel[_sync] paths acquire and release WORK_STRUCT_PENDING, and
manipulate WORK_OFFQ_CANCELING. However, they assume that all the OFFQ bit
values except for the pool ID are statically known and don't preserve them,
which is not wrong in the current code as the pool ID and CANCELING are the
only information carried. However, the planned disable/enable support will
add more fields and need them to be preserved.
This patch updates work data handling so that only the bits which need
updating are updated.
- struct work_offq_data is added along with work_offqd_unpack() and
work_offqd_pack_flags() to help manipulating multiple fields contained in
work->data. Note that the helpers look a bit silly right now as there
isn't that much to pack. The next patch will add more.
- mark_work_canceling() which is used only by __cancel_work_sync() is
replaced by open-coded usage of work_offq_data and
set_work_pool_and_keep_pending() in __cancel_work_sync().
- __cancel_work[_sync]() uses offq_data helpers to preserve other OFFQ bits
when clearing WORK_STRUCT_PENDING and WORK_OFFQ_CANCELING at the end.
- This removes all users of get_work_pool_id() which is dropped. Note that
get_work_pool_id() could handle both WORK_STRUCT_PWQ and !WORK_STRUCT_PWQ
cases; however, it was only being called after try_to_grab_pending()
succeeded, in which case WORK_STRUCT_PWQ is never set and thus it's safe
to use work_offqd_unpack() instead.
No behavior changes intended.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
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Signed-off-by: Ingo Molnar <mingo@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core
Pull driver core updates from Greg KH:
"Here is the "big" set of driver core and kernfs changes for 6.9-rc1.
Nothing all that crazy here, just some good updates that include:
- automatic attribute group hiding from Dan Williams (he fixed up my
horrible attempt at doing this.)
- kobject lock contention fixes from Eric Dumazet
- driver core cleanups from Andy
- kernfs rcu work from Tejun
- fw_devlink changes to resolve some reported issues
- other minor changes, all details in the shortlog
All of these have been in linux-next for a long time with no reported
issues"
* tag 'driver-core-6.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core: (28 commits)
device: core: Log warning for devices pending deferred probe on timeout
driver: core: Use dev_* instead of pr_* so device metadata is added
driver: core: Log probe failure as error and with device metadata
of: property: fw_devlink: Add support for "post-init-providers" property
driver core: Add FWLINK_FLAG_IGNORE to completely ignore a fwnode link
driver core: Adds flags param to fwnode_link_add()
debugfs: fix wait/cancellation handling during remove
device property: Don't use "proxy" headers
device property: Move enum dev_dma_attr to fwnode.h
driver core: Move fw_devlink stuff to where it belongs
driver core: Drop unneeded 'extern' keyword in fwnode.h
firmware_loader: Suppress warning on FW_OPT_NO_WARN flag
sysfs:Addresses documentation in sysfs_merge_group and sysfs_unmerge_group.
firmware_loader: introduce __free() cleanup hanler
platform-msi: Remove usage of the deprecated ida_simple_xx() API
sysfs: Introduce DEFINE_SIMPLE_SYSFS_GROUP_VISIBLE()
sysfs: Document new "group visible" helpers
sysfs: Fix crash on empty group attributes array
sysfs: Introduce a mechanism to hide static attribute_groups
sysfs: Introduce a mechanism to hide static attribute_groups
...
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- Standardize on prefixing scheduler-internal functions defined
in <linux/sched.h> with sched_*() prefix. scheduler_tick() was
the only function using the scheduler_ prefix. Harmonize it.
- The other reason to rename it is the NOHZ scheduler tick
handling functions are already named sched_tick_*().
Make the 'git grep sched_tick' more meaningful.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Valentin Schneider <vschneid@redhat.com>
Reviewed-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Link: https://lore.kernel.org/r/20240308111819.1101550-3-mingo@kernel.org
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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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Boqun pointed out that workqueues aren't handling BH work items on offlined
CPUs. Unlike tasklet which transfers out the pending tasks from
CPUHP_SOFTIRQ_DEAD, BH workqueue would just leave them pending which is
problematic. Note that this behavior is specific to BH workqueues as the
non-BH per-CPU workers just become unbound when the CPU goes offline.
This patch fixes the issue by draining the pending BH work items from an
offlined CPU from CPUHP_SOFTIRQ_DEAD. Because work items carry more context,
it's not as easy to transfer the pending work items from one pool to
another. Instead, run BH work items which execute the offlined pools on an
online CPU.
Note that this assumes that no further BH work items will be queued on the
offlined CPUs. This assumption is shared with tasklet and should be fine for
conversions. However, this issue also exists for per-CPU workqueues which
will just keep executing work items queued after CPU offline on unbound
workers and workqueue should reject per-CPU and BH work items queued on
offline CPUs. This will be addressed separately later.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-and-reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Link: http://lkml.kernel.org/r/Zdvw0HdSXcU3JZ4g@boqun-archlinux
|
|
When CONFIG_WQ_CPU_INTENSIVE_REPORT is set, the kernel will report
the work functions which violate the intensive_threshold_us repeatedly.
And now, only when the violate times exceed 4 and is a power of 2,
the kernel warning could be triggered.
However, sometimes, even if a long work execution time occurs only once,
it may cause other work to be delayed for a long time. This may also
cause some problems sometimes.
In order to freely control the threshold of warninging, a boot argument
is added so that the user can control the warning threshold to be printed.
At the same time, keep the exponential backoff to prevent reporting too much.
By default, the warning threshold is 4.
tj: Updated kernel-parameters.txt description.
Signed-off-by: Xuewen Yan <xuewen.yan@unisoc.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
|
|
The implementation of the NOHZ pull at expiry model will change the timer
bases per CPU. Timers, that have to expire on a specific CPU, require the
TIMER_PINNED flag. If the CPU doesn't matter, the TIMER_PINNED flag must be
dropped. This is required for call sites which use the timer alternately as
pinned and not pinned timer like workqueues do.
Therefore use add_timer_global() in __queue_delayed_work() for non-bound
delayed work to make sure the TIMER_PINNED flag is dropped.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20240221090548.36600-7-anna-maria@linutronix.de
|
|
- set_work_data() takes a separate @flags argument but just ORs it to @data.
This is more confusing than helpful. Just take @data.
- Use the name @flags consistently and add the parameter to
set_work_pool_and_{keep|clear}_pending(). This will be used by the planned
disable/enable support.
No functional changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
|
|
clear_work_data() is only used in one place and immediately followed by
smp_mb(), making it equivalent to set_work_pool_and_clear_pending() w/
WORK_OFFQ_POOL_NONE for @pool_id. Drop it. No functional changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
|
|
The planned disable/enable support will need the same logic. Let's factor it
out. No functional changes.
v2: Update function comment to include @irq_flags.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
|
|
The bits of work->data are used for a few different purposes. How the bits
are used is determined by enum work_bits. The planned disable/enable support
will add another use, so let's clean it up a bit in preparation.
- Let WORK_STRUCT_*_BIT's values be determined by enum definition order.
- Deliminate different bit sections the same way using SHIFT and BITS
values.
- Rename __WORK_OFFQ_CANCELING to WORK_OFFQ_CANCELING_BIT for consistency.
- Introduce WORK_STRUCT_PWQ_SHIFT and replace WORK_STRUCT_FLAG_MASK and
WORK_STRUCT_WQ_DATA_MASK with WQ_STRUCT_PWQ_MASK for clarity.
- Improve documentation.
No functional changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
|
|
The cancel path used bool @is_dwork to distinguish canceling a regular work
and a delayed one. The planned disable/enable support will need passing
around another flag in the code path. As passing them around with bools will
be confusing, let's introduce named flags to pass around in the cancel path.
WORK_CANCEL_DELAYED replaces @is_dwork. No functional changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
|
|
Using the generic term `flags` for irq flags is conventional but can be
confusing as there's quite a bit of code dealing with work flags which
involves some subtleties. Let's use a more explicit name `irq_flags` for
local irq flags. No functional changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
|
|
They are currently a bit disorganized with flush and cancel functions mixed.
Reoranize them so that flush functions come first, cancel next and
cancel_sync last. This way, we won't have to add prototypes for internal
functions for the planned disable/enable support.
This is pure code reorganization. No functional changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
|
|
__cancel_work_timer() is used to implement cancel_work_sync() and
cancel_delayed_work_sync(), similarly to how __cancel_work() is used to
implement cancel_work() and cancel_delayed_work(). ie. The _timer part of
the name is a complete misnomer. The difference from __cancel_work() is the
fact that it syncs against work item execution not whether it handles timers
or not.
Let's rename it to less confusing __cancel_work_sync(). No functional
change.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
|
|
The different flavors of RCU read critical sections have been unified. Let's
update the locking assertion macros accordingly to avoid requiring
unnecessary explicit rcu_read_[un]lock() calls.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
|
|
Reorder some global declarations and adjust comments and whitespaces for
clarity and consistency. No functional changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
|
|
We need the driver core changes in here as well.
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
|
|
2f34d7337d98 ("workqueue: Fix queue_work_on() with BH workqueues") added
irq_work usage to workqueue; however, it turns out irq_work is actually
optional and the change breaks build on configuration which doesn't have
CONFIG_IRQ_WORK enabled.
Fix build by making workqueue use irq_work only when CONFIG_SMP and enabling
CONFIG_IRQ_WORK when CONFIG_SMP is set. It's reasonable to argue that it may
be better to just always enable it. However, this still saves a small bit of
memory for tiny UP configs and also the least amount of change, so, for now,
let's keep it conditional.
Verified to do the right thing for x86_64 allnoconfig and defconfig, and
aarch64 allnoconfig, allnoconfig + prink disable (SMP but nothing selects
IRQ_WORK) and a modified aarch64 Kconfig where !SMP and nothing selects
IRQ_WORK.
v2: `depends on SMP` leads to Kconfig warnings when CONFIG_IRQ_WORK is
selected by something else when !CONFIG_SMP. Use `def_bool y if SMP`
instead.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Tested-by: Anders Roxell <anders.roxell@linaro.org>
Fixes: 2f34d7337d98 ("workqueue: Fix queue_work_on() with BH workqueues")
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
|
|
When queue_work_on() is used to queue a BH work item on a remote CPU, the
work item is queued on that CPU but kick_pool() raises softirq on the local
CPU. This leads to stalls as the work item won't be executed until something
else on the remote CPU schedules a BH work item or tasklet locally.
Fix it by bouncing raising softirq to the target CPU using per-cpu irq_work.
Signed-off-by: Tejun Heo <tj@kernel.org>
Fixes: 4cb1ef64609f ("workqueue: Implement BH workqueues to eventually replace tasklets")
|
|
Since 5797b1c18919 ("workqueue: Implement system-wide nr_active enforcement
for unbound workqueues"), unbound workqueues have separate min_active which
sets the number of interdependent work items that can be handled. This value
is currently initialized to WQ_DFL_MIN_ACTIVE which is 8. This isn't high
enough for some users, let's add an interface to adjust the setting.
Signed-off-by: Tejun Heo <tj@kernel.org>
|
|
Fix the kernel-doc comment of the unplug_oldest_pwq() function to enable
proper processing and formatting of the embedded ASCII diagram.
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
|
|
Commit 85f0ab43f9de ("kernel/workqueue: Bind rescuer to unbound
cpumask for WQ_UNBOUND") modified init_rescuer() to bind rescuer of
an unbound workqueue to the cpumask in wq->unbound_attrs. However
unbound_attrs->cpumask's of all workqueues are initialized to
cpu_possible_mask and will only be changed if it has the WQ_SYSFS flag
to expose a cpumask sysfs file to be written by users. So this patch
doesn't achieve what it is intended to do.
If an unbound workqueue is created after wq_unbound_cpumask is modified
and there is no more unbound cpumask update after that, the unbound
rescuer will be bound to all CPUs unless the workqueue is created
with the WQ_SYSFS flag and a user explicitly modified its cpumask
sysfs file. Fix this problem by binding directly to wq_unbound_cpumask
in init_rescuer().
Fixes: 85f0ab43f9de ("kernel/workqueue: Bind rescuer to unbound cpumask for WQ_UNBOUND")
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
|
|
When workqueue cpumask changes are committed the associated rescuer (if
one exists) affinity is not touched and this might be a problem down the
line for isolated setups.
Make sure rescuers affinity is updated every time a workqueue cpumask
changes, so that rescuers can't break isolation.
[longman: set_cpus_allowed_ptr() will block until the designated task
is enqueued on an allowed CPU, no wake_up_process() needed. Also use
the unbound_effective_cpumask() helper as suggested by Tejun.]
Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
|
|
Ordered workqueues does not currently follow changes made to the
global unbound cpumask because per-pool workqueue changes may break
the ordering guarantee. IOW, a work function in an ordered workqueue
may run on an isolated CPU.
This patch enables ordered workqueues to follow changes made to the
global unbound cpumask by temporaily plug or suspend the newly allocated
pool_workqueue from executing newly queued work items until the old
pwq has been properly drained. For ordered workqueues, there should
only be one pwq that is unplugged, the rests should be plugged.
This enables ordered workqueues to follow the unbound cpumask changes
like other unbound workqueues at the expense of some delay in execution
of work functions during the transition period.
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
|
|
Add a new pwq into the tail of wq->pwqs so that pwq iteration will
start from the oldest pwq to the newest. This ordering will facilitate
the inclusion of ordered workqueues in a wq_unbound_cpumask update.
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
|
|
Now that the driver core can properly handle constant struct bus_type,
move the wq_subsys variable to be a constant structure as well,
placing it into read-only memory which can not be modified at runtime.
Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: "Ricardo B. Marliere" <ricardo@marliere.net>
Cc: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20240206-bus_cleanup-workqueue-v1-1-72b10d282d58@marliere.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
|
|
The for-6.8-fixes commit ae9cc8956944 ("Revert "workqueue: Override implicit
ordered attribute in workqueue_apply_unbound_cpumask()") also fixes build for
Signed-off-by: Tejun Heo <tj@kernel.org>
|
|
workqueue_apply_unbound_cpumask()"
This reverts commit ca10d851b9ad0338c19e8e3089e24d565ebfffd7.
The commit allowed workqueue_apply_unbound_cpumask() to clear __WQ_ORDERED
on now removed implicitly ordered workqueues. This was incorrect in that
system-wide config change shouldn't break ordering properties of all
workqueues. The reason why apply_workqueue_attrs() path was allowed to do so
was because it was targeting the specific workqueue - either the workqueue
had WQ_SYSFS set or the workqueue user specifically tried to change
max_active, both of which indicate that the workqueue doesn't need to be
ordered.
The implicitly ordered workqueue promotion was removed by the previous
commit 3bc1e711c26b ("workqueue: Don't implicitly make UNBOUND workqueues w/
@max_active==1 ordered"). However, it didn't update this path and broke
build. Let's revert the commit which was incorrect in the first place which
also fixes build.
Signed-off-by: Tejun Heo <tj@kernel.org>
Fixes: 3bc1e711c26b ("workqueue: Don't implicitly make UNBOUND workqueues w/ @max_active==1 ordered")
Fixes: ca10d851b9ad ("workqueue: Override implicit ordered attribute in workqueue_apply_unbound_cpumask()")
Cc: stable@vger.kernel.org # v6.6+
Signed-off-by: Tejun Heo <tj@kernel.org>
|
|
5c0338c68706 ("workqueue: restore WQ_UNBOUND/max_active==1 to be ordered")
automoatically promoted UNBOUND workqueues w/ @max_active==1 to ordered
workqueues because UNBOUND workqueues w/ @max_active==1 used to be the way
to create ordered workqueues and the new NUMA support broke it. These
problems can be subtle and the fact that they can only trigger on NUMA
machines made them even more difficult to debug.
However, overloading the UNBOUND allocation interface this way creates other
issues. It's difficult to tell whether a given workqueue actually needs to
be ordered and users that legitimately want a min concurrency level wq
unexpectedly gets an ordered one instead. With planned UNBOUND workqueue
udpates to improve execution locality and more prevalence of chiplet designs
which can benefit from such improvements, this isn't a state we wanna be in
forever.
There aren't that many UNBOUND w/ @max_active==1 users in the tree and the
preceding patches audited all and converted them to
alloc_ordered_workqueue() as appropriate. This patch removes the implicit
promotion of UNBOUND w/ @max_active==1 workqueues to ordered ones.
v2: v1 patch incorrectly dropped !list_empty(&wq->pwqs) condition in
apply_workqueue_attrs_locked() which spuriously triggers WARNING and
fails workqueue creation. Fix it.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: kernel test robot <oliver.sang@intel.com>
Link: https://lore.kernel.org/oe-lkp/202304251050.45a5df1f-oliver.sang@intel.com
|
|
Skip updating workqueues with __WQ_DESTROYING bit set when updating
global unbound cpumask to avoid unnecessary work and other complications.
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
|
|
There should be three, fix it.
Signed-off-by: Wang Jinchao <wangjinchao@xfusion.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
|
|
This reverts commit d412ace11144aa2bf692c7cf9778351efc15c827. This leads to
build failures as it depends on a driver-core commit 32f78abe59c7 ("driver
core: bus: constantify subsys_register() calls"). Let's drop it from wq tree
and route it through driver-core tree.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202402051505.kM9Rr3CJ-lkp@intel.com/
|
|
The only generic interface to execute asynchronously in the BH context is
tasklet; however, it's marked deprecated and has some design flaws such as
the execution code accessing the tasklet item after the execution is
complete which can lead to subtle use-after-free in certain usage scenarios
and less-developed flush and cancel mechanisms.
This patch implements BH workqueues which share the same semantics and
features of regular workqueues but execute their work items in the softirq
context. As there is always only one BH execution context per CPU, none of
the concurrency management mechanisms applies and a BH workqueue can be
thought of as a convenience wrapper around softirq.
Except for the inability to sleep while executing and lack of max_active
adjustments, BH workqueues and work items should behave the same as regular
workqueues and work items.
Currently, the execution is hooked to tasklet[_hi]. However, the goal is to
convert all tasklet users over to BH workqueues. Once the conversion is
complete, tasklet can be removed and BH workqueues can directly take over
the tasklet softirqs.
system_bh[_highpri]_wq are added. As queue-wide flushing doesn't exist in
tasklet, all existing tasklet users should be able to use the system BH
workqueues without creating their own workqueues.
v3: - Add missing interrupt.h include.
v2: - Instead of using tasklets, hook directly into its softirq action
functions - tasklet[_hi]_action(). This is slightly cheaper and closer
to the eventual code structure we want to arrive at. Suggested by Lai.
- Lai also pointed out several places which need NULL worker->task
handling or can use clarification. Updated.
Signed-off-by: Tejun Heo <tj@kernel.org>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/CAHk-=wjDW53w4-YcSmgKC5RruiRLHmJ1sXeYdp_ZgVoBw=5byA@mail.gmail.com
Tested-by: Allen Pais <allen.lkml@gmail.com>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
|
|
Factor out init_cpu_worker_pool() from workqueue_init_early(). This is pure
reorganization in preparation of BH workqueue support.
Signed-off-by: Tejun Heo <tj@kernel.org>
Tested-by: Allen Pais <allen.lkml@gmail.com>
|
|
These changes are in preparation of BH workqueue which will execute work
items from BH context.
- Update lock and RCU depth checks in process_one_work() so that it
remembers and checks against the starting depths and prints out the depth
changes.
- Factor out lockdep annotations in the flush paths into
touch_{wq|work}_lockdep_map(). The work->lockdep_map touching is moved
from __flush_work() to its callee - start_flush_work(). This brings it
closer to the wq counterpart and will allow testing the associated wq's
flags which will be needed to support BH workqueues. This is not expected
to cause any functional changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Tested-by: Allen Pais <allen.lkml@gmail.com>
|
|
Now that the driver core can properly handle constant struct bus_type,
move the wq_subsys variable to be a constant structure as well,
placing it into read-only memory which can not be modified at runtime.
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Suggested-and-reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ricardo B. Marliere <ricardo@marliere.net>
Signed-off-by: Tejun Heo <tj@kernel.org>
|
|
dd6c3c544126 ("workqueue: Move pwq_dec_nr_in_flight() to the end of work
item handling") relocated pwq_dec_nr_in_flight() after
set_work_pool_and_keep_pending(). However, the latter destroys information
contained in work->data that's needed by pwq_dec_nr_in_flight() including
the flush color. With flush color destroyed, flush_workqueue() can stall
easily when mixed with cancel_work*() usages.
This is easily triggered by running xfstests generic/001 test on xfs:
INFO: task umount:6305 blocked for more than 122 seconds.
...
task:umount state:D stack:13008 pid:6305 tgid:6305 ppid:6301 flags:0x00004000
Call Trace:
<TASK>
__schedule+0x2f6/0xa20
schedule+0x36/0xb0
schedule_timeout+0x20b/0x280
wait_for_completion+0x8a/0x140
__flush_workqueue+0x11a/0x3b0
xfs_inodegc_flush+0x24/0xf0
xfs_unmountfs+0x14/0x180
xfs_fs_put_super+0x3d/0x90
generic_shutdown_super+0x7c/0x160
kill_block_super+0x1b/0x40
xfs_kill_sb+0x12/0x30
deactivate_locked_super+0x35/0x90
deactivate_super+0x42/0x50
cleanup_mnt+0x109/0x170
__cleanup_mnt+0x12/0x20
task_work_run+0x60/0x90
syscall_exit_to_user_mode+0x146/0x150
do_syscall_64+0x5d/0x110
entry_SYSCALL_64_after_hwframe+0x6c/0x74
Fix it by stashing work_data before calling set_work_pool_and_keep_pending()
and using the stashed value for pwq_dec_nr_in_flight().
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Chandan Babu R <chandanbabu@kernel.org>
Link: http://lkml.kernel.org/r/87o7cxeehy.fsf@debian-BULLSEYE-live-builder-AMD64
Fixes: dd6c3c544126 ("workqueue: Move pwq_dec_nr_in_flight() to the end of work item handling")
|
|
System workqueues are allocated early during boot from
workqueue_init_early(). While allocating unbound workqueues,
wq_update_node_max_active() is invoked from apply_workqueue_attrs() and
accesses NUMA topology to initialize wq->node_nr_active[].max.
However, topology information may not be set up at this point.
wq_update_node_max_active() is explicitly invoked from
workqueue_init_topology() later when topology information is known to be
available.
This doesn't seem to crash anything but it's doing useless work with dubious
data. Let's skip the premature and duplicate node_max_active updates by
initializing the field to WQ_DFL_MIN_ACTIVE on allocation and making
wq_update_node_max_active() noop until workqueue_init_topology().
Signed-off-by: Tejun Heo <tj@kernel.org>
---
kernel/workqueue.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 9221a4c57ae1..a65081ec6780 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -386,6 +386,8 @@ static const char *wq_affn_names[WQ_AFFN_NR_TYPES] = {
[WQ_AFFN_SYSTEM] = "system",
};
+static bool wq_topo_initialized = false;
+
/*
* Per-cpu work items which run for longer than the following threshold are
* automatically considered CPU intensive and excluded from concurrency
@@ -1510,6 +1512,9 @@ static void wq_update_node_max_active(struct workqueue_struct *wq, int off_cpu)
lockdep_assert_held(&wq->mutex);
+ if (!wq_topo_initialized)
+ return;
+
if (!cpumask_test_cpu(off_cpu, effective))
off_cpu = -1;
@@ -4356,6 +4361,7 @@ static void free_node_nr_active(struct wq_node_nr_active **nna_ar)
static void init_node_nr_active(struct wq_node_nr_active *nna)
{
+ nna->max = WQ_DFL_MIN_ACTIVE;
atomic_set(&nna->nr, 0);
raw_spin_lock_init(&nna->lock);
INIT_LIST_HEAD(&nna->pending_pwqs);
@@ -7400,6 +7406,8 @@ void __init workqueue_init_topology(void)
init_pod_type(&wq_pod_types[WQ_AFFN_CACHE], cpus_share_cache);
init_pod_type(&wq_pod_types[WQ_AFFN_NUMA], cpus_share_numa);
+ wq_topo_initialized = true;
+
mutex_lock(&wq_pool_mutex);
/*
|
|
wq_update_node_max_active()
For wq_update_node_max_active(), @off_cpu of -1 indicates that no CPU is
going down. The function was incorrectly calling cpumask_test_cpu() with -1
CPU leading to oopses like the following on some archs:
Unable to handle kernel paging request at virtual address ffff0002100296e0
..
pc : wq_update_node_max_active+0x50/0x1fc
lr : wq_update_node_max_active+0x1f0/0x1fc
...
Call trace:
wq_update_node_max_active+0x50/0x1fc
apply_wqattrs_commit+0xf0/0x114
apply_workqueue_attrs_locked+0x58/0xa0
alloc_workqueue+0x5ac/0x774
workqueue_init_early+0x460/0x540
start_kernel+0x258/0x684
__primary_switched+0xb8/0xc0
Code: 9100a273 35000d01 53067f00 d0016dc1 (f8607a60)
---[ end trace 0000000000000000 ]---
Kernel panic - not syncing: Attempted to kill the idle task!
---[ end Kernel panic - not syncing: Attempted to kill the idle task! ]---
Fix it.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reported-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Link: http://lkml.kernel.org/r/91eacde0-df99-4d5c-a980-91046f66e612@samsung.com
Fixes: 5797b1c18919 ("workqueue: Implement system-wide nr_active enforcement for unbound workqueues")
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When __queue_delayed_work() is called, it chooses a cpu for handling the
timer interrupt. As of today, it will pick either the cpu passed as
parameter or the last cpu used for this.
This is not good if a system does use CPU isolation, because it can take
away some valuable cpu time to:
1 - deal with the timer interrupt,
2 - schedule-out the desired task,
3 - queue work on a random workqueue, and
4 - schedule the desired task back to the cpu.
So to fix this, during __queue_delayed_work(), if cpu isolation is in
place, pick a random non-isolated cpu to handle the timer interrupt.
As an optimization, if the current cpu is not isolated, use it instead
of looking for another candidate.
Signed-off-by: Leonardo Bras <leobras@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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A pool_workqueue (pwq) represents the connection between a workqueue and a
worker_pool. One of the roles that a pwq plays is enforcement of the
max_active concurrency limit. Before 636b927eba5b ("workqueue: Make unbound
workqueues to use per-cpu pool_workqueues"), there was one pwq per each CPU
for per-cpu workqueues and per each NUMA node for unbound workqueues, which
was a natural result of per-cpu workqueues being served by per-cpu pools and
unbound by per-NUMA pools.
In terms of max_active enforcement, this was, while not perfect, workable.
For per-cpu workqueues, it was fine. For unbound, it wasn't great in that
NUMA machines would get max_active that's multiplied by the number of nodes
but didn't cause huge problems because NUMA machines are relatively rare and
the node count is usually pretty low.
However, cache layouts are more complex now and sharing a worker pool across
a whole node didn't really work well for unbound workqueues. Thus, a series
of commits culminating on 8639ecebc9b1 ("workqueue: Make unbound workqueues
to use per-cpu pool_workqueues") implemented more flexible affinity
mechanism for unbound workqueues which enables using e.g. last-level-cache
aligned pools. In the process, 636b927eba5b ("workqueue: Make unbound
workqueues to use per-cpu pool_workqueues") made unbound workqueues use
per-cpu pwqs like per-cpu workqueues.
While the change was necessary to enable more flexible affinity scopes, this
came with the side effect of blowing up the effective max_active for unbound
workqueues. Before, the effective max_active for unbound workqueues was
multiplied by the number of nodes. After, by the number of CPUs.
636b927eba5b ("workqueue: Make unbound workqueues to use per-cpu
pool_workqueues") claims that this should generally be okay. It is okay for
users which self-regulates concurrency level which are the vast majority;
however, there are enough use cases which actually depend on max_active to
prevent the level of concurrency from going bonkers including several IO
handling workqueues that can issue a work item for each in-flight IO. With
targeted benchmarks, the misbehavior can easily be exposed as reported in
http://lkml.kernel.org/r/dbu6wiwu3sdhmhikb2w6lns7b27gbobfavhjj57kwi2quafgwl@htjcc5oikcr3.
Unfortunately, there is no way to express what these use cases need using
per-cpu max_active. A CPU may issue most of in-flight IOs, so we don't want
to set max_active too low but as soon as we increase max_active a bit, we
can end up with unreasonable number of in-flight work items when many CPUs
issue IOs at the same time. ie. The acceptable lowest max_active is higher
than the acceptable highest max_active.
Ideally, max_active for an unbound workqueue should be system-wide so that
the users can regulate the total level of concurrency regardless of node and
cache layout. The reasons workqueue hasn't implemented that yet are:
- One max_active enforcement decouples from pool boundaires, chaining
execution after a work item finishes requires inter-pool operations which
would require lock dancing, which is nasty.
- Sharing a single nr_active count across the whole system can be pretty
expensive on NUMA machines.
- Per-pwq enforcement had been more or less okay while we were using
per-node pools.
It looks like we no longer can avoid decoupling max_active enforcement from
pool boundaries. This patch implements system-wide nr_active mechanism with
the following design characteristics:
- To avoid sharing a single counter across multiple nodes, the configured
max_active is split across nodes according to the proportion of each
workqueue's online effective CPUs per node. e.g. A node with twice more
online effective CPUs will get twice higher portion of max_active.
- Workqueue used to be able to process a chain of interdependent work items
which is as long as max_active. We can't do this anymore as max_active is
distributed across the nodes. Instead, a new parameter min_active is
introduced which determines the minimum level of concurrency within a node
regardless of how max_active distribution comes out to be.
It is set to the smaller of max_active and WQ_DFL_MIN_ACTIVE which is 8.
This can lead to higher effective max_weight than configured and also
deadlocks if a workqueue was depending on being able to handle chains of
interdependent work items that are longer than 8.
I believe these should be fine given that the number of CPUs in each NUMA
node is usually higher than 8 and work item chain longer than 8 is pretty
unlikely. However, if these assumptions turn out to be wrong, we'll need
to add an interface to adjust min_active.
- Each unbound wq has an array of struct wq_node_nr_active which tracks
per-node nr_active. When its pwq wants to run a work item, it has to
obtain the matching node's nr_active. If over the node's max_active, the
pwq is queued on wq_node_nr_active->pending_pwqs. As work items finish,
the completion path round-robins the pending pwqs activating the first
inactive work item of each, which involves some pool lock dancing and
kicking other pools. It's not the simplest code but doesn't look too bad.
v4: - wq_adjust_max_active() updated to invoke wq_update_node_max_active().
- wq_adjust_max_active() is now protected by wq->mutex instead of
wq_pool_mutex.
v3: - wq_node_max_active() used to calculate per-node max_active on the fly
based on system-wide CPU online states. Lai pointed out that this can
lead to skewed distributions for workqueues with restricted cpumasks.
Update the max_active distribution to use per-workqueue effective
online CPU counts instead of system-wide and cache the calculation
results in node_nr_active->max.
v2: - wq->min/max_active now uses WRITE/READ_ONCE() as suggested by Lai.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Naohiro Aota <Naohiro.Aota@wdc.com>
Link: http://lkml.kernel.org/r/dbu6wiwu3sdhmhikb2w6lns7b27gbobfavhjj57kwi2quafgwl@htjcc5oikcr3
Fixes: 636b927eba5b ("workqueue: Make unbound workqueues to use per-cpu pool_workqueues")
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
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Currently, for both percpu and unbound workqueues, max_active applies
per-cpu, which is a recent change for unbound workqueues. The change for
unbound workqueues was a significant departure from the previous behavior of
per-node application. It made some use cases create undesirable number of
concurrent work items and left no good way of fixing them. To address the
problem, workqueue is implementing a NUMA node segmented global nr_active
mechanism, which will be explained further in the next patch.
As a preparation, this patch introduces struct wq_node_nr_active. It's a
data structured allocated for each workqueue and NUMA node pair and
currently only tracks the workqueue's number of active work items on the
node. This is split out from the next patch to make it easier to understand
and review.
Note that there is an extra wq_node_nr_active allocated for the invalid node
nr_node_ids which is used to track nr_active for pools which don't have NUMA
node associated such as the default fallback system-wide pool.
This doesn't cause any behavior changes visible to userland yet. The next
patch will expand to implement the control mechanism on top.
v4: - Fixed out-of-bound access when freeing per-cpu workqueues.
v3: - Use flexible array for wq->node_nr_active as suggested by Lai.
v2: - wq->max_active now uses WRITE/READ_ONCE() as suggested by Lai.
- Lai pointed out that pwq_tryinc_nr_active() incorrectly dropped
pwq->max_active check. Restored. As the next patch replaces the
max_active enforcement mechanism, this doesn't change the end result.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
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The planned shared nr_active handling for unbound workqueues will make
pwq_dec_nr_active() sometimes drop the pool lock temporarily to acquire
other pool locks, which is necessary as retirement of an nr_active count
from one pool may need kick off an inactive work item in another pool.
This patch moves pwq_dec_nr_in_flight() call in try_to_grab_pending() to the
end of work item handling so that work item state changes stay atomic.
process_one_work() which is the other user of pwq_dec_nr_in_flight() already
calls it at the end of work item handling. Comments are added to both call
sites and pwq_dec_nr_in_flight().
This shouldn't cause any behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
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wq->cpu_pwq is RCU protected but wq->dfl_pwq isn't. This is okay because
currently wq->dfl_pwq is used only accessed to install it into wq->cpu_pwq
which doesn't require RCU access. However, we want to be able to access
wq->dfl_pwq under RCU in the future to access its __pod_cpumask and the code
can be made easier to read by making the two pwq fields behave in the same
way.
- Make wq->dfl_pwq RCU protected.
- Add unbound_pwq_slot() and unbound_pwq() which can access both ->dfl_pwq
and ->cpu_pwq. The former returns the double pointer that can be used
access and update the pwqs. The latter performs locking check and
dereferences the double pointer.
- pwq accesses and updates are converted to use unbound_pwq[_slot]().
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
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wq_adjust_max_active() needs to activate work items after max_active is
increased. Previously, it did that by visiting each pwq once activating all
that could be activated. While this makes sense with per-pwq nr_active,
nr_active will be shared across multiple pwqs for unbound wqs. Then, we'd
want to round-robin through pwqs to be fairer.
In preparation, this patch makes wq_adjust_max_active() round-robin pwqs
while activating. While the activation ordering changes, this shouldn't
cause user-noticeable behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
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__queue_work(), pwq_dec_nr_in_flight() and wq_adjust_max_active() were
open-coding nr_active handling, which is fine given that the operations are
trivial. However, the planned unbound nr_active update will make them more
complicated, so let's move them into helpers.
- pwq_tryinc_nr_active() is added. It increments nr_active if under
max_active limit and return a boolean indicating whether inc was
successful. Note that the function is structured to accommodate future
changes. __queue_work() is updated to use the new helper.
- pwq_activate_first_inactive() is updated to use pwq_tryinc_nr_active() and
thus no longer assumes that nr_active is under max_active and returns a
boolean to indicate whether a work item has been activated.
- wq_adjust_max_active() no longer tests directly whether a work item can be
activated. Instead, it's updated to use the return value of
pwq_activate_first_inactive() to tell whether a work item has been
activated.
- nr_active decrement and activating the first inactive work item is
factored into pwq_dec_nr_active().
v3: - WARN_ON_ONCE(!WORK_STRUCT_INACTIVE) added to __pwq_activate_work() as
now we're calling the function unconditionally from
pwq_activate_first_inactive().
v2: - wq->max_active now uses WRITE/READ_ONCE() as suggested by Lai.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
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To prepare for unbound nr_active handling improvements, move work activation
part of pwq_activate_inactive_work() into __pwq_activate_work() and add
pwq_activate_work() which tests WORK_STRUCT_INACTIVE and updates nr_active.
pwq_activate_first_inactive() and try_to_grab_pending() are updated to use
pwq_activate_work(). The latter conversion is functionally identical. For
the former, this conversion adds an unnecessary WORK_STRUCT_INACTIVE
testing. This is temporary and will be removed by the next patch.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
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"!pwq->nr_active && list_empty(&pwq->inactive_works)" test is repeated
multiple times. Let's factor it out into pwq_is_empty().
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
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max_active is a workqueue-wide setting and the configured value is stored in
wq->saved_max_active; however, the effective value was stored in
pwq->max_active. While this is harmless, it makes max_active update process
more complicated and gets in the way of the planned max_active semantic
updates for unbound workqueues.
This patches moves pwq->max_active to wq->max_active. This simplifies the
code and makes freezing and noop max_active updates cheaper too. No
user-visible behavior change is intended.
As wq->max_active is updated while holding wq mutex but read without any
locking, it now uses WRITE/READ_ONCE(). A new locking locking rule WO is
added for it.
v2: wq->max_active now uses WRITE/READ_ONCE() as suggested by Lai.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
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workqueue is collecting different sorts of enums into a single unnamed enum
type which can increase confusion around enum width. Also, unnamed enums
can't be accessed from BPF. Let's break up enum definitions according to
their purposes and give them type names.
Signed-off-by: Tejun Heo <tj@kernel.org>
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After creating a new worker, create_worker() is calling kick_pool() to wake
up the new worker task. However, as kick_pool() doesn't do anything if there
is no work pending, it also calls wake_up_process() explicitly. There's no
reason to call kick_pool() at all. wake_up_process() is enough by itself.
Drop the unnecessary kick_pool() call.
Signed-off-by: Tejun Heo <tj@kernel.org>
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Since we have set the WQ_NAME_LEN to 32, decrease the name of
events_freezable_power_efficient so that it does not trip the name length
warning when the workqueue is created.
Signed-off-by: Audra Mitchell <audra@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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A customer using nohz_full has experienced the following interruption:
oslat-1004510 [018] timer_cancel: timer=0xffff90a7ca663cf8
oslat-1004510 [018] timer_expire_entry: timer=0xffff90a7ca663cf8 function=delayed_work_timer_fn now=4709188240 baseclk=4709188240
oslat-1004510 [018] workqueue_queue_work: work struct=0xffff90a7ca663cd8 function=fb_flashcursor workqueue=events_power_efficient req_cpu=8192 cpu=18
oslat-1004510 [018] workqueue_activate_work: work struct 0xffff90a7ca663cd8
oslat-1004510 [018] sched_wakeup: kworker/18:1:326 [120] CPU:018
oslat-1004510 [018] timer_expire_exit: timer=0xffff90a7ca663cf8
oslat-1004510 [018] irq_work_entry: vector=246
oslat-1004510 [018] irq_work_exit: vector=246
oslat-1004510 [018] tick_stop: success=0 dependency=SCHED
oslat-1004510 [018] hrtimer_start: hrtimer=0xffff90a70009cb00 function=tick_sched_timer/0x0 ...
oslat-1004510 [018] softirq_exit: vec=1 [action=TIMER]
oslat-1004510 [018] softirq_entry: vec=7 [action=SCHED]
oslat-1004510 [018] softirq_exit: vec=7 [action=SCHED]
oslat-1004510 [018] tick_stop: success=0 dependency=SCHED
oslat-1004510 [018] sched_switch: oslat:1004510 [120] R ==> kworker/18:1:326 [120]
kworker/18:1-326 [018] workqueue_execute_start: work struct 0xffff90a7ca663cd8: function fb_flashcursor
kworker/18:1-326 [018] workqueue_queue_work: work struct=0xffff9078f119eed0 function=drm_fb_helper_damage_work workqueue=events req_cpu=8192 cpu=18
kworker/18:1-326 [018] workqueue_activate_work: work struct 0xffff9078f119eed0
kworker/18:1-326 [018] timer_start: timer=0xffff90a7ca663cf8 function=delayed_work_timer_fn ...
Set wq_power_efficient to true, in case nohz_full is enabled.
This makes the power efficient workqueue be unbounded, which allows
workqueue items there to be moved to HK CPUs.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Currently the workqueue just checks the atomic and locking states after work
execution ends. However, sometimes, a work item may not unlock rcu after
acquiring rcu_read_lock(). And as a result, it would cause rcu stall, but
the rcu stall warning can not dump the work func, because the work has
finished.
In order to quickly discover those works that do not call rcu_read_unlock()
after rcu_read_lock(), add the rcu lock check.
Use rcu_preempt_depth() to check the work's rcu status. Normally, this value
is 0. If this value is bigger than 0, it means the work are still holding
rcu lock. If so, print err info and the work func.
tj: Reworded the description for clarity. Minor formatting tweak.
Signed-off-by: Xuewen Yan <xuewen.yan@unisoc.com>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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At the time they are created unbound workqueues rescuers currently use
cpu_possible_mask as their affinity, but this can be too wide in case a
workqueue unbound mask has been set as a subset of cpu_possible_mask.
Make new rescuers use their associated workqueue unbound cpumask from
the start.
Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Currently we limit the size of the workqueue name to 24 characters due to
commit ecf6881ff349 ("workqueue: make workqueue->name[] fixed len")
Increase the size to 32 characters and print a warning in the event
the requested name is larger than the limit of 32 characters.
Signed-off-by: Audra Mitchell <audra@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq into for-6.8
cgroup/for-6.8 is carrying two workqueue changes to allow cpuset to restrict
the CPUs used by unbound workqueues. Unfortunately, this conflicts with a
new bug fix in wq/for-6.7-fixes. The conflict is contextual but can be a bit
confusing to resolve. Pull the fix branch to resolve the conflict.
Signed-off-by: Tejun Heo <tj@kernel.org>
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During boot, depending on how the housekeeping and workqueue.unbound_cpus
masks are set, wq_unbound_cpumask can end up empty. Since 8639ecebc9b1
("workqueue: Implement non-strict affinity scope for unbound workqueues"),
this may end up feeding -1 as a CPU number into scheduler leading to oopses.
BUG: unable to handle page fault for address: ffffffff8305e9c0
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
...
Call Trace:
<TASK>
select_idle_sibling+0x79/0xaf0
select_task_rq_fair+0x1cb/0x7b0
try_to_wake_up+0x29c/0x5c0
wake_up_process+0x19/0x20
kick_pool+0x5e/0xb0
__queue_work+0x119/0x430
queue_work_on+0x29/0x30
...
An empty wq_unbound_cpumask is a clear misconfiguration and already
disallowed once system is booted up. Let's warn on and ignore
unbound_cpumask restrictions which lead to no unbound cpus. While at it,
also remove now unncessary empty check on wq_unbound_cpumask in
wq_select_unbound_cpu().
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-and-Tested-by: Yong He <alexyonghe@tencent.com>
Link: http://lkml.kernel.org/r/20231120121623.119780-1-alexyonghe@tencent.com
Fixes: 8639ecebc9b1 ("workqueue: Implement non-strict affinity scope for unbound workqueues")
Cc: stable@vger.kernel.org # v6.6+
Reviewed-by: Waiman Long <longman@redhat.com>
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CONFIG_SYSFS
Commit fe28f631fa94 ("workqueue: Add workqueue_unbound_exclude_cpumask()
to exclude CPUs from wq_unbound_cpumask") makes
workqueue_set_unbound_cpumask() static as it is not used elsewhere in
the kernel. However, this triggers a kernel test robot warning about
'workqueue_set_unbound_cpumask' defined but not used when CONFIG_SYS
isn't defined. It happens that workqueue_set_unbound_cpumask() is only
called when CONFIG_SYS is defined.
Move workqueue_set_unbound_cpumask() and its helpers inside the
CONFIG_SYSFS compilation block to avoid the warning. There is no
functional change.
Fixes: fe28f631fa94 ("workqueue: Add workqueue_unbound_exclude_cpumask() to exclude CPUs from wq_unbound_cpumask")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202311130831.uh0AoCd1-lkp@intel.com/
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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wq_unbound_cpumask
When the "isolcpus" boot command line option is used to add a set
of isolated CPUs, those CPUs will be excluded automatically from
wq_unbound_cpumask to avoid running work functions from unbound
workqueues.
Recently cpuset has been extended to allow the creation of partitions
of isolated CPUs dynamically. To make it closer to the "isolcpus"
in functionality, the CPUs in those isolated cpuset partitions should be
excluded from wq_unbound_cpumask as well. This can be done currently by
explicitly writing to the workqueue's cpumask sysfs file after creating
the isolated partitions. However, this process can be error prone.
Ideally, the cpuset code should be allowed to request the workqueue code
to exclude those isolated CPUs from wq_unbound_cpumask so that this
operation can be done automatically and the isolated CPUs will be returned
back to wq_unbound_cpumask after the destructions of the isolated
cpuset partitions.
This patch adds a new workqueue_unbound_exclude_cpumask() function to
enable that. This new function will exclude the specified isolated
CPUs from wq_unbound_cpumask. To be able to restore those isolated
CPUs back after the destruction of isolated cpuset partitions, a new
wq_requested_unbound_cpumask is added to store the user provided unbound
cpumask either from the boot command line options or from writing to
the cpumask sysfs file. This new cpumask provides the basis for CPU
exclusion.
To enable users to understand how the wq_unbound_cpumask is being
modified internally, this patch also exposes the newly introduced
wq_requested_unbound_cpumask as well as a wq_isolated_cpumask to
store the cpumask to be excluded from wq_unbound_cpumask as read-only
sysfs files.
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Pull non-MM updates from Andrew Morton:
"As usual, lots of singleton and doubleton patches all over the tree
and there's little I can say which isn't in the individual changelogs.
The lengthier patch series are
- 'kdump: use generic functions to simplify crashkernel reservation
in arch', from Baoquan He. This is mainly cleanups and
consolidation of the 'crashkernel=' kernel parameter handling
- After much discussion, David Laight's 'minmax: Relax type checks in
min() and max()' is here. Hopefully reduces some typecasting and
the use of min_t() and max_t()
- A group of patches from Oleg Nesterov which clean up and slightly
fix our handling of reads from /proc/PID/task/... and which remove
task_struct.thread_group"
* tag 'mm-nonmm-stable-2023-11-02-14-08' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (64 commits)
scripts/gdb/vmalloc: disable on no-MMU
scripts/gdb: fix usage of MOD_TEXT not defined when CONFIG_MODULES=n
.mailmap: add address mapping for Tomeu Vizoso
mailmap: update email address for Claudiu Beznea
tools/testing/selftests/mm/run_vmtests.sh: lower the ptrace permissions
.mailmap: map Benjamin Poirier's address
scripts/gdb: add lx_current support for riscv
ocfs2: fix a spelling typo in comment
proc: test ProtectionKey in proc-empty-vm test
proc: fix proc-empty-vm test with vsyscall
fs/proc/base.c: remove unneeded semicolon
do_io_accounting: use sig->stats_lock
do_io_accounting: use __for_each_thread()
ocfs2: replace BUG_ON() at ocfs2_num_free_extents() with ocfs2_error()
ocfs2: fix a typo in a comment
scripts/show_delta: add __main__ judgement before main code
treewide: mark stuff as __ro_after_init
fs: ocfs2: check status values
proc: test /proc/${pid}/statm
compiler.h: move __is_constexpr() to compiler.h
...
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__read_mostly predates __ro_after_init. Many variables which are marked
__read_mostly should have been __ro_after_init from day 1.
Also, mark some stuff as "const" and "__init" while I'm at it.
[akpm@linux-foundation.org: revert sysctl_nr_open_min, sysctl_nr_open_max changes due to arm warning]
[akpm@linux-foundation.org: coding-style cleanups]
Link: https://lkml.kernel.org/r/4f6bb9c0-abba-4ee4-a7aa-89265e886817@p183
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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All callers of work_on_cpu() share the same lock class key for all the
functions queued. As a result the workqueue related locking scenario for
a function A may be spuriously accounted as an inversion against the
locking scenario of function B such as in the following model:
long A(void *arg)
{
mutex_lock(&mutex);
mutex_unlock(&mutex);
}
long B(void *arg)
{
}
void launchA(void)
{
work_on_cpu(0, A, NULL);
}
void launchB(void)
{
mutex_lock(&mutex);
work_on_cpu(1, B, NULL);
mutex_unlock(&mutex);
}
launchA and launchB running concurrently have no chance to deadlock.
However the above can be reported by lockdep as a possible locking
inversion because the works containing A() and B() are treated as
belonging to the same locking class.
The following shows an existing example of such a spurious lockdep splat:
======================================================
WARNING: possible circular locking dependency detected
6.6.0-rc1-00065-g934ebd6e5359 #35409 Not tainted
------------------------------------------------------
kworker/0:1/9 is trying to acquire lock:
ffffffff9bc72f30 (cpu_hotplug_lock){++++}-{0:0}, at: _cpu_down+0x57/0x2b0
but task is already holding lock:
ffff9e3bc0057e60 ((work_completion)(&wfc.work)){+.+.}-{0:0}, at: process_scheduled_works+0x216/0x500
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #2 ((work_completion)(&wfc.work)){+.+.}-{0:0}:
__flush_work+0x83/0x4e0
work_on_cpu+0x97/0xc0
rcu_nocb_cpu_offload+0x62/0xb0
rcu_nocb_toggle+0xd0/0x1d0
kthread+0xe6/0x120
ret_from_fork+0x2f/0x40
ret_from_fork_asm+0x1b/0x30
-> #1 (rcu_state.barrier_mutex){+.+.}-{3:3}:
__mutex_lock+0x81/0xc80
rcu_nocb_cpu_deoffload+0x38/0xb0
rcu_nocb_toggle+0x144/0x1d0
kthread+0xe6/0x120
ret_from_fork+0x2f/0x40
ret_from_fork_asm+0x1b/0x30
-> #0 (cpu_hotplug_lock){++++}-{0:0}:
__lock_acquire+0x1538/0x2500
lock_acquire+0xbf/0x2a0
percpu_down_write+0x31/0x200
_cpu_down+0x57/0x2b0
__cpu_down_maps_locked+0x10/0x20
work_for_cpu_fn+0x15/0x20
process_scheduled_works+0x2a7/0x500
worker_thread+0x173/0x330
kthread+0xe6/0x120
ret_from_fork+0x2f/0x40
ret_from_fork_asm+0x1b/0x30
other info that might help us debug this:
Chain exists of:
cpu_hotplug_lock --> rcu_state.barrier_mutex --> (work_completion)(&wfc.work)
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock((work_completion)(&wfc.work));
lock(rcu_state.barrier_mutex);
lock((work_completion)(&wfc.work));
lock(cpu_hotplug_lock);
*** DEADLOCK ***
2 locks held by kworker/0:1/9:
#0: ffff900481068b38 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0x212/0x500
#1: ffff9e3bc0057e60 ((work_completion)(&wfc.work)){+.+.}-{0:0}, at: process_scheduled_works+0x216/0x500
stack backtrace:
CPU: 0 PID: 9 Comm: kworker/0:1 Not tainted 6.6.0-rc1-00065-g934ebd6e5359 #35409
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014
Workqueue: events work_for_cpu_fn
Call Trace:
rcu-torture: rcu_torture_read_exit: Start of episode
<TASK>
dump_stack_lvl+0x4a/0x80
check_noncircular+0x132/0x150
__lock_acquire+0x1538/0x2500
lock_acquire+0xbf/0x2a0
? _cpu_down+0x57/0x2b0
percpu_down_write+0x31/0x200
? _cpu_down+0x57/0x2b0
_cpu_down+0x57/0x2b0
__cpu_down_maps_locked+0x10/0x20
work_for_cpu_fn+0x15/0x20
process_scheduled_works+0x2a7/0x500
worker_thread+0x173/0x330
? __pfx_worker_thread+0x10/0x10
kthread+0xe6/0x120
? __pfx_kthread+0x10/0x10
ret_from_fork+0x2f/0x40
? __pfx_kthread+0x10/0x10
ret_from_fork_asm+0x1b/0x30
</TASK
Fix this with providing one lock class key per work_on_cpu() caller.
Reported-and-tested-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Compiling with W=1 emitted the following warning
(Compiler: gcc (x86-64, ver. 13.2.1, .config: result of make allyesconfig,
"Treat warnings as errors" turned off):
kernel/workqueue.c:2188:54: warning: ‘%d’ directive output may be
truncated writing between 1 and 10 bytes into a region of size
between 5 and 14 [-Wformat-truncation=]
kernel/workqueue.c:2188:50: note: directive argument in the range
[0, 2147483647]
kernel/workqueue.c:2188:17: note: ‘snprintf’ output between 4 and 23 bytes
into a destination of size 16
setting "id_buf" to size 23 will silence the warning, since GCC
determines snprintf's output to be max. 23 bytes in line 2188.
Please let me know if there are any mistakes in my patch!
Signed-off-by: Lucy Mielke <lucymielke@icloud.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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workqueue_apply_unbound_cpumask()
Commit 5c0338c68706 ("workqueue: restore WQ_UNBOUND/max_active==1
to be ordered") enabled implicit ordered attribute to be added to
WQ_UNBOUND workqueues with max_active of 1. This prevented the changing
of attributes to these workqueues leading to fix commit 0a94efb5acbb
("workqueue: implicit ordered attribute should be overridable").
However, workqueue_apply_unbound_cpumask() was not updated at that time.
So sysfs changes to wq_unbound_cpumask has no effect on WQ_UNBOUND
workqueues with implicit ordered attribute. Since not all WQ_UNBOUND
workqueues are visible on sysfs, we are not able to make all the
necessary cpumask changes even if we iterates all the workqueue cpumasks
in sysfs and changing them one by one.
Fix this problem by applying the corresponding change made
to apply_workqueue_attrs_locked() in the fix commit to
workqueue_apply_unbound_cpumask().
Fixes: 5c0338c68706 ("workqueue: restore WQ_UNBOUND/max_active==1 to be ordered")
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Currently, the kfree() be used for pwq objects allocated with
kmem_cache_alloc() in alloc_and_link_pwqs(), this isn't wrong.
but usually, use "trace_kmem_cache_alloc/trace_kmem_cache_free"
to track memory allocation and free. this commit therefore use
kmem_cache_free() instead of kfree() in alloc_and_link_pwqs()
and also consistent with release of the pwq in rcu_free_pwq().
Signed-off-by: Zqiang <qiang.zhang1211@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Currently, for UNBOUND wq, if the apply_wqattrs_prepare() return error,
the apply_wqattr_cleanup() will be called and use the pwq_release_worker
kthread to release resources asynchronously. however, the kfree(wq) is
invoked directly in failure path of alloc_workqueue(), if the kfree(wq)
has been executed and when the pwq_release_workfn() accesses wq, this
leads to the following scenario:
BUG: KASAN: slab-use-after-free in pwq_release_workfn+0x339/0x380 kernel/workqueue.c:4124
Read of size 4 at addr ffff888027b831c0 by task pool_workqueue_/3
CPU: 0 PID: 3 Comm: pool_workqueue_ Not tainted 6.5.0-rc7-next-20230825-syzkaller #0
Hardware name: Google Compute Engine/Google Compute Engine, BIOS Google 07/26/2023
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106
print_address_description mm/kasan/report.c:364 [inline]
print_report+0xc4/0x620 mm/kasan/report.c:475
kasan_report+0xda/0x110 mm/kasan/report.c:588
pwq_release_workfn+0x339/0x380 kernel/workqueue.c:4124
kthread_worker_fn+0x2fc/0xa80 kernel/kthread.c:823
kthread+0x33a/0x430 kernel/kthread.c:388
ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:304
</TASK>
Allocated by task 5054:
kasan_save_stack+0x33/0x50 mm/kasan/common.c:45
kasan_set_track+0x25/0x30 mm/kasan/common.c:52
____kasan_kmalloc mm/kasan/common.c:374 [inline]
__kasan_kmalloc+0xa2/0xb0 mm/kasan/common.c:383
kmalloc include/linux/slab.h:599 [inline]
kzalloc include/linux/slab.h:720 [inline]
alloc_workqueue+0x16f/0x1490 kernel/workqueue.c:4684
kvm_mmu_init_tdp_mmu+0x23/0x100 arch/x86/kvm/mmu/tdp_mmu.c:19
kvm_mmu_init_vm+0x248/0x2e0 arch/x86/kvm/mmu/mmu.c:6180
kvm_arch_init_vm+0x39/0x720 arch/x86/kvm/x86.c:12311
kvm_create_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:1222 [inline]
kvm_dev_ioctl_create_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:5089 [inline]
kvm_dev_ioctl+0xa31/0x1c20 arch/x86/kvm/../../../virt/kvm/kvm_main.c:5131
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:871 [inline]
__se_sys_ioctl fs/ioctl.c:857 [inline]
__x64_sys_ioctl+0x18f/0x210 fs/ioctl.c:857
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
Freed by task 5054:
kasan_save_stack+0x33/0x50 mm/kasan/common.c:45
kasan_set_track+0x25/0x30 mm/kasan/common.c:52
kasan_save_free_info+0x2b/0x40 mm/kasan/generic.c:522
____kasan_slab_free mm/kasan/common.c:236 [inline]
____kasan_slab_free+0x15b/0x1b0 mm/kasan/common.c:200
kasan_slab_free include/linux/kasan.h:164 [inline]
slab_free_hook mm/slub.c:1800 [inline]
slab_free_freelist_hook+0x114/0x1e0 mm/slub.c:1826
slab_free mm/slub.c:3809 [inline]
__kmem_cache_free+0xb8/0x2f0 mm/slub.c:3822
alloc_workqueue+0xe76/0x1490 kernel/workqueue.c:4746
kvm_mmu_init_tdp_mmu+0x23/0x100 arch/x86/kvm/mmu/tdp_mmu.c:19
kvm_mmu_init_vm+0x248/0x2e0 arch/x86/kvm/mmu/mmu.c:6180
kvm_arch_init_vm+0x39/0x720 arch/x86/kvm/x86.c:12311
kvm_create_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:1222 [inline]
kvm_dev_ioctl_create_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:5089 [inline]
kvm_dev_ioctl+0xa31/0x1c20 arch/x86/kvm/../../../virt/kvm/kvm_main.c:5131
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:871 [inline]
__se_sys_ioctl fs/ioctl.c:857 [inline]
__x64_sys_ioctl+0x18f/0x210 fs/ioctl.c:857
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
This commit therefore flush pwq_release_worker in the alloc_and_link_pwqs()
before invoke kfree(wq).
Reported-by: syzbot+60db9f652c92d5bacba4@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=60db9f652c92d5bacba4
Signed-off-by: Zqiang <qiang.zhang1211@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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wq_cpu_intensive_thresh_init()
Currently, if the wq_cpu_intensive_thresh_us is set to specific
value, will cause the wq_cpu_intensive_thresh_init() early exit
and missed creation of pwq_release_worker. this commit therefore
create the pwq_release_worker in advance before checking the
wq_cpu_intensive_thresh_us.
Signed-off-by: Zqiang <qiang.zhang1211@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Fixes: 967b494e2fd1 ("workqueue: Use a kthread_worker to release pool_workqueues")
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First commit 2930155b2e272 ("workqueue: Initialize unbound CPU pods later in
the boot") added the initialization of wq_update_pod_attrs_buf to
workqueue_init_early(), and then latter on, commit 84193c07105c6
("workqueue: Generalize unbound CPU pods") added it as well. This appeared
in a kmemleak run where the second allocation made the first allocation
leak.
Fixes: 84193c07105c6 ("workqueue: Generalize unbound CPU pods")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Tejun Heo <tj@kernel.org>
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KCSAN has discovered a data race in kernel/workqueue.c:2598:
[ 1863.554079] ==================================================================
[ 1863.554118] BUG: KCSAN: data-race in process_one_work / process_one_work
[ 1863.554142] write to 0xffff963d99d79998 of 8 bytes by task 5394 on cpu 27:
[ 1863.554154] process_one_work (kernel/workqueue.c:2598)
[ 1863.554166] worker_thread (./include/linux/list.h:292 kernel/workqueue.c:2752)
[ 1863.554177] kthread (kernel/kthread.c:389)
[ 1863.554186] ret_from_fork (arch/x86/kernel/process.c:145)
[ 1863.554197] ret_from_fork_asm (arch/x86/entry/entry_64.S:312)
[ 1863.554213] read to 0xffff963d99d79998 of 8 bytes by task 5450 on cpu 12:
[ 1863.554224] process_one_work (kernel/workqueue.c:2598)
[ 1863.554235] worker_thread (./include/linux/list.h:292 kernel/workqueue.c:2752)
[ 1863.554247] kthread (kernel/kthread.c:389)
[ 1863.554255] ret_from_fork (arch/x86/kernel/process.c:145)
[ 1863.554266] ret_from_fork_asm (arch/x86/entry/entry_64.S:312)
[ 1863.554280] value changed: 0x0000000000001766 -> 0x000000000000176a
[ 1863.554295] Reported by Kernel Concurrency Sanitizer on:
[ 1863.554303] CPU: 12 PID: 5450 Comm: kworker/u64:1 Tainted: G L 6.5.0-rc6+ #44
[ 1863.554314] Hardware name: ASRock X670E PG Lightning/X670E PG Lightning, BIOS 1.21 04/26/2023
[ 1863.554322] Workqueue: btrfs-endio btrfs_end_bio_work [btrfs]
[ 1863.554941] ==================================================================
lockdep_invariant_state(true);
→ pwq->stats[PWQ_STAT_STARTED]++;
trace_workqueue_execute_start(work);
worker->current_func(work);
Moving pwq->stats[PWQ_STAT_STARTED]++; before the line
raw_spin_unlock_irq(&pool->lock);
resolves the data race without performance penalty.
KCSAN detected at least one additional data race:
[ 157.834751] ==================================================================
[ 157.834770] BUG: KCSAN: data-race in process_one_work / process_one_work
[ 157.834793] write to 0xffff9934453f77a0 of 8 bytes by task 468 on cpu 29:
[ 157.834804] process_one_work (/home/marvin/linux/kernel/linux_torvalds/kernel/workqueue.c:2606)
[ 157.834815] worker_thread (/home/marvin/linux/kernel/linux_torvalds/./include/linux/list.h:292 /home/marvin/linux/kernel/linux_torvalds/kernel/workqueue.c:2752)
[ 157.834826] kthread (/home/marvin/linux/kernel/linux_torvalds/kernel/kthread.c:389)
[ 157.834834] ret_from_fork (/home/marvin/linux/kernel/linux_torvalds/arch/x86/kernel/process.c:145)
[ 157.834845] ret_from_fork_asm (/home/marvin/linux/kernel/linux_torvalds/arch/x86/entry/entry_64.S:312)
[ 157.834859] read to 0xffff9934453f77a0 of 8 bytes by task 214 on cpu 7:
[ 157.834868] process_one_work (/home/marvin/linux/kernel/linux_torvalds/kernel/workqueue.c:2606)
[ 157.834879] worker_thread (/home/marvin/linux/kernel/linux_torvalds/./include/linux/list.h:292 /home/marvin/linux/kernel/linux_torvalds/kernel/workqueue.c:2752)
[ 157.834890] kthread (/home/marvin/linux/kernel/linux_torvalds/kernel/kthread.c:389)
[ 157.834897] ret_from_fork (/home/marvin/linux/kernel/linux_torvalds/arch/x86/kernel/process.c:145)
[ 157.834907] ret_from_fork_asm (/home/marvin/linux/kernel/linux_torvalds/arch/x86/entry/entry_64.S:312)
[ 157.834920] value changed: 0x000000000000052a -> 0x0000000000000532
[ 157.834933] Reported by Kernel Concurrency Sanitizer on:
[ 157.834941] CPU: 7 PID: 214 Comm: kworker/u64:2 Tainted: G L 6.5.0-rc7-kcsan-00169-g81eaf55a60fc #4
[ 157.834951] Hardware name: ASRock X670E PG Lightning/X670E PG Lightning, BIOS 1.21 04/26/2023
[ 157.834958] Workqueue: btrfs-endio btrfs_end_bio_work [btrfs]
[ 157.835567] ==================================================================
in code:
trace_workqueue_execute_end(work, worker->current_func);
→ pwq->stats[PWQ_STAT_COMPLETED]++;
lock_map_release(&lockdep_map);
lock_map_release(&pwq->wq->lockdep_map);
which needs to be resolved separately.
Fixes: 725e8ec59c56c ("workqueue: Add pwq->stats[] and a monitoring script")
Cc: Tejun Heo <tj@kernel.org>
Suggested-by: Lai Jiangshan <jiangshanlai@gmail.com>
Link: https://lore.kernel.org/lkml/20230818194448.29672-1-mirsad.todorovac@alu.unizg.hr/
Signed-off-by: Mirsad Goran Todorovac <mirsad.todorovac@alu.unizg.hr>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Each CPU-specific and unbound kworker kthread conforms to a particular
naming scheme. However, this does not extend to the rescuer kworker.
At present, a rescuer kworker is simply named according to its
workqueue's name. This can be cryptic.
This patch modifies a rescuer to follow the kworker naming scheme.
The "R" is indicative of a rescuer and after "-" is its workqueue's
name e.g. "kworker/R-ext4-rsv-conver".
tj: Use "R" instead of "r" as the prefix to make it more distinctive and
consistent with how highpri pools are marked.
Signed-off-by: Aaron Tomlin <atomlin@atomlin.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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While workqueue.default_affinity_scope is writable, it only affects
workqueues which are created afterwards and isn't very useful. Instead,
let's introduce explicit "default" scope and update the effective scope
dynamically when workqueue.default_affinity_scope is changed.
Signed-off-by: Tejun Heo <tj@kernel.org>
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An unbound workqueue can be served by multiple worker_pools to improve
locality. The segmentation is achieved by grouping CPUs into pods. By
default, the cache boundaries according to cpus_share_cache() define the
CPUs are grouped. Let's a workqueue is allowed to run on all CPUs and the
system has two L3 caches. The workqueue would be mapped to two worker_pools
each serving one L3 cache domains.
While this improves locality, because the pod boundaries are strict, it
limits the total bandwidth a given issuer can consume. For example, let's
say there is a thread pinned to a CPU issuing enough work items to saturate
the whole machine. With the machine segmented into two pods, no matter how
many work items it issues, it can only use half of the CPUs on the system.
While this limitation has existed for a very long time, it wasn't very
pronounced because the affinity grouping used to be always by NUMA nodes.
With cache boundaries as the default and support for even finer grained
scopes (smt and cpu), it is now an a lot more pressing problem.
This patch implements non-strict affinity scope where the pod boundaries
aren't enforced strictly. Going back to the previous example, the workqueue
would still be mapped to two worker_pools; however, the affinity enforcement
would be soft. The workers in both pools would have their cpus_allowed set
to the whole machine thus allowing the scheduler to migrate them anywhere on
the machine. However, whenever an idle worker is woken up, the workqueue
code asks the scheduler to bring back the task within the pod if the worker
is outside. ie. work items start executing within its affinity scope but can
be migrated outside as the scheduler sees fit. This removes the hard cap on
utilization while maintaining the benefits of affinity scopes.
After the earlier ->__pod_cpumask changes, the implementation is pretty
simple. When non-strict which is the new default:
* pool_allowed_cpus() returns @pool->attrs->cpumask instead of
->__pod_cpumask so that the workers are allowed to run on any CPU that
the associated workqueues allow.
* If the idle worker task's ->wake_cpu is outside the pod, kick_pool() sets
the field to a CPU within the pod.
This would be the first use of task_struct->wake_cpu outside scheduler
proper, so it isn't clear whether this would be acceptable. However, other
methods of migrating tasks are significantly more expensive and are likely
prohibitively so if we want to do this on every work item. This needs
discussion with scheduler folks.
There is also a race window where setting ->wake_cpu wouldn't be effective
as the target task is still on CPU. However, the window is pretty small and
this being a best-effort optimization, it doesn't seem to warrant more
complexity at the moment.
While the non-strict cache affinity scopes seem to be the best option, the
performance picture interacts with the affinity scope and is a bit
complicated to fully discuss in this patch, so the behavior is made easily
selectable through wqattrs and sysfs and the next patch will add
documentation to discuss performance implications.
v2: pool->attrs->affn_strict is set to true for per-cpu worker_pools.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
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workqueue_attrs has two uses:
* to specify the required unouned workqueue properties by users
* to match worker_pool's properties to workqueues by core code
For example, if the user wants to restrict a workqueue to run only CPUs 0
and 2, and the two CPUs are on different affinity scopes, the workqueue's
attrs->cpumask would contains CPUs 0 and 2, and the workqueue would be
associated with two worker_pools, one with attrs->cpumask containing just
CPU 0 and the other CPU 2.
Workqueue wants to support non-strict affinity scopes where work items are
started in their matching affinity scopes but the scheduler is free to
migrate them outside the starting scopes, which can enable utilizing the
whole machine while maintaining most of the locality benefits from affinity
scopes.
To enable that, worker_pools need to distinguish the strict affinity that it
has to follow (because that's the restriction coming from the user) and the
soft affinity that it wants to apply when dispatching work items. Note that
two worker_pools with different soft dispatching requirements have to be
separate; otherwise, for example, we'd be ping-ponging worker threads across
NUMA boundaries constantly.
This patch adds workqueue_attrs->__pod_cpumask. The new field is double
underscored as it's only used internally to distinguish worker_pools. A
worker_pool's ->cpumask is now always the same as the online subset of
allowed CPUs of the associated workqueues, and ->__pod_cpumask is the pod's
subset of that ->cpumask. Going back to the example above, both worker_pools
would have ->cpumask containing both CPUs 0 and 2 but one's ->__pod_cpumask
would contain 0 while the other's 2.
* pool_allowed_cpus() is added. It returns the worker_pool's strict cpumask
that the pool's workers must stay within. This is currently always
->__pod_cpumask as all boundaries are still strict.
* As a workqueue_attrs can now track both the associated workqueues' cpumask
and its per-pod subset, wq_calc_pod_cpumask() no longer needs an external
out-argument. Drop @cpumask and instead store the result in
->__pod_cpumask.
* The above also simplifies apply_wqattrs_prepare() as the same
workqueue_attrs can be used to create all pods associated with a
workqueue. tmp_attrs is dropped.
* wq_update_pod() is updated to use wqattrs_equal() to test whether a pwq
update is needed instead of only comparing ->cpumask so that
->__pod_cpumask is compared too. It can directly compare ->__pod_cpumaks
but the code is easier to understand and more robust this way.
The only user-visible behavior change is that two workqueues with different
cpumasks no longer can share worker_pools even when their pod subsets
coincide. Going back to the example, let's say there's another workqueue
with cpumask 0, 2, 3, where 2 and 3 are in the same pod. It would be mapped
to two worker_pools - one with CPU 0, the other with 2 and 3. The former has
the same cpumask as the first pod of the earlier example and would have
shared the same worker_pool but that's no longer the case after this patch.
The worker_pools would have the same ->__pod_cpumask but their ->cpumask's
wouldn't match.
While this is necessary to support non-strict affinity scopes, there can be
further optimizations to maintain sharing among strict affinity scopes.
However, non-strict affinity scopes are going to be preferable for most use
cases and we don't see very diverse mixture of unbound workqueue cpumasks
anyway, so the additional overhead doesn't seem to justify the extra
complexity.
v2: - wq_update_pod() was incorrectly comparing target_attrs->__pod_cpumask
to pool->attrs->cpumask instead of its ->__pod_cpumask. Fix it by
using wqattrs_equal() for comparison instead.
- Per-cpu worker pools weren't initializing ->__pod_cpumask which caused
a subtle problem later on. Set it to cpumask_of(cpu) like ->cpumask.
Signed-off-by: Tejun Heo <tj@kernel.org>
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Checking need_more_worker() and calling wake_up_worker() is a repeated
pattern. Let's add kick_pool(), which checks need_more_worker() and
open-code wake_up_worker(), and replace wake_up_worker() uses. The following
conversions aren't one-to-one:
* __queue_work() was using __need_more_work() because it knows that
pool->worklist isn't empty. Switching to kick_pool() adds an extra
list_empty() test.
* create_worker() always needs to wake up the newly minted worker whether
there's more work to do or not to avoid triggering hung task check on the
new task. Keep the current wake_up_process() and still add kick_pool().
This may lead to an extra wakeup which isn't harmful.
* pwq_adjust_max_active() was explicitly checking whether it needs to wake
up a worker or not to avoid spurious wakeups. As kick_pool() only wakes up
a worker when necessary, this explicit check is no longer necessary and
dropped.
* unbind_workers() now calls kick_pool() instead of wake_up_worker() adding
a need_more_worker() test. This avoids spurious wakeups and shouldn't
break anything.
wake_up_worker() is dropped as kick_pool() replaces all its users. After
this patch, all paths that wakes up a non-rescuer worker to initiate work
item execution use kick_pool(). This will enable future changes to improve
locality.
Signed-off-by: Tejun Heo <tj@kernel.org>
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The two work execution paths in worker_thread() and rescuer_thread() use
move_linked_works() to claim work items from @pool->worklist. Once claimed,
process_schedule_works() is called which invokes process_one_work() on each
work item. process_one_work() then uses find_worker_executing_work() to
detect and handle collisions - situations where the work item to be executed
is still running on another worker.
This works fine, but, to improve work execution locality, we want to
establish work to worker association earlier and know for sure that the
worker is going to excute the work once asssigned, which requires performing
collision handling earlier while trying to assign the work item to the
worker.
This patch introduces assign_work() which assigns a work item to a worker
using move_linked_works() and then performs collision handling. As collision
handling is handled earlier, process_one_work() no longer needs to worry
about them.
After the this patch, collision checks for linked work items are skipped,
which should be fine as they can't be queued multiple times concurrently.
For work items running from rescuers, the timing of collision handling may
change but the invariant that the work items go through collision handling
before starting execution does not.
This patch shouldn't cause noticeable behavior changes, especially given
that worker_thread() behavior remains the same.
Signed-off-by: Tejun Heo <tj@kernel.org>
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Add three more affinity scopes - WQ_AFFN_CPU, SMT and CACHE - and make CACHE
the default. The code changes to actually add the additional scopes are
trivial.
Also add module parameter "workqueue.default_affinity_scope" to override the
default scope and "affinity_scope" sysfs file to configure it per workqueue.
wq_dump.py and documentations are updated accordingly.
This enables significant flexibility in configuring how unbound workqueues
behave. If affinity scope is set to "cpu", it'll behave close to a per-cpu
workqueue. On the other hand, "system" removes all locality boundaries.
Many modern machines have multiple L3 caches often while being mostly
uniform in terms of memory access. Thus, workqueue's previous behavior of
spreading work items in each NUMA node had negative performance implications
from unncessarily crossing L3 boundaries between issue and execution.
However, picking a finer grained affinity scope also has a downside in that
an issuer in one group can't utilize CPUs in other groups.
While dependent on the specifics of workload, there's usually a noticeable
penalty in crossing L3 boundaries, so let's default to CACHE. This issue
will be further addressed and documented with examples in future patches.
Signed-off-by: Tejun Heo <tj@kernel.org>
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While wq_pod_type[] can now group CPUs in any aribitrary way, WQ_AFFN_NUM
init is hard coded into workqueue_init_topology(). This patch modularizes
the init path by introducing init_pod_type() which takes a callback to
determine whether two CPUs should share a pod as an argument.
init_pod_type() first scans the CPU combinations testing for sharing to
assign consecutive pod IDs and initialize pod_type->cpu_pod[]. Once
->cpu_pod[] is determined, ->pod_cpus[] and ->pod_node[] are initialized
accordingly. WQ_AFFN_NUMA is now initialized by calling init_pod_type() with
cpus_share_numa() which tests whether the CPU belongs to the same NUMA node.
This patch may change the pod ID assigned to each NUMA node but that
shouldn't cause any behavior changes as the NUMA node to use for allocations
are tracked separately in pod_type->pod_node[]. This makes adding new
affinty types pretty easy.
Signed-off-by: Tejun Heo <tj@kernel.org>
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While renamed to pod, the code still assumes that the pods are defined by
NUMA boundaries. Let's generalize it:
* workqueue_attrs->affn_scope is added. Each enum represents the type of
boundaries that define the pods. There are currently two scopes -
WQ_AFFN_NUMA and WQ_AFFN_SYSTEM. The former is the same behavior as before
- one pod per NUMA node. The latter defines one global pod across the
whole system.
* struct wq_pod_type is added which describes how pods are configured for
each affnity scope. For each pod, it lists the member CPUs and the
preferred NUMA node for memory allocations. The reverse mapping from CPU
to pod is also available.
* wq_pod_enabled is dropped. Pod is now always enabled. The previously
disabled behavior is now implemented through WQ_AFFN_SYSTEM.
* get_unbound_pool() wants to determine the NUMA node to allocate memory
from for the new pool. The variables are renamed from node to pod but the
logic still assumes they're one and the same. Clearly distinguish them -
walk the WQ_AFFN_NUMA pods to find the matching pod and then use the pod's
NUMA node.
* wq_calc_pod_cpumask() was taking @pod but assumed that it was the NUMA
node. Take @cpu instead and determine the cpumask to use from the pod_type
matching @attrs.
* apply_wqattrs_prepare() is update to return ERR_PTR() on error instead of
NULL so that it can indicate -EINVAL on invalid affinity scopes.
This patch allows CPUs to be grouped into pods however desired per type.
While this patch causes some internal behavior changes, nothing material
should change for workqueue users.
v2: Trigger WARN_ON_ONCE() in wqattrs_pod_type() if affn_scope is
WQ_AFFN_NR_TYPES which indicates that the function is called with a
worker_pool's attrs instead of a workqueue's.
Signed-off-by: Tejun Heo <tj@kernel.org>
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workqueue_attrs can be used for both workqueues and worker_pools. However,
some fields, currently only ->ordered, only apply to workqueues and should
be cleared to the default / invalid values.
Currently, an unbound workqueue explicitly clears attrs->ordered in
get_unbound_pool() after copying the source workqueue attrs, while per-cpu
workqueues rely on the fact that zeroing on allocation gives us the desired
default value for pool->attrs->ordered.
This is fragile. Let's add wqattrs_clear_for_pool() which clears
attrs->ordered and is called from both init_worker_pool() and
get_unbound_pool(). This will ease adding more workqueue-only attrs fields.
In get_unbound_pool(), pool->node initialization is moved upwards for
readability. This shouldn't cause any behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
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wq_update_pod()
For an unbound pool, multiple cpumasks are involved.
U: The user-specified cpumask (may be filtered with cpu_possible_mask).
A: The actual cpumask filtered by wq_unbound_cpumask. If the filtering
leaves no CPU, wq_unbound_cpumask is used.
P: Per-pod subsets of #A.
wq->attrs stores #U, wq->dfl_pwq->pool->attrs->cpumask #A, and
wq->cpu_pwq[CPU]->pool->attrs->cpumask #P.
wq_update_pod() is called to update per-pod pwq's during CPU hotplug. To
calculate the new #P for each workqueue, it needs to call
wq_calc_pod_cpumask() with @attrs that contains #A. Currently,
wq_update_pod() achieves this by calling wq_calc_pod_cpumask() with
wq->dfl_pwq->pool->attrs.
This is rather fragile because we're calling wq_calc_pod_cpumask() with
@attrs of a worker_pool rather than the workqueue's actual attrs when what
we want to calculate is the workqueue's cpumask on the pod. While this works
fine currently, future changes will add fields which are used differently
between workqueues and worker_pools and this subtlety will bite us.
This patch factors out #U -> #A calculation from apply_wqattrs_prepare()
into wqattrs_actualize_cpumask and updates wq_update_pod() to copy
wq->unbound_attrs and use the new helper to obtain #A freshly instead of
abusing wq->dfl_pwq->pool_attrs.
This shouldn't cause any behavior changes in the current code.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: K Prateek Nayak <kprateek.nayak@amd.com>
Reference: http://lkml.kernel.org/r/30625cdd-4d61-594b-8db9-6816b017dde3@amd.com
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During boot, to initialize unbound CPU pods, wq_pod_init() was called from
workqueue_init(). This is early enough for NUMA nodes to be set up but
before SMP is brought up and CPU topology information is populated.
Workqueue is in the process of improving CPU locality for unbound workqueues
and will need access to topology information during pod init. This adds a
new init function workqueue_init_topology() which is called after CPU
topology information is available and replaces wq_pod_init().
As unbound CPU pods are now initialized after workqueues are activated, we
need to revisit the workqueues to apply the pod configuration. Workqueues
which are created before workqueue_init_topology() are set up so that they
always use the default worker pool. After pods are set up in
workqueue_init_topology(), wq_update_pod() is called on all existing
workqueues to update the pool associations accordingly.
Note that wq_update_pod_attrs_buf allocation is moved to
workqueue_init_early(). This isn't necessary right now but enables further
generalization of pod handling in the future.
This patch changes the initialization sequence but the end result should be
the same.
Signed-off-by: Tejun Heo <tj@kernel.org>
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wq_pod_init() is called from workqueue_init() and responsible for
initializing unbound CPU pods according to NUMA node. Workqueue is in the
process of improving affinity awareness and wants to use other topology
information to initialize unbound CPU pods; however, unlike NUMA nodes,
other topology information isn't yet available in workqueue_init().
The next patch will introduce a later stage init function for workqueue
which will be responsible for initializing unbound CPU pods. Relocate
wq_pod_init() below workqueue_init() where the new init function is going to
be located so that the diff can show the content differences.
Just a relocation. No functional changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
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Workqueue is in the process of improving CPU affinity awareness. It will
become more flexible and won't be tied to NUMA node boundaries. This patch
renames all NUMA related names in workqueue.c to use "pod" instead.
While "pod" isn't a very common term, it short and captures the grouping of
CPUs well enough. These names are only going to be used within workqueue
implementation proper, so the specific naming doesn't matter that much.
* wq_numa_possible_cpumask -> wq_pod_cpus
* wq_numa_enabled -> wq_pod_enabled
* wq_update_unbound_numa_attrs_buf -> wq_update_pod_attrs_buf
* workqueue_select_cpu_near -> select_numa_node_cpu
This rename is different from others. The function is only used by
queue_work_node() and specifically tries to find a CPU in the specified
NUMA node. As workqueue affinity will become more flexible and untied from
NUMA, this function's name should specifically describe that it's for
NUMA.
* wq_calc_node_cpumask -> wq_calc_pod_cpumask
* wq_update_unbound_numa -> wq_update_pod
* wq_numa_init -> wq_pod_init
* node -> pod in local variables
Only renames. No functional changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
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With the recent removal of NUMA related module param and sysfs knob,
workqueue_attrs->no_numa is now only used to implement ordered workqueues.
Let's rename the field so that it's less confusing especially with the
planned CPU affinity awareness improvements.
Just a rename. No functional changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
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A pwq (pool_workqueue) represents an association between a workqueue and a
worker_pool. When a work item is queued, the workqueue selects the pwq to
use, which in turn determines the pool, and queues the work item to the pool
through the pwq. pwq is also what implements the maximum concurrency limit -
@max_active.
As a per-cpu workqueue should be assocaited with a different worker_pool on
each CPU, it always had per-cpu pwq's that are accessed through wq->cpu_pwq.
However, unbound workqueues were sharing a pwq within each NUMA node by
default. The sharing has several downsides:
* Because @max_active is per-pwq, the meaning of @max_active changes
depending on the machine configuration and whether workqueue NUMA locality
support is enabled.
* Makes per-cpu and unbound code deviate.
* Gets in the way of making workqueue CPU locality awareness more flexible.
This patch makes unbound workqueues use per-cpu pwq's the same way per-cpu
workqueues do by making the following changes:
* wq->numa_pwq_tbl[] is removed and unbound workqueues now use wq->cpu_pwq
just like per-cpu workqueues. wq->cpu_pwq is now RCU protected for unbound
workqueues.
* numa_pwq_tbl_install() is renamed to install_unbound_pwq() and installs
the specified pwq to the target CPU's wq->cpu_pwq.
* apply_wqattrs_prepare() now always allocates a separate pwq for each CPU
unless the workqueue is ordered. If ordered, all CPUs use wq->dfl_pwq.
This makes the return value of wq_calc_node_cpumask() unnecessary. It now
returns void.
* @max_active now means the same thing for both per-cpu and unbound
workqueues. WQ_UNBOUND_MAX_ACTIVE now equals WQ_MAX_ACTIVE and
documentation is updated accordingly. WQ_UNBOUND_MAX_ACTIVE is no longer
used in workqueue implementation and will be removed later.
* All unbound pwq operations which used to be per-numa-node are now per-cpu.
For most unbound workqueue users, this shouldn't cause noticeable changes.
Work item issue and completion will be a small bit faster, flush_workqueue()
would become a bit more expensive, and the total concurrency limit would
likely become higher. All @max_active==1 use cases are currently being
audited for conversion into alloc_ordered_workqueue() and they shouldn't be
affected once the audit and conversion is complete.
One area where the behavior change may be more noticeable is
workqueue_congested() as the reported congestion state is now per CPU
instead of NUMA node. There are only two users of this interface -
drivers/infiniband/hw/hfi1 and net/smc. Maintainers of both subsystems are
cc'd. Inputs on the behavior change would be very much appreciated.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Dennis Dalessandro <dennis.dalessandro@cornelisnetworks.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Karsten Graul <kgraul@linux.ibm.com>
Cc: Wenjia Zhang <wenjia@linux.ibm.com>
Cc: Jan Karcher <jaka@linux.ibm.com>
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When a CPU went online or offline, wq_update_unbound_numa() was called only
on the CPU which was going up or down. This works fine because all CPUs on
the same NUMA node share the same pool_workqueue slot - one CPU updating it
updates it for everyone in the node.
However, future changes will make each CPU use a separate pool_workqueue
even when they're sharing the same worker_pool, which requires updating
pool_workqueue's for all CPUs which may be sharing the same pool_workqueue
on hotplug.
To accommodate the planned changes, this patch updates
workqueue_on/offline_cpu() so that they call wq_update_unbound_numa() for
all CPUs sharing the same NUMA node as the CPU going up or down. In the
current code, the second+ calls would be noops and there shouldn't be any
behavior changes.
* As wq_update_unbound_numa() is now called on multiple CPUs per each
hotplug event, @cpu is renamed to @hotplug_cpu and another @cpu argument
is added. The former indicates the CPU being hot[un]plugged and the latter
the CPU whose pool_workqueue is being updated.
* In wq_update_unbound_numa(), cpu_off is renamed to off_cpu for consistency
with the new @hotplug_cpu.
Signed-off-by: Tejun Heo <tj@kernel.org>
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Currently, all per-cpu pwq's (pool_workqueue's) are allocated directly
through a per-cpu allocation and thus, unlike unbound workqueues, not
reference counted. This difference in lifetime management between the two
types is a bit confusing.
Unbound workqueues are currently accessed through wq->numa_pwq_tbl[] which
isn't suitiable for the planned CPU locality related improvements. The plan
is to unify pwq handling across per-cpu and unbound workqueues so that
they're always accessed through wq->cpu_pwq.
In preparation, this patch makes per-cpu pwq's to be allocated, reference
counted and released the same way as unbound pwq's. wq->cpu_pwq now holds
pointers to pwq's instead of containing them directly.
pwq_unbound_release_workfn() is renamed to pwq_release_workfn() as it's now
also used for per-cpu work items.
Signed-off-by: Tejun Heo <tj@kernel.org>
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pool_workqueue release path is currently bounced to system_wq; however, this
is a bit tricky because this bouncing occurs while holding a pool lock and
thus has risk of causing a A-A deadlock. This is currently addressed by the
fact that only unbound workqueues use this bouncing path and system_wq is a
per-cpu workqueue.
While this works, it's brittle and requires a work-around like setting the
lockdep subclass for the lock of unbound pools. Besides, future changes will
use the bouncing path for per-cpu workqueues too making the current approach
unusable.
Let's just use a dedicated kthread_worker to untangle the dependency. This
is just one more kthread for all workqueues and makes the pwq release logic
simpler and more robust.
Signed-off-by: Tejun Heo <tj@kernel.org>
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Unbound workqueue CPU affinity is going to receive an overhaul and the NUMA
specific knobs won't make sense anymore. Remove them. Also, the pool_ids
knob was used for debugging and not really meaningful given that there is no
visibility into the pools associated with those IDs. Remove it too. A future
patch will improve overall visibility.
Signed-off-by: Tejun Heo <tj@kernel.org>
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Collect first_idle_worker(), worker_enter/leave_idle(),
find_worker_executing_work(), move_linked_works() and wake_up_worker() into
one place. These functions will later be used to implement higher level
worker management logic.
No functional changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
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wq->cpu_pwqs is a percpu variable carraying one pointer to a pool_workqueue.
The field name being plural is unusual and confusing. Rename it to singular.
This patch doesn't cause any functional changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
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insert_work() always tried to wake up a worker; however, the only time it
needs to try to wake up a worker is when a new active work item is queued.
When a work item goes on the inactive list or queueing a flush work item,
there's no reason to try to wake up a worker.
This patch moves the worker wakeup logic out of insert_work() and places it
in the active new work item queueing path in __queue_work().
While at it:
* __queue_work() is dereferencing pwq->pool repeatedly. Add local variable
pool.
* Every caller of insert_work() calls debug_work_activate(). Consolidate the
invocations into insert_work().
* In __queue_work() pool->watchdog_ts update is relocated slightly. This is
to better accommodate future changes.
This makes wakeups more precise and will help the planned change to assign
work items to workers before waking them up. No behavior changes intended.
v2: WARN_ON_ONCE(pool != last_pool) added in __queue_work() to clarify as
suggested by Lai.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
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* Drop the trivial optimization in worker_thread() where it bypasses calling
process_scheduled_works() if the first work item isn't linked. This is a
mostly pointless micro optimization and gets in the way of improving the
work processing path.
* Consolidate pool->watchdog_ts updates in the two callers into
process_scheduled_works().
Signed-off-by: Tejun Heo <tj@kernel.org>
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worker_pool->flags
worker->flags used to be accessed from scheduler hooks without grabbing
pool->lock for concurrency management. This is no longer true since
6d25be5782e4 ("sched/core, workqueues: Distangle worker accounting from rq
lock"). Also, it's unclear why worker_pool->flags was using the "X" rule.
All relevant users are accessing it under the pool lock.
Let's drop the special "X" rule and use the "L" rule for these flag fields
instead. While at it, replace the CONTEXT comment with
lockdep_assert_held().
This allows worker_set/clr_flags() to be used from context which isn't the
worker itself. This will be used later to implement assinging work items to
workers before waking them up so that workqueue can have better control over
which worker executes which work item on which CPU.
The only actual changes are sanity checks. There shouldn't be any visible
behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
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Unbound workqueue execution locality improvement patchset is about to
applied which will cause merge conflicts with changes in for-6.5-fixes.
Let's avoid future merge conflict by pulling in for-6.5-fixes.
Signed-off-by: Tejun Heo <tj@kernel.org>
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Use LIST_HEAD() to initialize cull_list instead of open-coding it.
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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wq_cpu_intensive_thresh_us is used to detect CPU-hogging per-cpu work items.
Once detected, they're excluded from concurrency management to prevent them
from blocking other per-cpu work items. If CONFIG_WQ_CPU_INTENSIVE_REPORT is
enabled, repeat offenders are also reported so that the code can be updated.
The default threshold is 10ms which is long enough to do fair bit of work on
modern CPUs while short enough to be usually not noticeable. This
unfortunately leads to a lot of, arguable spurious, detections on very slow
CPUs. Using the same threshold across CPUs whose performance levels may be
apart by multiple levels of magnitude doesn't make whole lot of sense.
This patch scales up wq_cpu_intensive_thresh_us upto 1 second when BogoMIPS
is below 4000. This is obviously very inaccurate but it doesn't have to be
accurate to be useful. The mechanism is still useful when the threshold is
fully scaled up and the benefits of reports are usually shared with everyone
regardless of who's reporting, so as long as there are sufficient number of
fast machines reporting, we don't lose much.
Some (or is it all?) ARM CPUs systemtically report significantly lower
BogoMIPS. While this doesn't break anything, given how widespread ARM CPUs
are, it's at least a missed opportunity and it probably would be a good idea
to teach workqueue about it.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-and-Tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
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constrain wq_unbound_cpumask at boot time
Motivation of doing this is to better improve boot times for devices when
we want to prevent our workqueue works from running on some specific CPUs,
e,g, some CPUs are busy with interrupts.
Signed-off-by: tiozhang <tiozhang@didiglobal.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Based on commit c4f135d643823a86 ("workqueue: Wrap flush_workqueue() using
a macro"), all in-tree users stopped flushing system-wide workqueues.
Therefore, start emitting runtime message so that all out-of-tree users
will understand that they need to update their code.
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Pull workqueue updates from Tejun Heo:
- Concurrency-managed per-cpu work items that hog CPUs and delay the
execution of other work items are now automatically detected and
excluded from concurrency management. Reporting on such work items
can also be enabled through a config option.
- Added tools/workqueue/wq_monitor.py which improves visibility into
workqueue usages and behaviors.
- Arnd's minimal fix for gcc-13 enum warning on 32bit compiles,
superseded by commit afa4bb778e48 in mainline.
* tag 'wq-for-6.5' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq:
workqueue: Disable per-cpu CPU hog detection when wq_cpu_intensive_thresh_us is 0
workqueue: Fix WARN_ON_ONCE() triggers in worker_enter_idle()
workqueue: fix enum type for gcc-13
workqueue: Track and monitor per-workqueue CPU time usage
workqueue: Report work funcs that trigger automatic CPU_INTENSIVE mechanism
workqueue: Automatically mark CPU-hogging work items CPU_INTENSIVE
workqueue: Improve locking rule description for worker fields
workqueue: Move worker_set/clr_flags() upwards
workqueue: Re-order struct worker fields
workqueue: Add pwq->stats[] and a monitoring script
Further upgrade queue_work_on() comment
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Dave Airlie reports that gcc-13.1.1 has started complaining about some
of the workqueue code in 32-bit arm builds:
kernel/workqueue.c: In function ‘get_work_pwq’:
kernel/workqueue.c:713:24: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
713 | return (void *)(data & WORK_STRUCT_WQ_DATA_MASK);
| ^
[ ... a couple of other cases ... ]
and while it's not immediately clear exactly why gcc started complaining
about it now, I suspect it's some C23-induced enum type handlign fixup in
gcc-13 is the cause.
Whatever the reason for starting to complain, the code and data types
are indeed disgusting enough that the complaint is warranted.
The wq code ends up creating various "helper constants" (like that
WORK_STRUCT_WQ_DATA_MASK) using an enum type, which is all kinds of
confused. The mask needs to be 'unsigned long', not some unspecified
enum type.
To make matters worse, the actual "mask and cast to a pointer" is
repeated a couple of times, and the cast isn't even always done to the
right pointer, but - as the error case above - to a 'void *' with then
the compiler finishing the job.
That's now how we roll in the kernel.
So create the masks using the proper types rather than some ambiguous
enumeration, and use a nice helper that actually does the type
conversion in one well-defined place.
Incidentally, this magically makes clang generate better code. That,
admittedly, is really just a sign of clang having been seriously
confused before, and cleaning up the typing unconfuses the compiler too.
Reported-by: Dave Airlie <airlied@gmail.com>
Link: https://lore.kernel.org/lkml/CAPM=9twNnV4zMCvrPkw3H-ajZOH-01JVh_kDrxdPYQErz8ZTdA@mail.gmail.com/
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Tejun Heo <tj@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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is 0
If workqueue.cpu_intensive_thresh_us is set to 0, the detection mechanism
for CPU-hogging per-cpu work item will keep triggering spuriously:
workqueue: process_srcu hogged CPU for >0us 4 times, consider switching to WQ_UNBOUND
workqueue: gc_worker hogged CPU for >0us 4 times, consider switching to WQ_UNBOUND
workqueue: gc_worker hogged CPU for >0us 8 times, consider switching to WQ_UNBOUND
workqueue: wait_rcu_exp_gp hogged CPU for >0us 4 times, consider switching to WQ_UNBOUND
workqueue: kfree_rcu_monitor hogged CPU for >0us 4 times, consider switching to WQ_UNBOUND
workqueue: kfree_rcu_monitor hogged CPU for >0us 8 times, consider switching to WQ_UNBOUND
workqueue: reg_todo hogged CPU for >0us 4 times, consider switching to WQ_UNBOUND
This commit therefore disables the CPU-hog detection mechanism when
workqueue.cpu_intensive_thresh_us is set to 0.
tj: Patch description updated and the condition check on
cpu_intensive_thresh_us separated into a separate if statement for
readability.
Signed-off-by: Zqiang <qiang.zhang1211@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Currently, pool->nr_running can be modified from timer tick, that means the
timer tick can run nested inside a not-irq-protected section that's in the
process of modifying nr_running. Consider the following scenario:
CPU0
kworker/0:2 (events)
worker_clr_flags(worker, WORKER_PREP | WORKER_REBOUND);
->pool->nr_running++; (1)
process_one_work()
->worker->current_func(work);
->schedule()
->wq_worker_sleeping()
->worker->sleeping = 1;
->pool->nr_running--; (0)
....
->wq_worker_running()
....
CPU0 by interrupt:
wq_worker_tick()
->worker_set_flags(worker, WORKER_CPU_INTENSIVE);
->pool->nr_running--; (-1)
->worker->flags |= WORKER_CPU_INTENSIVE;
....
->if (!(worker->flags & WORKER_NOT_RUNNING))
->pool->nr_running++; (will not execute)
->worker->sleeping = 0;
....
->worker_clr_flags(worker, WORKER_CPU_INTENSIVE);
->pool->nr_running++; (0)
....
worker_set_flags(worker, WORKER_PREP);
->pool->nr_running--; (-1)
....
worker_enter_idle()
->WARN_ON_ONCE(pool->nr_workers == pool->nr_idle && pool->nr_running);
if the nr_workers is equal to nr_idle, due to the nr_running is not zero,
will trigger WARN_ON_ONCE().
[ 2.460602] WARNING: CPU: 0 PID: 63 at kernel/workqueue.c:1999 worker_enter_idle+0xb2/0xc0
[ 2.462163] Modules linked in:
[ 2.463401] CPU: 0 PID: 63 Comm: kworker/0:2 Not tainted 6.4.0-rc2-next-20230519 #1
[ 2.463771] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2 04/01/2014
[ 2.465127] Workqueue: 0x0 (events)
[ 2.465678] RIP: 0010:worker_enter_idle+0xb2/0xc0
...
[ 2.472614] Call Trace:
[ 2.473152] <TASK>
[ 2.474182] worker_thread+0x71/0x430
[ 2.474992] ? _raw_spin_unlock_irqrestore+0x28/0x50
[ 2.475263] kthread+0x103/0x120
[ 2.475493] ? __pfx_worker_thread+0x10/0x10
[ 2.476355] ? __pfx_kthread+0x10/0x10
[ 2.476635] ret_from_fork+0x2c/0x50
[ 2.477051] </TASK>
This commit therefore add the check of worker->sleeping in wq_worker_tick(),
if the worker->sleeping is not zero, directly return.
tj: Updated comment and description.
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
Tested-by: Anders Roxell <anders.roxell@linaro.org>
Closes: https://qa-reports.linaro.org/lkft/linux-next-master/build/next-20230519/testrun/17078554/suite/boot/test/clang-nightly-lkftconfig/log
Signed-off-by: Zqiang <qiang.zhang1211@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Now that wq_worker_tick() is there, we can easily track the rough CPU time
consumption of each workqueue by charging the whole tick whenever a tick
hits an active workqueue. While not super accurate, it provides reasonable
visibility into the workqueues that consume a lot of CPU cycles.
wq_monitor.py is updated to report the per-workqueue CPU times.
v2: wq_monitor.py was using "cputime" as the key when outputting in json
format. Use "cpu_time" instead for consistency with other fields.
Signed-off-by: Tejun Heo <tj@kernel.org>
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Workqueue now automatically marks per-cpu work items that hog CPU for too
long as CPU_INTENSIVE, which excludes them from concurrency management and
prevents stalling other concurrency-managed work items. If a work function
keeps running over the thershold, it likely needs to be switched to use an
unbound workqueue.
This patch adds a debug mechanism which tracks the work functions which
trigger the automatic CPU_INTENSIVE mechanism and report them using
pr_warn() with exponential backoff.
v3: Documentation update.
v2: Drop bouncing to kthread_worker for printing messages. It was to avoid
introducing circular locking dependency through printk but not effective
as it still had pool lock -> wci_lock -> printk -> pool lock loop. Let's
just print directly using printk_deferred().
Signed-off-by: Tejun Heo <tj@kernel.org>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
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If a per-cpu work item hogs the CPU, it can prevent other work items from
starting through concurrency management. A per-cpu workqueue which intends
to host such CPU-hogging work items can choose to not participate in
concurrency management by setting %WQ_CPU_INTENSIVE; however, this can be
error-prone and difficult to debug when missed.
This patch adds an automatic CPU usage based detection. If a
concurrency-managed work item consumes more CPU time than the threshold
(10ms by default) continuously without intervening sleeps, wq_worker_tick()
which is called from scheduler_tick() will detect the condition and
automatically mark it CPU_INTENSIVE.
The mechanism isn't foolproof:
* Detection depends on tick hitting the work item. Getting preempted at the
right timings may allow a violating work item to evade detection at least
temporarily.
* nohz_full CPUs may not be running ticks and thus can fail detection.
* Even when detection is working, the 10ms detection delays can add up if
many CPU-hogging work items are queued at the same time.
However, in vast majority of cases, this should be able to detect violations
reliably and provide reasonable protection with a small increase in code
complexity.
If some work items trigger this condition repeatedly, the bigger problem
likely is the CPU being saturated with such per-cpu work items and the
solution would be making them UNBOUND. The next patch will add a debug
mechanism to help spot such cases.
v4: Documentation for workqueue.cpu_intensive_thresh_us added to
kernel-parameters.txt.
v3: Switch to use wq_worker_tick() instead of hooking into preemptions as
suggested by Peter.
v2: Lai pointed out that wq_worker_stopping() also needs to be called from
preemption and rtlock paths and an earlier patch was updated
accordingly. This patch adds a comment describing the risk of infinte
recursions and how they're avoided.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
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* Some worker fields are modified only by the worker itself while holding
pool->lock thus making them safe to read from self, IRQ context if the CPU
is running the worker or while holding pool->lock. Add 'K' locking rule
for them.
* worker->sleeping is currently marked "None" which isn't very descriptive.
It's used only by the worker itself. Add 'S' locking rule for it.
A future patch will depend on the 'K' rule to access worker->current_* from
the scheduler ticks.
Signed-off-by: Tejun Heo <tj@kernel.org>
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They are going to be used in wq_worker_stopping(). Move them upwards.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
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Currently, the only way to peer into workqueue operations is through
tracing. While possible, it isn't easy or convenient to monitor
per-workqueue behaviors over time this way. Let's add pwq->stats[] that
track relevant events and a drgn monitoring script -
tools/workqueue/wq_monitor.py.
It's arguable whether this needs to be configurable. However, it currently
only has several counters and the runtime overhead shouldn't be noticeable
given that they're on pwq's which are per-cpu on per-cpu workqueues and
per-numa-node on unbound ones. Let's keep it simple for the time being.
v2: Patch reordered to earlier with fewer fields. Field will be added back
gradually. Help message improved.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
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The current queue_work_on() docbook comment says that the caller must
ensure that the specified CPU can't go away, and further says that the
penalty for failing to nail down the specified CPU is that the workqueue
handler might find itself executing on some other CPU. This is true
as far as it goes, but fails to note what happens if the specified CPU
never was online. Therefore, further expand this comment to say that
specifying a CPU that was never online will result in a splat.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Pull workqueue updates from Tejun Heo:
"Mostly changes from Petr to improve warning and error reporting.
Workqueue now reports more of the relevant failures with better
context which should help debugging"
* tag 'wq-for-6.4' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq:
workqueue: Introduce show_freezable_workqueues
workqueue: Print backtraces from CPUs with hung CPU bound workqueues
workqueue: Warn when a rescuer could not be created
workqueue: Interrupted create_worker() is not a repeated event
workqueue: Warn when a new worker could not be created
workqueue: Fix hung time report of worker pools
workqueue: Simplify a pr_warn() call in wq_select_unbound_cpu()
MAINTAINERS: Add workqueue_internal.h to the WORKQUEUE entry
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Currently show_all_workqueue is called if freeze fails at the time of
freeze the workqueues, which shows the status of all workqueues and of
all worker pools. In this cases we may only need to dump state of only
workqueues that are freezable and busy.
This patch defines show_freezable_workqueues, which uses
show_one_workqueue, a granular function that shows the state of individual
workqueues, so that dump only the state of freezable workqueues
at that time.
tj: Minor message adjustment.
Signed-off-by: Jungseung Lee <js07.lee@samsung.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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The workqueue watchdog reports a lockup when there was not any progress
in the worker pool for a long time. The progress means that a pending
work item starts being proceed.
Worker pools for unbound workqueues always wake up an idle worker and
try to process the work immediately. The last idle worker has to create
new worker first. The stall might happen only when a new worker could
not be created in which case an error should get printed. Another problem
might be too high load. In this case, workers are victims of a global
system problem.
Worker pools for CPU bound workqueues are designed for lightweight
work items that do not need much CPU time. They are proceed one by
one on a single worker. New worker is used only when a work is sleeping.
It creates one additional scenario. The stall might happen when
the CPU-bound workqueue is used for CPU-intensive work.
More precisely, the stall is detected when a CPU-bound worker is in
the TASK_RUNNING state for too long. In this case, it might be useful
to see the backtrace from the problematic worker.
The information how long a worker is in the running state is not available.
But the CPU-bound worker pools do not have many workers in the running
state by definition. And only few pools are typically blocked.
It should be acceptable to print backtraces from all workers in
TASK_RUNNING state in the stalled worker pools. The number of false
positives should be very low.
Signed-off-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Rescuers are created when a workqueue with WQ_MEM_RECLAIM is allocated.
It typically happens during the system boot.
systemd switches the root filesystem from initrd to the booted system
during boot. It kills processes that block the switch for too long.
One of the process might be modprobe that tries to create a workqueue.
These problems are hard to reproduce. Also alloc_workqueue() does not
pass the error code. Make the debugging easier by printing an error,
similar to create_worker().
Signed-off-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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kthread_create_on_node() might get interrupted(). It is rare but realistic.
For example, when an unbound workqueue is allocated in module_init()
callback. It is done in the context of the "modprobe" process. And,
for example, systemd might kill pending processes when switching root
from initrd to the booted system.
The interrupt is a one-off event and the race might be hard to reproduce.
It is always worth printing.
Signed-off-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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The workqueue watchdog reports a lockup when there was not any progress
in the worker pool for a long time. The progress means that a pending
work item starts being proceed.
The progress is guaranteed by using idle workers or creating new workers
for pending work items.
There are several reasons why a new worker could not be created:
+ there is not enough memory
+ there is no free pool ID (IDR API)
+ the system reached PID limit
+ the process creating the new worker was interrupted
+ the last idle worker (manager) has not been scheduled for a long
time. It was not able to even start creating the kthread.
None of these failures is reported at the moment. The only clue is that
show_one_worker_pool() prints that there is a manager. It is the last
idle worker that is responsible for creating a new one. But it is not
clear if create_worker() is failing and why.
Make the debugging easier by printing errors in create_worker().
The error code is important, especially from kthread_create_on_node().
It helps to distinguish the various reasons. For example, reaching
memory limit (-ENOMEM), other system limits (-EAGAIN), or process
interrupted (-EINTR).
Use pr_once() to avoid repeating the same error every CREATE_COOLDOWN
for each stuck worker pool.
Ratelimited printk() might be better. It would help to know if the problem
remains. It would be more clear if the create_worker() errors and workqueue
stalls are related. Also old messages might get lost when the internal log
buffer is full. The problem is that printk() might touch the watchdog.
For example, see touch_nmi_watchdog() in serial8250_console_write().
It would require synchronization of the begin and length of the ratelimit
interval with the workqueue watchdog. Otherwise, the error messages
might break the watchdog. This does not look worth the complexity.
Signed-off-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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The workqueue watchdog prints a warning when there is no progress in
a worker pool. Where the progress means that the pool started processing
a pending work item.
Note that it is perfectly fine to process work items much longer.
The progress should be guaranteed by waking up or creating idle
workers.
show_one_worker_pool() prints state of non-idle worker pool. It shows
a delay since the last pool->watchdog_ts.
The timestamp is updated when a first pending work is queued in
__queue_work(). Also it is updated when a work is dequeued for
processing in worker_thread() and rescuer_thread().
The delay is misleading when there is no pending work item. In this
case it shows how long the last work item is being proceed. Show
zero instead. There is no stall if there is no pending work.
Fixes: 82607adcf9cdf40fb7b ("workqueue: implement lockup detector")
Signed-off-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Use pr_warn_once() to achieve the same thing. It's simpler.
Signed-off-by: Ammar Faizi <ammarfaizi2@gnuweeb.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.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: Lai Jiangshan <jiangshanlai@gmail.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20230313182918.1312597-8-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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!CONFIG_SMP builds complain about rebind_worker() being unused. Its only
user, rebind_workers() is indeed only defined for CONFIG_SMP, so just fold
the two lines back up there.
Link: http://lore.kernel.org/r/20230113143102.2e94d74f@canb.auug.org.au
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Valentin Schneider <vschneid@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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It has been reported that isolated CPUs can suffer from interference due to
per-CPU kworkers waking up just to die.
A surge of workqueue activity during initial setup of a latency-sensitive
application (refresh_vm_stats() being one of the culprits) can cause extra
per-CPU kworkers to be spawned. Then, said latency-sensitive task can be
running merrily on an isolated CPU only to be interrupted sometime later by
a kworker marked for death (cf. IDLE_WORKER_TIMEOUT, 5 minutes after last
kworker activity).
Prevent this by affining kworkers to the wq_unbound_cpumask (which doesn't
contain isolated CPUs, cf. HK_TYPE_WQ) before waking them up after marking
them with WORKER_DIE.
Changing the affinity does require a sleepable context, leverage the newly
introduced pool->idle_cull_work to get that.
Remove dying workers from pool->workers and keep track of them in a
separate list. This intentionally prevents for_each_loop_worker() from
iterating over workers that are marked for death.
Rename destroy_worker() to set_working_dying() to better reflect its
effects and relationship with wake_dying_workers().
Signed-off-by: Valentin Schneider <vschneid@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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put_unbound_pool() currently passes wq_manager_inactive() as exit condition
to rcuwait_wait_event(), which grabs pool->lock to check for
pool->flags & POOL_MANAGER_ACTIVE
A later patch will require destroy_worker() to be invoked with
wq_pool_attach_mutex held, which needs to be acquired before
pool->lock. A mutex cannot be acquired within rcuwait_wait_event(), as
it could clobber the task state set by rcuwait_wait_event()
Instead, restructure the waiting logic to acquire any necessary lock
outside of rcuwait_wait_event().
Since further work cannot be inserted into unbound pwqs that have reached
->refcnt==0, this is bound to make forward progress as eventually the
worklist will be drained and need_more_worker(pool) will remain false,
preventing any worker from stealing the manager position from us.
Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Valentin Schneider <vschneid@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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A later patch will require a sleepable context in the idle worker timeout
function. Converting worker_pool.idle_timer to a delayed_work gives us just
that, however this would imply turning all idle_timer expiries into
scheduler events (waking up a worker to handle the dwork).
Instead, implement a "custom dwork" where the timer callback does some
extra checks before queuing the associated work.
No change in functionality intended.
Signed-off-by: Valentin Schneider <vschneid@redhat.com>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Later patches will reuse this code, move it into reusable functions.
Signed-off-by: Valentin Schneider <vschneid@redhat.com>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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When unbind_workers() reads wq_unbound_cpumask to set the affinity of
freshly-unbound kworkers, it only holds wq_pool_attach_mutex. This isn't
sufficient as wq_unbound_cpumask is only protected by wq_pool_mutex.
Make wq_unbound_cpumask protected with wq_pool_attach_mutex and also
remove the need of temporary saved_cpumask.
Fixes: 10a5a651e3af ("workqueue: Restrict kworker in the offline CPU pool running on housekeeping CPUs")
Reported-by: Valentin Schneider <vschneid@redhat.com>
Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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The show_pwq() function dumps out a pool_workqueue structure's activity,
including the pending work-queue handlers:
Showing busy workqueues and worker pools:
workqueue events: flags=0x0
pwq 0: cpus=0 node=0 flags=0x1 nice=0 active=10/256 refcnt=11
in-flight: 7:test_work_func, 64:test_work_func, 249:test_work_func
pending: test_work_func, test_work_func, test_work_func1, test_work_func1, test_work_func1, test_work_func1, test_work_func1
When large systems are facing certain types of hang conditions, it is not
unusual for this "pending" list to contain runs of hundreds of identical
function names. This "wall of text" is difficult to read, and worse yet,
it can be interleaved with other output such as stack traces.
Therefore, make show_pwq() use run-length encoding so that the above
printout instead looks like this:
Showing busy workqueues and worker pools:
workqueue events: flags=0x0
pwq 0: cpus=0 node=0 flags=0x1 nice=0 active=10/256 refcnt=11
in-flight: 7:test_work_func, 64:test_work_func, 249:test_work_func
pending: 2*test_work_func, 5*test_work_func1
When no comma would be printed, including the WORK_STRUCT_LINKED case,
a new run is started unconditionally.
This output is more readable, places less stress on the hardware,
firmware, and software on the console-log path, and reduces interference
with other output.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Dave Jones <davej@codemonkey.org.uk>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Currently if the user queues a new work item unintentionally
into a wq after the destroy_workqueue(wq), the work still can
be queued and scheduled without any noticeable kernel message
before the end of a RCU grace period.
As a debug-aid facility, this commit adds a new flag
__WQ_DESTROYING to spot that issue by triggering a kernel WARN
message.
Signed-off-by: Richard Clark <richard.xnu.clark@gmail.com>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Earlier commits in this series allow battery-powered systems to build
their kernels with the default-disabled CONFIG_RCU_LAZY=y Kconfig option.
This Kconfig option causes call_rcu() to delay its callbacks in order
to batch them. This means that a given RCU grace period covers more
callbacks, thus reducing the number of grace periods, in turn reducing
the amount of energy consumed, which increases battery lifetime which
can be a very good thing. This is not a subtle effect: In some important
use cases, the battery lifetime is increased by more than 10%.
This CONFIG_RCU_LAZY=y option is available only for CPUs that offload
callbacks, for example, CPUs mentioned in the rcu_nocbs kernel boot
parameter passed to kernels built with CONFIG_RCU_NOCB_CPU=y.
Delaying callbacks is normally not a problem because most callbacks do
nothing but free memory. If the system is short on memory, a shrinker
will kick all currently queued lazy callbacks out of their laziness,
thus freeing their memory in short order. Similarly, the rcu_barrier()
function, which blocks until all currently queued callbacks are invoked,
will also kick lazy callbacks, thus enabling rcu_barrier() to complete
in a timely manner.
However, there are some cases where laziness is not a good option.
For example, synchronize_rcu() invokes call_rcu(), and blocks until
the newly queued callback is invoked. It would not be a good for
synchronize_rcu() to block for ten seconds, even on an idle system.
Therefore, synchronize_rcu() invokes call_rcu_hurry() instead of
call_rcu(). The arrival of a non-lazy call_rcu_hurry() callback on a
given CPU kicks any lazy callbacks that might be already queued on that
CPU. After all, if there is going to be a grace period, all callbacks
might as well get full benefit from it.
Yes, this could be done the other way around by creating a
call_rcu_lazy(), but earlier experience with this approach and
feedback at the 2022 Linux Plumbers Conference shifted the approach
to call_rcu() being lazy with call_rcu_hurry() for the few places
where laziness is inappropriate.
And another call_rcu() instance that cannot be lazy is the one
in queue_rcu_work(), given that callers to queue_rcu_work() are
not necessarily OK with long delays.
Therefore, make queue_rcu_work() use call_rcu_hurry() in order to revert
to the old behavior.
[ paulmck: Apply s/call_rcu_flush/call_rcu_hurry/ feedback from Tejun Heo. ]
Signed-off-by: Uladzislau Rezki <urezki@gmail.com>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
|
|
git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux
Pull kcfi updates from Kees Cook:
"This replaces the prior support for Clang's standard Control Flow
Integrity (CFI) instrumentation, which has required a lot of special
conditions (e.g. LTO) and work-arounds.
The new implementation ("Kernel CFI") is specific to C, directly
designed for the Linux kernel, and takes advantage of architectural
features like x86's IBT. This series retains arm64 support and adds
x86 support.
GCC support is expected in the future[1], and additional "generic"
architectural support is expected soon[2].
Summary:
- treewide: Remove old CFI support details
- arm64: Replace Clang CFI support with Clang KCFI support
- x86: Introduce Clang KCFI support"
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107048 [1]
Link: https://github.com/samitolvanen/llvm-project/commits/kcfi_generic [2]
* tag 'kcfi-v6.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux: (22 commits)
x86: Add support for CONFIG_CFI_CLANG
x86/purgatory: Disable CFI
x86: Add types to indirectly called assembly functions
x86/tools/relocs: Ignore __kcfi_typeid_ relocations
kallsyms: Drop CONFIG_CFI_CLANG workarounds
objtool: Disable CFI warnings
objtool: Preserve special st_shndx indexes in elf_update_symbol
treewide: Drop __cficanonical
treewide: Drop WARN_ON_FUNCTION_MISMATCH
treewide: Drop function_nocfi
init: Drop __nocfi from __init
arm64: Drop unneeded __nocfi attributes
arm64: Add CFI error handling
arm64: Add types to indirect called assembly functions
psci: Fix the function type for psci_initcall_t
lkdtm: Emit an indirect call for CFI tests
cfi: Add type helper macros
cfi: Switch to -fsanitize=kcfi
cfi: Drop __CFI_ADDRESSABLE
cfi: Remove CONFIG_CFI_CLANG_SHADOW
...
|
|
CONFIG_CFI_CLANG no longer breaks cross-module function address
equality, which makes WARN_ON_FUNCTION_MISMATCH unnecessary. Remove
the definition and switch back to WARN_ON_ONCE.
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Tested-by: Kees Cook <keescook@chromium.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20220908215504.3686827-15-samitolvanen@google.com
|
|
Like Hillf Danton mentioned
syzbot should have been able to catch cancel_work_sync() in work context
by checking lockdep_map in __flush_work() for both flush and cancel.
in [1], being unable to report an obvious deadlock scenario shown below is
broken. From locking dependency perspective, sync version of cancel request
should behave as if flush request, for it waits for completion of work if
that work has already started execution.
----------
#include <linux/module.h>
#include <linux/sched.h>
static DEFINE_MUTEX(mutex);
static void work_fn(struct work_struct *work)
{
schedule_timeout_uninterruptible(HZ / 5);
mutex_lock(&mutex);
mutex_unlock(&mutex);
}
static DECLARE_WORK(work, work_fn);
static int __init test_init(void)
{
schedule_work(&work);
schedule_timeout_uninterruptible(HZ / 10);
mutex_lock(&mutex);
cancel_work_sync(&work);
mutex_unlock(&mutex);
return -EINVAL;
}
module_init(test_init);
MODULE_LICENSE("GPL");
----------
The check this patch restores was added by commit 0976dfc1d0cd80a4
("workqueue: Catch more locking problems with flush_work()").
Then, lockdep's crossrelease feature was added by commit b09be676e0ff25bd
("locking/lockdep: Implement the 'crossrelease' feature"). As a result,
this check was once removed by commit fd1a5b04dfb899f8 ("workqueue: Remove
now redundant lock acquisitions wrt. workqueue flushes").
But lockdep's crossrelease feature was removed by commit e966eaeeb623f099
("locking/lockdep: Remove the cross-release locking checks"). At this
point, this check should have been restored.
Then, commit d6e89786bed977f3 ("workqueue: skip lockdep wq dependency in
cancel_work_sync()") introduced a boolean flag in order to distinguish
flush_work() and cancel_work_sync(), for checking "struct workqueue_struct"
dependency when called from cancel_work_sync() was causing false positives.
Then, commit 87915adc3f0acdf0 ("workqueue: re-add lockdep dependencies for
flushing") tried to restore "struct work_struct" dependency check, but by
error checked this boolean flag. Like an example shown above indicates,
"struct work_struct" dependency needs to be checked for both flush_work()
and cancel_work_sync().
Link: https://lkml.kernel.org/r/20220504044800.4966-1-hdanton@sina.com [1]
Reported-by: Hillf Danton <hdanton@sina.com>
Suggested-by: Lai Jiangshan <jiangshanlai@gmail.com>
Fixes: 87915adc3f0acdf0 ("workqueue: re-add lockdep dependencies for flushing")
Cc: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Tejun Heo <tj@kernel.org>
|
|
Pull drm updates from Dave Airlie:
"Highlights:
- New driver for logicvc - which is a display IP core.
- EDID parser rework to add new extensions
- fbcon scrolling improvements
- i915 has some more DG2 work but not enabled by default, but should
have enough features for userspace to work now.
Otherwise it's lots of work all over the place. Detailed summary:
New driver:
- logicvc
vfio:
- use aperture API
core:
- of: Add data-lane helpers and convert drivers
- connector: Remove deprecated ida_simple_get()
media:
- Add various RGB666 and RGB888 format constants
panel:
- Add HannStar HSD101PWW
- Add ETML0700Y5DHA
dma-buf:
- add sync-file API
- set dma mask for udmabuf devices
fbcon:
- Improve scrolling performance
- Sanitize input
fbdev:
- device unregistering fixes
- vesa: Support COMPILE_TEST
- Disable firmware-device registration when first native driver loads
aperture:
- fix segfault during hot-unplug
- export for use with other subsystems
client:
- use driver validated modes
dp:
- aux: make probing more reliable
- mst: Read extended DPCD capabilities during system resume
- Support waiting for HDP signal
- Port-validation fixes
edid:
- CEA data-block iterators
- struct drm_edid introduction
- implement HF-EEODB extension
gem:
- don't use fb format non-existing planes
probe-helper:
- use 640x480 as displayport fallback
scheduler:
- don't kill jobs in interrupt context
bridge:
- Add support for i.MX8qxp and i.MX8qm
- lots of fixes/cleanups
- Add TI-DLPC3433
- fy07024di26a30d: Optional GPIO reset
- ldb: Add reg and reg-name properties to bindings, Kconfig fixes
- lt9611: Fix display sensing;
- tc358767: DSI/DPI refactoring and DSI-to-eDP support, DSI lane handling
- tc358775: Fix clock settings
- ti-sn65dsi83: Allow GPIO to sleep
- adv7511: I2C fixes
- anx7625: Fix error handling; DPI fixes; Implement HDP timeout via callback
- fsl-ldb: Drop DE flip
- ti-sn65dsi86: Convert to atomic modesetting
amdgpu:
- use atomic fence helpers in DM
- fix VRAM address calculations
- export CRTC bpc via debugfs
- Initial devcoredump support
- Enable high priority gfx queue on asics which support it
- Adjust GART size on newer APUs for S/G display
- Soft reset for GFX 11 / SDMA 6
- Add gfxoff status query for vangogh
- Fix timestamps for cursor only commits
- Adjust GART size on newer APUs for S/G display
- fix buddy memory corruption
amdkfd:
- MMU notifier fixes
- P2P DMA support using dma-buf
- Add available memory IOCTL
- HMM profiler support
- Simplify GPUVM validation
- Unified memory for CWSR save/restore area
i915:
- General driver clean-up
- DG2 enabling (still under force probe)
- DG2 small BAR memory support
- HuC loading support
- DG2 workarounds
- DG2/ATS-M device IDs added
- Ponte Vecchio prep work and new blitter engines
- add Meteorlake support
- Fix sparse warnings
- DMC MMIO range checks
- Audio related fixes
- Runtime PM fixes
- PSR fixes
- Media freq factor and per-gt enhancements
- DSI fixes for ICL+
- Disable DMC flip queue handlers
- ADL_P voltage swing updates
- Use more the VBT for panel information
- Fix on Type-C ports with TBT mode
- Improve fastset and allow seamless M/N changes
- Accept more fixed modes with VRR/DMRRS panels
- Disable connector polling for a headless SKU
- ADL-S display PLL w/a
- Enable THP on Icelake and beyond
- Fix i915_gem_object_ggtt_pin_ww regression on old platforms
- Expose per tile media freq factor in sysfs
- Fix dma_resv fence handling in multi-batch execbuf
- Improve on suspend / resume time with VT-d enabled
- export CRTC bpc settings via debugfs
msm:
- gpu: a619 support
- gpu: Fix for unclocked GMU register access
- gpu: Devcore dump enhancements
- client utilization via fdinfo support
- fix fence rollover issue
- gem: Lockdep false-positive warning fix
- gem: Switch to pfn mappings
- WB support on sc7180
- dp: dropped custom bulk clock implementation
- fix link retraining on resolution change
- hdmi: dropped obsolete GPIO support
tegra:
- context isolation for host1x engines
- tegra234 soc support
mediatek:
- add vdosys0/1 for mt8195
- add MT8195 dp_intf driver
exynos:
- Fix resume function issue of exynos decon driver by calling
clk_disable_unprepare() properly if clk_prepare_enable() failed.
nouveau:
- set of misc fixes/cleanups
- display cleanups
gma500:
- Cleanup connector I2C handling
hyperv:
- Unify VRAM allocation of Gen1 and Gen2
meson:
- Support YUV422 output; Refcount fixes
mgag200:
- Support damage clipping
- Support gamma handling
- Protect concurrent HW access
- Fixes to connector
- Store model-specific limits in device-info structure
- fix PCI register init
panfrost:
- Valhall support
r128:
- Fix bit-shift overflow
rockchip:
- Locking fixes in error path
ssd130x:
- Fix built-in linkage
udl:
- Always advertize VGA connector
ast:
- Support multiple outputs
- fix black screen on resume
sun4i:
- HDMI PHY cleanups
vc4:
- Add support for BCM2711
vkms:
- Allocate output buffer with vmalloc()
mcde:
- Fix ref-count leak
mxsfb/lcdif:
- Support i.MX8MP LCD controller
stm/ltdc:
- Support dynamic Z order
- Support mirroring
ingenic:
- Fix display at maximum resolution"
* tag 'drm-next-2022-08-03' of git://anongit.freedesktop.org/drm/drm: (1480 commits)
drm/amd/display: Fix a compilation failure on PowerPC caused by FPU code
drm/amdgpu: enable support for psp 13.0.4 block
drm/amdgpu: add files for PSP 13.0.4
drm/amdgpu: add header files for MP 13.0.4
drm/amdgpu: correct RLC_RLCS_BOOTLOAD_STATUS offset and index
drm/amdgpu: send msg to IMU for the front-door loading
drm/amdkfd: use time_is_before_jiffies(a + b) to replace "jiffies - a > b"
drm/amdgpu: fix hive reference leak when reflecting psp topology info
drm/amd/pm: enable GFX ULV feature support for SMU13.0.0
drm/amd/pm: update driver if header for SMU 13.0.0
drm/amdgpu: move mes self test after drm sched re-started
drm/amdgpu: drop non-necessary call trace dump
drm/amdgpu: enable VCN cg and JPEG cg/pg
drm/amdgpu: vcn_4_0_2 video codec query
drm/amdgpu: add VCN_4_0_2 firmware support
drm/amdgpu: add VCN function in NBIO v7.7
drm/amdgpu: fix a vcn4 boot poll bug in emulation mode
drm/amd/amdgpu: add memory training support for PSP_V13
drm/amdkfd: remove an unnecessary amdgpu_bo_ref
drm/amd/pm: Add get_gfx_off_status interface for yellow carp
...
|
|
Doing set_cpus_allowed_ptr() with wq_unbound_cpumask can be possible
fails and trigger the false warning.
Use cpu_possible_mask instead when wq_unbound_cpumask has no active CPUs.
It is very easy to trigger the warning:
Set wq_unbound_cpumask to a small set of CPUs.
Offline all the CPUs of wq_unbound_cpumask.
Offline an extra CPU and trigger the warning.
Fixes: 10a5a651e3af ("workqueue: Restrict kworker in the offline CPU pool running on housekeeping CPUs")
Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
|
|
https://gitlab.freedesktop.org/agd5f/linux into drm-next
amd-drm-next-5.20-2022-07-05:
amdgpu:
- Various spelling and grammer fixes
- Various eDP fixes
- Various DMCUB fixes
- VCN fixes
- GMC 11 fixes
- RAS fixes
- TMZ support for GC 10.3.7
- GPUVM TLB flush fixes
- SMU 13.0.x updates
- DCN 3.2 Support
- DCN 3.2.1 Support
- MES updates
- GFX11 modifiers support
- USB-C fixes
- MMHUB 3.0.1 support
- SDMA 6.0 doorbell fixes
- Initial devcoredump support
- Enable high priority gfx queue on asics which support it
- Enable GPU reset for SMU 13.0.4
- OLED display fixes
- MPO fixes
- DC frame size fixes
- ASPM support for PCIE 7.4/7.6
- GPU reset support for SMU 13.0.0
- GFX11 updates
- VCN JPEG fix
- BACO support for SMU 13.0.7
- VCN instance handling fix
- GFX8 GPUVM TLB flush fix
- GPU reset rework
- VCN 4.0.2 support
- GTT size fixes
- DP link training fixes
- LSDMA 6.0.1 support
- Various backlight fixes
- Color encoding fixes
- Backlight config cleanup
- VCN 4.x unified queue cleanup
amdkfd:
- MMU notifier fixes
- Updates for GC 10.3.6 and 10.3.7
- P2P DMA support using dma-buf
- Add available memory IOCTL
- SDMA 6.0.1 fix
- MES fixes
- HMM profiler support
radeon:
- License fix
- Backlight config cleanup
UAPI:
- Add available memory IOCTL to amdkfd
Proposed userspace: https://www.mail-archive.com/amd-gfx@lists.freedesktop.org/msg75743.html
- HMM profiler support for amdkfd
Proposed userspace: https://lists.freedesktop.org/archives/amd-gfx/2022-June/080805.html
Signed-off-by: Dave Airlie <airlied@redhat.com>
From: Alex Deucher <alexander.deucher@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220705212633.6037-1-alexander.deucher@amd.com
|
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This reverts commit 6417250d3f894e66a68ba1cd93676143f2376a6f.
amdpgu need this function in order to prematurly stop pending
reset works when another reset work already in progress.
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Reviewed-by: Lai Jiangshan<jiangshanlai@gmail.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
|
|
Since flush operation synchronously waits for completion, flushing
system-wide WQs (e.g. system_wq) might introduce possibility of deadlock
due to unexpected locking dependency. Tejun Heo commented at [1] that it
makes no sense at all to call flush_workqueue() on the shared WQs as the
caller has no idea what it's gonna end up waiting for.
Although there is flush_scheduled_work() which flushes system_wq WQ with
"Think twice before calling this function! It's very easy to get into
trouble if you don't take great care." warning message, syzbot found a
circular locking dependency caused by flushing system_wq WQ [2].
Therefore, let's change the direction to that developers had better use
their local WQs if flush_scheduled_work()/flush_workqueue(system_*_wq) is
inevitable.
Steps for converting system-wide WQs into local WQs are explained at [3],
and a conversion to stop flushing system-wide WQs is in progress. Now we
want some mechanism for preventing developers who are not aware of this
conversion from again start flushing system-wide WQs.
Since I found that WARN_ON() is complete but awkward approach for teaching
developers about this problem, let's use __compiletime_warning() for
incomplete but handy approach. For completeness, we will also insert
WARN_ON() into __flush_workqueue() after all in-tree users stopped calling
flush_scheduled_work().
Link: https://lore.kernel.org/all/YgnQGZWT%2Fn3VAITX@slm.duckdns.org/ [1]
Link: https://syzkaller.appspot.com/bug?extid=bde0f89deacca7c765b8 [2]
Link: https://lkml.kernel.org/r/49925af7-78a8-a3dd-bce6-cfc02e1a9236@I-love.SAKURA.ne.jp [3]
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Tejun Heo <tj@kernel.org>
|
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When a CPU is going offline, all workers on the CPU's pool will have their
cpus_allowed cleared to cpu_possible_mask and can run on any CPUs including
the isolated ones. Instead, set cpus_allowed to wq_unbound_cpumask so that
the can avoid isolated CPUs.
Signed-off-by: Zqiang <qiang1.zhang@intel.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
|
|
Pull workqueue updates from Tejun Heo:
"Nothing major. Just follow-up cleanups from Lai after the earlier
synchronization simplification"
* 'for-5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq:
workqueue: Convert the type of pool->nr_running to int
workqueue: Use wake_up_worker() in wq_worker_sleeping() instead of open code
workqueue: Change the comments of the synchronization about the idle_list
workqueue: Remove the mb() pair between wq_worker_sleeping() and insert_work()
|
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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 prepare for supporting each feature of the housekeeping cpumask
toward cpuset, prepare each of the HK_FLAG_* entries to move to their
own cpumask with enforcing to fetch them individually. The new
constraint is that multiple HK_FLAG_* entries can't be mixed together
anymore in a single call to housekeeping cpumask().
This will later allow, for example, to runtime modify the cpulist passed
through "isolcpus=", "nohz_full=" and "rcu_nocbs=" kernel boot
parameters.
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>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20220207155910.527133-3-frederic@kernel.org
|
|
It is only modified in associated CPU, so it doesn't need to be atomic.
tj: Comment updated.
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
|
|
The wakeup code in wq_worker_sleeping() is the same as wake_up_worker().
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
|
|
The access to idle_list in wq_worker_sleeping() is changed to be
protected by pool->lock, so the comments above idle_list can be changed
to "L:" which is the meaning of "access with pool->lock held".
And the outdated comments in wq_worker_sleeping() is removed since
the function is not called with rq lock held any more, idle_list is
dereferenced with pool lock now.
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
|
|
In wq_worker_sleeping(), the access to worklist is protected by the
pool->lock, so the memory barrier is unneeded.
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
|
|
for-5.16-fixes contains two subtle race conditions which were introduced by
scheduler side code cleanups. The branch didn't get pushed out, so merge
into for-5.17.
|
|
nr_running is never modified remotely after the schedule callback in
wakeup path is removed.
Rather nr_running is often accessed with other fields in the pool
together, so the cacheline_aligned for nr_running isn't needed.
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
|
|
In unbind_workers(), there are two pool->lock held sections separated
by the code of zapping nr_running. wake_up_worker() needs to be in
pool->lock held section and after zapping nr_running. And zapping
nr_running had to be after schedule() when the local wake up
functionality was in use. Now, the call to schedule() has been removed
along with the local wake up functionality, so the code can be merged
into the same pool->lock held section.
The diffstat shows that it is other code moved down because the diff
tools can not know the meaning of merging lock sections by swapping
two code blocks.
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
|
|
The commit 6d25be5782e4 ("sched/core, workqueues: Distangle worker
accounting from rq lock") changed the schedule callbacks for workqueue
and moved the schedule callback from the wakeup code to at end of
schedule() in the worker's process context.
It means that the callback wq_worker_running() is guaranteed that
it sees the %WORKER_UNBOUND flag after scheduled since unbind_workers()
is running on the same CPU that all the pool's workers bound to.
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
|
|
Long time before, workers are not ALL bound after CPU_ONLINE, they can
still be running in other CPUs before self rebinding.
But the commit a9ab775bcadf ("workqueue: directly restore CPU affinity
of workers from CPU_ONLINE") makes rebind_workers() bind them all.
So all workers are on the CPU before the CPU is down.
And the comment in unbind_workers() refers to the workers "which are
still executing works from before the last CPU down" is outdated.
Just removed it.
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
|
|
The commit 6d25be5782e4 ("sched/core, workqueues: Distangle worker
accounting from rq lock") changed the schedule callbacks for workqueue
and removed the local-wake-up functionality.
Now the wakingup of workers is done by normal fashion and workers not
yet migrated to the specific CPU in concurrency managed pool can also
be woken up by workers that already bound to the specific cpu now.
So this advanced kicking of the idle workers to migrate them to the
associated CPU is unneeded now.
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
|
|
It isn't called with preempt disabled now.
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
|
|
At CPU-hotplug time, unbind_workers() may preempt a worker while it is
going to sleep. In that case the following scenario can happen:
unbind_workers() wq_worker_sleeping()
-------------- -------------------
if (worker->flags & WORKER_NOT_RUNNING)
return;
//PREEMPTED by unbind_workers
worker->flags |= WORKER_UNBOUND;
[...]
atomic_set(&pool->nr_running, 0);
//resume to worker
atomic_dec_and_test(&pool->nr_running);
After unbind_worker() resets pool->nr_running, the value is expected to
remain 0 until the pool ever gets rebound in case cpu_up() is called on
the target CPU in the future. But here the race leaves pool->nr_running
with a value of -1, triggering the following warning when the worker goes
idle:
WARNING: CPU: 3 PID: 34 at kernel/workqueue.c:1823 worker_enter_idle+0x95/0xc0
Modules linked in:
CPU: 3 PID: 34 Comm: kworker/3:0 Not tainted 5.16.0-rc1+ #34
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.12.0-59-gc9ba527-rebuilt.opensuse.org 04/01/2014
Workqueue: 0x0 (rcu_par_gp)
RIP: 0010:worker_enter_idle+0x95/0xc0
Code: 04 85 f8 ff ff ff 39 c1 7f 09 48 8b 43 50 48 85 c0 74 1b 83 e2 04 75 99 8b 43 34 39 43 30 75 91 8b 83 00 03 00 00 85 c0 74 87 <0f> 0b 5b c3 48 8b 35 70 f1 37 01 48 8d 7b 48 48 81 c6 e0 93 0
RSP: 0000:ffff9b7680277ed0 EFLAGS: 00010086
RAX: 00000000ffffffff RBX: ffff93465eae9c00 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffff9346418a0000 RDI: ffff934641057140
RBP: ffff934641057170 R08: 0000000000000001 R09: ffff9346418a0080
R10: ffff9b768027fdf0 R11: 0000000000002400 R12: ffff93465eae9c20
R13: ffff93465eae9c20 R14: ffff93465eae9c70 R15: ffff934641057140
FS: 0000000000000000(0000) GS:ffff93465eac0000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000001cc0c000 CR4: 00000000000006e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
worker_thread+0x89/0x3d0
? process_one_work+0x400/0x400
kthread+0x162/0x190
? set_kthread_struct+0x40/0x40
ret_from_fork+0x22/0x30
</TASK>
Also due to this incorrect "nr_running == -1", all sorts of hazards can
happen, starting with queued works being ignored because no workers are
awaken at insert_work() time.
Fix this with checking again the worker flags while pool->lock is locked.
Fixes: b945efcdd07d ("sched: Remove pointless preemption disable in sched_submit_work()")
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
Tested-by: Paul E. McKenney <paulmck@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
|
|
At CPU-hotplug time, unbind_worker() may preempt a worker while it is
waking up. In that case the following scenario can happen:
unbind_workers() wq_worker_running()
-------------- -------------------
if (!(worker->flags & WORKER_NOT_RUNNING))
//PREEMPTED by unbind_workers
worker->flags |= WORKER_UNBOUND;
[...]
atomic_set(&pool->nr_running, 0);
//resume to worker
atomic_inc(&worker->pool->nr_running);
After unbind_worker() resets pool->nr_running, the value is expected to
remain 0 until the pool ever gets rebound in case cpu_up() is called on
the target CPU in the future. But here the race leaves pool->nr_running
with a value of 1, triggering the following warning when the worker goes
idle:
WARNING: CPU: 3 PID: 34 at kernel/workqueue.c:1823 worker_enter_idle+0x95/0xc0
Modules linked in:
CPU: 3 PID: 34 Comm: kworker/3:0 Not tainted 5.16.0-rc1+ #34
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.12.0-59-gc9ba527-rebuilt.opensuse.org 04/01/2014
Workqueue: 0x0 (rcu_par_gp)
RIP: 0010:worker_enter_idle+0x95/0xc0
Code: 04 85 f8 ff ff ff 39 c1 7f 09 48 8b 43 50 48 85 c0 74 1b 83 e2 04 75 99 8b 43 34 39 43 30 75 91 8b 83 00 03 00 00 85 c0 74 87 <0f> 0b 5b c3 48 8b 35 70 f1 37 01 48 8d 7b 48 48 81 c6 e0 93 0
RSP: 0000:ffff9b7680277ed0 EFLAGS: 00010086
RAX: 00000000ffffffff RBX: ffff93465eae9c00 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffff9346418a0000 RDI: ffff934641057140
RBP: ffff934641057170 R08: 0000000000000001 R09: ffff9346418a0080
R10: ffff9b768027fdf0 R11: 0000000000002400 R12: ffff93465eae9c20
R13: ffff93465eae9c20 R14: ffff93465eae9c70 R15: ffff934641057140
FS: 0000000000000000(0000) GS:ffff93465eac0000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000001cc0c000 CR4: 00000000000006e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
worker_thread+0x89/0x3d0
? process_one_work+0x400/0x400
kthread+0x162/0x190
? set_kthread_struct+0x40/0x40
ret_from_fork+0x22/0x30
</TASK>
Also due to this incorrect "nr_running == 1", further queued work may
end up not being served, because no worker is awaken at work insert time.
This raises rcutorture writer stalls for example.
Fix this with disabling preemption in the right place in
wq_worker_running().
It's worth noting that if the worker migrates and runs concurrently with
unbind_workers(), it is guaranteed to see the WORKER_UNBOUND flag update
due to set_cpus_allowed_ptr() acquiring/releasing rq->lock.
Fixes: 6d25be5782e4 ("sched/core, workqueues: Distangle worker accounting from rq lock")
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
Tested-by: Paul E. McKenney <paulmck@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
|
|
The current queue_work_on() docbook comment says that the caller must
ensure that the specified CPU can't go away, but does not spell out the
consequences, which turn out to be quite mild. Therefore expand this
comment to explicitly say that the penalty for failing to nail down the
specified CPU is that the workqueue handler might find itself executing
on some other CPU.
Cc: Tejun Heo <tj@kernel.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
|
|
Merge misc updates from Andrew Morton:
"257 patches.
Subsystems affected by this patch series: scripts, ocfs2, vfs, and
mm (slab-generic, slab, slub, kconfig, dax, kasan, debug, pagecache,
gup, swap, memcg, pagemap, mprotect, mremap, iomap, tracing, vmalloc,
pagealloc, memory-failure, hugetlb, userfaultfd, vmscan, tools,
memblock, oom-kill, hugetlbfs, migration, thp, readahead, nommu, ksm,
vmstat, madvise, memory-hotplug, rmap, zsmalloc, highmem, zram,
cleanups, kfence, and damon)"
* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (257 commits)
mm/damon: remove return value from before_terminate callback
mm/damon: fix a few spelling mistakes in comments and a pr_debug message
mm/damon: simplify stop mechanism
Docs/admin-guide/mm/pagemap: wordsmith page flags descriptions
Docs/admin-guide/mm/damon/start: simplify the content
Docs/admin-guide/mm/damon/start: fix a wrong link
Docs/admin-guide/mm/damon/start: fix wrong example commands
mm/damon/dbgfs: add adaptive_targets list check before enable monitor_on
mm/damon: remove unnecessary variable initialization
Documentation/admin-guide/mm/damon: add a document for DAMON_RECLAIM
mm/damon: introduce DAMON-based Reclamation (DAMON_RECLAIM)
selftests/damon: support watermarks
mm/damon/dbgfs: support watermarks
mm/damon/schemes: activate schemes based on a watermarks mechanism
tools/selftests/damon: update for regions prioritization of schemes
mm/damon/dbgfs: support prioritization weights
mm/damon/vaddr,paddr: support pageout prioritization
mm/damon/schemes: prioritize regions within the quotas
mm/damon/selftests: support schemes quotas
mm/damon/dbgfs: support quotas of schemes
...
|
|
Shuah Khan reported:
| When CONFIG_PROVE_RAW_LOCK_NESTING=y and CONFIG_KASAN are enabled,
| kasan_record_aux_stack() runs into "BUG: Invalid wait context" when
| it tries to allocate memory attempting to acquire spinlock in page
| allocation code while holding workqueue pool raw_spinlock.
|
| There are several instances of this problem when block layer tries
| to __queue_work(). Call trace from one of these instances is below:
|
| kblockd_mod_delayed_work_on()
| mod_delayed_work_on()
| __queue_delayed_work()
| __queue_work() (rcu_read_lock, raw_spin_lock pool->lock held)
| insert_work()
| kasan_record_aux_stack()
| kasan_save_stack()
| stack_depot_save()
| alloc_pages()
| __alloc_pages()
| get_page_from_freelist()
| rm_queue()
| rm_queue_pcplist()
| local_lock_irqsave(&pagesets.lock, flags);
| [ BUG: Invalid wait context triggered ]
The default kasan_record_aux_stack() calls stack_depot_save() with
GFP_NOWAIT, which in turn can then call alloc_pages(GFP_NOWAIT, ...).
In general, however, it is not even possible to use either GFP_ATOMIC
nor GFP_NOWAIT in certain non-preemptive contexts, including
raw_spin_locks (see gfp.h and commmit ab00db216c9c7).
Fix it by instructing stackdepot to not expand stack storage via
alloc_pages() in case it runs out by using
kasan_record_aux_stack_noalloc().
While there is an increased risk of failing to insert the stack trace,
this is typically unlikely, especially if the same insertion had already
succeeded previously (stack depot hit).
For frequent calls from the same location, it therefore becomes
extremely unlikely that kasan_record_aux_stack_noalloc() fails.
Link: https://lkml.kernel.org/r/20210902200134.25603-1-skhan@linuxfoundation.org
Link: https://lkml.kernel.org/r/20210913112609.2651084-7-elver@google.com
Signed-off-by: Marco Elver <elver@google.com>
Reported-by: Shuah Khan <skhan@linuxfoundation.org>
Tested-by: Shuah Khan <skhan@linuxfoundation.org>
Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Taras Madan <tarasmadan@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vijayanand Jitta <vjitta@codeaurora.org>
Cc: Vinayak Menon <vinmenon@codeaurora.org>
Cc: Walter Wu <walter-zh.wu@mediatek.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Currently show_workqueue_state shows the state of all workqueues and of
all worker pools. In certain cases we may need to dump state of only a
specific workqueue or worker pool. For example in destroy_workqueue we
only need to show state of the workqueue which is getting destroyed.
So rename show_workqueue_state to show_all_workqueues(to signify it
dumps state of all busy workqueues) and divide it into more granular
functions (show_one_workqueue and show_one_worker_pool), that would show
states of individual workqueues and worker pools and can be used in
cases such as the one mentioned above.
Also, as mentioned earlier, make destroy_workqueue dump data pertaining
to only the workqueue that is being destroyed and make user(s) of
earlier interface(show_workqueue_state), use new interface
(show_all_workqueues).
Signed-off-by: Imran Khan <imran.f.khan@oracle.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
|
|
Some unfriendly component, such as dpdk, write the same mask to
unbound kworker cpumask again and again. Every time it write to
this interface some work is queue to cpu, even though the mask
is same with the original mask.
So, fix it by return success and do nothing if the cpumask is
equal with the old one.
Signed-off-by: Mengen Sun <mengensun@tencent.com>
Signed-off-by: Menglong Dong <imagedong@tencent.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
|
|
Console drivers often queue work while holding locks also taken in their
console write paths, something which can lead to deadlocks on SMP when
dumping workqueue state (e.g. sysrq-t or on suspend failures).
For serial console drivers this could look like:
CPU0 CPU1
---- ----
show_workqueue_state();
lock(&pool->lock); <IRQ>
lock(&port->lock);
schedule_work();
lock(&pool->lock);
printk();
lock(console_owner);
lock(&port->lock);
where workqueues are, for example, used to push data to the line
discipline, process break signals and handle modem-status changes. Line
disciplines and serdev drivers can also queue work on write-wakeup
notifications, etc.
Reworking every console driver to avoid queuing work while holding locks
also taken in their write paths would complicate drivers and is neither
desirable or feasible.
Instead use the deferred-printk mechanism to avoid printing while
holding pool locks when dumping workqueue state.
Note that there are a few WARN_ON() assertions in the workqueue code
which could potentially also trigger a deadlock. Hopefully the ongoing
printk rework will provide a general solution for this eventually.
This was originally reported after a lockdep splat when executing
sysrq-t with the imx serial driver.
Fixes: 3494fc30846d ("workqueue: dump workqueues on sysrq-t")
Cc: stable@vger.kernel.org # 4.0
Reported-by: Fabio Estevam <festevam@denx.de>
Tested-by: Fabio Estevam <festevam@denx.de>
Signed-off-by: Johan Hovold <johan@kernel.org>
Reviewed-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Tejun Heo <tj@kernel.org>
|
|
There was no strong reason to or not to flush barrier work items in
flush_workqueue(). And we have to make barrier work items not participate
in nr_active so we had been using WORK_NO_COLOR for them which also makes
them can't be flushed by flush_workqueue().
And the users of flush_workqueue() often do not intend to wait barrier work
items issued by flush_work(). That made the choice sound perfect.
But barrier work items have reference to internal structure (pool_workqueue)
and the worker thread[s] is/are still busy for the workqueue user when the
barrrier work items are not done. So it is reasonable to make flush_workqueue()
also watch for flush_work() to make it more robust.
And a problem[1] reported by Li Zhe shows that we need such robustness.
The warning logs are listed below:
WARNING: CPU: 0 PID: 19336 at kernel/workqueue.c:4430 destroy_workqueue+0x11a/0x2f0
*****
destroy_workqueue: test_workqueue9 has the following busy pwq
pwq 4: cpus=2 node=0 flags=0x0 nice=0 active=0/1 refcnt=2
in-flight: 5658:wq_barrier_func
Showing busy workqueues and worker pools:
*****
It shows that even after drain_workqueue() returns, the barrier work item
is still in flight and the pwq (and a worker) is still busy on it.
The problem is caused by flush_workqueue() not watching flush_work():
Thread A Worker
/* normal work item with linked */
process_scheduled_works()
destroy_workqueue() process_one_work()
drain_workqueue() /* run normal work item */
/-- pwq_dec_nr_in_flight()
flush_workqueue() <---/
/* the last normal work item is done */
sanity_check process_one_work()
/-- raw_spin_unlock_irq(&pool->lock)
raw_spin_lock_irq(&pool->lock) <-/ /* maybe preempt */
*WARNING* wq_barrier_func()
/* maybe preempt by cond_resched() */
Thread A can get the pool lock after the Worker unlocks the pool lock before
running wq_barrier_func(). And if there is any preemption happen around
wq_barrier_func(), destroy_workqueue()'s sanity check is more likely to
get the lock and catch it. (Note: preemption is not necessary to cause the bug,
the unlocking is enough to possibly trigger the WARNING.)
A simple solution might be just executing all linked barrier work items
once without releasing pool lock after the head work item's
pwq_dec_nr_in_flight(). But this solution has two problems:
1) the head work item might also be barrier work item when the user-queued
work item is cancelled. For example:
thread 1: thread 2:
queue_work(wq, &my_work)
flush_work(&my_work)
cancel_work_sync(&my_work);
/* Neiter my_work nor the barrier work is scheduled. */
destroy_workqueue(wq);
/* This is an easier way to catch the WARNING. */
2) there might be too much linked barrier work items and running them
all once without releasing pool lock just causes trouble.
The only solution is to make flush_workqueue() aslo watch barrier work
items. So we have to assign a color to these barrier work items which
is the color of the head (user-queued) work item.
Assigning a color doesn't cause any problem in ative management, because
the prvious patch made barrier work items not participate in nr_active
via WORK_STRUCT_INACTIVE rather than reliance on the (old) WORK_NO_COLOR.
[1]: https://lore.kernel.org/lkml/20210812083814.32453-1-lizhe.67@bytedance.com/
Reported-by: Li Zhe <lizhe.67@bytedance.com>
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
|
|
Currently, WORK_NO_COLOR has two meanings:
Not participate in flushing
Not participate in nr_active
And only non-barrier work items are marked with WORK_STRUCT_INACTIVE
when they are in inactive_works list. The barrier work items are not
marked INACTIVE even linked in inactive_works list since these tail
items are always moved together with the head work item.
These definitions are simple, clean and practical. (Except a small
blemish that only the first meaning of WORK_NO_COLOR is documented in
include/linux/workqueue.h while both meanings are in workqueue.c)
But dual-purpose WORK_NO_COLOR used for barrier work items has proven to
be problematical[1]. Only the second purpose is obligatory. So we plan
to make barrier work items participate in flushing but keep them still
not participating in nr_active.
So the plan is to mark barrier work items inactive without using
WORK_NO_COLOR in this patch so that we can assign a flushing color to
them in next patch.
The reasonable way is to add or reuse a bit in work data of the work
item. But adding a bit will double the size of pool_workqueue.
Currently, WORK_STRUCT_INACTIVE is only used in try_to_grab_pending()
for user-queued work items and try_to_grab_pending() can't work for
barrier work items. So we extend WORK_STRUCT_INACTIVE to also mark
barrier work items no matter which list they are in because we don't
need to determind which list a barrier work item is in.
So the meaning of WORK_STRUCT_INACTIVE becomes just "the work items don't
participate in nr_active" (no matter whether it is a barrier work item or
a user-queued work item). And WORK_STRUCT_INACTIVE for user-queued work
items means they are in inactive_works list.
This patch does it by setting WORK_STRUCT_INACTIVE for barrier work items
in insert_wq_barrier() and checking WORK_STRUCT_INACTIVE first in
pwq_dec_nr_in_flight(). And the meaning of WORK_NO_COLOR is reduced to
only "not participating in flushing".
There is no functionality change intended in this patch. Because
WORK_NO_COLOR+WORK_STRUCT_INACTIVE represents the previous WORK_NO_COLOR
in meaning and try_to_grab_pending() doesn't use for barrier work items
and avoids being confused by this extended WORK_STRUCT_INACTIVE.
A bunch of comment for nr_active & WORK_STRUCT_INACTIVE is also added for
documenting how WORK_STRUCT_INACTIVE works in nr_active management.
[1]: https://lore.kernel.org/lkml/20210812083814.32453-1-lizhe.67@bytedance.com/
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
|
|
Add a local var @work_flags to calculate work_flags step by step, so that
we don't need to squeeze several flags in only the last line of code.
Parepare for next patch to add a bit to barrier work item's flag. Not
squshing this to next patch makes it clear that what it will have changed.
No functional change intended.
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
|
|
Make pwq_dec_nr_in_flight() use work_data rather just work_color.
Prepare for later patch to get WORK_STRUCT_INACTIVE bit from work_data
in pwq_dec_nr_in_flight().
No functional change intended.
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
|
|
There are two kinds of "delayed" work items in workqueue subsystem.
One is for timer-delayed work items which are visible to workqueue users.
The other kind is for work items delayed by active management which can
not be directly visible to workqueue users. We mixed the word "delayed"
for both kinds and caused somewhat ambiguity.
This patch renames the later one (delayed by active management) to
"inactive", because it is used for workqueue active management and
most of its related symbols are named with "active" or "activate".
All "delayed" and "DELAYED" are carefully checked and renamed one by
one to avoid accidentally changing the name of the other kind for
timer-delayed.
No functional change intended.
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
|
|
The functions get_online_cpus() and put_online_cpus() have been
deprecated during the CPU hotplug rework. They map directly to
cpus_read_lock() and cpus_read_unlock().
Replace deprecated CPU-hotplug functions with the official version.
The behavior remains unchanged.
Cc: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Tejun Heo <tj@kernel.org>
|
|
Replace ida_simple_get() with ida_alloc() and ida_simple_remove() with
ida_free(), the latter is more concise and intuitive.
In addition, if ida_alloc() fails, NULL is returned directly. This
eliminates unnecessary initialization of two local variables and an 'if'
judgment.
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
|
|
Fix typo:
*assing ==> assign
*alloced ==> allocated
*Retun ==> Return
*excute ==> execute
v1->v2:
*reverse 'iff'
*update changelog
Signed-off-by: Cai Huoqing <caihuoqing@baidu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
|
|
In error handling branch "if (WARN_ON(node == NUMA_NO_NODE))", the
previously allocated memories are not released. Doing this before
allocating memory eliminates memory leaks.
tj: Note that the condition only occurs when the arch code is pretty broken
and the WARN_ON might as well be BUG_ON().
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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I got a UAF report when doing fuzz test:
[ 152.880091][ T8030] ==================================================================
[ 152.881240][ T8030] BUG: KASAN: use-after-free in pwq_unbound_release_workfn+0x50/0x190
[ 152.882442][ T8030] Read of size 4 at addr ffff88810d31bd00 by task kworker/3:2/8030
[ 152.883578][ T8030]
[ 152.883932][ T8030] CPU: 3 PID: 8030 Comm: kworker/3:2 Not tainted 5.13.0+ #249
[ 152.885014][ T8030] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014
[ 152.886442][ T8030] Workqueue: events pwq_unbound_release_workfn
[ 152.887358][ T8030] Call Trace:
[ 152.887837][ T8030] dump_stack_lvl+0x75/0x9b
[ 152.888525][ T8030] ? pwq_unbound_release_workfn+0x50/0x190
[ 152.889371][ T8030] print_address_description.constprop.10+0x48/0x70
[ 152.890326][ T8030] ? pwq_unbound_release_workfn+0x50/0x190
[ 152.891163][ T8030] ? pwq_unbound_release_workfn+0x50/0x190
[ 152.891999][ T8030] kasan_report.cold.15+0x82/0xdb
[ 152.892740][ T8030] ? pwq_unbound_release_workfn+0x50/0x190
[ 152.893594][ T8030] __asan_load4+0x69/0x90
[ 152.894243][ T8030] pwq_unbound_release_workfn+0x50/0x190
[ 152.895057][ T8030] process_one_work+0x47b/0x890
[ 152.895778][ T8030] worker_thread+0x5c/0x790
[ 152.896439][ T8030] ? process_one_work+0x890/0x890
[ 152.897163][ T8030] kthread+0x223/0x250
[ 152.897747][ T8030] ? set_kthread_struct+0xb0/0xb0
[ 152.898471][ T8030] ret_from_fork+0x1f/0x30
[ 152.899114][ T8030]
[ 152.899446][ T8030] Allocated by task 8884:
[ 152.900084][ T8030] kasan_save_stack+0x21/0x50
[ 152.900769][ T8030] __kasan_kmalloc+0x88/0xb0
[ 152.901416][ T8030] __kmalloc+0x29c/0x460
[ 152.902014][ T8030] alloc_workqueue+0x111/0x8e0
[ 152.902690][ T8030] __btrfs_alloc_workqueue+0x11e/0x2a0
[ 152.903459][ T8030] btrfs_alloc_workqueue+0x6d/0x1d0
[ 152.904198][ T8030] scrub_workers_get+0x1e8/0x490
[ 152.904929][ T8030] btrfs_scrub_dev+0x1b9/0x9c0
[ 152.905599][ T8030] btrfs_ioctl+0x122c/0x4e50
[ 152.906247][ T8030] __x64_sys_ioctl+0x137/0x190
[ 152.906916][ T8030] do_syscall_64+0x34/0xb0
[ 152.907535][ T8030] entry_SYSCALL_64_after_hwframe+0x44/0xae
[ 152.908365][ T8030]
[ 152.908688][ T8030] Freed by task 8884:
[ 152.909243][ T8030] kasan_save_stack+0x21/0x50
[ 152.909893][ T8030] kasan_set_track+0x20/0x30
[ 152.910541][ T8030] kasan_set_free_info+0x24/0x40
[ 152.911265][ T8030] __kasan_slab_free+0xf7/0x140
[ 152.911964][ T8030] kfree+0x9e/0x3d0
[ 152.912501][ T8030] alloc_workqueue+0x7d7/0x8e0
[ 152.913182][ T8030] __btrfs_alloc_workqueue+0x11e/0x2a0
[ 152.913949][ T8030] btrfs_alloc_workqueue+0x6d/0x1d0
[ 152.914703][ T8030] scrub_workers_get+0x1e8/0x490
[ 152.915402][ T8030] btrfs_scrub_dev+0x1b9/0x9c0
[ 152.916077][ T8030] btrfs_ioctl+0x122c/0x4e50
[ 152.916729][ T8030] __x64_sys_ioctl+0x137/0x190
[ 152.917414][ T8030] do_syscall_64+0x34/0xb0
[ 152.918034][ T8030] entry_SYSCALL_64_after_hwframe+0x44/0xae
[ 152.918872][ T8030]
[ 152.919203][ T8030] The buggy address belongs to the object at ffff88810d31bc00
[ 152.919203][ T8030] which belongs to the cache kmalloc-512 of size 512
[ 152.921155][ T8030] The buggy address is located 256 bytes inside of
[ 152.921155][ T8030] 512-byte region [ffff88810d31bc00, ffff88810d31be00)
[ 152.922993][ T8030] The buggy address belongs to the page:
[ 152.923800][ T8030] page:ffffea000434c600 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10d318
[ 152.925249][ T8030] head:ffffea000434c600 order:2 compound_mapcount:0 compound_pincount:0
[ 152.926399][ T8030] flags: 0x57ff00000010200(slab|head|node=1|zone=2|lastcpupid=0x7ff)
[ 152.927515][ T8030] raw: 057ff00000010200 dead000000000100 dead000000000122 ffff888009c42c80
[ 152.928716][ T8030] raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000
[ 152.929890][ T8030] page dumped because: kasan: bad access detected
[ 152.930759][ T8030]
[ 152.931076][ T8030] Memory state around the buggy address:
[ 152.931851][ T8030] ffff88810d31bc00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[ 152.932967][ T8030] ffff88810d31bc80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[ 152.934068][ T8030] >ffff88810d31bd00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[ 152.935189][ T8030] ^
[ 152.935763][ T8030] ffff88810d31bd80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[ 152.936847][ T8030] ffff88810d31be00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[ 152.937940][ T8030] ==================================================================
If apply_wqattrs_prepare() fails in alloc_workqueue(), it will call put_pwq()
which invoke a work queue to call pwq_unbound_release_workfn() and use the 'wq'.
The 'wq' allocated in alloc_workqueue() will be freed in error path when
apply_wqattrs_prepare() fails. So it will lead a UAF.
CPU0 CPU1
alloc_workqueue()
alloc_and_link_pwqs()
apply_wqattrs_prepare() fails
apply_wqattrs_cleanup()
schedule_work(&pwq->unbound_release_work)
kfree(wq)
worker_thread()
pwq_unbound_release_workfn() <- trigger uaf here
If apply_wqattrs_prepare() fails, the new pwq are not linked, it doesn't
hold any reference to the 'wq', 'wq' is invalid to access in the worker,
so add check pwq if linked to fix this.
Fixes: 2d5f0764b526 ("workqueue: split apply_workqueue_attrs() into 3 stages")
Cc: stable@vger.kernel.org # v4.2+
Reported-by: Hulk Robot <hulkci@huawei.com>
Suggested-by: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
Tested-by: Pavel Skripkin <paskripkin@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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If VCPU is suspended (VM suspend) in wq_watchdog_timer_fn() then
once this VCPU resumes it will see the new jiffies value, while it
may take a while before IRQ detects PVCLOCK_GUEST_STOPPED on this
VCPU and updates all the watchdogs via pvclock_touch_watchdogs().
There is a small chance of misreported WQ stalls in the meantime,
because new jiffies is time_after() old 'ts + thresh'.
wq_watchdog_timer_fn()
{
for_each_pool(pool, pi) {
if (time_after(jiffies, ts + thresh)) {
pr_emerg("BUG: workqueue lockup - pool");
}
}
}
Save jiffies at the beginning of this function and use that value
for stall detection. If VM gets suspended then we continue using
"old" jiffies value and old WQ touch timestamps. If IRQ at some
point restarts the stall detection cycle (pvclock_touch_watchdogs())
then old jiffies will always be before new 'ts + thresh'.
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux
Pull CFI on arm64 support from Kees Cook:
"This builds on last cycle's LTO work, and allows the arm64 kernels to
be built with Clang's Control Flow Integrity feature. This feature has
happily lived in Android kernels for almost 3 years[1], so I'm excited
to have it ready for upstream.
The wide diffstat is mainly due to the treewide fixing of mismatched
list_sort prototypes. Other things in core kernel are to address
various CFI corner cases. The largest code portion is the CFI runtime
implementation itself (which will be shared by all architectures
implementing support for CFI). The arm64 pieces are Acked by arm64
maintainers rather than coming through the arm64 tree since carrying
this tree over there was going to be awkward.
CFI support for x86 is still under development, but is pretty close.
There are a handful of corner cases on x86 that need some improvements
to Clang and objtool, but otherwise works well.
Summary:
- Clean up list_sort prototypes (Sami Tolvanen)
- Introduce CONFIG_CFI_CLANG for arm64 (Sami Tolvanen)"
* tag 'cfi-v5.13-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
arm64: allow CONFIG_CFI_CLANG to be selected
KVM: arm64: Disable CFI for nVHE
arm64: ftrace: use function_nocfi for ftrace_call
arm64: add __nocfi to __apply_alternatives
arm64: add __nocfi to functions that jump to a physical address
arm64: use function_nocfi with __pa_symbol
arm64: implement function_nocfi
psci: use function_nocfi for cpu_resume
lkdtm: use function_nocfi
treewide: Change list_sort to use const pointers
bpf: disable CFI in dispatcher functions
kallsyms: strip ThinLTO hashes from static functions
kthread: use WARN_ON_FUNCTION_MISMATCH
workqueue: use WARN_ON_FUNCTION_MISMATCH
module: ensure __cfi_check alignment
mm: add generic function_nocfi macro
cfi: add __cficanonical
add support for Clang CFI
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With CONFIG_CFI_CLANG, a callback function passed to
__queue_delayed_work from a module points to a jump table entry
defined in the module instead of the one used in the core kernel,
which breaks function address equality in this check:
WARN_ON_ONCE(timer->function != delayed_work_timer_fn);
Use WARN_ON_FUNCTION_MISMATCH() instead to disable the warning
when CFI and modules are both enabled.
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210408182843.1754385-6-samitolvanen@google.com
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84;0;0c84;0;0c
There are two workqueue-specific watchdog timestamps:
+ @wq_watchdog_touched_cpu (per-CPU) updated by
touch_softlockup_watchdog()
+ @wq_watchdog_touched (global) updated by
touch_all_softlockup_watchdogs()
watchdog_timer_fn() checks only the global @wq_watchdog_touched for
unbound workqueues. As a result, unbound workqueues are not aware
of touch_softlockup_watchdog(). The watchdog might report a stall
even when the unbound workqueues are blocked by a known slow code.
Solution:
touch_softlockup_watchdog() must touch also the global @wq_watchdog_touched
timestamp.
The global timestamp can no longer be used for bound workqueues because
it is now updated from all CPUs. Instead, bound workqueues have to check
only @wq_watchdog_touched_cpu and these timestamps have to be updated for
all CPUs in touch_all_softlockup_watchdogs().
Beware:
The change might cause the opposite problem. An unbound workqueue
might get blocked on CPU A because of a real softlockup. The workqueue
watchdog would miss it when the timestamp got touched on CPU B.
It is acceptable because softlockups are detected by softlockup
watchdog. The workqueue watchdog is there to detect stalls where
a work never finishes, for example, because of dependencies of works
queued into the same workqueue.
V3:
- Modify the commit message clearly according to Petr's suggestion.
Signed-off-by: Wang Qing <wangqing@vivo.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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The debug_work_activate() is called on the premise that
the work can be inserted, because if wq be in WQ_DRAINING
status, insert work may be failed.
Fixes: e41e704bc4f4 ("workqueue: improve destroy_workqueue() debuggability")
Signed-off-by: Zqiang <qiang.zhang@windriver.com>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
|
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Pull qorkqueue updates from Tejun Heo:
"Tracepoint and comment updates only"
* 'for-5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq:
workqueue: Use %s instead of function name
workqueue: tracing the name of the workqueue instead of it's address
workqueue: fix annotation for WQ_SYSFS
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It is better to replace the function name with %s, in case the function
name changes.
Signed-off-by: Stephen Zhang <stephenzhangzsd@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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create_worker() will already set the right affinity using
kthread_bind_mask(), this means only the rescuer will need to change
it's affinity.
Howveer, while in cpu-hot-unplug a regular task is not allowed to run
on online&&!active as it would be pushed away quite agressively. We
need KTHREAD_IS_PER_CPU to survive in that environment.
Therefore set the affinity after getting that magic flag.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Tested-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210121103506.826629830@infradead.org
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Mark the per-cpu workqueue workers as KTHREAD_IS_PER_CPU.
Workqueues have unfortunate semantics in that per-cpu workers are not
default flushed and parked during hotplug, however a subset does
manual flush on hotplug and hard relies on them for correctness.
Therefore play silly games..
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Tested-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210121103506.693465814@infradead.org
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The scheduler won't break affinity for us any more, and we should
"emulate" the same behavior when the scheduler breaks affinity for
us. The behavior is "changing the cpumask to cpu_possible_mask".
And there might be some other CPUs online later while the worker is
still running with the pending work items. The worker should be allowed
to use the later online CPUs as before and process the work items ASAP.
If we use cpu_active_mask here, we can't achieve this goal but
using cpu_possible_mask can.
Fixes: 06249738a41a ("workqueue: Manually break affinity on hotplug")
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Acked-by: Tejun Heo <tj@kernel.org>
Tested-by: Paul E. McKenney <paulmck@kernel.org>
Tested-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210111152638.2417-4-jiangshanlai@gmail.com
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|
Pull workqueue update from Tejun Heo:
"The same as the cgroup tree - one commit which was scheduled for the
5.11 merge window.
All the commit does is avoding spurious worker wakeups from workqueue
allocation / config change path to help cpuisol use cases"
* 'for-5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq:
workqueue: Kick a worker based on the actual activation of delayed works
|
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Merge misc updates from Andrew Morton:
- a few random little subsystems
- almost all of the MM patches which are staged ahead of linux-next
material. I'll trickle to post-linux-next work in as the dependents
get merged up.
Subsystems affected by this patch series: kthread, kbuild, ide, ntfs,
ocfs2, arch, and mm (slab-generic, slab, slub, dax, debug, pagecache,
gup, swap, shmem, memcg, pagemap, mremap, hmm, vmalloc, documentation,
kasan, pagealloc, memory-failure, hugetlb, vmscan, z3fold, compaction,
oom-kill, migration, cma, page-poison, userfaultfd, zswap, zsmalloc,
uaccess, zram, and cleanups).
* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (200 commits)
mm: cleanup kstrto*() usage
mm: fix fall-through warnings for Clang
mm: slub: convert sysfs sprintf family to sysfs_emit/sysfs_emit_at
mm: shmem: convert shmem_enabled_show to use sysfs_emit_at
mm:backing-dev: use sysfs_emit in macro defining functions
mm: huge_memory: convert remaining use of sprintf to sysfs_emit and neatening
mm: use sysfs_emit for struct kobject * uses
mm: fix kernel-doc markups
zram: break the strict dependency from lzo
zram: add stat to gather incompressible pages since zram set up
zram: support page writeback
mm/process_vm_access: remove redundant initialization of iov_r
mm/zsmalloc.c: rework the list_add code in insert_zspage()
mm/zswap: move to use crypto_acomp API for hardware acceleration
mm/zswap: fix passing zero to 'PTR_ERR' warning
mm/zswap: make struct kernel_param_ops definitions const
userfaultfd/selftests: hint the test runner on required privilege
userfaultfd/selftests: fix retval check for userfaultfd_open()
userfaultfd/selftests: always dump something in modes
userfaultfd: selftests: make __{s,u}64 format specifiers portable
...
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Patch series "kasan: add workqueue stack for generic KASAN", v5.
Syzbot reports many UAF issues for workqueue, see [1].
In some of these access/allocation happened in process_one_work(), we
see the free stack is useless in KASAN report, it doesn't help
programmers to solve UAF for workqueue issue.
This patchset improves KASAN reports by making them to have workqueue
queueing stack. It is useful for programmers to solve use-after-free or
double-free memory issue.
Generic KASAN also records the last two workqueue stacks and prints them
in KASAN report. It is only suitable for generic KASAN.
[1] https://groups.google.com/g/syzkaller-bugs/search?q=%22use-after-free%22+process_one_work
[2] https://bugzilla.kernel.org/show_bug.cgi?id=198437
This patch (of 4):
When analyzing use-after-free or double-free issue, recording the
enqueuing work stacks is helpful to preserve usage history which
potentially gives a hint about the affected code.
For workqueue it has turned out to be useful to record the enqueuing work
call stacks. Because user can see KASAN report to determine whether it is
root cause. They don't need to enable debugobjects, but they have a
chance to find out the root cause.
Link: https://lkml.kernel.org/r/20201203022148.29754-1-walter-zh.wu@mediatek.com
Link: https://lkml.kernel.org/r/20201203022442.30006-1-walter-zh.wu@mediatek.com
Signed-off-by: Walter Wu <walter-zh.wu@mediatek.com>
Suggested-by: Marco Elver <elver@google.com>
Acked-by: Marco Elver <elver@google.com>
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Marco Elver <elver@google.com>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
In realtime scenario, We do not want to have interference on the
isolated cpu cores. but when invoking alloc_workqueue() for percpu wq
on the housekeeping cpu, it kick a kworker on the isolated cpu.
alloc_workqueue
pwq_adjust_max_active
wake_up_worker
The comment in pwq_adjust_max_active() said:
"Need to kick a worker after thawed or an unbound wq's
max_active is bumped"
So it is unnecessary to kick a kworker for percpu's wq when invoking
alloc_workqueue(). this patch only kick a worker based on the actual
activation of delayed works.
Signed-off-by: Yunfeng Ye <yeyunfeng@huawei.com>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
|
