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| author | Stephen Rothwell <sfr@canb.auug.org.au> | 2024-05-02 12:54:50 +1000 |
|---|---|---|
| committer | Stephen Rothwell <sfr@canb.auug.org.au> | 2024-05-02 12:54:50 +1000 |
| commit | 8a625f4238aed4a7108301b2b2541f4e9c282f82 (patch) | |
| tree | 891280b4cb92a3dfb6c38d113e6ec62e824067fb | |
| parent | 271755ff88287afa18497ce76e4325715a98cbe9 (diff) | |
| parent | e7d6f9dff52c43bca09f3b175f0e6dfeadc37760 (diff) | |
| download | linux-next-history-8a625f4238aed4a7108301b2b2541f4e9c282f82.tar.gz | |
Merge branch 'rcu/next' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git
Notice: this object is not reachable from any branch.
# Conflicts:
# arch/Kconfig
Notice: this object is not reachable from any branch.
56 files changed, 1230 insertions, 447 deletions
diff --git a/.mailmap b/.mailmap index cddfabc7eed394..1906f52a56e448 100644 --- a/.mailmap +++ b/.mailmap @@ -462,7 +462,8 @@ Nadia Yvette Chambers <nyc@holomorphy.com> William Lee Irwin III <wli@holomorphy Naoya Horiguchi <nao.horiguchi@gmail.com> <n-horiguchi@ah.jp.nec.com> Naoya Horiguchi <nao.horiguchi@gmail.com> <naoya.horiguchi@nec.com> Nathan Chancellor <nathan@kernel.org> <natechancellor@gmail.com> -Neeraj Upadhyay <quic_neeraju@quicinc.com> <neeraju@codeaurora.org> +Neeraj Upadhyay <neeraj.upadhyay@kernel.org> <quic_neeraju@quicinc.com> +Neeraj Upadhyay <neeraj.upadhyay@kernel.org> <neeraju@codeaurora.org> Neil Armstrong <neil.armstrong@linaro.org> <narmstrong@baylibre.com> Nguyen Anh Quynh <aquynh@gmail.com> Nicholas Piggin <npiggin@gmail.com> <npiggen@suse.de> diff --git a/Documentation/RCU/Design/Requirements/Requirements.rst b/Documentation/RCU/Design/Requirements/Requirements.rst index cccafdaa1f849d..f511476b45506e 100644 --- a/Documentation/RCU/Design/Requirements/Requirements.rst +++ b/Documentation/RCU/Design/Requirements/Requirements.rst @@ -2357,6 +2357,7 @@ section. #. `Sched Flavor (Historical)`_ #. `Sleepable RCU`_ #. `Tasks RCU`_ +#. `Tasks Trace RCU`_ Bottom-Half Flavor (Historical) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ @@ -2610,6 +2611,16 @@ critical sections that are delimited by voluntary context switches, that is, calls to schedule(), cond_resched(), and synchronize_rcu_tasks(). In addition, transitions to and from userspace execution also delimit tasks-RCU read-side critical sections. +Idle tasks are ignored by Tasks RCU, and Tasks Rude RCU may be used to +interact with them. + +Note well that involuntary context switches are *not* Tasks-RCU quiescent +states. After all, in preemptible kernels, a task executing code in a +trampoline might be preempted. In this case, the Tasks-RCU grace period +clearly cannot end until that task resumes and its execution leaves that +trampoline. This means, among other things, that cond_resched() does +not provide a Tasks RCU quiescent state. (Instead, use rcu_softirq_qs() +from softirq or rcu_tasks_classic_qs() otherwise.) The tasks-RCU API is quite compact, consisting only of call_rcu_tasks(), synchronize_rcu_tasks(), and @@ -2632,6 +2643,11 @@ moniker. And this operation is considered to be quite rude by real-time workloads that don't want their ``nohz_full`` CPUs receiving IPIs and by battery-powered systems that don't want their idle CPUs to be awakened. +Once kernel entry/exit and deep-idle functions have been properly tagged +``noinstr``, Tasks RCU can start paying attention to idle tasks (except +those that are idle from RCU's perspective) and then Tasks Rude RCU can +be removed from the kernel. + The tasks-rude-RCU API is also reader-marking-free and thus quite compact, consisting of call_rcu_tasks_rude(), synchronize_rcu_tasks_rude(), and rcu_barrier_tasks_rude(). diff --git a/Documentation/RCU/whatisRCU.rst b/Documentation/RCU/whatisRCU.rst index 872ac665223fbd..94838c65c7d971 100644 --- a/Documentation/RCU/whatisRCU.rst +++ b/Documentation/RCU/whatisRCU.rst @@ -427,7 +427,7 @@ their assorted primitives. This section shows a simple use of the core RCU API to protect a global pointer to a dynamically allocated structure. More-typical -uses of RCU may be found in listRCU.rst, arrayRCU.rst, and NMI-RCU.rst. +uses of RCU may be found in listRCU.rst and NMI-RCU.rst. :: struct foo { @@ -510,8 +510,8 @@ So, to sum up: data item. See checklist.rst for additional rules to follow when using RCU. -And again, more-typical uses of RCU may be found in listRCU.rst, -arrayRCU.rst, and NMI-RCU.rst. +And again, more-typical uses of RCU may be found in listRCU.rst +and NMI-RCU.rst. .. _4_whatisRCU: diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index af4adc3ec771ef..c4cf963f20ab4a 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -5103,6 +5103,20 @@ delay, memory pressure or callback list growing too big. + rcutree.rcu_normal_wake_from_gp= [KNL] + Reduces a latency of synchronize_rcu() call. This approach + maintains its own track of synchronize_rcu() callers, so it + does not interact with regular callbacks because it does not + use a call_rcu[_hurry]() path. Please note, this is for a + normal grace period. + + How to enable it: + + echo 1 > /sys/module/rcutree/parameters/rcu_normal_wake_from_gp + or pass a boot parameter "rcutree.rcu_normal_wake_from_gp=1" + + Default is 0. + rcuscale.gp_async= [KNL] Measure performance of asynchronous grace-period primitives such as call_rcu(). diff --git a/Documentation/atomic_t.txt b/Documentation/atomic_t.txt index d7adc6d543db4f..bee3b1bca9a7b4 100644 --- a/Documentation/atomic_t.txt +++ b/Documentation/atomic_t.txt @@ -171,14 +171,14 @@ The rule of thumb: - RMW operations that are conditional are unordered on FAILURE, otherwise the above rules apply. -Except of course when an operation has an explicit ordering like: +Except of course when a successful operation has an explicit ordering like: {}_relaxed: unordered {}_acquire: the R of the RMW (or atomic_read) is an ACQUIRE {}_release: the W of the RMW (or atomic_set) is a RELEASE Where 'unordered' is against other memory locations. Address dependencies are -not defeated. +not defeated. Conditional operations are still unordered on FAILURE. Fully ordered primitives are ordered against everything prior and everything subsequent. Therefore a fully ordered primitive is like having an smp_mb() diff --git a/Documentation/litmus-tests/README b/Documentation/litmus-tests/README index 658d37860d3974..6c666f3422ea3a 100644 --- a/Documentation/litmus-tests/README +++ b/Documentation/litmus-tests/README @@ -21,6 +21,51 @@ Atomic-RMW-ops-are-atomic-WRT-atomic_set.litmus Test that atomic_set() cannot break the atomicity of atomic RMWs. NOTE: Require herd7 7.56 or later which supports "(void)expr". +cmpxchg-fail-ordered-1.litmus + Demonstrate that a failing cmpxchg() operation acts as a full barrier + when followed by smp_mb__after_atomic(). + +cmpxchg-fail-ordered-2.litmus + Demonstrate that a failing cmpxchg() operation acts as an acquire + operation when followed by smp_mb__after_atomic(). + +cmpxchg-fail-unordered-1.litmus + Demonstrate that a failing cmpxchg() operation does not act as a + full barrier. + +cmpxchg-fail-unordered-2.litmus + Demonstrate that a failing cmpxchg() operation does not act as an + acquire operation. + + +locking (/locking directory) +---------------------------- + +DCL-broken.litmus + Demonstrates that double-checked locking needs more than just + the obvious lock acquisitions and releases. + +DCL-fixed.litmus + Demonstrates corrected double-checked locking that uses + smp_store_release() and smp_load_acquire() in addition to the + obvious lock acquisitions and releases. + +RM-broken.litmus + Demonstrates problems with "roach motel" locking, where code is + freely moved into lock-based critical sections. This example also + shows how to use the "filter" clause to discard executions that + would be excluded by other code not modeled in the litmus test. + Note also that this "roach motel" optimization is emulated by + physically moving P1()'s two reads from x under the lock. + + What is a roach motel? This is from an old advertisement for + a cockroach trap, much later featured in one of the "Men in + Black" movies. "The roaches check in. They don't check out." + +RM-fixed.litmus + The counterpart to RM-broken.litmus, showing P0()'s two loads from + x safely outside of the critical section. + RCU (/rcu directory) -------------------- diff --git a/Documentation/litmus-tests/atomic/cmpxchg-fail-ordered-1.litmus b/Documentation/litmus-tests/atomic/cmpxchg-fail-ordered-1.litmus new file mode 100644 index 00000000000000..c0f93dc07105e0 --- /dev/null +++ b/Documentation/litmus-tests/atomic/cmpxchg-fail-ordered-1.litmus @@ -0,0 +1,35 @@ +C cmpxchg-fail-ordered-1 + +(* + * Result: Never + * + * Demonstrate that a failing cmpxchg() operation will act as a full + * barrier when followed by smp_mb__after_atomic(). + *) + +{} + +P0(int *x, int *y, int *z) +{ + int r0; + int r1; + + WRITE_ONCE(*x, 1); + r1 = cmpxchg(z, 1, 0); + smp_mb__after_atomic(); + r0 = READ_ONCE(*y); +} + +P1(int *x, int *y, int *z) +{ + int r0; + int r1; + + WRITE_ONCE(*y, 1); + r1 = cmpxchg(z, 1, 0); + smp_mb__after_atomic(); + r0 = READ_ONCE(*x); +} + +locations[0:r1;1:r1] +exists (0:r0=0 /\ 1:r0=0) diff --git a/Documentation/litmus-tests/atomic/cmpxchg-fail-ordered-2.litmus b/Documentation/litmus-tests/atomic/cmpxchg-fail-ordered-2.litmus new file mode 100644 index 00000000000000..5c06054f469476 --- /dev/null +++ b/Documentation/litmus-tests/atomic/cmpxchg-fail-ordered-2.litmus @@ -0,0 +1,30 @@ +C cmpxchg-fail-ordered-2 + +(* + * Result: Never + * + * Demonstrate use of smp_mb__after_atomic() to make a failing cmpxchg + * operation have acquire ordering. + *) + +{} + +P0(int *x, int *y) +{ + int r1; + + WRITE_ONCE(*x, 1); + r1 = cmpxchg(y, 0, 1); +} + +P1(int *x, int *y) +{ + int r1; + int r2; + + r1 = cmpxchg(y, 0, 1); + smp_mb__after_atomic(); + r2 = READ_ONCE(*x); +} + +exists (0:r1=0 /\ 1:r1=1 /\ 1:r2=0) diff --git a/Documentation/litmus-tests/atomic/cmpxchg-fail-unordered-1.litmus b/Documentation/litmus-tests/atomic/cmpxchg-fail-unordered-1.litmus new file mode 100644 index 00000000000000..39ea1f56a28d28 --- /dev/null +++ b/Documentation/litmus-tests/atomic/cmpxchg-fail-unordered-1.litmus @@ -0,0 +1,34 @@ +C cmpxchg-fail-unordered-1 + +(* + * Result: Sometimes + * + * Demonstrate that a failing cmpxchg() operation does not act as a + * full barrier. (In contrast, a successful cmpxchg() does act as a + * full barrier.) + *) + +{} + +P0(int *x, int *y, int *z) +{ + int r0; + int r1; + + WRITE_ONCE(*x, 1); + r1 = cmpxchg(z, 1, 0); + r0 = READ_ONCE(*y); +} + +P1(int *x, int *y, int *z) +{ + int r0; + int r1; + + WRITE_ONCE(*y, 1); + r1 = cmpxchg(z, 1, 0); + r0 = READ_ONCE(*x); +} + +locations[0:r1;1:r1] +exists (0:r0=0 /\ 1:r0=0) diff --git a/Documentation/litmus-tests/atomic/cmpxchg-fail-unordered-2.litmus b/Documentation/litmus-tests/atomic/cmpxchg-fail-unordered-2.litmus new file mode 100644 index 00000000000000..61aab24a4a6438 --- /dev/null +++ b/Documentation/litmus-tests/atomic/cmpxchg-fail-unordered-2.litmus @@ -0,0 +1,30 @@ +C cmpxchg-fail-unordered-2 + +(* + * Result: Sometimes + * + * Demonstrate that a failing cmpxchg() operation does not act as either + * an acquire release operation. (In contrast, a successful cmpxchg() + * does act as both an acquire and a release operation.) + *) + +{} + +P0(int *x, int *y) +{ + int r1; + + WRITE_ONCE(*x, 1); + r1 = cmpxchg(y, 0, 1); +} + +P1(int *x, int *y) +{ + int r1; + int r2; + + r1 = cmpxchg(y, 0, 1); + r2 = READ_ONCE(*x); +} + +exists (0:r1=0 /\ 1:r1=1 /\ 1:r2=0) diff --git a/MAINTAINERS b/MAINTAINERS index 647ae032d4a297..b434900eec1cfd 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -18726,7 +18726,7 @@ F: tools/testing/selftests/resctrl/ READ-COPY UPDATE (RCU) M: "Paul E. McKenney" <paulmck@kernel.org> M: Frederic Weisbecker <frederic@kernel.org> (kernel/rcu/tree_nocb.h) -M: Neeraj Upadhyay <quic_neeraju@quicinc.com> (kernel/rcu/tasks.h) +M: Neeraj Upadhyay <neeraj.upadhyay@kernel.org> (kernel/rcu/tasks.h) M: Joel Fernandes <joel@joelfernandes.org> M: Josh Triplett <josh@joshtriplett.org> M: Boqun Feng <boqun.feng@gmail.com> diff --git a/arch/Kconfig b/arch/Kconfig index ff8bfebf683b43..3411c5739a9e7e 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -63,7 +63,7 @@ config KPROBES depends on HAVE_KPROBES select KALLSYMS select EXECMEM - select TASKS_RCU if PREEMPTION + select NEED_TASKS_RCU help Kprobes allows you to trap at almost any kernel address and execute a callback function. register_kprobe() establishes @@ -112,7 +112,7 @@ config STATIC_CALL_SELFTEST config OPTPROBES def_bool y depends on KPROBES && HAVE_OPTPROBES - select TASKS_RCU if PREEMPTION + select NEED_TASKS_RCU config KPROBES_ON_FTRACE def_bool y @@ -1631,4 +1631,7 @@ config CC_HAS_SANE_FUNCTION_ALIGNMENT # strict alignment always, even with -falign-functions. def_bool CC_HAS_MIN_FUNCTION_ALIGNMENT || CC_IS_CLANG +config ARCH_NEED_CMPXCHG_1_EMU + bool + endmenu diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig index 4092bec198beca..1778b87d680eaa 100644 --- a/arch/arc/Kconfig +++ b/arch/arc/Kconfig @@ -13,6 +13,7 @@ config ARC select ARCH_HAS_SETUP_DMA_OPS select ARCH_HAS_SYNC_DMA_FOR_CPU select ARCH_HAS_SYNC_DMA_FOR_DEVICE + select ARCH_NEED_CMPXCHG_1_EMU select ARCH_SUPPORTS_ATOMIC_RMW if ARC_HAS_LLSC select ARCH_32BIT_OFF_T select BUILDTIME_TABLE_SORT diff --git a/arch/arc/include/asm/cmpxchg.h b/arch/arc/include/asm/cmpxchg.h index e138fde067dea5..2102ce076f28b5 100644 --- a/arch/arc/include/asm/cmpxchg.h +++ b/arch/arc/include/asm/cmpxchg.h @@ -8,6 +8,7 @@ #include <linux/build_bug.h> #include <linux/types.h> +#include <linux/cmpxchg-emu.h> #include <asm/barrier.h> #include <asm/smp.h> @@ -46,6 +47,9 @@ __typeof__(*(ptr)) _prev_; \ \ switch(sizeof((_p_))) { \ + case 1: \ + _prev_ = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *)_p_, (uintptr_t)_o_, (uintptr_t)_n_); \ + break; \ case 4: \ _prev_ = __cmpxchg(_p_, _o_, _n_); \ break; \ @@ -65,16 +69,27 @@ __typeof__(*(ptr)) _prev_; \ unsigned long __flags; \ \ - BUILD_BUG_ON(sizeof(_p_) != 4); \ + switch(sizeof((_p_))) { \ + case 1: \ + __flags = cmpxchg_emu_u8((volatile u8 *)_p_, (uintptr_t)_o_, (uintptr_t)_n_); \ + _prev_ = (__typeof__(*(ptr)))__flags; \ + break; \ + break; \ + case 4: \ + /* \ + * spin lock/unlock provide the needed smp_mb() \ + * before/after \ + */ \ + atomic_ops_lock(__flags); \ + _prev_ = *_p_; \ + if (_prev_ == _o_) \ + *_p_ = _n_; \ + atomic_ops_unlock(__flags); \ + break; \ + default: \ + BUILD_BUG(); \ + } \ \ - /* \ - * spin lock/unlock provide the needed smp_mb() before/after \ - */ \ - atomic_ops_lock(__flags); \ - _prev_ = *_p_; \ - if (_prev_ == _o_) \ - *_p_ = _n_; \ - atomic_ops_unlock(__flags); \ _prev_; \ }) diff --git a/arch/csky/Kconfig b/arch/csky/Kconfig index d3ac36751ad1f6..5479707eb5d10d 100644 --- a/arch/csky/Kconfig +++ b/arch/csky/Kconfig @@ -37,6 +37,7 @@ config CSKY select ARCH_INLINE_SPIN_UNLOCK_BH if !PREEMPTION select ARCH_INLINE_SPIN_UNLOCK_IRQ if !PREEMPTION select ARCH_INLINE_SPIN_UNLOCK_IRQRESTORE if !PREEMPTION + select ARCH_NEED_CMPXCHG_1_EMU select ARCH_WANT_FRAME_POINTERS if !CPU_CK610 && $(cc-option,-mbacktrace) select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT select COMMON_CLK diff --git a/arch/csky/include/asm/cmpxchg.h b/arch/csky/include/asm/cmpxchg.h index 916043b845f142..db6dda47184e4b 100644 --- a/arch/csky/include/asm/cmpxchg.h +++ b/arch/csky/include/asm/cmpxchg.h @@ -6,6 +6,7 @@ #ifdef CONFIG_SMP #include <linux/bug.h> #include <asm/barrier.h> +#include <linux/cmpxchg-emu.h> #define __xchg_relaxed(new, ptr, size) \ ({ \ @@ -61,6 +62,9 @@ __typeof__(old) __old = (old); \ __typeof__(*(ptr)) __ret; \ switch (size) { \ + case 1: \ + __ret = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *)__ptr, (uintptr_t)__old, (uintptr_t)__new); \ + break; \ case 4: \ asm volatile ( \ "1: ldex.w %0, (%3) \n" \ @@ -91,6 +95,9 @@ __typeof__(old) __old = (old); \ __typeof__(*(ptr)) __ret; \ switch (size) { \ + case 1: \ + __ret = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *)__ptr, (uintptr_t)__old, (uintptr_t)__new); \ + break; \ case 4: \ asm volatile ( \ "1: ldex.w %0, (%3) \n" \ @@ -122,6 +129,9 @@ __typeof__(old) __old = (old); \ __typeof__(*(ptr)) __ret; \ switch (size) { \ + case 1: \ + __ret = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *)__ptr, (uintptr_t)__old, (uintptr_t)__new); \ + break; \ case 4: \ asm volatile ( \ RELEASE_FENCE \ diff --git a/arch/parisc/include/asm/cmpxchg.h b/arch/parisc/include/asm/cmpxchg.h index c1d776bb16b4ed..bf0a0f1189eb21 100644 --- a/arch/parisc/include/asm/cmpxchg.h +++ b/arch/parisc/include/asm/cmpxchg.h @@ -56,26 +56,24 @@ __arch_xchg(unsigned long x, volatile void *ptr, int size) /* bug catcher for when unsupported size is used - won't link */ extern void __cmpxchg_called_with_bad_pointer(void); -/* __cmpxchg_u32/u64 defined in arch/parisc/lib/bitops.c */ -extern unsigned long __cmpxchg_u32(volatile unsigned int *m, unsigned int old, - unsigned int new_); -extern u64 __cmpxchg_u64(volatile u64 *ptr, u64 old, u64 new_); +/* __cmpxchg_u... defined in arch/parisc/lib/bitops.c */ extern u8 __cmpxchg_u8(volatile u8 *ptr, u8 old, u8 new_); +extern u16 __cmpxchg_u16(volatile u16 *ptr, u16 old, u16 new_); +extern u32 __cmpxchg_u32(volatile u32 *m, u32 old, u32 new_); +extern u64 __cmpxchg_u64(volatile u64 *ptr, u64 old, u64 new_); /* don't worry...optimizer will get rid of most of this */ static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old, unsigned long new_, int size) { - switch (size) { + return #ifdef CONFIG_64BIT - case 8: return __cmpxchg_u64((u64 *)ptr, old, new_); + size == 8 ? __cmpxchg_u64(ptr, old, new_) : #endif - case 4: return __cmpxchg_u32((unsigned int *)ptr, - (unsigned int)old, (unsigned int)new_); - case 1: return __cmpxchg_u8((u8 *)ptr, old & 0xff, new_ & 0xff); - } - __cmpxchg_called_with_bad_pointer(); - return old; + size == 4 ? __cmpxchg_u32(ptr, old, new_) : + size == 2 ? __cmpxchg_u16(ptr, old, new_) : + size == 1 ? __cmpxchg_u8(ptr, old, new_) : + (__cmpxchg_called_with_bad_pointer(), old); } #define arch_cmpxchg(ptr, o, n) \ diff --git a/arch/parisc/kernel/parisc_ksyms.c b/arch/parisc/kernel/parisc_ksyms.c index 6f0c92e8149d82..c1587aa35beb6e 100644 --- a/arch/parisc/kernel/parisc_ksyms.c +++ b/arch/parisc/kernel/parisc_ksyms.c @@ -22,6 +22,8 @@ EXPORT_SYMBOL(memset); #include <linux/atomic.h> EXPORT_SYMBOL(__xchg8); EXPORT_SYMBOL(__xchg32); +EXPORT_SYMBOL(__cmpxchg_u8); +EXPORT_SYMBOL(__cmpxchg_u16); EXPORT_SYMBOL(__cmpxchg_u32); EXPORT_SYMBOL(__cmpxchg_u64); #ifdef CONFIG_SMP diff --git a/arch/parisc/lib/bitops.c b/arch/parisc/lib/bitops.c index 36a31419907467..9df81005064278 100644 --- a/arch/parisc/lib/bitops.c +++ b/arch/parisc/lib/bitops.c @@ -56,38 +56,20 @@ unsigned long notrace __xchg8(char x, volatile char *ptr) } -u64 notrace __cmpxchg_u64(volatile u64 *ptr, u64 old, u64 new) -{ - unsigned long flags; - u64 prev; - - _atomic_spin_lock_irqsave(ptr, flags); - if ((prev = *ptr) == old) - *ptr = new; - _atomic_spin_unlock_irqrestore(ptr, flags); - return prev; -} - -unsigned long notrace __cmpxchg_u32(volatile unsigned int *ptr, unsigned int old, unsigned int new) -{ - unsigned long flags; - unsigned int prev; - - _atomic_spin_lock_irqsave(ptr, flags); - if ((prev = *ptr) == old) - *ptr = new; - _atomic_spin_unlock_irqrestore(ptr, flags); - return (unsigned long)prev; -} - -u8 notrace __cmpxchg_u8(volatile u8 *ptr, u8 old, u8 new) -{ - unsigned long flags; - u8 prev; - - _atomic_spin_lock_irqsave(ptr, flags); - if ((prev = *ptr) == old) - *ptr = new; - _atomic_spin_unlock_irqrestore(ptr, flags); - return prev; -} +#define CMPXCHG(T) \ + T notrace __cmpxchg_##T(volatile T *ptr, T old, T new) \ + { \ + unsigned long flags; \ + T prev; \ + \ + _atomic_spin_lock_irqsave(ptr, flags); \ + if ((prev = *ptr) == old) \ + *ptr = new; \ + _atomic_spin_unlock_irqrestore(ptr, flags); \ + return prev; \ + } + +CMPXCHG(u64) +CMPXCHG(u32) +CMPXCHG(u16) +CMPXCHG(u8) diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig index 94895a387ed523..217bdc4d0201bb 100644 --- a/arch/sh/Kconfig +++ b/arch/sh/Kconfig @@ -16,6 +16,7 @@ config SUPERH select ARCH_HIBERNATION_POSSIBLE if MMU select ARCH_MIGHT_HAVE_PC_PARPORT select ARCH_WANT_IPC_PARSE_VERSION + select ARCH_NEED_CMPXCHG_1_EMU select CPU_NO_EFFICIENT_FFS select DMA_DECLARE_COHERENT select GENERIC_ATOMIC64 diff --git a/arch/sh/include/asm/cmpxchg.h b/arch/sh/include/asm/cmpxchg.h index 5d617b3ef78f77..1e5dc5ccf7bf50 100644 --- a/arch/sh/include/asm/cmpxchg.h +++ b/arch/sh/include/asm/cmpxchg.h @@ -9,6 +9,7 @@ #include <linux/compiler.h> #include <linux/types.h> +#include <linux/cmpxchg-emu.h> #if defined(CONFIG_GUSA_RB) #include <asm/cmpxchg-grb.h> @@ -56,6 +57,8 @@ static inline unsigned long __cmpxchg(volatile void * ptr, unsigned long old, unsigned long new, int size) { switch (size) { + case 1: + return cmpxchg_emu_u8(ptr, old, new); case 4: return __cmpxchg_u32(ptr, old, new); } diff --git a/arch/sparc/include/asm/cmpxchg_32.h b/arch/sparc/include/asm/cmpxchg_32.h index d0af82c240b731..8c1a3ca34eeb7a 100644 --- a/arch/sparc/include/asm/cmpxchg_32.h +++ b/arch/sparc/include/asm/cmpxchg_32.h @@ -38,21 +38,19 @@ static __always_inline unsigned long __arch_xchg(unsigned long x, __volatile__ v /* bug catcher for when unsupported size is used - won't link */ void __cmpxchg_called_with_bad_pointer(void); -/* we only need to support cmpxchg of a u32 on sparc */ -unsigned long __cmpxchg_u32(volatile u32 *m, u32 old, u32 new_); +u8 __cmpxchg_u8(volatile u8 *m, u8 old, u8 new_); +u16 __cmpxchg_u16(volatile u16 *m, u16 old, u16 new_); +u32 __cmpxchg_u32(volatile u32 *m, u32 old, u32 new_); /* don't worry...optimizer will get rid of most of this */ static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old, unsigned long new_, int size) { - switch (size) { - case 4: - return __cmpxchg_u32((u32 *)ptr, (u32)old, (u32)new_); - default: - __cmpxchg_called_with_bad_pointer(); - break; - } - return old; + return + size == 1 ? __cmpxchg_u8(ptr, old, new_) : + size == 2 ? __cmpxchg_u16(ptr, old, new_) : + size == 4 ? __cmpxchg_u32(ptr, old, new_) : + (__cmpxchg_called_with_bad_pointer(), old); } #define arch_cmpxchg(ptr, o, n) \ @@ -63,7 +61,7 @@ __cmpxchg(volatile void *ptr, unsigned long old, unsigned long new_, int size) (unsigned long)_n_, sizeof(*(ptr))); \ }) -u64 __cmpxchg_u64(u64 *ptr, u64 old, u64 new); +u64 __cmpxchg_u64(volatile u64 *ptr, u64 old, u64 new); #define arch_cmpxchg64(ptr, old, new) __cmpxchg_u64(ptr, old, new) #include <asm-generic/cmpxchg-local.h> diff --git a/arch/sparc/lib/atomic32.c b/arch/sparc/lib/atomic32.c index cf80d1ae352be6..8ae880ebf07aac 100644 --- a/arch/sparc/lib/atomic32.c +++ b/arch/sparc/lib/atomic32.c @@ -159,32 +159,27 @@ unsigned long sp32___change_bit(unsigned long *addr, unsigned long mask) } EXPORT_SYMBOL(sp32___change_bit); -unsigned long __cmpxchg_u32(volatile u32 *ptr, u32 old, u32 new) -{ - unsigned long flags; - u32 prev; - - spin_lock_irqsave(ATOMIC_HASH(ptr), flags); - if ((prev = *ptr) == old) - *ptr = new; - spin_unlock_irqrestore(ATOMIC_HASH(ptr), flags); - - return (unsigned long)prev; -} +#define CMPXCHG(T) \ + T __cmpxchg_##T(volatile T *ptr, T old, T new) \ + { \ + unsigned long flags; \ + T prev; \ + \ + spin_lock_irqsave(ATOMIC_HASH(ptr), flags); \ + if ((prev = *ptr) == old) \ + *ptr = new; \ + spin_unlock_irqrestore(ATOMIC_HASH(ptr), flags);\ + \ + return prev; \ + } + +CMPXCHG(u8) +CMPXCHG(u16) +CMPXCHG(u32) +CMPXCHG(u64) +EXPORT_SYMBOL(__cmpxchg_u8); +EXPORT_SYMBOL(__cmpxchg_u16); EXPORT_SYMBOL(__cmpxchg_u32); - -u64 __cmpxchg_u64(u64 *ptr, u64 old, u64 new) -{ - unsigned long flags; - u64 prev; - - spin_lock_irqsave(ATOMIC_HASH(ptr), flags); - if ((prev = *ptr) == old) - *ptr = new; - spin_unlock_irqrestore(ATOMIC_HASH(ptr), flags); - - return prev; -} EXPORT_SYMBOL(__cmpxchg_u64); unsigned long __xchg_u32(volatile u32 *ptr, u32 new) diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 06b170759e5bf5..3640bf119f1278 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -1289,7 +1289,7 @@ int unsynchronized_tsc(void) */ if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) { /* assume multi socket systems are not synchronized: */ - if (num_possible_cpus() > 1) + if (topology_max_packages() > 1) return 1; } diff --git a/arch/xtensa/Kconfig b/arch/xtensa/Kconfig index f200a4ec044e64..d3db28f2f81108 100644 --- a/arch/xtensa/Kconfig +++ b/arch/xtensa/Kconfig @@ -14,6 +14,7 @@ config XTENSA select ARCH_HAS_DMA_SET_UNCACHED if MMU select ARCH_HAS_STRNCPY_FROM_USER if !KASAN select ARCH_HAS_STRNLEN_USER + select ARCH_NEED_CMPXCHG_1_EMU select ARCH_USE_MEMTEST select ARCH_USE_QUEUED_RWLOCKS select ARCH_USE_QUEUED_SPINLOCKS diff --git a/arch/xtensa/include/asm/cmpxchg.h b/arch/xtensa/include/asm/cmpxchg.h index 675a11ea8de76b..95e33a913962d8 100644 --- a/arch/xtensa/include/asm/cmpxchg.h +++ b/arch/xtensa/include/asm/cmpxchg.h @@ -15,6 +15,7 @@ #include <linux/bits.h> #include <linux/stringify.h> +#include <linux/cmpxchg-emu.h> /* * cmpxchg @@ -74,6 +75,7 @@ static __inline__ unsigned long __cmpxchg(volatile void *ptr, unsigned long old, unsigned long new, int size) { switch (size) { + case 1: return cmpxchg_emu_u8(ptr, old, new); case 4: return __cmpxchg_u32(ptr, old, new); default: __cmpxchg_called_with_bad_pointer(); return old; diff --git a/include/linux/cmpxchg-emu.h b/include/linux/cmpxchg-emu.h new file mode 100644 index 00000000000000..998deec67740aa --- /dev/null +++ b/include/linux/cmpxchg-emu.h @@ -0,0 +1,15 @@ +/* SPDX-License-Identifier: GPL-2.0+ */ +/* + * Emulated 1-byte and 2-byte cmpxchg operations for architectures + * lacking direct support for these sizes. These are implemented in terms + * of 4-byte cmpxchg operations. + * + * Copyright (C) 2024 Paul E. McKenney. + */ + +#ifndef __LINUX_CMPXCHG_EMU_H +#define __LINUX_CMPXCHG_EMU_H + +uintptr_t cmpxchg_emu_u8(volatile u8 *p, uintptr_t old, uintptr_t new); + +#endif /* __LINUX_CMPXCHG_EMU_H */ diff --git a/include/linux/rcu_segcblist.h b/include/linux/rcu_segcblist.h index 659d13a7ddaaad..ba95c06675e113 100644 --- a/include/linux/rcu_segcblist.h +++ b/include/linux/rcu_segcblist.h @@ -80,36 +80,35 @@ struct rcu_cblist { * | SEGCBLIST_RCU_CORE | SEGCBLIST_LOCKING | SEGCBLIST_OFFLOADED | * | | * | Callbacks processed by rcu_core() from softirqs or local | - * | rcuc kthread, while holding nocb_lock. Waking up CB and GP kthreads, | - * | allowing nocb_timer to be armed. | + * | rcuc kthread, while holding nocb_lock. Waking up CB and GP kthreads. | * ---------------------------------------------------------------------------- * | * v - * ----------------------------------- - * | | - * v v - * --------------------------------------- ----------------------------------| - * | SEGCBLIST_RCU_CORE | | | SEGCBLIST_RCU_CORE | | - * | SEGCBLIST_LOCKING | | | SEGCBLIST_LOCKING | | - * | SEGCBLIST_OFFLOADED | | | SEGCBLIST_OFFLOADED | | - * | SEGCBLIST_KTHREAD_CB | | SEGCBLIST_KTHREAD_GP | - * | | | | - * | | | | - * | CB kthread woke up and | | GP kthread woke up and | - * | acknowledged SEGCBLIST_OFFLOADED. | | acknowledged SEGCBLIST_OFFLOADED| - * | Processes callbacks concurrently | | | - * | with rcu_core(), holding | | | - * | nocb_lock. | | | - * --------------------------------------- ----------------------------------- - * | | - * ----------------------------------- + * ---------------------------------------------------------------------------- + * | SEGCBLIST_RCU_CORE | SEGCBLIST_LOCKING | SEGCBLIST_OFFLOADED | + * | + unparked CB kthread | + * | | + * | CB kthread got unparked and processes callbacks concurrently with | + * | rcu_core(), holding nocb_lock. | + * --------------------------------------------------------------------------- + * | + * v + * ---------------------------------------------------------------------------| + * | SEGCBLIST_RCU_CORE | | + * | SEGCBLIST_LOCKING | | + * | SEGCBLIST_OFFLOADED | | + * | SEGCBLIST_KTHREAD_GP | + * | + unparked CB kthread | + * | | + * | GP kthread woke up and acknowledged nocb_lock. | + * ---------------------------------------- ----------------------------------- * | * v * |--------------------------------------------------------------------------| - * | SEGCBLIST_LOCKING | | - * | SEGCBLIST_OFFLOADED | | + * | SEGCBLIST_LOCKING | | + * | SEGCBLIST_OFFLOADED | | * | SEGCBLIST_KTHREAD_GP | | - * | SEGCBLIST_KTHREAD_CB | + * | + unparked CB kthread | * | | * | Kthreads handle callbacks holding nocb_lock, local rcu_core() stops | * | handling callbacks. Enable bypass queueing. | @@ -125,8 +124,8 @@ struct rcu_cblist { * |--------------------------------------------------------------------------| * | SEGCBLIST_LOCKING | | * | SEGCBLIST_OFFLOADED | | - * | SEGCBLIST_KTHREAD_CB | | * | SEGCBLIST_KTHREAD_GP | + * | + unparked CB kthread | * | | * | CB/GP kthreads handle callbacks holding nocb_lock, local rcu_core() | * | ignores callbacks. Bypass enqueue is enabled. | @@ -137,11 +136,11 @@ struct rcu_cblist { * | SEGCBLIST_RCU_CORE | | * | SEGCBLIST_LOCKING | | * | SEGCBLIST_OFFLOADED | | - * | SEGCBLIST_KTHREAD_CB | | * | SEGCBLIST_KTHREAD_GP | + * | + unparked CB kthread | * | | * | CB/GP kthreads handle callbacks holding nocb_lock, local rcu_core() | - * | handles callbacks concurrently. Bypass enqueue is enabled. | + * | handles callbacks concurrently. Bypass enqueue is disabled. | * | Invoke RCU core so we make sure not to preempt it in the middle with | * | leaving some urgent work unattended within a jiffy. | * ---------------------------------------------------------------------------- @@ -150,42 +149,31 @@ struct rcu_cblist { * |--------------------------------------------------------------------------| * | SEGCBLIST_RCU_CORE | | * | SEGCBLIST_LOCKING | | - * | SEGCBLIST_KTHREAD_CB | | * | SEGCBLIST_KTHREAD_GP | + * | + unparked CB kthread | * | | * | CB/GP kthreads and local rcu_core() handle callbacks concurrently | - * | holding nocb_lock. Wake up CB and GP kthreads if necessary. Disable | - * | bypass enqueue. | + * | holding nocb_lock. Wake up GP kthread if necessary. | * ---------------------------------------------------------------------------- * | * v - * ----------------------------------- - * | | - * v v - * ---------------------------------------------------------------------------| - * | | | - * | SEGCBLIST_RCU_CORE | | SEGCBLIST_RCU_CORE | | - * | SEGCBLIST_LOCKING | | SEGCBLIST_LOCKING | | - * | SEGCBLIST_KTHREAD_CB | SEGCBLIST_KTHREAD_GP | - * | | | - * | GP kthread woke up and | CB kthread woke up and | - * | acknowledged the fact that | acknowledged the fact that | - * | SEGCBLIST_OFFLOADED got cleared. | SEGCBLIST_OFFLOADED got cleared. | - * | | The CB kthread goes to sleep | - * | The callbacks from the target CPU | until it ever gets re-offloaded. | - * | will be ignored from the GP kthread | | - * | loop. | | + * |--------------------------------------------------------------------------| + * | SEGCBLIST_RCU_CORE | | + * | SEGCBLIST_LOCKING | | + * | + unparked CB kthread | + * | | + * | GP kthread woke up and acknowledged the fact that SEGCBLIST_OFFLOADED | + * | got cleared. The callbacks from the target CPU will be ignored from the| + * | GP kthread loop. | * ---------------------------------------------------------------------------- - * | | - * ----------------------------------- * | * v * ---------------------------------------------------------------------------- * | SEGCBLIST_RCU_CORE | SEGCBLIST_LOCKING | + * | + parked CB kthread | * | | - * | Callbacks processed by rcu_core() from softirqs or local | - * | rcuc kthread, while holding nocb_lock. Forbid nocb_timer to be armed. | - * | Flush pending nocb_timer. Flush nocb bypass callbacks. | + * | CB kthread is parked. Callbacks processed by rcu_core() from softirqs or | + * | local rcuc kthread, while holding nocb_lock. | * ---------------------------------------------------------------------------- * | * v diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 17d7ed5f3ae6e5..be450a3477bed2 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -209,7 +209,6 @@ void synchronize_rcu_tasks_rude(void); #define rcu_note_voluntary_context_switch(t) rcu_tasks_qs(t, false) void exit_tasks_rcu_start(void); -void exit_tasks_rcu_stop(void); void exit_tasks_rcu_finish(void); #else /* #ifdef CONFIG_TASKS_RCU_GENERIC */ #define rcu_tasks_classic_qs(t, preempt) do { } while (0) @@ -218,7 +217,6 @@ void exit_tasks_rcu_finish(void); #define call_rcu_tasks call_rcu #define synchronize_rcu_tasks synchronize_rcu static inline void exit_tasks_rcu_start(void) { } -static inline void exit_tasks_rcu_stop(void) { } static inline void exit_tasks_rcu_finish(void) { } #endif /* #else #ifdef CONFIG_TASKS_RCU_GENERIC */ @@ -401,15 +399,15 @@ static inline int debug_lockdep_rcu_enabled(void) } \ } while (0) -#if defined(CONFIG_PROVE_RCU) && !defined(CONFIG_PREEMPT_RCU) +#ifndef CONFIG_PREEMPT_RCU static inline void rcu_preempt_sleep_check(void) { RCU_LOCKDEP_WARN(lock_is_held(&rcu_lock_map), "Illegal context switch in RCU read-side critical section"); } -#else /* #ifdef CONFIG_PROVE_RCU */ +#else // #ifndef CONFIG_PREEMPT_RCU static inline void rcu_preempt_sleep_check(void) { } -#endif /* #else #ifdef CONFIG_PROVE_RCU */ +#endif // #else // #ifndef CONFIG_PREEMPT_RCU #define rcu_sleep_check() \ do { \ @@ -421,11 +419,71 @@ static inline void rcu_preempt_sleep_check(void) { } "Illegal context switch in RCU-sched read-side critical section"); \ } while (0) +// See RCU_LOCKDEP_WARN() for an explanation of the double call to +// debug_lockdep_rcu_enabled(). +static inline bool lockdep_assert_rcu_helper(bool c) +{ + return debug_lockdep_rcu_enabled() && + (c || !rcu_is_watching() || !rcu_lockdep_current_cpu_online()) && + debug_lockdep_rcu_enabled(); +} + +/** + * lockdep_assert_in_rcu_read_lock - WARN if not protected by rcu_read_lock() + * + * Splats if lockdep is enabled and there is no rcu_read_lock() in effect. + */ +#define lockdep_assert_in_rcu_read_lock() \ + WARN_ON_ONCE(lockdep_assert_rcu_helper(!lock_is_held(&rcu_lock_map))) + +/** + * lockdep_assert_in_rcu_read_lock_bh - WARN if not protected by rcu_read_lock_bh() + * + * Splats if lockdep is enabled and there is no rcu_read_lock_bh() in effect. + * Note that local_bh_disable() and friends do not suffice here, instead an + * actual rcu_read_lock_bh() is required. + */ +#define lockdep_assert_in_rcu_read_lock_bh() \ + WARN_ON_ONCE(lockdep_assert_rcu_helper(!lock_is_held(&rcu_bh_lock_map))) + +/** + * lockdep_assert_in_rcu_read_lock_sched - WARN if not protected by rcu_read_lock_sched() + * + * Splats if lockdep is enabled and there is no rcu_read_lock_sched() + * in effect. Note that preempt_disable() and friends do not suffice here, + * instead an actual rcu_read_lock_sched() is required. + */ +#define lockdep_assert_in_rcu_read_lock_sched() \ + WARN_ON_ONCE(lockdep_assert_rcu_helper(!lock_is_held(&rcu_sched_lock_map))) + +/** + * lockdep_assert_in_rcu_reader - WARN if not within some type of RCU reader + * + * Splats if lockdep is enabled and there is no RCU reader of any + * type in effect. Note that regions of code protected by things like + * preempt_disable, local_bh_disable(), and local_irq_disable() all qualify + * as RCU readers. + * + * Note that this will never trigger in PREEMPT_NONE or PREEMPT_VOLUNTARY + * kernels that are not also built with PREEMPT_COUNT. But if you have + * lockdep enabled, you might as well also enable PREEMPT_COUNT. + */ +#define lockdep_assert_in_rcu_reader() \ + WARN_ON_ONCE(lockdep_assert_rcu_helper(!lock_is_held(&rcu_lock_map) && \ + !lock_is_held(&rcu_bh_lock_map) && \ + !lock_is_held(&rcu_sched_lock_map) && \ + preemptible())) + #else /* #ifdef CONFIG_PROVE_RCU */ #define RCU_LOCKDEP_WARN(c, s) do { } while (0 && (c)) #define rcu_sleep_check() do { } while (0) +#define lockdep_assert_in_rcu_read_lock() do { } while (0) +#define lockdep_assert_in_rcu_read_lock_bh() do { } while (0) +#define lockdep_assert_in_rcu_read_lock_sched() do { } while (0) +#define lockdep_assert_in_rcu_reader() do { } while (0) + #endif /* #else #ifdef CONFIG_PROVE_RCU */ /* @@ -809,9 +867,9 @@ static inline void rcu_read_unlock(void) { RCU_LOCKDEP_WARN(!rcu_is_watching(), "rcu_read_unlock() used illegally while idle"); + rcu_lock_release(&rcu_lock_map); /* Keep acq info for rls diags. */ __release(RCU); __rcu_read_unlock(); - rcu_lock_release(&rcu_lock_map); /* Keep acq info for rls diags. */ } /** @@ -1090,6 +1148,18 @@ rcu_head_after_call_rcu(struct rcu_head *rhp, rcu_callback_t f) extern int rcu_expedited; extern int rcu_normal; -DEFINE_LOCK_GUARD_0(rcu, rcu_read_lock(), rcu_read_unlock()) +DEFINE_LOCK_GUARD_0(rcu, + do { + rcu_read_lock(); + /* + * sparse doesn't call the cleanup function, + * so just release immediately and don't track + * the context. We don't need to anyway, since + * the whole point of the guard is to not need + * the explicit unlock. + */ + __release(RCU); + } while (0), + rcu_read_unlock()) #endif /* __LINUX_RCUPDATE_H */ diff --git a/include/linux/rcupdate_wait.h b/include/linux/rcupdate_wait.h index d07f0848802e58..303ab9bee15520 100644 --- a/include/linux/rcupdate_wait.h +++ b/include/linux/rcupdate_wait.h @@ -19,18 +19,18 @@ struct rcu_synchronize { }; void wakeme_after_rcu(struct rcu_head *head); -void __wait_rcu_gp(bool checktiny, int n, call_rcu_func_t *crcu_array, +void __wait_rcu_gp(bool checktiny, unsigned int state, int n, call_rcu_func_t *crcu_array, struct rcu_synchronize *rs_array); -#define _wait_rcu_gp(checktiny, ...) \ -do { \ - call_rcu_func_t __crcu_array[] = { __VA_ARGS__ }; \ - struct rcu_synchronize __rs_array[ARRAY_SIZE(__crcu_array)]; \ - __wait_rcu_gp(checktiny, ARRAY_SIZE(__crcu_array), \ - __crcu_array, __rs_array); \ +#define _wait_rcu_gp(checktiny, state, ...) \ +do { \ + call_rcu_func_t __crcu_array[] = { __VA_ARGS__ }; \ + struct rcu_synchronize __rs_array[ARRAY_SIZE(__crcu_array)]; \ + __wait_rcu_gp(checktiny, state, ARRAY_SIZE(__crcu_array), __crcu_array, __rs_array); \ } while (0) -#define wait_rcu_gp(...) _wait_rcu_gp(false, __VA_ARGS__) +#define wait_rcu_gp(...) _wait_rcu_gp(false, TASK_UNINTERRUPTIBLE, __VA_ARGS__) +#define wait_rcu_gp_state(state, ...) _wait_rcu_gp(false, state, __VA_ARGS__) /** * synchronize_rcu_mult - Wait concurrently for multiple grace periods @@ -54,7 +54,7 @@ do { \ * grace period. */ #define synchronize_rcu_mult(...) \ - _wait_rcu_gp(IS_ENABLED(CONFIG_TINY_RCU), __VA_ARGS__) + _wait_rcu_gp(IS_ENABLED(CONFIG_TINY_RCU), TASK_UNINTERRUPTIBLE, __VA_ARGS__) static inline void cond_resched_rcu(void) { diff --git a/include/linux/srcutiny.h b/include/linux/srcutiny.h index 447133171d95fd..4d96bbdb45f086 100644 --- a/include/linux/srcutiny.h +++ b/include/linux/srcutiny.h @@ -64,8 +64,10 @@ static inline int __srcu_read_lock(struct srcu_struct *ssp) { int idx; + preempt_disable(); // Needed for PREEMPT_AUTO idx = ((READ_ONCE(ssp->srcu_idx) + 1) & 0x2) >> 1; WRITE_ONCE(ssp->srcu_lock_nesting[idx], READ_ONCE(ssp->srcu_lock_nesting[idx]) + 1); + preempt_enable(); return idx; } diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h index 2ef9c719772afb..31b3e0d3e65f78 100644 --- a/include/trace/events/rcu.h +++ b/include/trace/events/rcu.h @@ -708,6 +708,33 @@ TRACE_EVENT_RCU(rcu_invoke_kfree_bulk_callback, ); /* + * Tracepoint for a normal synchronize_rcu() states. The first argument + * is the RCU flavor, the second argument is a pointer to rcu_head the + * last one is an event. + */ +TRACE_EVENT_RCU(rcu_sr_normal, + + TP_PROTO(const char *rcuname, struct rcu_head *rhp, const char *srevent), + + TP_ARGS(rcuname, rhp, srevent), + + TP_STRUCT__entry( + __field(const char *, rcuname) + __field(void *, rhp) + __field(const char *, srevent) + ), + + TP_fast_assign( + __entry->rcuname = rcuname; + __entry->rhp = rhp; + __entry->srevent = srevent; + ), + + TP_printk("%s rhp=0x%p event=%s", + __entry->rcuname, __entry->rhp, __entry->srevent) +); + +/* * Tracepoint for exiting rcu_do_batch after RCU callbacks have been * invoked. The first argument is the name of the RCU flavor, * the second argument is number of callbacks actually invoked, diff --git a/kernel/bpf/Kconfig b/kernel/bpf/Kconfig index f999e4e0b344e3..17067dcb438610 100644 --- a/kernel/bpf/Kconfig +++ b/kernel/bpf/Kconfig @@ -28,7 +28,7 @@ config BPF_SYSCALL bool "Enable bpf() system call" select BPF select IRQ_WORK - select TASKS_RCU if PREEMPTION + select NEED_TASKS_RCU select TASKS_TRACE_RCU select BINARY_PRINTF select NET_SOCK_MSG if NET diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c index 26ae703d3c3bbc..f8302a5ca400da 100644 --- a/kernel/bpf/trampoline.c +++ b/kernel/bpf/trampoline.c @@ -333,7 +333,7 @@ static void bpf_tramp_image_put(struct bpf_tramp_image *im) int err = bpf_arch_text_poke(im->ip_after_call, BPF_MOD_JUMP, NULL, im->ip_epilogue); WARN_ON(err); - if (IS_ENABLED(CONFIG_PREEMPTION)) + if (IS_ENABLED(CONFIG_TASKS_RCU)) call_rcu_tasks(&im->rcu, __bpf_tramp_image_put_rcu_tasks); else percpu_ref_kill(&im->pcref); diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c index 7ade20e9523214..20a0b3ceb064fa 100644 --- a/kernel/pid_namespace.c +++ b/kernel/pid_namespace.c @@ -248,24 +248,7 @@ void zap_pid_ns_processes(struct pid_namespace *pid_ns) set_current_state(TASK_INTERRUPTIBLE); if (pid_ns->pid_allocated == init_pids) break; - /* - * Release tasks_rcu_exit_srcu to avoid following deadlock: - * - * 1) TASK A unshare(CLONE_NEWPID) - * 2) TASK A fork() twice -> TASK B (child reaper for new ns) - * and TASK C - * 3) TASK B exits, kills TASK C, waits for TASK A to reap it - * 4) TASK A calls synchronize_rcu_tasks() - * -> synchronize_srcu(tasks_rcu_exit_srcu) - * 5) *DEADLOCK* - * - * It is considered safe to release tasks_rcu_exit_srcu here - * because we assume the current task can not be concurrently - * reaped at this point. - */ - exit_tasks_rcu_stop(); schedule(); - exit_tasks_rcu_start(); } __set_current_state(TASK_RUNNING); diff --git a/kernel/rcu/Kconfig b/kernel/rcu/Kconfig index e7d2dd2675931f..3e079de0f5b434 100644 --- a/kernel/rcu/Kconfig +++ b/kernel/rcu/Kconfig @@ -31,7 +31,7 @@ config PREEMPT_RCU config TINY_RCU bool - default y if !PREEMPTION && !SMP + default y if !PREEMPT_RCU && !SMP help This option selects the RCU implementation that is designed for UP systems from which real-time response @@ -85,9 +85,13 @@ config FORCE_TASKS_RCU idle, and user-mode execution as quiescent states. Not for manual selection in most cases. -config TASKS_RCU +config NEED_TASKS_RCU bool default n + +config TASKS_RCU + bool + default NEED_TASKS_RCU && (PREEMPTION || PREEMPT_AUTO) select IRQ_WORK config FORCE_TASKS_RUDE_RCU diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h index 86fce206560e83..38238e595a61a4 100644 --- a/kernel/rcu/rcu.h +++ b/kernel/rcu/rcu.h @@ -522,12 +522,18 @@ static inline void show_rcu_tasks_gp_kthreads(void) {} #ifdef CONFIG_TASKS_RCU struct task_struct *get_rcu_tasks_gp_kthread(void); +void rcu_tasks_get_gp_data(int *flags, unsigned long *gp_seq); #endif // # ifdef CONFIG_TASKS_RCU #ifdef CONFIG_TASKS_RUDE_RCU struct task_struct *get_rcu_tasks_rude_gp_kthread(void); +void rcu_tasks_rude_get_gp_data(int *flags, unsigned long *gp_seq); #endif // # ifdef CONFIG_TASKS_RUDE_RCU +#ifdef CONFIG_TASKS_TRACE_RCU +void rcu_tasks_trace_get_gp_data(int *flags, unsigned long *gp_seq); +#endif + #ifdef CONFIG_TASKS_RCU_GENERIC void tasks_cblist_init_generic(void); #else /* #ifdef CONFIG_TASKS_RCU_GENERIC */ @@ -557,8 +563,7 @@ static inline void rcu_set_jiffies_lazy_flush(unsigned long j) { } #endif #if defined(CONFIG_TREE_RCU) -void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags, - unsigned long *gp_seq); +void rcutorture_get_gp_data(int *flags, unsigned long *gp_seq); void do_trace_rcu_torture_read(const char *rcutorturename, struct rcu_head *rhp, unsigned long secs, @@ -566,8 +571,7 @@ void do_trace_rcu_torture_read(const char *rcutorturename, unsigned long c); void rcu_gp_set_torture_wait(int duration); #else -static inline void rcutorture_get_gp_data(enum rcutorture_type test_type, - int *flags, unsigned long *gp_seq) +static inline void rcutorture_get_gp_data(int *flags, unsigned long *gp_seq) { *flags = 0; *gp_seq = 0; @@ -587,20 +591,16 @@ static inline void rcu_gp_set_torture_wait(int duration) { } #ifdef CONFIG_TINY_SRCU -static inline void srcutorture_get_gp_data(enum rcutorture_type test_type, - struct srcu_struct *sp, int *flags, +static inline void srcutorture_get_gp_data(struct srcu_struct *sp, int *flags, unsigned long *gp_seq) { - if (test_type != SRCU_FLAVOR) - return; *flags = 0; *gp_seq = sp->srcu_idx; } #elif defined(CONFIG_TREE_SRCU) -void srcutorture_get_gp_data(enum rcutorture_type test_type, - struct srcu_struct *sp, int *flags, +void srcutorture_get_gp_data(struct srcu_struct *sp, int *flags, unsigned long *gp_seq); #endif diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index 45d6b4c3d199c1..cafe047d046e84 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -381,12 +381,16 @@ struct rcu_torture_ops { void (*gp_kthread_dbg)(void); bool (*check_boost_failed)(unsigned long gp_state, int *cpup); int (*stall_dur)(void); + void (*get_gp_data)(int *flags, unsigned long *gp_seq); + void (*gp_slow_register)(atomic_t *rgssp); + void (*gp_slow_unregister)(atomic_t *rgssp); long cbflood_max; int irq_capable; int can_boost; int extendables; int slow_gps; int no_pi_lock; + int debug_objects; const char *name; }; @@ -461,12 +465,13 @@ rcu_torture_pipe_update_one(struct rcu_torture *rp) WRITE_ONCE(rp->rtort_chkp, NULL); smp_store_release(&rtrcp->rtc_ready, 1); // Pair with smp_load_acquire(). } - i = READ_ONCE(rp->rtort_pipe_count); + i = rp->rtort_pipe_count; if (i > RCU_TORTURE_PIPE_LEN) i = RCU_TORTURE_PIPE_LEN; atomic_inc(&rcu_torture_wcount[i]); WRITE_ONCE(rp->rtort_pipe_count, i + 1); - if (rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) { + ASSERT_EXCLUSIVE_WRITER(rp->rtort_pipe_count); + if (i + 1 >= RCU_TORTURE_PIPE_LEN) { rp->rtort_mbtest = 0; return true; } @@ -564,13 +569,16 @@ static struct rcu_torture_ops rcu_ops = { .call = call_rcu_hurry, .cb_barrier = rcu_barrier, .fqs = rcu_force_quiescent_state, - .stats = NULL, .gp_kthread_dbg = show_rcu_gp_kthreads, .check_boost_failed = rcu_check_boost_fail, .stall_dur = rcu_jiffies_till_stall_check, + .get_gp_data = rcutorture_get_gp_data, + .gp_slow_register = rcu_gp_slow_register, + .gp_slow_unregister = rcu_gp_slow_unregister, .irq_capable = 1, .can_boost = IS_ENABLED(CONFIG_RCU_BOOST), .extendables = RCUTORTURE_MAX_EXTEND, + .debug_objects = 1, .name = "rcu" }; @@ -611,9 +619,6 @@ static struct rcu_torture_ops rcu_busted_ops = { .sync = synchronize_rcu_busted, .exp_sync = synchronize_rcu_busted, .call = call_rcu_busted, - .cb_barrier = NULL, - .fqs = NULL, - .stats = NULL, .irq_capable = 1, .name = "busted" }; @@ -627,6 +632,11 @@ static struct srcu_struct srcu_ctld; static struct srcu_struct *srcu_ctlp = &srcu_ctl; static struct rcu_torture_ops srcud_ops; +static void srcu_get_gp_data(int *flags, unsigned long *gp_seq) +{ + srcutorture_get_gp_data(srcu_ctlp, flags, gp_seq); +} + static int srcu_torture_read_lock(void) { if (cur_ops == &srcud_ops) @@ -735,9 +745,11 @@ static struct rcu_torture_ops srcu_ops = { .call = srcu_torture_call, .cb_barrier = srcu_torture_barrier, .stats = srcu_torture_stats, + .get_gp_data = srcu_get_gp_data, .cbflood_max = 50000, .irq_capable = 1, .no_pi_lock = IS_ENABLED(CONFIG_TINY_SRCU), + .debug_objects = 1, .name = "srcu" }; @@ -773,9 +785,11 @@ static struct rcu_torture_ops srcud_ops = { .call = srcu_torture_call, .cb_barrier = srcu_torture_barrier, .stats = srcu_torture_stats, + .get_gp_data = srcu_get_gp_data, .cbflood_max = 50000, .irq_capable = 1, .no_pi_lock = IS_ENABLED(CONFIG_TINY_SRCU), + .debug_objects = 1, .name = "srcud" }; @@ -837,8 +851,6 @@ static struct rcu_torture_ops trivial_ops = { .get_gp_seq = rcu_no_completed, .sync = synchronize_rcu_trivial, .exp_sync = synchronize_rcu_trivial, - .fqs = NULL, - .stats = NULL, .irq_capable = 1, .name = "trivial" }; @@ -881,8 +893,7 @@ static struct rcu_torture_ops tasks_ops = { .call = call_rcu_tasks, .cb_barrier = rcu_barrier_tasks, .gp_kthread_dbg = show_rcu_tasks_classic_gp_kthread, - .fqs = NULL, - .stats = NULL, + .get_gp_data = rcu_tasks_get_gp_data, .irq_capable = 1, .slow_gps = 1, .name = "tasks" @@ -921,9 +932,8 @@ static struct rcu_torture_ops tasks_rude_ops = { .call = call_rcu_tasks_rude, .cb_barrier = rcu_barrier_tasks_rude, .gp_kthread_dbg = show_rcu_tasks_rude_gp_kthread, + .get_gp_data = rcu_tasks_rude_get_gp_data, .cbflood_max = 50000, - .fqs = NULL, - .stats = NULL, .irq_capable = 1, .name = "tasks-rude" }; @@ -973,9 +983,8 @@ static struct rcu_torture_ops tasks_tracing_ops = { .call = call_rcu_tasks_trace, .cb_barrier = rcu_barrier_tasks_trace, .gp_kthread_dbg = show_rcu_tasks_trace_gp_kthread, + .get_gp_data = rcu_tasks_trace_get_gp_data, .cbflood_max = 50000, - .fqs = NULL, - .stats = NULL, .irq_capable = 1, .slow_gps = 1, .name = "tasks-tracing" @@ -1399,6 +1408,7 @@ rcu_torture_writer(void *arg) if (rp == NULL) continue; rp->rtort_pipe_count = 0; + ASSERT_EXCLUSIVE_WRITER(rp->rtort_pipe_count); rcu_torture_writer_state = RTWS_DELAY; udelay(torture_random(&rand) & 0x3ff); rcu_torture_writer_state = RTWS_REPLACE; @@ -1414,6 +1424,7 @@ rcu_torture_writer(void *arg) atomic_inc(&rcu_torture_wcount[i]); WRITE_ONCE(old_rp->rtort_pipe_count, old_rp->rtort_pipe_count + 1); + ASSERT_EXCLUSIVE_WRITER(old_rp->rtort_pipe_count); // Make sure readers block polled grace periods. if (cur_ops->get_gp_state && cur_ops->poll_gp_state) { @@ -1586,7 +1597,8 @@ rcu_torture_writer(void *arg) if (list_empty(&rcu_tortures[i].rtort_free) && rcu_access_pointer(rcu_torture_current) != &rcu_tortures[i]) { tracing_off(); - show_rcu_gp_kthreads(); + if (cur_ops->gp_kthread_dbg) + cur_ops->gp_kthread_dbg(); WARN(1, "%s: rtort_pipe_count: %d\n", __func__, rcu_tortures[i].rtort_pipe_count); rcu_ftrace_dump(DUMP_ALL); } @@ -1997,7 +2009,8 @@ static bool rcu_torture_one_read(struct torture_random_state *trsp, long myid) preempt_disable(); pipe_count = READ_ONCE(p->rtort_pipe_count); if (pipe_count > RCU_TORTURE_PIPE_LEN) { - /* Should not happen, but... */ + // Should not happen in a correct RCU implementation, + // happens quite often for torture_type=busted. pipe_count = RCU_TORTURE_PIPE_LEN; } completed = cur_ops->get_gp_seq(); @@ -2259,10 +2272,8 @@ rcu_torture_stats_print(void) int __maybe_unused flags = 0; unsigned long __maybe_unused gp_seq = 0; - rcutorture_get_gp_data(cur_ops->ttype, - &flags, &gp_seq); - srcutorture_get_gp_data(cur_ops->ttype, srcu_ctlp, - &flags, &gp_seq); + if (cur_ops->get_gp_data) + cur_ops->get_gp_data(&flags, &gp_seq); wtp = READ_ONCE(writer_task); pr_alert("??? Writer stall state %s(%d) g%lu f%#x ->state %#x cpu %d\n", rcu_torture_writer_state_getname(), @@ -2486,8 +2497,8 @@ static int rcu_torture_stall(void *args) preempt_disable(); pr_alert("%s start on CPU %d.\n", __func__, raw_smp_processor_id()); - while (ULONG_CMP_LT((unsigned long)ktime_get_seconds(), - stop_at)) + while (ULONG_CMP_LT((unsigned long)ktime_get_seconds(), stop_at) && + !kthread_should_stop()) if (stall_cpu_block) { #ifdef CONFIG_PREEMPTION preempt_schedule(); @@ -2619,7 +2630,7 @@ static void rcu_torture_fwd_cb_cr(struct rcu_head *rhp) spin_lock_irqsave(&rfp->rcu_fwd_lock, flags); rfcpp = rfp->rcu_fwd_cb_tail; rfp->rcu_fwd_cb_tail = &rfcp->rfc_next; - WRITE_ONCE(*rfcpp, rfcp); + smp_store_release(rfcpp, rfcp); WRITE_ONCE(rfp->n_launders_cb, rfp->n_launders_cb + 1); i = ((jiffies - rfp->rcu_fwd_startat) / (HZ / FWD_CBS_HIST_DIV)); if (i >= ARRAY_SIZE(rfp->n_launders_hist)) @@ -2832,13 +2843,14 @@ static void rcu_torture_fwd_prog_cr(struct rcu_fwd *rfp) if (!torture_must_stop() && !READ_ONCE(rcu_fwd_emergency_stop) && !shutdown_time_arrived()) { - WARN_ON(n_max_gps < MIN_FWD_CBS_LAUNDERED); - pr_alert("%s Duration %lu barrier: %lu pending %ld n_launders: %ld n_launders_sa: %ld n_max_gps: %ld n_max_cbs: %ld cver %ld gps %ld\n", + if (WARN_ON(n_max_gps < MIN_FWD_CBS_LAUNDERED) && cur_ops->gp_kthread_dbg) + cur_ops->gp_kthread_dbg(); + pr_alert("%s Duration %lu barrier: %lu pending %ld n_launders: %ld n_launders_sa: %ld n_max_gps: %ld n_max_cbs: %ld cver %ld gps %ld #online %u\n", __func__, stoppedat - rfp->rcu_fwd_startat, jiffies - stoppedat, n_launders + n_max_cbs - n_launders_cb_snap, n_launders, n_launders_sa, - n_max_gps, n_max_cbs, cver, gps); + n_max_gps, n_max_cbs, cver, gps, num_online_cpus()); atomic_long_add(n_max_cbs, &rcu_fwd_max_cbs); mutex_lock(&rcu_fwd_mutex); // Serialize histograms. rcu_torture_fwd_cb_hist(rfp); @@ -3040,11 +3052,12 @@ static void rcu_torture_barrier_cbf(struct rcu_head *rcu) } /* IPI handler to get callback posted on desired CPU, if online. */ -static void rcu_torture_barrier1cb(void *rcu_void) +static int rcu_torture_barrier1cb(void *rcu_void) { struct rcu_head *rhp = rcu_void; cur_ops->call(rhp, rcu_torture_barrier_cbf); + return 0; } /* kthread function to register callbacks used to test RCU barriers. */ @@ -3070,11 +3083,9 @@ static int rcu_torture_barrier_cbs(void *arg) * The above smp_load_acquire() ensures barrier_phase load * is ordered before the following ->call(). */ - if (smp_call_function_single(myid, rcu_torture_barrier1cb, - &rcu, 1)) { - // IPI failed, so use direct call from current CPU. + if (smp_call_on_cpu(myid, rcu_torture_barrier1cb, &rcu, 1)) cur_ops->call(&rcu, rcu_torture_barrier_cbf); - } + if (atomic_dec_and_test(&barrier_cbs_count)) wake_up(&barrier_wq); } while (!torture_must_stop()); @@ -3340,12 +3351,12 @@ rcu_torture_cleanup(void) pr_info("%s: Invoking %pS().\n", __func__, cur_ops->cb_barrier); cur_ops->cb_barrier(); } - rcu_gp_slow_unregister(NULL); + if (cur_ops->gp_slow_unregister) + cur_ops->gp_slow_unregister(NULL); return; } if (!cur_ops) { torture_cleanup_end(); - rcu_gp_slow_unregister(NULL); return; } @@ -3384,8 +3395,8 @@ rcu_torture_cleanup(void) fakewriter_tasks = NULL; } - rcutorture_get_gp_data(cur_ops->ttype, &flags, &gp_seq); - srcutorture_get_gp_data(cur_ops->ttype, srcu_ctlp, &flags, &gp_seq); + if (cur_ops->get_gp_data) + cur_ops->get_gp_data(&flags, &gp_seq); pr_alert("%s: End-test grace-period state: g%ld f%#x total-gps=%ld\n", cur_ops->name, (long)gp_seq, flags, rcutorture_seq_diff(gp_seq, start_gp_seq)); @@ -3444,10 +3455,10 @@ rcu_torture_cleanup(void) else rcu_torture_print_module_parms(cur_ops, "End of test: SUCCESS"); torture_cleanup_end(); - rcu_gp_slow_unregister(&rcu_fwd_cb_nodelay); + if (cur_ops->gp_slow_unregister) + cur_ops->gp_slow_unregister(NULL); } -#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD static void rcu_torture_leak_cb(struct rcu_head *rhp) { } @@ -3465,7 +3476,6 @@ static void rcu_torture_err_cb(struct rcu_head *rhp) */ pr_alert("%s: duplicated callback was invoked.\n", KBUILD_MODNAME); } -#endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */ /* * Verify that double-free causes debug-objects to complain, but only @@ -3474,39 +3484,43 @@ static void rcu_torture_err_cb(struct rcu_head *rhp) */ static void rcu_test_debug_objects(void) { -#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD struct rcu_head rh1; struct rcu_head rh2; + int idx; + + if (!IS_ENABLED(CONFIG_DEBUG_OBJECTS_RCU_HEAD)) { + pr_alert("%s: !CONFIG_DEBUG_OBJECTS_RCU_HEAD, not testing duplicate call_%s()\n", + KBUILD_MODNAME, cur_ops->name); + return; + } + + if (WARN_ON_ONCE(cur_ops->debug_objects && + (!cur_ops->call || !cur_ops->cb_barrier))) + return; + struct rcu_head *rhp = kmalloc(sizeof(*rhp), GFP_KERNEL); init_rcu_head_on_stack(&rh1); init_rcu_head_on_stack(&rh2); - pr_alert("%s: WARN: Duplicate call_rcu() test starting.\n", KBUILD_MODNAME); + pr_alert("%s: WARN: Duplicate call_%s() test starting.\n", KBUILD_MODNAME, cur_ops->name); /* Try to queue the rh2 pair of callbacks for the same grace period. */ - preempt_disable(); /* Prevent preemption from interrupting test. */ - rcu_read_lock(); /* Make it impossible to finish a grace period. */ - call_rcu_hurry(&rh1, rcu_torture_leak_cb); /* Start grace period. */ - local_irq_disable(); /* Make it harder to start a new grace period. */ - call_rcu_hurry(&rh2, rcu_torture_leak_cb); - call_rcu_hurry(&rh2, rcu_torture_err_cb); /* Duplicate callback. */ + idx = cur_ops->readlock(); /* Make it impossible to finish a grace period. */ + cur_ops->call(&rh1, rcu_torture_leak_cb); /* Start grace period. */ + cur_ops->call(&rh2, rcu_torture_leak_cb); + cur_ops->call(&rh2, rcu_torture_err_cb); /* Duplicate callback. */ if (rhp) { - call_rcu_hurry(rhp, rcu_torture_leak_cb); - call_rcu_hurry(rhp, rcu_torture_err_cb); /* Another duplicate callback. */ + cur_ops->call(rhp, rcu_torture_leak_cb); + cur_ops->call(rhp, rcu_torture_err_cb); /* Another duplicate callback. */ } - local_irq_enable(); - rcu_read_unlock(); - preempt_enable(); + cur_ops->readunlock(idx); /* Wait for them all to get done so we can safely return. */ - rcu_barrier(); - pr_alert("%s: WARN: Duplicate call_rcu() test complete.\n", KBUILD_MODNAME); + cur_ops->cb_barrier(); + pr_alert("%s: WARN: Duplicate call_%s() test complete.\n", KBUILD_MODNAME, cur_ops->name); destroy_rcu_head_on_stack(&rh1); destroy_rcu_head_on_stack(&rh2); kfree(rhp); -#else /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */ - pr_alert("%s: !CONFIG_DEBUG_OBJECTS_RCU_HEAD, not testing duplicate call_rcu()\n", KBUILD_MODNAME); -#endif /* #else #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */ } static void rcutorture_sync(void) @@ -3756,8 +3770,8 @@ rcu_torture_init(void) nrealreaders = 1; } rcu_torture_print_module_parms(cur_ops, "Start of test"); - rcutorture_get_gp_data(cur_ops->ttype, &flags, &gp_seq); - srcutorture_get_gp_data(cur_ops->ttype, srcu_ctlp, &flags, &gp_seq); + if (cur_ops->get_gp_data) + cur_ops->get_gp_data(&flags, &gp_seq); start_gp_seq = gp_seq; pr_alert("%s: Start-test grace-period state: g%ld f%#x\n", cur_ops->name, (long)gp_seq, flags); @@ -3926,7 +3940,8 @@ rcu_torture_init(void) if (object_debug) rcu_test_debug_objects(); torture_init_end(); - rcu_gp_slow_register(&rcu_fwd_cb_nodelay); + if (cur_ops->gp_slow_register && !WARN_ON_ONCE(!cur_ops->gp_slow_unregister)) + cur_ops->gp_slow_register(&rcu_fwd_cb_nodelay); return 0; unwind: diff --git a/kernel/rcu/srcutiny.c b/kernel/rcu/srcutiny.c index c38e5933a5d693..5afd5cf494dba3 100644 --- a/kernel/rcu/srcutiny.c +++ b/kernel/rcu/srcutiny.c @@ -96,9 +96,12 @@ EXPORT_SYMBOL_GPL(cleanup_srcu_struct); */ void __srcu_read_unlock(struct srcu_struct *ssp, int idx) { - int newval = READ_ONCE(ssp->srcu_lock_nesting[idx]) - 1; + int newval; + preempt_disable(); // Needed for PREEMPT_AUTO + newval = READ_ONCE(ssp->srcu_lock_nesting[idx]) - 1; WRITE_ONCE(ssp->srcu_lock_nesting[idx], newval); + preempt_enable(); if (!newval && READ_ONCE(ssp->srcu_gp_waiting) && in_task()) swake_up_one(&ssp->srcu_wq); } @@ -117,8 +120,11 @@ void srcu_drive_gp(struct work_struct *wp) struct srcu_struct *ssp; ssp = container_of(wp, struct srcu_struct, srcu_work); - if (ssp->srcu_gp_running || ULONG_CMP_GE(ssp->srcu_idx, READ_ONCE(ssp->srcu_idx_max))) + preempt_disable(); // Needed for PREEMPT_AUTO + if (ssp->srcu_gp_running || ULONG_CMP_GE(ssp->srcu_idx, READ_ONCE(ssp->srcu_idx_max))) { return; /* Already running or nothing to do. */ + preempt_enable(); + } /* Remove recently arrived callbacks and wait for readers. */ WRITE_ONCE(ssp->srcu_gp_running, true); @@ -130,9 +136,12 @@ void srcu_drive_gp(struct work_struct *wp) idx = (ssp->srcu_idx & 0x2) / 2; WRITE_ONCE(ssp->srcu_idx, ssp->srcu_idx + 1); WRITE_ONCE(ssp->srcu_gp_waiting, true); /* srcu_read_unlock() wakes! */ + preempt_enable(); swait_event_exclusive(ssp->srcu_wq, !READ_ONCE(ssp->srcu_lock_nesting[idx])); + preempt_disable(); // Needed for PREEMPT_AUTO WRITE_ONCE(ssp->srcu_gp_waiting, false); /* srcu_read_unlock() cheap. */ WRITE_ONCE(ssp->srcu_idx, ssp->srcu_idx + 1); + preempt_enable(); /* Invoke the callbacks we removed above. */ while (lh) { @@ -150,8 +159,11 @@ void srcu_drive_gp(struct work_struct *wp) * at interrupt level, but the ->srcu_gp_running checks will * straighten that out. */ + preempt_disable(); // Needed for PREEMPT_AUTO WRITE_ONCE(ssp->srcu_gp_running, false); - if (ULONG_CMP_LT(ssp->srcu_idx, READ_ONCE(ssp->srcu_idx_max))) + idx = ULONG_CMP_LT(ssp->srcu_idx, READ_ONCE(ssp->srcu_idx_max)); + preempt_enable(); + if (idx) schedule_work(&ssp->srcu_work); } EXPORT_SYMBOL_GPL(srcu_drive_gp); @@ -160,9 +172,12 @@ static void srcu_gp_start_if_needed(struct srcu_struct *ssp) { unsigned long cookie; + preempt_disable(); // Needed for PREEMPT_AUTO cookie = get_state_synchronize_srcu(ssp); - if (ULONG_CMP_GE(READ_ONCE(ssp->srcu_idx_max), cookie)) + if (ULONG_CMP_GE(READ_ONCE(ssp->srcu_idx_max), cookie)) { + preempt_enable(); return; + } WRITE_ONCE(ssp->srcu_idx_max, cookie); if (!READ_ONCE(ssp->srcu_gp_running)) { if (likely(srcu_init_done)) @@ -170,6 +185,7 @@ static void srcu_gp_start_if_needed(struct srcu_struct *ssp) else if (list_empty(&ssp->srcu_work.entry)) list_add(&ssp->srcu_work.entry, &srcu_boot_list); } + preempt_enable(); } /* @@ -183,11 +199,13 @@ void call_srcu(struct srcu_struct *ssp, struct rcu_head *rhp, rhp->func = func; rhp->next = NULL; + preempt_disable(); // Needed for PREEMPT_AUTO local_irq_save(flags); *ssp->srcu_cb_tail = rhp; ssp->srcu_cb_tail = &rhp->next; local_irq_restore(flags); srcu_gp_start_if_needed(ssp); + preempt_enable(); } EXPORT_SYMBOL_GPL(call_srcu); @@ -241,9 +259,12 @@ EXPORT_SYMBOL_GPL(get_state_synchronize_srcu); */ unsigned long start_poll_synchronize_srcu(struct srcu_struct *ssp) { - unsigned long ret = get_state_synchronize_srcu(ssp); + unsigned long ret; + preempt_disable(); // Needed for PREEMPT_AUTO + ret = get_state_synchronize_srcu(ssp); srcu_gp_start_if_needed(ssp); + preempt_enable(); return ret; } EXPORT_SYMBOL_GPL(start_poll_synchronize_srcu); diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index e4d673fc30f42f..bc4b58b0204e98 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -1826,12 +1826,9 @@ static void process_srcu(struct work_struct *work) srcu_reschedule(ssp, curdelay); } -void srcutorture_get_gp_data(enum rcutorture_type test_type, - struct srcu_struct *ssp, int *flags, +void srcutorture_get_gp_data(struct srcu_struct *ssp, int *flags, unsigned long *gp_seq) { - if (test_type != SRCU_FLAVOR) - return; *flags = 0; *gp_seq = rcu_seq_current(&ssp->srcu_sup->srcu_gp_seq); } diff --git a/kernel/rcu/sync.c b/kernel/rcu/sync.c index 86df878a2fee8b..6c2bd9001adcdb 100644 --- a/kernel/rcu/sync.c +++ b/kernel/rcu/sync.c @@ -122,7 +122,7 @@ void rcu_sync_enter(struct rcu_sync *rsp) * we are called at early boot time but this shouldn't happen. */ } - rsp->gp_count++; + WRITE_ONCE(rsp->gp_count, rsp->gp_count + 1); spin_unlock_irq(&rsp->rss_lock); if (gp_state == GP_IDLE) { @@ -151,11 +151,15 @@ void rcu_sync_enter(struct rcu_sync *rsp) */ void rcu_sync_exit(struct rcu_sync *rsp) { + int gpc; + WARN_ON_ONCE(READ_ONCE(rsp->gp_state) == GP_IDLE); WARN_ON_ONCE(READ_ONCE(rsp->gp_count) == 0); spin_lock_irq(&rsp->rss_lock); - if (!--rsp->gp_count) { + gpc = rsp->gp_count - 1; + WRITE_ONCE(rsp->gp_count, gpc); + if (!gpc) { if (rsp->gp_state == GP_PASSED) { WRITE_ONCE(rsp->gp_state, GP_EXIT); rcu_sync_call(rsp); diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index 147b5945d67a04..4dc56b6e27c044 100644 --- a/kernel/rcu/tasks.h +++ b/kernel/rcu/tasks.h @@ -74,6 +74,7 @@ struct rcu_tasks_percpu { * @holdouts_func: This flavor's holdout-list scan function (optional). * @postgp_func: This flavor's post-grace-period function (optional). * @call_func: This flavor's call_rcu()-equivalent function. + * @wait_state: Task state for synchronous grace-period waits (default TASK_UNINTERRUPTIBLE). * @rtpcpu: This flavor's rcu_tasks_percpu structure. * @percpu_enqueue_shift: Shift down CPU ID this much when enqueuing callbacks. * @percpu_enqueue_lim: Number of per-CPU callback queues in use for enqueuing. @@ -107,6 +108,7 @@ struct rcu_tasks { holdouts_func_t holdouts_func; postgp_func_t postgp_func; call_rcu_func_t call_func; + unsigned int wait_state; struct rcu_tasks_percpu __percpu *rtpcpu; int percpu_enqueue_shift; int percpu_enqueue_lim; @@ -134,6 +136,7 @@ static struct rcu_tasks rt_name = \ .tasks_gp_mutex = __MUTEX_INITIALIZER(rt_name.tasks_gp_mutex), \ .gp_func = gp, \ .call_func = call, \ + .wait_state = TASK_UNINTERRUPTIBLE, \ .rtpcpu = &rt_name ## __percpu, \ .lazy_jiffies = DIV_ROUND_UP(HZ, 4), \ .name = n, \ @@ -147,7 +150,7 @@ static struct rcu_tasks rt_name = \ #ifdef CONFIG_TASKS_RCU -/* Report delay in synchronize_srcu() completion in rcu_tasks_postscan(). */ +/* Report delay of scan exiting tasklist in rcu_tasks_postscan(). */ static void tasks_rcu_exit_srcu_stall(struct timer_list *unused); static DEFINE_TIMER(tasks_rcu_exit_srcu_stall_timer, tasks_rcu_exit_srcu_stall); #endif @@ -638,7 +641,7 @@ static void synchronize_rcu_tasks_generic(struct rcu_tasks *rtp) // If the grace-period kthread is running, use it. if (READ_ONCE(rtp->kthread_ptr)) { - wait_rcu_gp(rtp->call_func); + wait_rcu_gp_state(rtp->wait_state, rtp->call_func); return; } rcu_tasks_one_gp(rtp, true); @@ -855,7 +858,7 @@ static void rcu_tasks_wait_gp(struct rcu_tasks *rtp) // not know to synchronize with this RCU Tasks grace period) have // completed exiting. The synchronize_rcu() in rcu_tasks_postgp() // will take care of any tasks stuck in the non-preemptible region -// of do_exit() following its call to exit_tasks_rcu_stop(). +// of do_exit() following its call to exit_tasks_rcu_finish(). // check_all_holdout_tasks(), repeatedly until holdout list is empty: // Scans the holdout list, attempting to identify a quiescent state // for each task on the list. If there is a quiescent state, the @@ -1160,6 +1163,7 @@ static int __init rcu_spawn_tasks_kthread(void) rcu_tasks.postscan_func = rcu_tasks_postscan; rcu_tasks.holdouts_func = check_all_holdout_tasks; rcu_tasks.postgp_func = rcu_tasks_postgp; + rcu_tasks.wait_state = TASK_IDLE; rcu_spawn_tasks_kthread_generic(&rcu_tasks); return 0; } @@ -1178,6 +1182,13 @@ struct task_struct *get_rcu_tasks_gp_kthread(void) } EXPORT_SYMBOL_GPL(get_rcu_tasks_gp_kthread); +void rcu_tasks_get_gp_data(int *flags, unsigned long *gp_seq) +{ + *flags = 0; + *gp_seq = rcu_seq_current(&rcu_tasks.tasks_gp_seq); +} +EXPORT_SYMBOL_GPL(rcu_tasks_get_gp_data); + /* * Protect against tasklist scan blind spot while the task is exiting and * may be removed from the tasklist. Do this by adding the task to yet @@ -1199,8 +1210,7 @@ void exit_tasks_rcu_start(void) rtpcp = this_cpu_ptr(rcu_tasks.rtpcpu); t->rcu_tasks_exit_cpu = smp_processor_id(); raw_spin_lock_irqsave_rcu_node(rtpcp, flags); - if (!rtpcp->rtp_exit_list.next) - INIT_LIST_HEAD(&rtpcp->rtp_exit_list); + WARN_ON_ONCE(!rtpcp->rtp_exit_list.next); list_add(&t->rcu_tasks_exit_list, &rtpcp->rtp_exit_list); raw_spin_unlock_irqrestore_rcu_node(rtpcp, flags); preempt_enable(); @@ -1210,7 +1220,7 @@ void exit_tasks_rcu_start(void) * Remove the task from the "yet another list" because do_exit() is now * non-preemptible, allowing synchronize_rcu() to wait beyond this point. */ -void exit_tasks_rcu_stop(void) +void exit_tasks_rcu_finish(void) { unsigned long flags; struct rcu_tasks_percpu *rtpcp; @@ -1221,22 +1231,12 @@ void exit_tasks_rcu_stop(void) raw_spin_lock_irqsave_rcu_node(rtpcp, flags); list_del_init(&t->rcu_tasks_exit_list); raw_spin_unlock_irqrestore_rcu_node(rtpcp, flags); -} -/* - * Contribute to protect against tasklist scan blind spot while the - * task is exiting and may be removed from the tasklist. See - * corresponding synchronize_srcu() for further details. - */ -void exit_tasks_rcu_finish(void) -{ - exit_tasks_rcu_stop(); - exit_tasks_rcu_finish_trace(current); + exit_tasks_rcu_finish_trace(t); } #else /* #ifdef CONFIG_TASKS_RCU */ void exit_tasks_rcu_start(void) { } -void exit_tasks_rcu_stop(void) { } void exit_tasks_rcu_finish(void) { exit_tasks_rcu_finish_trace(current); } #endif /* #else #ifdef CONFIG_TASKS_RCU */ @@ -1358,6 +1358,13 @@ struct task_struct *get_rcu_tasks_rude_gp_kthread(void) } EXPORT_SYMBOL_GPL(get_rcu_tasks_rude_gp_kthread); +void rcu_tasks_rude_get_gp_data(int *flags, unsigned long *gp_seq) +{ + *flags = 0; + *gp_seq = rcu_seq_current(&rcu_tasks_rude.tasks_gp_seq); +} +EXPORT_SYMBOL_GPL(rcu_tasks_rude_get_gp_data); + #endif /* #ifdef CONFIG_TASKS_RUDE_RCU */ //////////////////////////////////////////////////////////////////////// @@ -1457,6 +1464,7 @@ static void rcu_st_need_qs(struct task_struct *t, u8 v) /* * Do a cmpxchg() on ->trc_reader_special.b.need_qs, allowing for * the four-byte operand-size restriction of some platforms. + * * Returns the old value, which is often ignored. */ u8 rcu_trc_cmpxchg_need_qs(struct task_struct *t, u8 old, u8 new) @@ -1468,7 +1476,14 @@ u8 rcu_trc_cmpxchg_need_qs(struct task_struct *t, u8 old, u8 new) if (trs_old.b.need_qs != old) return trs_old.b.need_qs; trs_new.b.need_qs = new; - ret.s = cmpxchg(&t->trc_reader_special.s, trs_old.s, trs_new.s); + + // Although cmpxchg() appears to KCSAN to update all four bytes, + // only the .b.need_qs byte actually changes. + instrument_atomic_read_write(&t->trc_reader_special.b.need_qs, + sizeof(t->trc_reader_special.b.need_qs)); + // Avoid false-positive KCSAN failures. + ret.s = data_race(cmpxchg(&t->trc_reader_special.s, trs_old.s, trs_new.s)); + return ret.b.need_qs; } EXPORT_SYMBOL_GPL(rcu_trc_cmpxchg_need_qs); @@ -1994,7 +2009,7 @@ void show_rcu_tasks_trace_gp_kthread(void) { char buf[64]; - sprintf(buf, "N%lu h:%lu/%lu/%lu", + snprintf(buf, sizeof(buf), "N%lu h:%lu/%lu/%lu", data_race(n_trc_holdouts), data_race(n_heavy_reader_ofl_updates), data_race(n_heavy_reader_updates), @@ -2010,6 +2025,13 @@ struct task_struct *get_rcu_tasks_trace_gp_kthread(void) } EXPORT_SYMBOL_GPL(get_rcu_tasks_trace_gp_kthread); +void rcu_tasks_trace_get_gp_data(int *flags, unsigned long *gp_seq) +{ + *flags = 0; + *gp_seq = rcu_seq_current(&rcu_tasks_trace.tasks_gp_seq); +} +EXPORT_SYMBOL_GPL(rcu_tasks_trace_get_gp_data); + #else /* #ifdef CONFIG_TASKS_TRACE_RCU */ static void exit_tasks_rcu_finish_trace(struct task_struct *t) { } #endif /* #else #ifdef CONFIG_TASKS_TRACE_RCU */ diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c index 705c0d16850aa2..4402d6f5f85778 100644 --- a/kernel/rcu/tiny.c +++ b/kernel/rcu/tiny.c @@ -130,9 +130,7 @@ static __latent_entropy void rcu_process_callbacks(struct softirq_action *unused next = list->next; prefetch(next); debug_rcu_head_unqueue(list); - local_bh_disable(); rcu_reclaim_tiny(list); - local_bh_enable(); list = next; } } @@ -155,7 +153,9 @@ void synchronize_rcu(void) lock_is_held(&rcu_lock_map) || lock_is_held(&rcu_sched_lock_map), "Illegal synchronize_rcu() in RCU read-side critical section"); + preempt_disable(); WRITE_ONCE(rcu_ctrlblk.gp_seq, rcu_ctrlblk.gp_seq + 2); + preempt_enable(); } EXPORT_SYMBOL_GPL(synchronize_rcu); diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index d9642dd06c2535..2fe08e6186b4de 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -75,6 +75,7 @@ #define MODULE_PARAM_PREFIX "rcutree." /* Data structures. */ +static void rcu_sr_normal_gp_cleanup_work(struct work_struct *); static DEFINE_PER_CPU_SHARED_ALIGNED(struct rcu_data, rcu_data) = { .gpwrap = true, @@ -93,6 +94,9 @@ static struct rcu_state rcu_state = { .exp_mutex = __MUTEX_INITIALIZER(rcu_state.exp_mutex), .exp_wake_mutex = __MUTEX_INITIALIZER(rcu_state.exp_wake_mutex), .ofl_lock = __ARCH_SPIN_LOCK_UNLOCKED, + .srs_cleanup_work = __WORK_INITIALIZER(rcu_state.srs_cleanup_work, + rcu_sr_normal_gp_cleanup_work), + .srs_cleanups_pending = ATOMIC_INIT(0), }; /* Dump rcu_node combining tree at boot to verify correct setup. */ @@ -240,8 +244,36 @@ static long rcu_get_n_cbs_cpu(int cpu) return 0; } +/** + * rcu_softirq_qs - Provide a set of RCU quiescent states in softirq processing + * + * Mark a quiescent state for RCU, Tasks RCU, and Tasks Trace RCU. + * This is a special-purpose function to be used in the softirq + * infrastructure and perhaps the occasional long-running softirq + * handler. + * + * Note that from RCU's viewpoint, a call to rcu_softirq_qs() is + * equivalent to momentarily completely enabling preemption. For + * example, given this code:: + * + * local_bh_disable(); + * do_something(); + * rcu_softirq_qs(); // A + * do_something_else(); + * local_bh_enable(); // B + * + * A call to synchronize_rcu() that began concurrently with the + * call to do_something() would be guaranteed to wait only until + * execution reached statement A. Without that rcu_softirq_qs(), + * that same synchronize_rcu() would instead be guaranteed to wait + * until execution reached statement B. + */ void rcu_softirq_qs(void) { + RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) || + lock_is_held(&rcu_lock_map) || + lock_is_held(&rcu_sched_lock_map), + "Illegal rcu_softirq_qs() in RCU read-side critical section"); rcu_qs(); rcu_preempt_deferred_qs(current); rcu_tasks_qs(current, false); @@ -508,17 +540,10 @@ static struct rcu_node *rcu_get_root(void) /* * Send along grace-period-related data for rcutorture diagnostics. */ -void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags, - unsigned long *gp_seq) +void rcutorture_get_gp_data(int *flags, unsigned long *gp_seq) { - switch (test_type) { - case RCU_FLAVOR: - *flags = READ_ONCE(rcu_state.gp_flags); - *gp_seq = rcu_seq_current(&rcu_state.gp_seq); - break; - default: - break; - } + *flags = READ_ONCE(rcu_state.gp_flags); + *gp_seq = rcu_seq_current(&rcu_state.gp_seq); } EXPORT_SYMBOL_GPL(rcutorture_get_gp_data); @@ -813,8 +838,8 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) __func__, rnp1->grplo, rnp1->grphi, rnp1->qsmask, rnp1->qsmaskinit, rnp1->qsmaskinitnext, rnp1->rcu_gp_init_mask); pr_info("%s %d: %c online: %ld(%d) offline: %ld(%d)\n", __func__, rdp->cpu, ".o"[rcu_rdp_cpu_online(rdp)], - (long)rdp->rcu_onl_gp_seq, rdp->rcu_onl_gp_flags, - (long)rdp->rcu_ofl_gp_seq, rdp->rcu_ofl_gp_flags); + (long)rdp->rcu_onl_gp_seq, rdp->rcu_onl_gp_state, + (long)rdp->rcu_ofl_gp_seq, rdp->rcu_ofl_gp_state); return 1; /* Break things loose after complaining. */ } @@ -1423,6 +1448,335 @@ static void rcu_poll_gp_seq_end_unlocked(unsigned long *snap) } /* + * There is a single llist, which is used for handling + * synchronize_rcu() users' enqueued rcu_synchronize nodes. + * Within this llist, there are two tail pointers: + * + * wait tail: Tracks the set of nodes, which need to + * wait for the current GP to complete. + * done tail: Tracks the set of nodes, for which grace + * period has elapsed. These nodes processing + * will be done as part of the cleanup work + * execution by a kworker. + * + * At every grace period init, a new wait node is added + * to the llist. This wait node is used as wait tail + * for this new grace period. Given that there are a fixed + * number of wait nodes, if all wait nodes are in use + * (which can happen when kworker callback processing + * is delayed), first node in the llist is used as wait + * tail for this grace period. This means, the first node + * has to go through additional grace periods before it is + * part of the wait callbacks. This should be ok, as + * the system is slow in processing callbacks anyway. + * + * Below is an illustration of how the done and wait + * tail pointers move from one set of rcu_synchronize nodes + * to the other, as grace periods start and finish and + * nodes are processed by kworker. + * + * + * a. Initial llist callbacks list: + * + * +----------+ +--------+ +-------+ + * | | | | | | + * | head |---------> | cb2 |--------->| cb1 | + * | | | | | | + * +----------+ +--------+ +-------+ + * + * + * + * b. New GP1 Start: + * + * WAIT TAIL + * | + * | + * v + * +----------+ +--------+ +--------+ +-------+ + * | | | | | | | | + * | head ------> wait |------> cb2 |------> | cb1 | + * | | | head1 | | | | | + * +----------+ +--------+ +--------+ +-------+ + * + * + * + * c. GP completion: + * + * WAIT_TAIL == DONE_TAIL + * + * DONE TAIL + * | + * | + * v + * +----------+ +--------+ +--------+ +-------+ + * | | | | | | | | + * | head ------> wait |------> cb2 |------> | cb1 | + * | | | head1 | | | | | + * +----------+ +--------+ +--------+ +-------+ + * + * + * + * d. New callbacks and GP2 start: + * + * WAIT TAIL DONE TAIL + * | | + * | | + * v v + * +----------+ +------+ +------+ +------+ +-----+ +-----+ +-----+ + * | | | | | | | | | | | | | | + * | head ------> wait |--->| cb4 |--->| cb3 |--->|wait |--->| cb2 |--->| cb1 | + * | | | head2| | | | | |head1| | | | | + * +----------+ +------+ +------+ +------+ +-----+ +-----+ +-----+ + * + * + * + * e. GP2 completion: + * + * WAIT_TAIL == DONE_TAIL + * DONE TAIL + * | + * | + * v + * +----------+ +------+ +------+ +------+ +-----+ +-----+ +-----+ + * | | | | | | | | | | | | | | + * | head ------> wait |--->| cb4 |--->| cb3 |--->|wait |--->| cb2 |--->| cb1 | + * | | | head2| | | | | |head1| | | | | + * +----------+ +------+ +------+ +------+ +-----+ +-----+ +-----+ + * + * + * While the llist state transitions from d to e, a kworker + * can start executing rcu_sr_normal_gp_cleanup_work() and + * can observe either the old done tail (@c) or the new + * done tail (@e). So, done tail updates and reads need + * to use the rel-acq semantics. If the concurrent kworker + * observes the old done tail, the newly queued work + * execution will process the updated done tail. If the + * concurrent kworker observes the new done tail, then + * the newly queued work will skip processing the done + * tail, as workqueue semantics guarantees that the new + * work is executed only after the previous one completes. + * + * f. kworker callbacks processing complete: + * + * + * DONE TAIL + * | + * | + * v + * +----------+ +--------+ + * | | | | + * | head ------> wait | + * | | | head2 | + * +----------+ +--------+ + * + */ +static bool rcu_sr_is_wait_head(struct llist_node *node) +{ + return &(rcu_state.srs_wait_nodes)[0].node <= node && + node <= &(rcu_state.srs_wait_nodes)[SR_NORMAL_GP_WAIT_HEAD_MAX - 1].node; +} + +static struct llist_node *rcu_sr_get_wait_head(void) +{ + struct sr_wait_node *sr_wn; + int i; + + for (i = 0; i < SR_NORMAL_GP_WAIT_HEAD_MAX; i++) { + sr_wn = &(rcu_state.srs_wait_nodes)[i]; + + if (!atomic_cmpxchg_acquire(&sr_wn->inuse, 0, 1)) + return &sr_wn->node; + } + + return NULL; +} + +static void rcu_sr_put_wait_head(struct llist_node *node) +{ + struct sr_wait_node *sr_wn = container_of(node, struct sr_wait_node, node); + + atomic_set_release(&sr_wn->inuse, 0); +} + +/* Disabled by default. */ +static int rcu_normal_wake_from_gp; +module_param(rcu_normal_wake_from_gp, int, 0644); +static struct workqueue_struct *sync_wq; + +static void rcu_sr_normal_complete(struct llist_node *node) +{ + struct rcu_synchronize *rs = container_of( + (struct rcu_head *) node, struct rcu_synchronize, head); + unsigned long oldstate = (unsigned long) rs->head.func; + + WARN_ONCE(IS_ENABLED(CONFIG_PROVE_RCU) && + !poll_state_synchronize_rcu(oldstate), + "A full grace period is not passed yet: %lu", + rcu_seq_diff(get_state_synchronize_rcu(), oldstate)); + + /* Finally. */ + complete(&rs->completion); +} + +static void rcu_sr_normal_gp_cleanup_work(struct work_struct *work) +{ + struct llist_node *done, *rcu, *next, *head; + + /* + * This work execution can potentially execute + * while a new done tail is being updated by + * grace period kthread in rcu_sr_normal_gp_cleanup(). + * So, read and updates of done tail need to + * follow acq-rel semantics. + * + * Given that wq semantics guarantees that a single work + * cannot execute concurrently by multiple kworkers, + * the done tail list manipulations are protected here. + */ + done = smp_load_acquire(&rcu_state.srs_done_tail); + if (!done) { + /* See comments below. */ + atomic_dec_return_release(&rcu_state.srs_cleanups_pending); + return; + } + + head = done->next; + done->next = NULL; + + /* + * The dummy node, which is pointed to by the + * done tail which is acq-read above is not removed + * here. This allows lockless additions of new + * rcu_synchronize nodes in rcu_sr_normal_add_req(), + * while the cleanup work executes. The dummy + * nodes is removed, in next round of cleanup + * work execution. + */ + llist_for_each_safe(rcu, next, head) { + if (!rcu_sr_is_wait_head(rcu)) { + rcu_sr_normal_complete(rcu); + continue; + } + + rcu_sr_put_wait_head(rcu); + } + + /* Order list manipulations with atomic access. */ + atomic_dec_return_release(&rcu_state.srs_cleanups_pending); +} + +/* + * Helper function for rcu_gp_cleanup(). + */ +static void rcu_sr_normal_gp_cleanup(void) +{ + struct llist_node *wait_tail, *next = NULL, *rcu = NULL; + int done = 0; + + wait_tail = rcu_state.srs_wait_tail; + if (wait_tail == NULL) + return; + + rcu_state.srs_wait_tail = NULL; + ASSERT_EXCLUSIVE_WRITER(rcu_state.srs_wait_tail); + + /* + * Process (a) and (d) cases. See an illustration. + */ + llist_for_each_safe(rcu, next, wait_tail->next) { + /* + * The done tail may reference a rcu_synchronize node. + * Stop at done tail, as using rcu_sr_normal_complete() + * from this path can result in use-after-free. This + * may occur if, following the wake-up of the synchronize_rcu() + * wait contexts and freeing up of node memory, + * rcu_sr_normal_gp_cleanup_work() accesses the done tail and + * its subsequent nodes. + */ + if (wait_tail->next == rcu_state.srs_done_tail) + break; + + rcu_sr_normal_complete(rcu); + // It can be last, update a next on this step. + wait_tail->next = next; + + if (++done == SR_MAX_USERS_WAKE_FROM_GP) + break; + } + + /* + * Fast path, no more users to process except putting the second last + * wait head if no inflight-workers. If there are in-flight workers, + * they will remove the last wait head. + * + * Note that the ACQUIRE orders atomic access with list manipulation. + */ + if (wait_tail->next && wait_tail->next->next == NULL && + rcu_sr_is_wait_head(wait_tail->next) && + !atomic_read_acquire(&rcu_state.srs_cleanups_pending)) { + rcu_sr_put_wait_head(wait_tail->next); + wait_tail->next = NULL; + } + + /* Concurrent sr_normal_gp_cleanup work might observe this update. */ + ASSERT_EXCLUSIVE_WRITER(rcu_state.srs_done_tail); + smp_store_release(&rcu_state.srs_done_tail, wait_tail); + + /* + * We schedule a work in order to perform a final processing + * of outstanding users(if still left) and releasing wait-heads + * added by rcu_sr_normal_gp_init() call. + */ + if (wait_tail->next) { + atomic_inc(&rcu_state.srs_cleanups_pending); + if (!queue_work(sync_wq, &rcu_state.srs_cleanup_work)) + atomic_dec(&rcu_state.srs_cleanups_pending); + } +} + +/* + * Helper function for rcu_gp_init(). + */ +static bool rcu_sr_normal_gp_init(void) +{ + struct llist_node *first; + struct llist_node *wait_head; + bool start_new_poll = false; + + first = READ_ONCE(rcu_state.srs_next.first); + if (!first || rcu_sr_is_wait_head(first)) + return start_new_poll; + + wait_head = rcu_sr_get_wait_head(); + if (wait_head) { + /* Inject a wait-dummy-node. */ + llist_add(wait_head, &rcu_state.srs_next); + } else { + // Kick another GP for first node. + start_new_poll = true; + if (first == rcu_state.srs_done_tail) + return start_new_poll; + wait_head = first; + } + + /* + * A waiting list of rcu_synchronize nodes should be empty on + * this step, since a GP-kthread, rcu_gp_init() -> gp_cleanup(), + * rolls it over. If not, it is a BUG, warn a user. + */ + WARN_ON_ONCE(rcu_state.srs_wait_tail != NULL); + rcu_state.srs_wait_tail = wait_head; + ASSERT_EXCLUSIVE_WRITER(rcu_state.srs_wait_tail); + + return start_new_poll; +} + +static void rcu_sr_normal_add_req(struct rcu_synchronize *rs) +{ + llist_add((struct llist_node *) &rs->head, &rcu_state.srs_next); +} + +/* * Initialize a new grace period. Return false if no grace period required. */ static noinline_for_stack bool rcu_gp_init(void) @@ -1432,10 +1786,11 @@ static noinline_for_stack bool rcu_gp_init(void) unsigned long mask; struct rcu_data *rdp; struct rcu_node *rnp = rcu_get_root(); + bool start_new_poll; WRITE_ONCE(rcu_state.gp_activity, jiffies); raw_spin_lock_irq_rcu_node(rnp); - if (!READ_ONCE(rcu_state.gp_flags)) { + if (!rcu_state.gp_flags) { /* Spurious wakeup, tell caller to go back to sleep. */ raw_spin_unlock_irq_rcu_node(rnp); return false; @@ -1456,11 +1811,25 @@ static noinline_for_stack bool rcu_gp_init(void) /* Record GP times before starting GP, hence rcu_seq_start(). */ rcu_seq_start(&rcu_state.gp_seq); ASSERT_EXCLUSIVE_WRITER(rcu_state.gp_seq); + start_new_poll = rcu_sr_normal_gp_init(); trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq, TPS("start")); rcu_poll_gp_seq_start(&rcu_state.gp_seq_polled_snap); raw_spin_unlock_irq_rcu_node(rnp); /* + * The "start_new_poll" is set to true, only when this GP is not able + * to handle anything and there are outstanding users. It happens when + * the rcu_sr_normal_gp_init() function was not able to insert a dummy + * separator to the llist, because there were no left any dummy-nodes. + * + * Number of dummy-nodes is fixed, it could be that we are run out of + * them, if so we start a new pool request to repeat a try. It is rare + * and it means that a system is doing a slow processing of callbacks. + */ + if (start_new_poll) + (void) start_poll_synchronize_rcu(); + + /* * Apply per-leaf buffered online and offline operations to * the rcu_node tree. Note that this new grace period need not * wait for subsequent online CPUs, and that RCU hooks in the CPU @@ -1620,8 +1989,7 @@ static void rcu_gp_fqs(bool first_time) /* Clear flag to prevent immediate re-entry. */ if (READ_ONCE(rcu_state.gp_flags) & RCU_GP_FLAG_FQS) { raw_spin_lock_irq_rcu_node(rnp); - WRITE_ONCE(rcu_state.gp_flags, - READ_ONCE(rcu_state.gp_flags) & ~RCU_GP_FLAG_FQS); + WRITE_ONCE(rcu_state.gp_flags, rcu_state.gp_flags & ~RCU_GP_FLAG_FQS); raw_spin_unlock_irq_rcu_node(rnp); } } @@ -1825,6 +2193,9 @@ static noinline void rcu_gp_cleanup(void) } raw_spin_unlock_irq_rcu_node(rnp); + // Make synchronize_rcu() users aware of the end of old grace period. + rcu_sr_normal_gp_cleanup(); + // If strict, make all CPUs aware of the end of the old grace period. if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD)) on_each_cpu(rcu_strict_gp_boundary, NULL, 0); @@ -1882,8 +2253,7 @@ static void rcu_report_qs_rsp(unsigned long flags) { raw_lockdep_assert_held_rcu_node(rcu_get_root()); WARN_ON_ONCE(!rcu_gp_in_progress()); - WRITE_ONCE(rcu_state.gp_flags, - READ_ONCE(rcu_state.gp_flags) | RCU_GP_FLAG_FQS); + WRITE_ONCE(rcu_state.gp_flags, rcu_state.gp_flags | RCU_GP_FLAG_FQS); raw_spin_unlock_irqrestore_rcu_node(rcu_get_root(), flags); rcu_gp_kthread_wake(); } @@ -2398,8 +2768,7 @@ void rcu_force_quiescent_state(void) raw_spin_unlock_irqrestore_rcu_node(rnp_old, flags); return; /* Someone beat us to it. */ } - WRITE_ONCE(rcu_state.gp_flags, - READ_ONCE(rcu_state.gp_flags) | RCU_GP_FLAG_FQS); + WRITE_ONCE(rcu_state.gp_flags, rcu_state.gp_flags | RCU_GP_FLAG_FQS); raw_spin_unlock_irqrestore_rcu_node(rnp_old, flags); rcu_gp_kthread_wake(); } @@ -3559,6 +3928,43 @@ static int rcu_blocking_is_gp(void) return true; } +/* + * Helper function for the synchronize_rcu() API. + */ +static void synchronize_rcu_normal(void) +{ + struct rcu_synchronize rs; + + trace_rcu_sr_normal(rcu_state.name, &rs.head, TPS("request")); + + if (!READ_ONCE(rcu_normal_wake_from_gp)) { + wait_rcu_gp(call_rcu_hurry); + goto trace_complete_out; + } + + init_rcu_head_on_stack(&rs.head); + init_completion(&rs.completion); + + /* + * This code might be preempted, therefore take a GP + * snapshot before adding a request. + */ + if (IS_ENABLED(CONFIG_PROVE_RCU)) + rs.head.func = (void *) get_state_synchronize_rcu(); + + rcu_sr_normal_add_req(&rs); + + /* Kick a GP and start waiting. */ + (void) start_poll_synchronize_rcu(); + + /* Now we can wait. */ + wait_for_completion(&rs.completion); + destroy_rcu_head_on_stack(&rs.head); + +trace_complete_out: + trace_rcu_sr_normal(rcu_state.name, &rs.head, TPS("complete")); +} + /** * synchronize_rcu - wait until a grace period has elapsed. * @@ -3610,7 +4016,7 @@ void synchronize_rcu(void) if (rcu_gp_is_expedited()) synchronize_rcu_expedited(); else - wait_rcu_gp(call_rcu_hurry); + synchronize_rcu_normal(); return; } @@ -4303,7 +4709,7 @@ EXPORT_SYMBOL_GPL(rcu_lockdep_current_cpu_online); // whether spinlocks may be acquired safely. static bool rcu_init_invoked(void) { - return !!rcu_state.n_online_cpus; + return !!READ_ONCE(rcu_state.n_online_cpus); } /* @@ -4395,9 +4801,9 @@ rcu_boot_init_percpu_data(int cpu) WARN_ON_ONCE(rcu_dynticks_in_eqs(rcu_dynticks_snap(cpu))); rdp->barrier_seq_snap = rcu_state.barrier_sequence; rdp->rcu_ofl_gp_seq = rcu_state.gp_seq; - rdp->rcu_ofl_gp_flags = RCU_GP_CLEANED; + rdp->rcu_ofl_gp_state = RCU_GP_CLEANED; rdp->rcu_onl_gp_seq = rcu_state.gp_seq; - rdp->rcu_onl_gp_flags = RCU_GP_CLEANED; + rdp->rcu_onl_gp_state = RCU_GP_CLEANED; rdp->last_sched_clock = jiffies; rdp->cpu = cpu; rcu_boot_init_nocb_percpu_data(rdp); @@ -4513,6 +4919,7 @@ int rcutree_prepare_cpu(unsigned int cpu) raw_spin_unlock_irqrestore_rcu_node(rnp, flags); rcu_spawn_rnp_kthreads(rnp); rcu_spawn_cpu_nocb_kthread(cpu); + ASSERT_EXCLUSIVE_WRITER(rcu_state.n_online_cpus); WRITE_ONCE(rcu_state.n_online_cpus, rcu_state.n_online_cpus + 1); return 0; @@ -4656,7 +5063,7 @@ void rcutree_report_cpu_starting(unsigned int cpu) ASSERT_EXCLUSIVE_WRITER(rcu_state.ncpus); rcu_gpnum_ovf(rnp, rdp); /* Offline-induced counter wrap? */ rdp->rcu_onl_gp_seq = READ_ONCE(rcu_state.gp_seq); - rdp->rcu_onl_gp_flags = READ_ONCE(rcu_state.gp_flags); + rdp->rcu_onl_gp_state = READ_ONCE(rcu_state.gp_state); /* An incoming CPU should never be blocking a grace period. */ if (WARN_ON_ONCE(rnp->qsmask & mask)) { /* RCU waiting on incoming CPU? */ @@ -4707,7 +5114,7 @@ void rcutree_report_cpu_dead(void) arch_spin_lock(&rcu_state.ofl_lock); raw_spin_lock_irqsave_rcu_node(rnp, flags); /* Enforce GP memory-order guarantee. */ rdp->rcu_ofl_gp_seq = READ_ONCE(rcu_state.gp_seq); - rdp->rcu_ofl_gp_flags = READ_ONCE(rcu_state.gp_flags); + rdp->rcu_ofl_gp_state = READ_ONCE(rcu_state.gp_state); if (rnp->qsmask & mask) { /* RCU waiting on outgoing CPU? */ /* Report quiescent state -before- changing ->qsmaskinitnext! */ rcu_disable_urgency_upon_qs(rdp); @@ -4781,6 +5188,7 @@ void rcutree_migrate_callbacks(int cpu) */ int rcutree_dead_cpu(unsigned int cpu) { + ASSERT_EXCLUSIVE_WRITER(rcu_state.n_online_cpus); WRITE_ONCE(rcu_state.n_online_cpus, rcu_state.n_online_cpus - 1); // Stop-machine done, so allow nohz_full to disable tick. tick_dep_clear(TICK_DEP_BIT_RCU); @@ -5229,6 +5637,9 @@ void __init rcu_init(void) rcu_gp_wq = alloc_workqueue("rcu_gp", WQ_MEM_RECLAIM, 0); WARN_ON(!rcu_gp_wq); + sync_wq = alloc_workqueue("sync_wq", WQ_MEM_RECLAIM, 0); + WARN_ON(!sync_wq); + /* Fill in default value for rcutree.qovld boot parameter. */ /* -After- the rcu_node ->lock fields are initialized! */ if (qovld < 0) diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h index df48160b3136dc..fcf2b4aa34417e 100644 --- a/kernel/rcu/tree.h +++ b/kernel/rcu/tree.h @@ -223,7 +223,6 @@ struct rcu_data { struct swait_queue_head nocb_state_wq; /* For offloading state changes */ struct task_struct *nocb_gp_kthread; raw_spinlock_t nocb_lock; /* Guard following pair of fields. */ - atomic_t nocb_lock_contended; /* Contention experienced. */ int nocb_defer_wakeup; /* Defer wakeup of nocb_kthread. */ struct timer_list nocb_timer; /* Enforce finite deferral. */ unsigned long nocb_gp_adv_time; /* Last call_rcu() CB adv (jiffies). */ @@ -273,9 +272,9 @@ struct rcu_data { bool rcu_iw_pending; /* Is ->rcu_iw pending? */ unsigned long rcu_iw_gp_seq; /* ->gp_seq associated with ->rcu_iw. */ unsigned long rcu_ofl_gp_seq; /* ->gp_seq at last offline. */ - short rcu_ofl_gp_flags; /* ->gp_flags at last offline. */ + short rcu_ofl_gp_state; /* ->gp_state at last offline. */ unsigned long rcu_onl_gp_seq; /* ->gp_seq at last online. */ - short rcu_onl_gp_flags; /* ->gp_flags at last online. */ + short rcu_onl_gp_state; /* ->gp_state at last online. */ unsigned long last_fqs_resched; /* Time of last rcu_resched(). */ unsigned long last_sched_clock; /* Jiffies of last rcu_sched_clock_irq(). */ struct rcu_snap_record snap_record; /* Snapshot of core stats at half of */ @@ -316,6 +315,19 @@ do { \ } while (0) /* + * A max threshold for synchronize_rcu() users which are + * awaken directly by the rcu_gp_kthread(). Left part is + * deferred to the main worker. + */ +#define SR_MAX_USERS_WAKE_FROM_GP 5 +#define SR_NORMAL_GP_WAIT_HEAD_MAX 5 + +struct sr_wait_node { + atomic_t inuse; + struct llist_node node; +}; + +/* * RCU global state, including node hierarchy. This hierarchy is * represented in "heap" form in a dense array. The root (first level) * of the hierarchy is in ->node[0] (referenced by ->level[0]), the second @@ -400,6 +412,14 @@ struct rcu_state { /* Synchronize offline with */ /* GP pre-initialization. */ int nocb_is_setup; /* nocb is setup from boot */ + + /* synchronize_rcu() part. */ + struct llist_head srs_next; /* request a GP users. */ + struct llist_node *srs_wait_tail; /* wait for GP users. */ + struct llist_node *srs_done_tail; /* ready for GP users. */ + struct sr_wait_node srs_wait_nodes[SR_NORMAL_GP_WAIT_HEAD_MAX]; + struct work_struct srs_cleanup_work; + atomic_t srs_cleanups_pending; /* srs inflight worker cleanups. */ }; /* Values for rcu_state structure's gp_flags field. */ diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h index 6b83537480b12f..8a1d9c8bd9f748 100644 --- a/kernel/rcu/tree_exp.h +++ b/kernel/rcu/tree_exp.h @@ -930,7 +930,7 @@ void synchronize_rcu_expedited(void) /* If expedited grace periods are prohibited, fall back to normal. */ if (rcu_gp_is_normal()) { - wait_rcu_gp(call_rcu_hurry); + synchronize_rcu_normal(); return; } diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h index 3f85577bddd4ef..3ce30841119ade 100644 --- a/kernel/rcu/tree_nocb.h +++ b/kernel/rcu/tree_nocb.h @@ -91,8 +91,7 @@ module_param(nocb_nobypass_lim_per_jiffy, int, 0); /* * Acquire the specified rcu_data structure's ->nocb_bypass_lock. If the - * lock isn't immediately available, increment ->nocb_lock_contended to - * flag the contention. + * lock isn't immediately available, perform minimal sanity check. */ static void rcu_nocb_bypass_lock(struct rcu_data *rdp) __acquires(&rdp->nocb_bypass_lock) @@ -100,29 +99,12 @@ static void rcu_nocb_bypass_lock(struct rcu_data *rdp) lockdep_assert_irqs_disabled(); if (raw_spin_trylock(&rdp->nocb_bypass_lock)) return; - atomic_inc(&rdp->nocb_lock_contended); + /* + * Contention expected only when local enqueue collide with + * remote flush from kthreads. + */ WARN_ON_ONCE(smp_processor_id() != rdp->cpu); - smp_mb__after_atomic(); /* atomic_inc() before lock. */ raw_spin_lock(&rdp->nocb_bypass_lock); - smp_mb__before_atomic(); /* atomic_dec() after lock. */ - atomic_dec(&rdp->nocb_lock_contended); -} - -/* - * Spinwait until the specified rcu_data structure's ->nocb_lock is - * not contended. Please note that this is extremely special-purpose, - * relying on the fact that at most two kthreads and one CPU contend for - * this lock, and also that the two kthreads are guaranteed to have frequent - * grace-period-duration time intervals between successive acquisitions - * of the lock. This allows us to use an extremely simple throttling - * mechanism, and further to apply it only to the CPU doing floods of - * call_rcu() invocations. Don't try this at home! - */ -static void rcu_nocb_wait_contended(struct rcu_data *rdp) -{ - WARN_ON_ONCE(smp_processor_id() != rdp->cpu); - while (WARN_ON_ONCE(atomic_read(&rdp->nocb_lock_contended))) - cpu_relax(); } /* @@ -510,7 +492,6 @@ static bool rcu_nocb_try_bypass(struct rcu_data *rdp, struct rcu_head *rhp, } // We need to use the bypass. - rcu_nocb_wait_contended(rdp); rcu_nocb_bypass_lock(rdp); ncbs = rcu_cblist_n_cbs(&rdp->nocb_bypass); rcu_segcblist_inc_len(&rdp->cblist); /* Must precede enqueue. */ @@ -635,8 +616,7 @@ static void call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *head, } } -static int nocb_gp_toggle_rdp(struct rcu_data *rdp, - bool *wake_state) +static int nocb_gp_toggle_rdp(struct rcu_data *rdp) { struct rcu_segcblist *cblist = &rdp->cblist; unsigned long flags; @@ -650,8 +630,6 @@ static int nocb_gp_toggle_rdp(struct rcu_data *rdp, * We will handle this rdp until it ever gets de-offloaded. */ rcu_segcblist_set_flags(cblist, SEGCBLIST_KTHREAD_GP); - if (rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_CB)) - *wake_state = true; ret = 1; } else if (!rcu_segcblist_test_flags(cblist, SEGCBLIST_OFFLOADED) && rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_GP)) { @@ -660,8 +638,6 @@ static int nocb_gp_toggle_rdp(struct rcu_data *rdp, * We will ignore this rdp until it ever gets re-offloaded. */ rcu_segcblist_clear_flags(cblist, SEGCBLIST_KTHREAD_GP); - if (!rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_CB)) - *wake_state = true; ret = 0; } else { WARN_ON_ONCE(1); @@ -877,16 +853,15 @@ static void nocb_gp_wait(struct rcu_data *my_rdp) } if (rdp_toggling) { - bool wake_state = false; int ret; - ret = nocb_gp_toggle_rdp(rdp_toggling, &wake_state); + ret = nocb_gp_toggle_rdp(rdp_toggling); if (ret == 1) list_add_tail(&rdp_toggling->nocb_entry_rdp, &my_rdp->nocb_head_rdp); else if (ret == 0) list_del(&rdp_toggling->nocb_entry_rdp); - if (wake_state) - swake_up_one(&rdp_toggling->nocb_state_wq); + + swake_up_one(&rdp_toggling->nocb_state_wq); } my_rdp->nocb_gp_seq = -1; @@ -913,16 +888,9 @@ static int rcu_nocb_gp_kthread(void *arg) return 0; } -static inline bool nocb_cb_can_run(struct rcu_data *rdp) -{ - u8 flags = SEGCBLIST_OFFLOADED | SEGCBLIST_KTHREAD_CB; - - return rcu_segcblist_test_flags(&rdp->cblist, flags); -} - static inline bool nocb_cb_wait_cond(struct rcu_data *rdp) { - return nocb_cb_can_run(rdp) && !READ_ONCE(rdp->nocb_cb_sleep); + return !READ_ONCE(rdp->nocb_cb_sleep) || kthread_should_park(); } /* @@ -934,21 +902,19 @@ static void nocb_cb_wait(struct rcu_data *rdp) struct rcu_segcblist *cblist = &rdp->cblist; unsigned long cur_gp_seq; unsigned long flags; - bool needwake_state = false; bool needwake_gp = false; - bool can_sleep = true; struct rcu_node *rnp = rdp->mynode; - do { - swait_event_interruptible_exclusive(rdp->nocb_cb_wq, - nocb_cb_wait_cond(rdp)); - - if (READ_ONCE(rdp->nocb_cb_sleep)) { - WARN_ON(signal_pending(current)); - trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("WokeEmpty")); - } - } while (!nocb_cb_can_run(rdp)); + swait_event_interruptible_exclusive(rdp->nocb_cb_wq, + nocb_cb_wait_cond(rdp)); + if (kthread_should_park()) { + kthread_parkme(); + } else if (READ_ONCE(rdp->nocb_cb_sleep)) { + WARN_ON(signal_pending(current)); + trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("WokeEmpty")); + } + WARN_ON_ONCE(!rcu_rdp_is_offloaded(rdp)); local_irq_save(flags); rcu_momentary_dyntick_idle(); @@ -971,37 +937,16 @@ static void nocb_cb_wait(struct rcu_data *rdp) raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */ } - if (rcu_segcblist_test_flags(cblist, SEGCBLIST_OFFLOADED)) { - if (!rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_CB)) { - rcu_segcblist_set_flags(cblist, SEGCBLIST_KTHREAD_CB); - if (rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_GP)) - needwake_state = true; - } - if (rcu_segcblist_ready_cbs(cblist)) - can_sleep = false; + if (!rcu_segcblist_ready_cbs(cblist)) { + WRITE_ONCE(rdp->nocb_cb_sleep, true); + trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("CBSleep")); } else { - /* - * De-offloading. Clear our flag and notify the de-offload worker. - * We won't touch the callbacks and keep sleeping until we ever - * get re-offloaded. - */ - WARN_ON_ONCE(!rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_CB)); - rcu_segcblist_clear_flags(cblist, SEGCBLIST_KTHREAD_CB); - if (!rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_GP)) - needwake_state = true; + WRITE_ONCE(rdp->nocb_cb_sleep, false); } - WRITE_ONCE(rdp->nocb_cb_sleep, can_sleep); - - if (rdp->nocb_cb_sleep) - trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("CBSleep")); - rcu_nocb_unlock_irqrestore(rdp, flags); if (needwake_gp) rcu_gp_kthread_wake(); - - if (needwake_state) - swake_up_one(&rdp->nocb_state_wq); } /* @@ -1094,17 +1039,8 @@ static int rdp_offload_toggle(struct rcu_data *rdp, bool wake_gp = false; rcu_segcblist_offload(cblist, offload); - - if (rdp->nocb_cb_sleep) - rdp->nocb_cb_sleep = false; rcu_nocb_unlock_irqrestore(rdp, flags); - /* - * Ignore former value of nocb_cb_sleep and force wake up as it could - * have been spuriously set to false already. - */ - swake_up_one(&rdp->nocb_cb_wq); - raw_spin_lock_irqsave(&rdp_gp->nocb_gp_lock, flags); // Queue this rdp for add/del to/from the list to iterate on rcuog WRITE_ONCE(rdp_gp->nocb_toggling_rdp, rdp); @@ -1161,19 +1097,11 @@ static long rcu_nocb_rdp_deoffload(void *arg) if (wake_gp) wake_up_process(rdp_gp->nocb_gp_kthread); - /* - * If rcuo[p] kthread spawn failed, directly remove SEGCBLIST_KTHREAD_CB. - * Just wait SEGCBLIST_KTHREAD_GP to be cleared by rcuog. - */ - if (!rdp->nocb_cb_kthread) { - rcu_nocb_lock_irqsave(rdp, flags); - rcu_segcblist_clear_flags(&rdp->cblist, SEGCBLIST_KTHREAD_CB); - rcu_nocb_unlock_irqrestore(rdp, flags); - } - swait_event_exclusive(rdp->nocb_state_wq, - !rcu_segcblist_test_flags(cblist, - SEGCBLIST_KTHREAD_CB | SEGCBLIST_KTHREAD_GP)); + !rcu_segcblist_test_flags(cblist, + SEGCBLIST_KTHREAD_GP)); + if (rdp->nocb_cb_kthread) + kthread_park(rdp->nocb_cb_kthread); } else { /* * No kthread to clear the flags for us or remove the rdp from the nocb list @@ -1181,8 +1109,7 @@ static long rcu_nocb_rdp_deoffload(void *arg) * but we stick to paranoia in this rare path. */ rcu_nocb_lock_irqsave(rdp, flags); - rcu_segcblist_clear_flags(&rdp->cblist, - SEGCBLIST_KTHREAD_CB | SEGCBLIST_KTHREAD_GP); + rcu_segcblist_clear_flags(&rdp->cblist, SEGCBLIST_KTHREAD_GP); rcu_nocb_unlock_irqrestore(rdp, flags); list_del(&rdp->nocb_entry_rdp); @@ -1282,8 +1209,10 @@ static long rcu_nocb_rdp_offload(void *arg) wake_gp = rdp_offload_toggle(rdp, true, flags); if (wake_gp) wake_up_process(rdp_gp->nocb_gp_kthread); + + kthread_unpark(rdp->nocb_cb_kthread); + swait_event_exclusive(rdp->nocb_state_wq, - rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_CB) && rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_GP)); /* @@ -1468,7 +1397,7 @@ void __init rcu_init_nohz(void) if (rcu_segcblist_empty(&rdp->cblist)) rcu_segcblist_init(&rdp->cblist); rcu_segcblist_offload(&rdp->cblist, true); - rcu_segcblist_set_flags(&rdp->cblist, SEGCBLIST_KTHREAD_CB | SEGCBLIST_KTHREAD_GP); + rcu_segcblist_set_flags(&rdp->cblist, SEGCBLIST_KTHREAD_GP); rcu_segcblist_clear_flags(&rdp->cblist, SEGCBLIST_RCU_CORE); } rcu_organize_nocb_kthreads(); @@ -1526,11 +1455,16 @@ static void rcu_spawn_cpu_nocb_kthread(int cpu) mutex_unlock(&rdp_gp->nocb_gp_kthread_mutex); /* Spawn the kthread for this CPU. */ - t = kthread_run(rcu_nocb_cb_kthread, rdp, - "rcuo%c/%d", rcu_state.abbr, cpu); + t = kthread_create(rcu_nocb_cb_kthread, rdp, + "rcuo%c/%d", rcu_state.abbr, cpu); if (WARN_ONCE(IS_ERR(t), "%s: Could not start rcuo CB kthread, OOM is now expected behavior\n", __func__)) goto end; + if (rcu_rdp_is_offloaded(rdp)) + wake_up_process(t); + else + kthread_park(t); + if (IS_ENABLED(CONFIG_RCU_NOCB_CPU_CB_BOOST) && kthread_prio) sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); @@ -1678,12 +1612,11 @@ static void show_rcu_nocb_state(struct rcu_data *rdp) sprintf(bufw, "%ld", rsclp->gp_seq[RCU_WAIT_TAIL]); sprintf(bufr, "%ld", rsclp->gp_seq[RCU_NEXT_READY_TAIL]); - pr_info(" CB %d^%d->%d %c%c%c%c%c%c F%ld L%ld C%d %c%c%s%c%s%c%c q%ld %c CPU %d%s\n", + pr_info(" CB %d^%d->%d %c%c%c%c%c F%ld L%ld C%d %c%c%s%c%s%c%c q%ld %c CPU %d%s\n", rdp->cpu, rdp->nocb_gp_rdp->cpu, nocb_next_rdp ? nocb_next_rdp->cpu : -1, "kK"[!!rdp->nocb_cb_kthread], "bB"[raw_spin_is_locked(&rdp->nocb_bypass_lock)], - "cC"[!!atomic_read(&rdp->nocb_lock_contended)], "lL"[raw_spin_is_locked(&rdp->nocb_lock)], "sS"[!!rdp->nocb_cb_sleep], ".W"[swait_active(&rdp->nocb_cb_wq)], diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 36a8b5dbf5b52e..340bbefe5f652d 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -805,8 +805,8 @@ dump_blkd_tasks(struct rcu_node *rnp, int ncheck) rdp = per_cpu_ptr(&rcu_data, cpu); pr_info("\t%d: %c online: %ld(%d) offline: %ld(%d)\n", cpu, ".o"[rcu_rdp_cpu_online(rdp)], - (long)rdp->rcu_onl_gp_seq, rdp->rcu_onl_gp_flags, - (long)rdp->rcu_ofl_gp_seq, rdp->rcu_ofl_gp_flags); + (long)rdp->rcu_onl_gp_seq, rdp->rcu_onl_gp_state, + (long)rdp->rcu_ofl_gp_seq, rdp->rcu_ofl_gp_state); } } diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h index 5d666428546b03..460efecd077be1 100644 --- a/kernel/rcu/tree_stall.h +++ b/kernel/rcu/tree_stall.h @@ -504,7 +504,8 @@ static void print_cpu_stall_info(int cpu) rcu_dynticks_in_eqs(rcu_dynticks_snap(cpu)); rcuc_starved = rcu_is_rcuc_kthread_starving(rdp, &j); if (rcuc_starved) - sprintf(buf, " rcuc=%ld jiffies(starved)", j); + // Print signed value, as negative values indicate a probable bug. + snprintf(buf, sizeof(buf), " rcuc=%ld jiffies(starved)", j); pr_err("\t%d-%c%c%c%c: (%lu %s) idle=%04x/%ld/%#lx softirq=%u/%u fqs=%ld%s%s\n", cpu, "O."[!!cpu_online(cpu)], @@ -579,7 +580,7 @@ static void rcu_check_gp_kthread_expired_fqs_timer(void) pr_err("%s kthread timer wakeup didn't happen for %ld jiffies! g%ld f%#x %s(%d) ->state=%#x\n", rcu_state.name, (jiffies - jiffies_fqs), (long)rcu_seq_current(&rcu_state.gp_seq), - data_race(rcu_state.gp_flags), + data_race(READ_ONCE(rcu_state.gp_flags)), // Diagnostic read gp_state_getname(RCU_GP_WAIT_FQS), RCU_GP_WAIT_FQS, data_race(READ_ONCE(gpk->__state))); pr_err("\tPossible timer handling issue on cpu=%d timer-softirq=%u\n", @@ -628,7 +629,8 @@ static void print_other_cpu_stall(unsigned long gp_seq, unsigned long gps) totqlen += rcu_get_n_cbs_cpu(cpu); pr_err("\t(detected by %d, t=%ld jiffies, g=%ld, q=%lu ncpus=%d)\n", smp_processor_id(), (long)(jiffies - gps), - (long)rcu_seq_current(&rcu_state.gp_seq), totqlen, rcu_state.n_online_cpus); + (long)rcu_seq_current(&rcu_state.gp_seq), totqlen, + data_race(rcu_state.n_online_cpus)); // Diagnostic read if (ndetected) { rcu_dump_cpu_stacks(); @@ -689,7 +691,8 @@ static void print_cpu_stall(unsigned long gps) totqlen += rcu_get_n_cbs_cpu(cpu); pr_err("\t(t=%lu jiffies g=%ld q=%lu ncpus=%d)\n", jiffies - gps, - (long)rcu_seq_current(&rcu_state.gp_seq), totqlen, rcu_state.n_online_cpus); + (long)rcu_seq_current(&rcu_state.gp_seq), totqlen, + data_race(rcu_state.n_online_cpus)); // Diagnostic read rcu_check_gp_kthread_expired_fqs_timer(); rcu_check_gp_kthread_starvation(); diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c index 46aaaa9fe33907..f8436969e0c89e 100644 --- a/kernel/rcu/update.c +++ b/kernel/rcu/update.c @@ -408,7 +408,7 @@ void wakeme_after_rcu(struct rcu_head *head) } EXPORT_SYMBOL_GPL(wakeme_after_rcu); -void __wait_rcu_gp(bool checktiny, int n, call_rcu_func_t *crcu_array, +void __wait_rcu_gp(bool checktiny, unsigned int state, int n, call_rcu_func_t *crcu_array, struct rcu_synchronize *rs_array) { int i; @@ -440,7 +440,7 @@ void __wait_rcu_gp(bool checktiny, int n, call_rcu_func_t *crcu_array, if (crcu_array[j] == crcu_array[i]) break; if (j == i) { - wait_for_completion(&rs_array[i].completion); + wait_for_completion_state(&rs_array[i].completion, state); destroy_rcu_head_on_stack(&rs_array[i].head); } } diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig index 47345bf1d4a9f7..b3d7f62ac58115 100644 --- a/kernel/trace/Kconfig +++ b/kernel/trace/Kconfig @@ -163,7 +163,7 @@ config TRACING select BINARY_PRINTF select EVENT_TRACING select TRACE_CLOCK - select TASKS_RCU if PREEMPTION + select NEED_TASKS_RCU config GENERIC_TRACER bool @@ -204,7 +204,7 @@ config FUNCTION_TRACER select GENERIC_TRACER select CONTEXT_SWITCH_TRACER select GLOB - select TASKS_RCU if PREEMPTION + select NEED_TASKS_RCU select TASKS_RUDE_RCU help Enable the kernel to trace every kernel function. This is done diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index da1710499698b0..32ea92934268c0 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -3157,8 +3157,7 @@ out: * synchronize_rcu_tasks() will wait for those tasks to * execute and either schedule voluntarily or enter user space. */ - if (IS_ENABLED(CONFIG_PREEMPTION)) - synchronize_rcu_tasks(); + synchronize_rcu_tasks(); ftrace_trampoline_free(ops); } @@ -5366,6 +5365,13 @@ static void remove_direct_functions_hash(struct ftrace_hash *hash, unsigned long } } +static void register_ftrace_direct_cb(struct rcu_head *rhp) +{ + struct ftrace_hash *fhp = container_of(rhp, struct ftrace_hash, rcu); + + free_ftrace_hash(fhp); +} + /** * register_ftrace_direct - Call a custom trampoline directly * for multiple functions registered in @ops @@ -5464,10 +5470,8 @@ int register_ftrace_direct(struct ftrace_ops *ops, unsigned long addr) out_unlock: mutex_unlock(&direct_mutex); - if (free_hash && free_hash != EMPTY_HASH) { - synchronize_rcu_tasks(); - free_ftrace_hash(free_hash); - } + if (free_hash && free_hash != EMPTY_HASH) + call_rcu_tasks(&free_hash->rcu, register_ftrace_direct_cb); if (new_hash) free_ftrace_hash(new_hash); diff --git a/lib/Makefile b/lib/Makefile index 1f6c51420bf6b3..ef4f4c66a52c16 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -219,6 +219,7 @@ obj-$(CONFIG_MEM_ALLOC_PROFILING) += alloc_tag.o lib-$(CONFIG_GENERIC_BUG) += bug.o obj-$(CONFIG_HAVE_ARCH_TRACEHOOK) += syscall.o +obj-$(CONFIG_ARCH_NEED_CMPXCHG_1_EMU) += cmpxchg-emu.o obj-$(CONFIG_DYNAMIC_DEBUG_CORE) += dynamic_debug.o #ensure exported functions have prototypes diff --git a/lib/cmpxchg-emu.c b/lib/cmpxchg-emu.c new file mode 100644 index 00000000000000..27f6f97cb60dd5 --- /dev/null +++ b/lib/cmpxchg-emu.c @@ -0,0 +1,45 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * Emulated 1-byte cmpxchg operation for architectures lacking direct + * support for this size. This is implemented in terms of 4-byte cmpxchg + * operations. + * + * Copyright (C) 2024 Paul E. McKenney. + */ + +#include <linux/types.h> +#include <linux/export.h> +#include <linux/instrumented.h> +#include <linux/atomic.h> +#include <linux/panic.h> +#include <linux/bug.h> +#include <asm-generic/rwonce.h> +#include <linux/cmpxchg-emu.h> + +union u8_32 { + u8 b[4]; + u32 w; +}; + +/* Emulate one-byte cmpxchg() in terms of 4-byte cmpxchg. */ +uintptr_t cmpxchg_emu_u8(volatile u8 *p, uintptr_t old, uintptr_t new) +{ + u32 *p32 = (u32 *)(((uintptr_t)p) & ~0x3); + int i = ((uintptr_t)p) & 0x3; + union u8_32 old32; + union u8_32 new32; + u32 ret; + + ret = READ_ONCE(*p32); + do { + old32.w = ret; + if (old32.b[i] != old) + return old32.b[i]; + new32.w = old32.w; + new32.b[i] = new; + instrument_atomic_read_write(p, 1); + ret = data_race(cmpxchg(p32, old32.w, new32.w)); // Overridden above. + } while (ret != old32.w); + return old; +} +EXPORT_SYMBOL_GPL(cmpxchg_emu_u8); diff --git a/tools/testing/selftests/rcutorture/bin/torture.sh b/tools/testing/selftests/rcutorture/bin/torture.sh index bbac5f4b03d04b..990d24696fd341 100755 --- a/tools/testing/selftests/rcutorture/bin/torture.sh +++ b/tools/testing/selftests/rcutorture/bin/torture.sh @@ -391,7 +391,7 @@ __EOF__ forceflavor="`echo $flavor | sed -e 's/^CONFIG/CONFIG_FORCE/'`" deselectedflavors="`grep -v $flavor $T/rcutasksflavors | tr '\012' ' ' | tr -s ' ' | sed -e 's/ *$//'`" echo " --- Running RCU Tasks Trace flavor $flavor `date`" >> $rtfdir/log - tools/testing/selftests/rcutorture/bin/kvm.sh --datestamp "$ds/results-rcutasksflavors/$flavor" --buildonly --configs "TINY01 TREE04" --kconfig "CONFIG_RCU_EXPERT=y CONFIG_RCU_SCALE_TEST=y $forceflavor=y $deselectedflavors" --trust-make > $T/$flavor.out 2>&1 + tools/testing/selftests/rcutorture/bin/kvm.sh --datestamp "$ds/results-rcutasksflavors/$flavor" --buildonly --configs "TINY01 TREE04" --kconfig "CONFIG_RCU_EXPERT=y CONFIG_RCU_SCALE_TEST=y CONFIG_KPROBES=n CONFIG_RCU_TRACE=n CONFIG_TRACING=n CONFIG_BLK_DEV_IO_TRACE=n CONFIG_UPROBE_EVENTS=n $forceflavor=y $deselectedflavors" --trust-make > $T/$flavor.out 2>&1 retcode=$? if test "$retcode" -ne 0 then @@ -425,7 +425,7 @@ fi if test "$do_scftorture" = "yes" then # Scale memory based on the number of CPUs. - scfmem=$((2+HALF_ALLOTED_CPUS/16)) + scfmem=$((3+HALF_ALLOTED_CPUS/16)) torture_bootargs="scftorture.nthreads=$HALF_ALLOTED_CPUS torture.disable_onoff_at_boot csdlock_debug=1" torture_set "scftorture" tools/testing/selftests/rcutorture/bin/kvm.sh --torture scf --allcpus --duration "$duration_scftorture" --configs "$configs_scftorture" --kconfig "CONFIG_NR_CPUS=$HALF_ALLOTED_CPUS" --memory ${scfmem}G --trust-make fi @@ -559,7 +559,7 @@ do_kcsan="$do_kcsan_save" if test "$do_kvfree" = "yes" then torture_bootargs="rcuscale.kfree_rcu_test=1 rcuscale.kfree_nthreads=16 rcuscale.holdoff=20 rcuscale.kfree_loops=10000 torture.disable_onoff_at_boot" - torture_set "rcuscale-kvfree" tools/testing/selftests/rcutorture/bin/kvm.sh --torture rcuscale --allcpus --duration 10 --kconfig "CONFIG_NR_CPUS=$HALF_ALLOTED_CPUS" --memory 2G --trust-make + torture_set "rcuscale-kvfree" tools/testing/selftests/rcutorture/bin/kvm.sh --torture rcuscale --allcpus --duration $duration_rcutorture --kconfig "CONFIG_NR_CPUS=$HALF_ALLOTED_CPUS" --memory 2G --trust-make fi if test "$do_clocksourcewd" = "yes" diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE09 b/tools/testing/selftests/rcutorture/configs/rcu/TREE09 index fc45645bb5f421..9ecd1b4e653d3f 100644 --- a/tools/testing/selftests/rcutorture/configs/rcu/TREE09 +++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE09 @@ -10,8 +10,9 @@ CONFIG_NO_HZ_FULL=n CONFIG_RCU_TRACE=n CONFIG_RCU_NOCB_CPU=n CONFIG_DEBUG_LOCK_ALLOC=n -CONFIG_RCU_BOOST=n +CONFIG_RCU_BOOST=y +CONFIG_RCU_BOOST_DELAY=100 CONFIG_DEBUG_OBJECTS_RCU_HEAD=n -#CHECK#CONFIG_RCU_EXPERT=n +CONFIG_RCU_EXPERT=y CONFIG_KPROBES=n CONFIG_FTRACE=n |