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* sched/headers: Prepare for new header dependencies before moving code to ↵Ingo Molnar2017-03-021-0/+1
| | | | | | | | | | | | | | | | | | | | <linux/sched/debug.h> We are going to split <linux/sched/debug.h> out of <linux/sched.h>, which will have to be picked up from other headers and a couple of .c files. Create a trivial placeholder <linux/sched/debug.h> file that just maps to <linux/sched.h> to make this patch obviously correct and bisectable. Include the new header in the files that are going to need it. Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched/headers: Prepare to move signal wakeup & sigpending methods from ↵Ingo Molnar2017-03-021-1/+1
| | | | | | | | | | | | | <linux/sched.h> into <linux/sched/signal.h> Fix up affected files that include this signal functionality via sched.h. Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched/headers: Prepare for new header dependencies before moving code to ↵Ingo Molnar2017-03-021-0/+1
| | | | | | | | | | | | | | | | | | | <linux/sched/wake_q.h> We are going to split <linux/sched/wake_q.h> out of <linux/sched.h>, which will have to be picked up from other headers and a couple of .c files. Create a trivial placeholder <linux/sched/wake_q.h> file that just maps to <linux/sched.h> to make this patch obviously correct and bisectable. Include the new header in the files that are going to need it. Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@kernel.org>
* Merge branch 'locking-core-for-linus' of ↵Linus Torvalds2017-02-201-184/+332
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull locking updates from Ingo Molnar: "The main changes in this cycle were: - Implement wraparound-safe refcount_t and kref_t types based on generic atomic primitives (Peter Zijlstra) - Improve and fix the ww_mutex code (Nicolai Hähnle) - Add self-tests to the ww_mutex code (Chris Wilson) - Optimize percpu-rwsems with the 'rcuwait' mechanism (Davidlohr Bueso) - Micro-optimize the current-task logic all around the core kernel (Davidlohr Bueso) - Tidy up after recent optimizations: remove stale code and APIs, clean up the code (Waiman Long) - ... plus misc fixes, updates and cleanups" * 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (50 commits) fork: Fix task_struct alignment locking/spinlock/debug: Remove spinlock lockup detection code lockdep: Fix incorrect condition to print bug msgs for MAX_LOCKDEP_CHAIN_HLOCKS lkdtm: Convert to refcount_t testing kref: Implement 'struct kref' using refcount_t refcount_t: Introduce a special purpose refcount type sched/wake_q: Clarify queue reinit comment sched/wait, rcuwait: Fix typo in comment locking/mutex: Fix lockdep_assert_held() fail locking/rtmutex: Flip unlikely() branch to likely() in __rt_mutex_slowlock() locking/rwsem: Reinit wake_q after use locking/rwsem: Remove unnecessary atomic_long_t casts jump_labels: Move header guard #endif down where it belongs locking/atomic, kref: Implement kref_put_lock() locking/ww_mutex: Turn off __must_check for now locking/atomic, kref: Avoid more abuse locking/atomic, kref: Use kref_get_unless_zero() more locking/atomic, kref: Kill kref_sub() locking/atomic, kref: Add kref_read() locking/atomic, kref: Add KREF_INIT() ...
| * locking/mutex: Fix lockdep_assert_held() failPeter Zijlstra2017-01-301-14/+11
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | In commit: 659cf9f5824a ("locking/ww_mutex: Optimize ww-mutexes by waking at most one waiter for backoff when acquiring the lock") I replaced a comment with a lockdep_assert_held(). However it turns out we hide that lock from lockdep for hysterical raisins, which results in the assertion always firing. Remove the old debug code as lockdep will easily spot the abuse it was meant to catch, which will make the lock visible to lockdep and make the assertion work as intended. Reported-by: Mike Galbraith <efault@gmx.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Nicolai Haehnle <Nicolai.Haehnle@amd.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Fixes: 659cf9f5824a ("locking/ww_mutex: Optimize ww-mutexes by waking at most one waiter for backoff when acquiring the lock") Link: http://lkml.kernel.org/r/20170117150609.GB32474@worktop Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * locking/mutex: Initialize mutex_waiter::ww_ctx with poison when debuggingNicolai Hähnle2017-01-141-0/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Help catch cases where mutex_lock is used directly on w/w mutexes, which otherwise result in the w/w tasks reading uninitialized data. Signed-off-by: Nicolai Hähnle <Nicolai.Haehnle@amd.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Chris Wilson <chris@chris-wilson.co.uk> Cc: Daniel Vetter <daniel@ffwll.ch> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Maarten Lankhorst <dev@mblankhorst.nl> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: dri-devel@lists.freedesktop.org Link: http://lkml.kernel.org/r/1482346000-9927-12-git-send-email-nhaehnle@gmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * locking/ww_mutex: Optimize ww-mutexes by yielding to other waiters from ↵Nicolai Hähnle2017-01-141-26/+52
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | optimistic spin Lock stealing is less beneficial for w/w mutexes since we may just end up backing off if we stole from a thread with an earlier acquire stamp that already holds another w/w mutex that we also need. So don't spin optimistically unless we are sure that there is no other waiter that might cause us to back off. Median timings taken of a contention-heavy GPU workload: Before: real 0m52.946s user 0m7.272s sys 1m55.964s After: real 0m53.086s user 0m7.360s sys 1m46.204s This particular workload still spends 20%-25% of CPU in mutex_spin_on_owner according to perf, but my attempts to further reduce this spinning based on various heuristics all lead to an increase in measured wall time despite the decrease in sys time. Signed-off-by: Nicolai Hähnle <Nicolai.Haehnle@amd.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Chris Wilson <chris@chris-wilson.co.uk> Cc: Daniel Vetter <daniel@ffwll.ch> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Maarten Lankhorst <dev@mblankhorst.nl> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: dri-devel@lists.freedesktop.org Link: http://lkml.kernel.org/r/1482346000-9927-11-git-send-email-nhaehnle@gmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * locking/ww_mutex: Re-check ww->ctx in the inner optimistic spin loopNicolai Hähnle2017-01-141-20/+29
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | In the following scenario, thread #1 should back off its attempt to lock ww1 and unlock ww2 (assuming the acquire context stamps are ordered accordingly). Thread #0 Thread #1 --------- --------- successfully lock ww2 set ww1->base.owner attempt to lock ww1 confirm ww1->ctx == NULL enter mutex_spin_on_owner set ww1->ctx What was likely to happen previously is: attempt to lock ww2 refuse to spin because ww2->ctx != NULL schedule() detect thread #0 is off CPU stop optimistic spin return -EDEADLK unlock ww2 wakeup thread #0 lock ww2 Now, we are more likely to see: detect ww1->ctx != NULL stop optimistic spin return -EDEADLK unlock ww2 successfully lock ww2 ... because thread #1 will stop its optimistic spin as soon as possible. The whole scenario is quite unlikely, since it requires thread #1 to get between thread #0 setting the owner and setting the ctx. But since we're idling here anyway, the additional check is basically free. Found by inspection. Signed-off-by: Nicolai Hähnle <Nicolai.Haehnle@amd.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Chris Wilson <chris@chris-wilson.co.uk> Cc: Daniel Vetter <daniel@ffwll.ch> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Maarten Lankhorst <dev@mblankhorst.nl> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: dri-devel@lists.freedesktop.org Link: http://lkml.kernel.org/r/1482346000-9927-10-git-send-email-nhaehnle@gmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * locking/mutex: Improve inliningPeter Zijlstra2017-01-141-41/+44
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Instead of inlining __mutex_lock_common() 5 times, once for each {state,ww} variant. Reduce this to two, ww and !ww. Then add __always_inline to mutex_optimistic_spin(), so that that will get inlined all 4 remaining times, for all {waiter,ww} variants. text data bss dec hex filename 6301 0 0 6301 189d defconfig-build/kernel/locking/mutex.o 4053 0 0 4053 fd5 defconfig-build/kernel/locking/mutex.o 4257 0 0 4257 10a1 defconfig-build/kernel/locking/mutex.o This reduces total text size and better separates the ww and !ww mutex code generation. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * locking/ww_mutex: Optimize ww-mutexes by waking at most one waiter for ↵Nicolai Hähnle2017-01-141-19/+40
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | backoff when acquiring the lock The wait list is sorted by stamp order, and the only waiting task that may have to back off is the first waiter with a context. The regular slow path does not have to wake any other tasks at all, since all other waiters that would have to back off were either woken up when the waiter was added to the list, or detected the condition before they added themselves. Median timings taken of a contention-heavy GPU workload: Without this series: real 0m59.900s user 0m7.516s sys 2m16.076s With changes up to and including this patch: real 0m52.946s user 0m7.272s sys 1m55.964s Signed-off-by: Nicolai Hähnle <Nicolai.Haehnle@amd.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Chris Wilson <chris@chris-wilson.co.uk> Cc: Daniel Vetter <daniel@ffwll.ch> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Maarten Lankhorst <dev@mblankhorst.nl> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: dri-devel@lists.freedesktop.org Link: http://lkml.kernel.org/r/1482346000-9927-9-git-send-email-nhaehnle@gmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * locking/ww_mutex: Notify waiters that have to back off while adding tasks to ↵Nicolai Hähnle2017-01-141-10/+30
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | wait list While adding our task as a waiter, detect if another task should back off because of us. With this patch, we establish the invariant that the wait list contains at most one (sleeping) waiter with ww_ctx->acquired > 0, and this waiter will be the first waiter with a context. Since only waiters with ww_ctx->acquired > 0 have to back off, this allows us to be much more economical with wakeups. Signed-off-by: Nicolai Hähnle <Nicolai.Haehnle@amd.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Chris Wilson <chris@chris-wilson.co.uk> Cc: Daniel Vetter <daniel@ffwll.ch> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Maarten Lankhorst <dev@mblankhorst.nl> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: dri-devel@lists.freedesktop.org Link: http://lkml.kernel.org/r/1482346000-9927-8-git-send-email-nhaehnle@gmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * locking/ww_mutex: Add waiters in stamp orderNicolai Hähnle2017-01-141-7/+69
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Add regular waiters in stamp order. Keep adding waiters that have no context in FIFO order and take care not to starve them. While adding our task as a waiter, back off if we detect that there is a waiter with a lower stamp in front of us. Make sure to call lock_contended even when we back off early. For w/w mutexes, being first in the wait list is only stable when taking the lock without a context. Therefore, the purpose of the first flag is split into two: 'first' remains to indicate whether we want to spin optimistically, while 'handoff' indicates that we should be prepared to accept a handoff. For w/w locking with a context, we always accept handoffs after the first schedule(), to handle the following sequence of events: 1. Task #0 unlocks and hands off to Task #2 which is first in line 2. Task #1 adds itself in front of Task #2 3. Task #2 wakes up and must accept the handoff even though it is no longer first in line Signed-off-by: Nicolai Hähnle <nicolai.haehnle@amd.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: =?UTF-8?q?Nicolai=20H=C3=A4hnle?= <Nicolai.Haehnle@amd.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Chris Wilson <chris@chris-wilson.co.uk> Cc: Daniel Vetter <daniel@ffwll.ch> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Maarten Lankhorst <dev@mblankhorst.nl> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: dri-devel@lists.freedesktop.org Link: http://lkml.kernel.org/r/1482346000-9927-7-git-send-email-nhaehnle@gmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * locking/ww_mutex: Remove the __ww_mutex_lock*() inline wrappersNicolai Hähnle2017-01-141-8/+8
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Keep the documentation in the header file since there is no good place for it in mutex.c: there are two rather different implementations with different EXPORT_SYMBOLs for each function. Signed-off-by: Nicolai Hähnle <nicolai.haehnle@amd.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: =?UTF-8?q?Nicolai=20H=C3=A4hnle?= <Nicolai.Haehnle@amd.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Chris Wilson <chris@chris-wilson.co.uk> Cc: Daniel Vetter <daniel@ffwll.ch> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Maarten Lankhorst <dev@mblankhorst.nl> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: dri-devel@lists.freedesktop.org Link: http://lkml.kernel.org/r/1482346000-9927-6-git-send-email-nhaehnle@gmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * locking/ww_mutex: Set use_ww_ctx even when locking without a contextNicolai Hähnle2017-01-141-12/+17
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | We will add a new field to struct mutex_waiter. This field must be initialized for all waiters if any waiter uses the ww_use_ctx path. So there is a trade-off: Keep ww_mutex locking without a context on the faster non-use_ww_ctx path, at the cost of adding the initialization to all mutex locks (including non-ww_mutexes), or avoid the additional cost for non-ww_mutex locks, at the cost of adding additional checks to the use_ww_ctx path. We take the latter choice. It may be worth eliminating the users of ww_mutex_lock(lock, NULL), but there are a lot of them. Signed-off-by: Nicolai Hähnle <Nicolai.Haehnle@amd.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Chris Wilson <chris@chris-wilson.co.uk> Cc: Daniel Vetter <daniel@ffwll.ch> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Maarten Lankhorst <dev@mblankhorst.nl> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: dri-devel@lists.freedesktop.org Link: http://lkml.kernel.org/r/1482346000-9927-5-git-send-email-nhaehnle@gmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * locking/ww_mutex: Extract stamp comparison to __ww_mutex_stamp_after()Nicolai Hähnle2017-01-141-2/+8
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The function will be re-used in subsequent patches. Signed-off-by: Nicolai Hähnle <Nicolai.Haehnle@amd.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Daniel Vetter <daniel@ffwll.ch> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Maarten Lankhorst <dev@mblankhorst.nl> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: dri-devel@lists.freedesktop.org Link: http://lkml.kernel.org/r/1482346000-9927-4-git-send-email-nhaehnle@gmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * locking/mutex: Fix mutex handoffPeter Zijlstra2017-01-141-56/+52
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | While reviewing the ww_mutex patches, I noticed that it was still possible to (incorrectly) succeed for (incorrect) code like: mutex_lock(&a); mutex_lock(&a); This was possible if the second mutex_lock() would block (as expected) but then receive a spurious wakeup. At that point it would find itself at the front of the queue, request a handoff and instantly claim ownership and continue, since owner would point to itself. Avoid this scenario and simplify the code by introducing a third low bit to signal handoff pickup. So once we request handoff, unlock clears the handoff bit and sets the pickup bit along with the new owner. This also removes the need for the .handoff argument to __mutex_trylock(), since that becomes superfluous with PICKUP. In order to guarantee enough low bits, ensure task_struct alignment is at least L1_CACHE_BYTES (which seems a good ideal regardless). Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Fixes: 9d659ae14b54 ("locking/mutex: Add lock handoff to avoid starvation") Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * sched/core: Remove set_task_state()Davidlohr Bueso2017-01-141-4/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This is a nasty interface and setting the state of a foreign task must not be done. As of the following commit: be628be0956 ("bcache: Make gc wakeup sane, remove set_task_state()") ... everyone in the kernel calls set_task_state() with current, allowing the helper to be removed. However, as the comment indicates, it is still around for those archs where computing current is more expensive than using a pointer, at least in theory. An important arch that is affected is arm64, however this has been addressed now [1] and performance is up to par making no difference with either calls. Of all the callers, if any, it's the locking bits that would care most about this -- ie: we end up passing a tsk pointer to a lot of the lock slowpath, and setting ->state on that. The following numbers are based on two tests: a custom ad-hoc microbenchmark that just measures latencies (for ~65 million calls) between get_task_state() vs get_current_state(). Secondly for a higher overview, an unlink microbenchmark was used, which pounds on a single file with open, close,unlink combos with increasing thread counts (up to 4x ncpus). While the workload is quite unrealistic, it does contend a lot on the inode mutex or now rwsem. [1] https://lkml.kernel.org/r/1483468021-8237-1-git-send-email-mark.rutland@arm.com == 1. x86-64 == Avg runtime set_task_state(): 601 msecs Avg runtime set_current_state(): 552 msecs vanilla dirty Hmean unlink1-processes-2 36089.26 ( 0.00%) 38977.33 ( 8.00%) Hmean unlink1-processes-5 28555.01 ( 0.00%) 29832.55 ( 4.28%) Hmean unlink1-processes-8 37323.75 ( 0.00%) 44974.57 ( 20.50%) Hmean unlink1-processes-12 43571.88 ( 0.00%) 44283.01 ( 1.63%) Hmean unlink1-processes-21 34431.52 ( 0.00%) 38284.45 ( 11.19%) Hmean unlink1-processes-30 34813.26 ( 0.00%) 37975.17 ( 9.08%) Hmean unlink1-processes-48 37048.90 ( 0.00%) 39862.78 ( 7.59%) Hmean unlink1-processes-79 35630.01 ( 0.00%) 36855.30 ( 3.44%) Hmean unlink1-processes-110 36115.85 ( 0.00%) 39843.91 ( 10.32%) Hmean unlink1-processes-141 32546.96 ( 0.00%) 35418.52 ( 8.82%) Hmean unlink1-processes-172 34674.79 ( 0.00%) 36899.21 ( 6.42%) Hmean unlink1-processes-203 37303.11 ( 0.00%) 36393.04 ( -2.44%) Hmean unlink1-processes-224 35712.13 ( 0.00%) 36685.96 ( 2.73%) == 2. ppc64le == Avg runtime set_task_state(): 938 msecs Avg runtime set_current_state: 940 msecs vanilla dirty Hmean unlink1-processes-2 19269.19 ( 0.00%) 30704.50 ( 59.35%) Hmean unlink1-processes-5 20106.15 ( 0.00%) 21804.15 ( 8.45%) Hmean unlink1-processes-8 17496.97 ( 0.00%) 17243.28 ( -1.45%) Hmean unlink1-processes-12 14224.15 ( 0.00%) 17240.21 ( 21.20%) Hmean unlink1-processes-21 14155.66 ( 0.00%) 15681.23 ( 10.78%) Hmean unlink1-processes-30 14450.70 ( 0.00%) 15995.83 ( 10.69%) Hmean unlink1-processes-48 16945.57 ( 0.00%) 16370.42 ( -3.39%) Hmean unlink1-processes-79 15788.39 ( 0.00%) 14639.27 ( -7.28%) Hmean unlink1-processes-110 14268.48 ( 0.00%) 14377.40 ( 0.76%) Hmean unlink1-processes-141 14023.65 ( 0.00%) 16271.69 ( 16.03%) Hmean unlink1-processes-172 13417.62 ( 0.00%) 16067.55 ( 19.75%) Hmean unlink1-processes-203 15293.08 ( 0.00%) 15440.40 ( 0.96%) Hmean unlink1-processes-234 13719.32 ( 0.00%) 16190.74 ( 18.01%) Hmean unlink1-processes-265 16400.97 ( 0.00%) 16115.22 ( -1.74%) Hmean unlink1-processes-296 14388.60 ( 0.00%) 16216.13 ( 12.70%) Hmean unlink1-processes-320 15771.85 ( 0.00%) 15905.96 ( 0.85%) x86-64 (known to be fast for get_current()/this_cpu_read_stable() caching) and ppc64 (with paca) show similar improvements in the unlink microbenches. The small delta for ppc64 (2ms), does not represent the gains on the unlink runs. In the case of x86, there was a decent amount of variation in the latency runs, but always within a 20 to 50ms increase), ppc was more constant. Signed-off-by: Davidlohr Bueso <dbueso@suse.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: dave@stgolabs.net Cc: mark.rutland@arm.com Link: http://lkml.kernel.org/r/1483479794-14013-5-git-send-email-dave@stgolabs.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * kernel/locking: Compute 'current' directlyDavidlohr Bueso2017-01-141-10/+9
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch effectively replaces the tsk pointer dereference (which is obviously == current), to directly use get_current() macro. This is to make the removal of setting foreign task states smoother and painfully obvious. Performance win on some archs such as x86-64 and ppc64. On a microbenchmark that calls set_task_state() vs set_current_state() and an inode rwsem pounding benchmark doing unlink: == 1. x86-64 == Avg runtime set_task_state(): 601 msecs Avg runtime set_current_state(): 552 msecs vanilla dirty Hmean unlink1-processes-2 36089.26 ( 0.00%) 38977.33 ( 8.00%) Hmean unlink1-processes-5 28555.01 ( 0.00%) 29832.55 ( 4.28%) Hmean unlink1-processes-8 37323.75 ( 0.00%) 44974.57 ( 20.50%) Hmean unlink1-processes-12 43571.88 ( 0.00%) 44283.01 ( 1.63%) Hmean unlink1-processes-21 34431.52 ( 0.00%) 38284.45 ( 11.19%) Hmean unlink1-processes-30 34813.26 ( 0.00%) 37975.17 ( 9.08%) Hmean unlink1-processes-48 37048.90 ( 0.00%) 39862.78 ( 7.59%) Hmean unlink1-processes-79 35630.01 ( 0.00%) 36855.30 ( 3.44%) Hmean unlink1-processes-110 36115.85 ( 0.00%) 39843.91 ( 10.32%) Hmean unlink1-processes-141 32546.96 ( 0.00%) 35418.52 ( 8.82%) Hmean unlink1-processes-172 34674.79 ( 0.00%) 36899.21 ( 6.42%) Hmean unlink1-processes-203 37303.11 ( 0.00%) 36393.04 ( -2.44%) Hmean unlink1-processes-224 35712.13 ( 0.00%) 36685.96 ( 2.73%) == 2. ppc64le == Avg runtime set_task_state(): 938 msecs Avg runtime set_current_state: 940 msecs vanilla dirty Hmean unlink1-processes-2 19269.19 ( 0.00%) 30704.50 ( 59.35%) Hmean unlink1-processes-5 20106.15 ( 0.00%) 21804.15 ( 8.45%) Hmean unlink1-processes-8 17496.97 ( 0.00%) 17243.28 ( -1.45%) Hmean unlink1-processes-12 14224.15 ( 0.00%) 17240.21 ( 21.20%) Hmean unlink1-processes-21 14155.66 ( 0.00%) 15681.23 ( 10.78%) Hmean unlink1-processes-30 14450.70 ( 0.00%) 15995.83 ( 10.69%) Hmean unlink1-processes-48 16945.57 ( 0.00%) 16370.42 ( -3.39%) Hmean unlink1-processes-79 15788.39 ( 0.00%) 14639.27 ( -7.28%) Hmean unlink1-processes-110 14268.48 ( 0.00%) 14377.40 ( 0.76%) Hmean unlink1-processes-141 14023.65 ( 0.00%) 16271.69 ( 16.03%) Hmean unlink1-processes-172 13417.62 ( 0.00%) 16067.55 ( 19.75%) Hmean unlink1-processes-203 15293.08 ( 0.00%) 15440.40 ( 0.96%) Hmean unlink1-processes-234 13719.32 ( 0.00%) 16190.74 ( 18.01%) Hmean unlink1-processes-265 16400.97 ( 0.00%) 16115.22 ( -1.74%) Hmean unlink1-processes-296 14388.60 ( 0.00%) 16216.13 ( 12.70%) Hmean unlink1-processes-320 15771.85 ( 0.00%) 15905.96 ( 0.85%) Signed-off-by: Davidlohr Bueso <dbueso@suse.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: dave@stgolabs.net Cc: mark.rutland@arm.com Link: http://lkml.kernel.org/r/1483479794-14013-4-git-send-email-dave@stgolabs.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
* | locking/mutex, sched/wait: Add mutex_lock_io()Tejun Heo2017-01-141-0/+24
|/ | | | | | | | | | | | | | | | | | | | | | | | | | We sometimes end up propagating IO blocking through mutexes; however, because there currently is no way of annotating mutex sleeps as iowait, there are cases where iowait and /proc/stat:procs_blocked report misleading numbers obscuring the actual state of the system. This patch adds mutex_lock_io() so that mutex sleeps can be marked as iowait in those cases. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Jens Axboe <axboe@kernel.dk> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: adilger.kernel@dilger.ca Cc: jack@suse.com Cc: kernel-team@fb.com Cc: mingbo@fb.com Cc: tytso@mit.edu Link: http://lkml.kernel.org/r/1477673892-28940-4-git-send-email-tj@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
* locking/mutex: Break out of expensive busy-loop on ↵Pan Xinhui2016-11-221-2/+11
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | {mutex,rwsem}_spin_on_owner() when owner vCPU is preempted An over-committed guest with more vCPUs than pCPUs has a heavy overload in the two spin_on_owner. This blames on the lock holder preemption issue. Break out of the loop if the vCPU is preempted: if vcpu_is_preempted(cpu) is true. test-case: perf record -a perf bench sched messaging -g 400 -p && perf report before patch: 20.68% sched-messaging [kernel.vmlinux] [k] mutex_spin_on_owner 8.45% sched-messaging [kernel.vmlinux] [k] mutex_unlock 4.12% sched-messaging [kernel.vmlinux] [k] system_call 3.01% sched-messaging [kernel.vmlinux] [k] system_call_common 2.83% sched-messaging [kernel.vmlinux] [k] copypage_power7 2.64% sched-messaging [kernel.vmlinux] [k] rwsem_spin_on_owner 2.00% sched-messaging [kernel.vmlinux] [k] osq_lock after patch: 9.99% sched-messaging [kernel.vmlinux] [k] mutex_unlock 5.28% sched-messaging [unknown] [H] 0xc0000000000768e0 4.27% sched-messaging [kernel.vmlinux] [k] __copy_tofrom_user_power7 3.77% sched-messaging [kernel.vmlinux] [k] copypage_power7 3.24% sched-messaging [kernel.vmlinux] [k] _raw_write_lock_irq 3.02% sched-messaging [kernel.vmlinux] [k] system_call 2.69% sched-messaging [kernel.vmlinux] [k] wait_consider_task Tested-by: Juergen Gross <jgross@suse.com> Signed-off-by: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Christian Borntraeger <borntraeger@de.ibm.com> Acked-by: Paolo Bonzini <pbonzini@redhat.com> Cc: David.Laight@ACULAB.COM Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: benh@kernel.crashing.org Cc: boqun.feng@gmail.com Cc: bsingharora@gmail.com Cc: dave@stgolabs.net Cc: kernellwp@gmail.com Cc: konrad.wilk@oracle.com Cc: linuxppc-dev@lists.ozlabs.org Cc: mpe@ellerman.id.au Cc: paulmck@linux.vnet.ibm.com Cc: paulus@samba.org Cc: rkrcmar@redhat.com Cc: virtualization@lists.linux-foundation.org Cc: will.deacon@arm.com Cc: xen-devel-request@lists.xenproject.org Cc: xen-devel@lists.xenproject.org Link: http://lkml.kernel.org/r/1478077718-37424-4-git-send-email-xinhui.pan@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched/wake_q: Rename WAKE_Q to DEFINE_WAKE_QWaiman Long2016-11-211-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | Currently the wake_q data structure is defined by the WAKE_Q() macro. This macro, however, looks like a function doing something as "wake" is a verb. Even checkpatch.pl was confused as it reported warnings like WARNING: Missing a blank line after declarations #548: FILE: kernel/futex.c:3665: + int ret; + WAKE_Q(wake_q); This patch renames the WAKE_Q() macro to DEFINE_WAKE_Q() which clarifies what the macro is doing and eliminates the checkpatch.pl warnings. Signed-off-by: Waiman Long <longman@redhat.com> Acked-by: Davidlohr Bueso <dave@stgolabs.net> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/1479401198-1765-1-git-send-email-longman@redhat.com [ Resolved conflict and added missing rename. ] Signed-off-by: Ingo Molnar <mingo@kernel.org>
* locking/core: Remove cpu_relax_lowlatency() usersChristian Borntraeger2016-11-161-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | With the s390 special case of a yielding cpu_relax() implementation gone, we can now remove all users of cpu_relax_lowlatency() and replace them with cpu_relax(). Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Noam Camus <noamc@ezchip.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Russell King <linux@armlinux.org.uk> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Will Deacon <will.deacon@arm.com> Cc: linuxppc-dev@lists.ozlabs.org Cc: virtualization@lists.linux-foundation.org Cc: xen-devel@lists.xenproject.org Link: http://lkml.kernel.org/r/1477386195-32736-5-git-send-email-borntraeger@de.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* locking/mutex: Enable optimistic spinning of woken waiterWaiman Long2016-10-251-23/+54
| | | | | | | | | | | | | | | | | | | | | | | | This patch makes the waiter that sets the HANDOFF flag start spinning instead of sleeping until the handoff is complete or the owner sleeps. Otherwise, the handoff will cause the optimistic spinners to abort spinning as the handed-off owner may not be running. Tested-by: Jason Low <jason.low2@hpe.com> Signed-off-by: Waiman Long <Waiman.Long@hpe.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Ding Tianhong <dingtianhong@huawei.com> Cc: Imre Deak <imre.deak@intel.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Paul E. McKenney <paulmck@us.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Tim Chen <tim.c.chen@linux.intel.com> Cc: Will Deacon <Will.Deacon@arm.com> Link: http://lkml.kernel.org/r/1472254509-27508-2-git-send-email-Waiman.Long@hpe.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* locking/mutex: Simplify some ww_mutex code in __mutex_lock_common()Waiman Long2016-10-251-9/+4
| | | | | | | | | | | | | | | | | | | | | | This patch removes some of the redundant ww_mutex code in __mutex_lock_common(). Tested-by: Jason Low <jason.low2@hpe.com> Signed-off-by: Waiman Long <Waiman.Long@hpe.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Ding Tianhong <dingtianhong@huawei.com> Cc: Imre Deak <imre.deak@intel.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Paul E. McKenney <paulmck@us.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Tim Chen <tim.c.chen@linux.intel.com> Cc: Will Deacon <Will.Deacon@arm.com> Link: http://lkml.kernel.org/r/1472254509-27508-1-git-send-email-Waiman.Long@hpe.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* locking/mutex: Restructure wait loopPeter Zijlstra2016-10-251-5/+25
| | | | | | | | | | | | | | | | | | | | | | | Doesn't really matter yet, but pull the HANDOFF and trylock out from under the wait_lock. The intention is to add an optimistic spin loop here, which requires we do not hold the wait_lock, so shuffle code around in preparation. Also clarify the purpose of taking the wait_lock in the wait loop, its tempting to want to avoid it altogether, but the cancellation cases need to to avoid losing wakeups. Suggested-by: Waiman Long <waiman.long@hpe.com> Tested-by: Jason Low <jason.low2@hpe.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
* locking/mutex: Add lock handoff to avoid starvationPeter Zijlstra2016-10-251-23/+119
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Implement lock handoff to avoid lock starvation. Lock starvation is possible because mutex_lock() allows lock stealing, where a running (or optimistic spinning) task beats the woken waiter to the acquire. Lock stealing is an important performance optimization because waiting for a waiter to wake up and get runtime can take a significant time, during which everyboy would stall on the lock. The down-side is of course that it allows for starvation. This patch has the waiter requesting a handoff if it fails to acquire the lock upon waking. This re-introduces some of the wait time, because once we do a handoff we have to wait for the waiter to wake up again. A future patch will add a round of optimistic spinning to attempt to alleviate this penalty, but if that turns out to not be enough, we can add a counter and only request handoff after multiple failed wakeups. There are a few tricky implementation details: - accepting a handoff must only be done in the wait-loop. Since the handoff condition is owner == current, it can easily cause recursive locking trouble. - accepting the handoff must be careful to provide the ACQUIRE semantics. - having the HANDOFF bit set on unlock requires care, we must not clear the owner. - we must be careful to not leave HANDOFF set after we've acquired the lock. The tricky scenario is setting the HANDOFF bit on an unlocked mutex. Tested-by: Jason Low <jason.low2@hpe.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Waiman Long <Waiman.Long@hpe.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
* locking/mutex: Rework mutex::ownerPeter Zijlstra2016-10-251-215/+156
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The current mutex implementation has an atomic lock word and a non-atomic owner field. This disparity leads to a number of issues with the current mutex code as it means that we can have a locked mutex without an explicit owner (because the owner field has not been set, or already cleared). This leads to a number of weird corner cases, esp. between the optimistic spinning and debug code. Where the optimistic spinning code needs the owner field updated inside the lock region, the debug code is more relaxed because the whole lock is serialized by the wait_lock. Also, the spinning code itself has a few corner cases where we need to deal with a held lock without an owner field. Furthermore, it becomes even more of a problem when trying to fix starvation cases in the current code. We end up stacking special case on special case. To solve this rework the basic mutex implementation to be a single atomic word that contains the owner and uses the low bits for extra state. This matches how PI futexes and rt_mutex already work. By having the owner an integral part of the lock state a lot of the problems dissapear and we get a better option to deal with starvation cases, direct owner handoff. Changing the basic mutex does however invalidate all the arch specific mutex code; this patch leaves that unused in-place, a later patch will remove that. Tested-by: Jason Low <jason.low2@hpe.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Will Deacon <will.deacon@arm.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
* locking: avoid passing around 'thread_info' in mutex debugging codeLinus Torvalds2016-06-231-3/+3
| | | | | | | | | | | | None of the code actually wants a thread_info, it all wants a task_struct, and it's just converting back and forth between the two ("ti->task" to get the task_struct from the thread_info, and "task_thread_info(task)" to go the other way). No semantic change. Acked-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* locking/ww_mutex: Report recursive ww_mutex locking earlyChris Wilson2016-06-031-3/+6
| | | | | | | | | | | | | | | | | | | | | | | | Recursive locking for ww_mutexes was originally conceived as an exception. However, it is heavily used by the DRM atomic modesetting code. Currently, the recursive deadlock is checked after we have queued up for a busy-spin and as we never release the lock, we spin until kicked, whereupon the deadlock is discovered and reported. A simple solution for the now common problem is to move the recursive deadlock discovery to the first action when taking the ww_mutex. Suggested-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/1464293297-19777-1-git-send-email-chris@chris-wilson.co.uk Signed-off-by: Ingo Molnar <mingo@kernel.org>
* locking/mutex: Allow next waiter lockless wakeupDavidlohr Bueso2016-02-291-2/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | Make use of wake-queues and enable the wakeup to occur after releasing the wait_lock. This is similar to what we do with rtmutex top waiter, slightly shortening the critical region and allow other waiters to acquire the wait_lock sooner. In low contention cases it can also help the recently woken waiter to find the wait_lock available (fastpath) when it continues execution. Reviewed-by: Waiman Long <Waiman.Long@hpe.com> Signed-off-by: Davidlohr Bueso <dbueso@suse.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Ding Tianhong <dingtianhong@huawei.com> Cc: Jason Low <jason.low2@hp.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Paul E. McKenney <paulmck@us.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Tim Chen <tim.c.chen@linux.intel.com> Cc: Waiman Long <waiman.long@hpe.com> Cc: Will Deacon <Will.Deacon@arm.com> Link: http://lkml.kernel.org/r/20160125022343.GA3322@linux-uzut.site Signed-off-by: Ingo Molnar <mingo@kernel.org>
* locking/mutex: Use acquire/release semanticsDavidlohr Bueso2015-10-061-4/+5
| | | | | | | | | | | | | | | | | | | | | | | | As of 654672d4ba1 (locking/atomics: Add _{acquire|release|relaxed}() variants of some atomic operations) and 6d79ef2d30e (locking, asm-generic: Add _{relaxed|acquire|release}() variants for 'atomic_long_t'), weakly ordered archs can benefit from more relaxed use of barriers when locking and unlocking, instead of regular full barrier semantics. While currently only arm64 supports such optimizations, updating corresponding locking primitives serves for other archs to immediately benefit as well, once the necessary machinery is implemented of course. Signed-off-by: Davidlohr Bueso <dbueso@suse.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Paul E.McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Will Deacon <will.deacon@arm.com> Cc: linux-kernel@vger.kernel.org Link: http://lkml.kernel.org/r/1443643395-17016-3-git-send-email-dave@stgolabs.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
* locking/mutex: Further simplify mutex_spin_on_owner()Jason Low2015-04-091-10/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | Similar to what Linus suggested for rwsem_spin_on_owner(), in mutex_spin_on_owner() instead of having while (true) and breaking out of the spin loop on lock->owner != owner, we can have the loop directly check for while (lock->owner == owner) to improve the readability of the code. It also shrinks the code a bit: text data bss dec hex filename 3721 0 0 3721 e89 mutex.o.before 3705 0 0 3705 e79 mutex.o.after Signed-off-by: Jason Low <jason.low2@hp.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Aswin Chandramouleeswaran <aswin@hp.com> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Tim Chen <tim.c.chen@linux.intel.com> Link: http://lkml.kernel.org/r/1428521960-5268-2-git-send-email-jason.low2@hp.com [ Added code generation info. ] Signed-off-by: Ingo Molnar <mingo@kernel.org>
* locking: Remove ACCESS_ONCE() usageDavidlohr Bueso2015-02-241-4/+4
| | | | | | | | | | | | | | | | | | | | | | | | | With the new standardized functions, we can replace all ACCESS_ONCE() calls across relevant locking - this includes lockref and seqlock while at it. ACCESS_ONCE() does not work reliably on non-scalar types. For example gcc 4.6 and 4.7 might remove the volatile tag for such accesses during the SRA (scalar replacement of aggregates) step: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145 Update the new calls regardless of if it is a scalar type, this is cleaner than having three alternatives. Signed-off-by: Davidlohr Bueso <dbueso@suse.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Link: http://lkml.kernel.org/r/1424662301.6539.18.camel@stgolabs.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
* locking/rwsem: Set lock ownership ASAPDavidlohr Bueso2015-02-181-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | In order to optimize the spinning step, we need to set the lock owner as soon as the lock is acquired; after a successful counter cmpxchg operation, that is. This is particularly useful as rwsems need to set the owner to nil for readers, so there is a greater chance of falling out of the spinning. Currently we only set the owner much later in the game, in the more generic level -- latency can be specially bad when waiting for a node->next pointer when releasing the osq in up_write calls. As such, update the owner inside rwsem_try_write_lock (when the lock is obtained after blocking) and rwsem_try_write_lock_unqueued (when the lock is obtained while spinning). This requires creating a new internal rwsem.h header to share the owner related calls. Also cleanup some headers for mutex and rwsem. Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Davidlohr Bueso <dbueso@suse.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Jason Low <jason.low2@hp.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Michel Lespinasse <walken@google.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Tim Chen <tim.c.chen@linux.intel.com> Link: http://lkml.kernel.org/r/1422609267-15102-4-git-send-email-dave@stgolabs.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
* locking/mutex: Refactor mutex_spin_on_owner()Jason Low2015-02-181-25/+22
| | | | | | | | | | | | | | | | | | | | | | | | | | | | As suggested by Davidlohr, we could refactor mutex_spin_on_owner(). Currently, we split up owner_running() with mutex_spin_on_owner(). When the owner changes, we make duplicate owner checks which are not necessary. It also makes the code a bit obscure as we are using a second check to figure out why we broke out of the loop. This patch modifies it such that we remove the owner_running() function and the mutex_spin_on_owner() loop directly checks for if the owner changes, if the owner is not running, or if we need to reschedule. If the owner changes, we break out of the loop and return true. If the owner is not running or if we need to reschedule, then break out of the loop and return false. Suggested-by: Davidlohr Bueso <dave@stgolabs.net> Signed-off-by: Jason Low <jason.low2@hp.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Aswin Chandramouleeswaran <aswin@hp.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Tim Chen <tim.c.chen@linux.intel.com> Cc: chegu_vinod@hp.com Cc: tglx@linutronix.de Link: http://lkml.kernel.org/r/1422914367-5574-3-git-send-email-jason.low2@hp.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* locking/mutex: In mutex_spin_on_owner(), return true when owner changesJason Low2015-02-181-4/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | In the mutex_spin_on_owner(), we return true only if lock->owner == NULL. This was beneficial in situations where there were multiple threads simultaneously spinning for the mutex. If another thread got the lock while other spinner(s) were also doing mutex_spin_on_owner(), then the other spinners would stop spinning. This workaround helped reduce the chance that many spinners were simultaneously spinning for the mutex which can help reduce contention in highly contended cases. However, recent changes were made to the optimistic spinning code such that instead of having all spinners simultaneously spin for the mutex, we queue the spinners with an MCS lock such that only one thread spins for the mutex at a time. Furthermore, the OSQ optimizations ensure that spinners in the queue will stop waiting if it needs to reschedule. Now, we don't have to worry about multiple threads spinning on owner at the same time, and if lock->owner is not NULL at this point, it likely means another thread happens to obtain the lock in the fastpath. In this case, it would make sense for the spinner to continue spinning as long as the spinner doesn't need to schedule and the mutex owner is running. This patch changes this so that mutex_spin_on_owner() returns true when the lock owner changes, which means a thread will only stop spinning if it either needs to reschedule or if the lock owner is not running. We saw up to a 5% performance improvement in the fserver workload with this patch. Signed-off-by: Jason Low <jason.low2@hp.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Davidlohr Bueso <dave@stgolabs.net> Cc: Aswin Chandramouleeswaran <aswin@hp.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Tim Chen <tim.c.chen@linux.intel.com> Cc: chegu_vinod@hp.com Cc: tglx@linutronix.de Link: http://lkml.kernel.org/r/1422914367-5574-2-git-send-email-jason.low2@hp.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* Merge branch 'sched-core-for-linus' of ↵Linus Torvalds2015-02-091-1/+1
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull scheduler updates from Ingo Molnar: "The main scheduler changes in this cycle were: - various sched/deadline fixes and enhancements - rescheduling latency fixes/cleanups - rework the rq->clock code to be more consistent and more robust. - minor micro-optimizations - ->avg.decay_count fixes - add a stack overflow check to might_sleep() - idle-poll handler fix, possibly resulting in power savings - misc smaller updates and fixes" * 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: sched/Documentation: Remove unneeded word sched/wait: Introduce wait_on_bit_timeout() sched: Pull resched loop to __schedule() callers sched/deadline: Remove cpu_active_mask from cpudl_find() sched: Fix hrtick_start() on UP sched/deadline: Avoid pointless __setscheduler() sched/deadline: Fix stale yield state sched/deadline: Fix hrtick for a non-leftmost task sched/deadline: Modify cpudl::free_cpus to reflect rd->online sched/idle: Add missing checks to the exit condition of cpu_idle_poll() sched: Fix missing preemption opportunity sched/rt: Reduce rq lock contention by eliminating locking of non-feasible target sched/debug: Print rq->clock_task sched/core: Rework rq->clock update skips sched/core: Validate rq_clock*() serialization sched/core: Remove check of p->sched_class sched/fair: Fix sched_entity::avg::decay_count initialization sched/debug: Fix potential call to __ffs(0) in sched_show_task() sched/debug: Check for stack overflow in ___might_sleep() sched/fair: Fix the dealing with decay_count in __synchronize_entity_decay()
| * sched/Documentation: Remove unneeded wordSharon Dvir2015-02-041-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | The second 'mutex' shouldn't be there, it can't be about the mutex, as the mutex can't be freed, but unlocked, the memory where the mutex resides however, can be freed. Signed-off-by: Sharon Dvir <sharon.dvir1@mail.huji.ac.il> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/1422827252-31363-1-git-send-email-sharon.dvir1@mail.huji.ac.il Signed-off-by: Ingo Molnar <mingo@kernel.org>
* | locking/mutex: Explicitly mark task as running after wakeupDavidlohr Bueso2015-02-041-0/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | By the time we wake up and get the lock after being asleep in the slowpath, we better be running. As good practice, be explicit about this and avoid any mischief. Signed-off-by: Davidlohr Bueso <dbueso@suse.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/1421717961.4903.11.camel@stgolabs.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
* | locking/mutex: Introduce ww_mutex_set_context_slowpath()Davidlohr Bueso2015-01-141-18/+26
| | | | | | | | | | | | | | | | | | | | | | | | | | | | ... which is equivalent to the fastpath counter part. This mainly allows getting some WW specific code out of generic mutex paths. Signed-off-by: Davidlohr Bueso <dbueso@suse.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/1420573509-24774-4-git-send-email-dave@stgolabs.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
* | locking/mutex: Move MCS related comments to proper locationDavidlohr Bueso2015-01-141-11/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | It serves much better if the comments are right before the osq_lock() call. Also delete a useless comment. Signed-off-by: Davidlohr Bueso <dbueso@suse.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/1420573509-24774-3-git-send-email-dave@stgolabs.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
* | locking/mutex: Checking the stamp is WW onlyDavidlohr Bueso2015-01-141-2/+2
|/ | | | | | | | | | | | Mark it so by renaming __mutex_lock_check_stamp(). Signed-off-by: Davidlohr Bueso <dbueso@suse.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/1420573509-24774-2-git-send-email-dave@stgolabs.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
* locking/mutex: Don't assume TASK_RUNNINGPeter Zijlstra2014-10-281-1/+7
| | | | | | | | | | | | | | | | | | | | | | | We're going to make might_sleep() test for TASK_RUNNING, because blocking without TASK_RUNNING will destroy the task state by setting it to TASK_RUNNING. There are a few occasions where its 'valid' to call blocking primitives (and mutex_lock in particular) and not have TASK_RUNNING, typically such cases are right before we set TASK_RUNNING anyhow. Robustify the code by not assuming this; this has the beneficial side effect of allowing optional code emission for fixing the above might_sleep() false positives. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: tglx@linutronix.de Cc: ilya.dryomov@inktank.com Cc: umgwanakikbuti@gmail.com Cc: Oleg Nesterov <oleg@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/20140924082241.988560063@infradead.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
* locking/Documentation: Move locking related docs into Documentation/locking/Davidlohr Bueso2014-08-131-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Specifically: Documentation/locking/lockdep-design.txt Documentation/locking/lockstat.txt Documentation/locking/mutex-design.txt Documentation/locking/rt-mutex-design.txt Documentation/locking/rt-mutex.txt Documentation/locking/spinlocks.txt Documentation/locking/ww-mutex-design.txt Signed-off-by: Davidlohr Bueso <davidlohr@hp.com> Acked-by: Randy Dunlap <rdunlap@infradead.org> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: jason.low2@hp.com Cc: aswin@hp.com Cc: Alexei Starovoitov <ast@plumgrid.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Chris Mason <clm@fb.com> Cc: Dan Streetman <ddstreet@ieee.org> Cc: David Airlie <airlied@linux.ie> Cc: Davidlohr Bueso <davidlohr@hp.com> Cc: David S. Miller <davem@davemloft.net> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Jason Low <jason.low2@hp.com> Cc: Josef Bacik <jbacik@fusionio.com> Cc: Kees Cook <keescook@chromium.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Lubomir Rintel <lkundrak@v3.sk> Cc: Masanari Iida <standby24x7@gmail.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Randy Dunlap <rdunlap@infradead.org> Cc: Tim Chen <tim.c.chen@linux.intel.com> Cc: Vineet Gupta <vgupta@synopsys.com> Cc: fengguang.wu@intel.com Link: http://lkml.kernel.org/r/1406752916-3341-6-git-send-email-davidlohr@hp.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* locking/mutexes: Refactor optimistic spinning codeDavidlohr Bueso2014-08-131-182/+214
| | | | | | | | | | | | | | | | | When we fail to acquire the mutex in the fastpath, we end up calling __mutex_lock_common(). A *lot* goes on in this function. Move out the optimistic spinning code into mutex_optimistic_spin() and simplify the former a bit. Furthermore, this is similar to what we have in rwsems. No logical changes. Signed-off-by: Davidlohr Bueso <davidlohr@hp.com> Acked-by: Jason Low <jason.low2@hp.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: aswin@hp.com Cc: mingo@kernel.org Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/1406752916-3341-4-git-send-email-davidlohr@hp.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* locking/mutexes: Document quick lock release when unlockingDavidlohr Bueso2014-08-131-2/+9
| | | | | | | | | | | | | | | | | | | | When unlocking, we always want to reach the slowpath with the lock's counter indicating it is unlocked. -- as returned by the asm fastpath call or by explicitly setting it. While doing so, at least in theory, we can optimize and allow faster lock stealing. When unlocking, we always want to reach the slowpath with the lock's counter indicating it is unlocked. -- as returned by the asm fastpath call or by explicitly setting it. While doing so, at least in theory, we can optimize and allow faster lock stealing. Signed-off-by: Davidlohr Bueso <davidlohr@hp.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: jason.low2@hp.com Cc: aswin@hp.com Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/1406752916-3341-2-git-send-email-davidlohr@hp.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* locking/mutexes: Standardize arguments in lock/unlock slowpathsDavidlohr Bueso2014-08-131-3/+4
| | | | | | | | | | | | | | | | | Just how the locking-end behaves, when unlocking, go ahead and obtain the proper data structure immediately after the previous (asm-end) call exits and there are (probably) pending waiters. This simplifies a bit some of the layering. Signed-off-by: Davidlohr Bueso <davidlohr@hp.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: jason.low2@hp.com Cc: aswin@hp.com Cc: mingo@kernel.org Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: linux-kernel@vger.kernel.org Link: http://lkml.kernel.org/r/1406752916-3341-1-git-send-email-davidlohr@hp.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* arch, locking: Ciao arch_mutex_cpu_relax()Davidlohr Bueso2014-07-171-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The arch_mutex_cpu_relax() function, introduced by 34b133f, is hacky and ugly. It was added a few years ago to address the fact that common cpu_relax() calls include yielding on s390, and thus impact the optimistic spinning functionality of mutexes. Nowadays we use this function well beyond mutexes: rwsem, qrwlock, mcs and lockref. Since the macro that defines the call is in the mutex header, any users must include mutex.h and the naming is misleading as well. This patch (i) renames the call to cpu_relax_lowlatency ("relax, but only if you can do it with very low latency") and (ii) defines it in each arch's asm/processor.h local header, just like for regular cpu_relax functions. On all archs, except s390, cpu_relax_lowlatency is simply cpu_relax, and thus we can take it out of mutex.h. While this can seem redundant, I believe it is a good choice as it allows us to move out arch specific logic from generic locking primitives and enables future(?) archs to transparently define it, similarly to System Z. Signed-off-by: Davidlohr Bueso <davidlohr@hp.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Anton Blanchard <anton@samba.org> Cc: Aurelien Jacquiot <a-jacquiot@ti.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Bharat Bhushan <r65777@freescale.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Chen Liqin <liqin.linux@gmail.com> Cc: Chris Metcalf <cmetcalf@tilera.com> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Cc: Chris Zankel <chris@zankel.net> Cc: David Howells <dhowells@redhat.com> Cc: David S. Miller <davem@davemloft.net> Cc: Deepthi Dharwar <deepthi@linux.vnet.ibm.com> Cc: Dominik Dingel <dingel@linux.vnet.ibm.com> Cc: Fenghua Yu <fenghua.yu@intel.com> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Guan Xuetao <gxt@mprc.pku.edu.cn> Cc: Haavard Skinnemoen <hskinnemoen@gmail.com> Cc: Hans-Christian Egtvedt <egtvedt@samfundet.no> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Helge Deller <deller@gmx.de> Cc: Hirokazu Takata <takata@linux-m32r.org> Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru> Cc: James E.J. Bottomley <jejb@parisc-linux.org> Cc: James Hogan <james.hogan@imgtec.com> Cc: Jason Wang <jasowang@redhat.com> Cc: Jesper Nilsson <jesper.nilsson@axis.com> Cc: Joe Perches <joe@perches.com> Cc: Jonas Bonn <jonas@southpole.se> Cc: Joseph Myers <joseph@codesourcery.com> Cc: Kees Cook <keescook@chromium.org> Cc: Koichi Yasutake <yasutake.koichi@jp.panasonic.com> Cc: Lennox Wu <lennox.wu@gmail.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mark Salter <msalter@redhat.com> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Matt Turner <mattst88@gmail.com> Cc: Max Filippov <jcmvbkbc@gmail.com> Cc: Michael Neuling <mikey@neuling.org> Cc: Michal Simek <monstr@monstr.eu> Cc: Mikael Starvik <starvik@axis.com> Cc: Nicolas Pitre <nico@linaro.org> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Paul Burton <paul.burton@imgtec.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Paul Mackerras <paulus@samba.org> Cc: Qais Yousef <qais.yousef@imgtec.com> Cc: Qiaowei Ren <qiaowei.ren@intel.com> Cc: Rafael Wysocki <rafael.j.wysocki@intel.com> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Richard Henderson <rth@twiddle.net> Cc: Richard Kuo <rkuo@codeaurora.org> Cc: Russell King <linux@arm.linux.org.uk> Cc: Steven Miao <realmz6@gmail.com> Cc: Steven Rostedt <srostedt@redhat.com> Cc: Stratos Karafotis <stratosk@semaphore.gr> Cc: Tim Chen <tim.c.chen@linux.intel.com> Cc: Tony Luck <tony.luck@intel.com> Cc: Vasily Kulikov <segoon@openwall.com> Cc: Vineet Gupta <vgupta@synopsys.com> Cc: Vineet Gupta <Vineet.Gupta1@synopsys.com> Cc: Waiman Long <Waiman.Long@hp.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Wolfram Sang <wsa@the-dreams.de> Cc: adi-buildroot-devel@lists.sourceforge.net Cc: linux390@de.ibm.com Cc: linux-alpha@vger.kernel.org Cc: linux-am33-list@redhat.com Cc: linux-arm-kernel@lists.infradead.org Cc: linux-c6x-dev@linux-c6x.org Cc: linux-cris-kernel@axis.com Cc: linux-hexagon@vger.kernel.org Cc: linux-ia64@vger.kernel.org Cc: linux@lists.openrisc.net Cc: linux-m32r-ja@ml.linux-m32r.org Cc: linux-m32r@ml.linux-m32r.org Cc: linux-m68k@lists.linux-m68k.org Cc: linux-metag@vger.kernel.org Cc: linux-mips@linux-mips.org Cc: linux-parisc@vger.kernel.org Cc: linuxppc-dev@lists.ozlabs.org Cc: linux-s390@vger.kernel.org Cc: linux-sh@vger.kernel.org Cc: linux-xtensa@linux-xtensa.org Cc: sparclinux@vger.kernel.org Link: http://lkml.kernel.org/r/1404079773.2619.4.camel@buesod1.americas.hpqcorp.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
* Merge branch 'locking/urgent' into locking/core, before applying larger ↵Ingo Molnar2014-07-171-1/+1
|\ | | | | | | | | | | changes and to refresh the branch with fixes Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * locking/spinlocks/mcs: Introduce and use init macro and function for osq locksJason Low2014-07-161-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Currently, we initialize the osq lock by directly setting the lock's values. It would be preferable if we use an init macro to do the initialization like we do with other locks. This patch introduces and uses a macro and function for initializing the osq lock. Signed-off-by: Jason Low <jason.low2@hp.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: Scott Norton <scott.norton@hp.com> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: Dave Chinner <david@fromorbit.com> Cc: Waiman Long <waiman.long@hp.com> Cc: Davidlohr Bueso <davidlohr@hp.com> Cc: Rik van Riel <riel@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Tim Chen <tim.c.chen@linux.intel.com> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: Aswin Chandramouleeswaran <aswin@hp.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Chris Mason <clm@fb.com> Cc: Josef Bacik <jbacik@fusionio.com> Link: http://lkml.kernel.org/r/1405358872-3732-4-git-send-email-jason.low2@hp.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
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