2 * kernel/locking/mutex.c
4 * Mutexes: blocking mutual exclusion locks
6 * Started by Ingo Molnar:
8 * Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
10 * Many thanks to Arjan van de Ven, Thomas Gleixner, Steven Rostedt and
11 * David Howells for suggestions and improvements.
13 * - Adaptive spinning for mutexes by Peter Zijlstra. (Ported to mainline
14 * from the -rt tree, where it was originally implemented for rtmutexes
15 * by Steven Rostedt, based on work by Gregory Haskins, Peter Morreale
18 * Also see Documentation/locking/mutex-design.txt.
20 #include <linux/mutex.h>
21 #include <linux/ww_mutex.h>
22 #include <linux/sched/signal.h>
23 #include <linux/sched/rt.h>
24 #include <linux/sched/wake_q.h>
25 #include <linux/export.h>
26 #include <linux/spinlock.h>
27 #include <linux/interrupt.h>
28 #include <linux/debug_locks.h>
29 #include <linux/osq_lock.h>
31 #ifdef CONFIG_DEBUG_MUTEXES
32 # include "mutex-debug.h"
38 __mutex_init(struct mutex *lock, const char *name, struct lock_class_key *key)
40 atomic_long_set(&lock->owner, 0);
41 spin_lock_init(&lock->wait_lock);
42 INIT_LIST_HEAD(&lock->wait_list);
43 #ifdef CONFIG_MUTEX_SPIN_ON_OWNER
44 osq_lock_init(&lock->osq);
47 debug_mutex_init(lock, name, key);
49 EXPORT_SYMBOL(__mutex_init);
52 * @owner: contains: 'struct task_struct *' to the current lock owner,
53 * NULL means not owned. Since task_struct pointers are aligned at
54 * at least L1_CACHE_BYTES, we have low bits to store extra state.
56 * Bit0 indicates a non-empty waiter list; unlock must issue a wakeup.
57 * Bit1 indicates unlock needs to hand the lock to the top-waiter
58 * Bit2 indicates handoff has been done and we're waiting for pickup.
60 #define MUTEX_FLAG_WAITERS 0x01
61 #define MUTEX_FLAG_HANDOFF 0x02
62 #define MUTEX_FLAG_PICKUP 0x04
64 #define MUTEX_FLAGS 0x07
66 static inline struct task_struct *__owner_task(unsigned long owner)
68 return (struct task_struct *)(owner & ~MUTEX_FLAGS);
71 static inline unsigned long __owner_flags(unsigned long owner)
73 return owner & MUTEX_FLAGS;
77 * Trylock variant that retuns the owning task on failure.
79 static inline struct task_struct *__mutex_trylock_or_owner(struct mutex *lock)
81 unsigned long owner, curr = (unsigned long)current;
83 owner = atomic_long_read(&lock->owner);
84 for (;;) { /* must loop, can race against a flag */
85 unsigned long old, flags = __owner_flags(owner);
86 unsigned long task = owner & ~MUTEX_FLAGS;
89 if (likely(task != curr))
92 if (likely(!(flags & MUTEX_FLAG_PICKUP)))
95 flags &= ~MUTEX_FLAG_PICKUP;
97 #ifdef CONFIG_DEBUG_MUTEXES
98 DEBUG_LOCKS_WARN_ON(flags & MUTEX_FLAG_PICKUP);
103 * We set the HANDOFF bit, we must make sure it doesn't live
104 * past the point where we acquire it. This would be possible
105 * if we (accidentally) set the bit on an unlocked mutex.
107 flags &= ~MUTEX_FLAG_HANDOFF;
109 old = atomic_long_cmpxchg_acquire(&lock->owner, owner, curr | flags);
116 return __owner_task(owner);
120 * Actual trylock that will work on any unlocked state.
122 static inline bool __mutex_trylock(struct mutex *lock)
124 return !__mutex_trylock_or_owner(lock);
127 #ifndef CONFIG_DEBUG_LOCK_ALLOC
129 * Lockdep annotations are contained to the slow paths for simplicity.
130 * There is nothing that would stop spreading the lockdep annotations outwards
135 * Optimistic trylock that only works in the uncontended case. Make sure to
136 * follow with a __mutex_trylock() before failing.
138 static __always_inline bool __mutex_trylock_fast(struct mutex *lock)
140 unsigned long curr = (unsigned long)current;
142 if (!atomic_long_cmpxchg_acquire(&lock->owner, 0UL, curr))
148 static __always_inline bool __mutex_unlock_fast(struct mutex *lock)
150 unsigned long curr = (unsigned long)current;
152 if (atomic_long_cmpxchg_release(&lock->owner, curr, 0UL) == curr)
159 static inline void __mutex_set_flag(struct mutex *lock, unsigned long flag)
161 atomic_long_or(flag, &lock->owner);
164 static inline void __mutex_clear_flag(struct mutex *lock, unsigned long flag)
166 atomic_long_andnot(flag, &lock->owner);
169 static inline bool __mutex_waiter_is_first(struct mutex *lock, struct mutex_waiter *waiter)
171 return list_first_entry(&lock->wait_list, struct mutex_waiter, list) == waiter;
175 * Give up ownership to a specific task, when @task = NULL, this is equivalent
176 * to a regular unlock. Sets PICKUP on a handoff, clears HANDOF, preserves
177 * WAITERS. Provides RELEASE semantics like a regular unlock, the
178 * __mutex_trylock() provides a matching ACQUIRE semantics for the handoff.
180 static void __mutex_handoff(struct mutex *lock, struct task_struct *task)
182 unsigned long owner = atomic_long_read(&lock->owner);
185 unsigned long old, new;
187 #ifdef CONFIG_DEBUG_MUTEXES
188 DEBUG_LOCKS_WARN_ON(__owner_task(owner) != current);
189 DEBUG_LOCKS_WARN_ON(owner & MUTEX_FLAG_PICKUP);
192 new = (owner & MUTEX_FLAG_WAITERS);
193 new |= (unsigned long)task;
195 new |= MUTEX_FLAG_PICKUP;
197 old = atomic_long_cmpxchg_release(&lock->owner, owner, new);
205 #ifndef CONFIG_DEBUG_LOCK_ALLOC
207 * We split the mutex lock/unlock logic into separate fastpath and
208 * slowpath functions, to reduce the register pressure on the fastpath.
209 * We also put the fastpath first in the kernel image, to make sure the
210 * branch is predicted by the CPU as default-untaken.
212 static void __sched __mutex_lock_slowpath(struct mutex *lock);
215 * mutex_lock - acquire the mutex
216 * @lock: the mutex to be acquired
218 * Lock the mutex exclusively for this task. If the mutex is not
219 * available right now, it will sleep until it can get it.
221 * The mutex must later on be released by the same task that
222 * acquired it. Recursive locking is not allowed. The task
223 * may not exit without first unlocking the mutex. Also, kernel
224 * memory where the mutex resides must not be freed with
225 * the mutex still locked. The mutex must first be initialized
226 * (or statically defined) before it can be locked. memset()-ing
227 * the mutex to 0 is not allowed.
229 * ( The CONFIG_DEBUG_MUTEXES .config option turns on debugging
230 * checks that will enforce the restrictions and will also do
231 * deadlock debugging. )
233 * This function is similar to (but not equivalent to) down().
235 void __sched mutex_lock(struct mutex *lock)
239 if (!__mutex_trylock_fast(lock))
240 __mutex_lock_slowpath(lock);
242 EXPORT_SYMBOL(mutex_lock);
245 static __always_inline void
246 ww_mutex_lock_acquired(struct ww_mutex *ww, struct ww_acquire_ctx *ww_ctx)
248 #ifdef CONFIG_DEBUG_MUTEXES
250 * If this WARN_ON triggers, you used ww_mutex_lock to acquire,
251 * but released with a normal mutex_unlock in this call.
253 * This should never happen, always use ww_mutex_unlock.
255 DEBUG_LOCKS_WARN_ON(ww->ctx);
258 * Not quite done after calling ww_acquire_done() ?
260 DEBUG_LOCKS_WARN_ON(ww_ctx->done_acquire);
262 if (ww_ctx->contending_lock) {
264 * After -EDEADLK you tried to
265 * acquire a different ww_mutex? Bad!
267 DEBUG_LOCKS_WARN_ON(ww_ctx->contending_lock != ww);
270 * You called ww_mutex_lock after receiving -EDEADLK,
271 * but 'forgot' to unlock everything else first?
273 DEBUG_LOCKS_WARN_ON(ww_ctx->acquired > 0);
274 ww_ctx->contending_lock = NULL;
278 * Naughty, using a different class will lead to undefined behavior!
280 DEBUG_LOCKS_WARN_ON(ww_ctx->ww_class != ww->ww_class);
285 static inline bool __sched
286 __ww_ctx_stamp_after(struct ww_acquire_ctx *a, struct ww_acquire_ctx *b)
288 return a->stamp - b->stamp <= LONG_MAX &&
289 (a->stamp != b->stamp || a > b);
293 * Wake up any waiters that may have to back off when the lock is held by the
296 * Due to the invariants on the wait list, this can only affect the first
297 * waiter with a context.
299 * The current task must not be on the wait list.
302 __ww_mutex_wakeup_for_backoff(struct mutex *lock, struct ww_acquire_ctx *ww_ctx)
304 struct mutex_waiter *cur;
306 lockdep_assert_held(&lock->wait_lock);
308 list_for_each_entry(cur, &lock->wait_list, list) {
312 if (cur->ww_ctx->acquired > 0 &&
313 __ww_ctx_stamp_after(cur->ww_ctx, ww_ctx)) {
314 debug_mutex_wake_waiter(lock, cur);
315 wake_up_process(cur->task);
323 * After acquiring lock with fastpath or when we lost out in contested
324 * slowpath, set ctx and wake up any waiters so they can recheck.
326 static __always_inline void
327 ww_mutex_set_context_fastpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
329 ww_mutex_lock_acquired(lock, ctx);
334 * The lock->ctx update should be visible on all cores before
335 * the atomic read is done, otherwise contended waiters might be
336 * missed. The contended waiters will either see ww_ctx == NULL
337 * and keep spinning, or it will acquire wait_lock, add itself
338 * to waiter list and sleep.
343 * Check if lock is contended, if not there is nobody to wake up
345 if (likely(!(atomic_long_read(&lock->base.owner) & MUTEX_FLAG_WAITERS)))
349 * Uh oh, we raced in fastpath, wake up everyone in this case,
350 * so they can see the new lock->ctx.
352 spin_lock(&lock->base.wait_lock);
353 __ww_mutex_wakeup_for_backoff(&lock->base, ctx);
354 spin_unlock(&lock->base.wait_lock);
358 * After acquiring lock in the slowpath set ctx.
360 * Unlike for the fast path, the caller ensures that waiters are woken up where
363 * Callers must hold the mutex wait_lock.
365 static __always_inline void
366 ww_mutex_set_context_slowpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
368 ww_mutex_lock_acquired(lock, ctx);
372 #ifdef CONFIG_MUTEX_SPIN_ON_OWNER
375 bool ww_mutex_spin_on_owner(struct mutex *lock, struct ww_acquire_ctx *ww_ctx,
376 struct mutex_waiter *waiter)
380 ww = container_of(lock, struct ww_mutex, base);
383 * If ww->ctx is set the contents are undefined, only
384 * by acquiring wait_lock there is a guarantee that
385 * they are not invalid when reading.
387 * As such, when deadlock detection needs to be
388 * performed the optimistic spinning cannot be done.
390 * Check this in every inner iteration because we may
391 * be racing against another thread's ww_mutex_lock.
393 if (ww_ctx->acquired > 0 && READ_ONCE(ww->ctx))
397 * If we aren't on the wait list yet, cancel the spin
398 * if there are waiters. We want to avoid stealing the
399 * lock from a waiter with an earlier stamp, since the
400 * other thread may already own a lock that we also
403 if (!waiter && (atomic_long_read(&lock->owner) & MUTEX_FLAG_WAITERS))
407 * Similarly, stop spinning if we are no longer the
410 if (waiter && !__mutex_waiter_is_first(lock, waiter))
417 * Look out! "owner" is an entirely speculative pointer access and not
420 * "noinline" so that this function shows up on perf profiles.
423 bool mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner,
424 struct ww_acquire_ctx *ww_ctx, struct mutex_waiter *waiter)
429 while (__mutex_owner(lock) == owner) {
431 * Ensure we emit the owner->on_cpu, dereference _after_
432 * checking lock->owner still matches owner. If that fails,
433 * owner might point to freed memory. If it still matches,
434 * the rcu_read_lock() ensures the memory stays valid.
439 * Use vcpu_is_preempted to detect lock holder preemption issue.
441 if (!owner->on_cpu || need_resched() ||
442 vcpu_is_preempted(task_cpu(owner))) {
447 if (ww_ctx && !ww_mutex_spin_on_owner(lock, ww_ctx, waiter)) {
460 * Initial check for entering the mutex spinning loop
462 static inline int mutex_can_spin_on_owner(struct mutex *lock)
464 struct task_struct *owner;
471 owner = __mutex_owner(lock);
474 * As lock holder preemption issue, we both skip spinning if task is not
475 * on cpu or its cpu is preempted
478 retval = owner->on_cpu && !vcpu_is_preempted(task_cpu(owner));
482 * If lock->owner is not set, the mutex has been released. Return true
483 * such that we'll trylock in the spin path, which is a faster option
484 * than the blocking slow path.
490 * Optimistic spinning.
492 * We try to spin for acquisition when we find that the lock owner
493 * is currently running on a (different) CPU and while we don't
494 * need to reschedule. The rationale is that if the lock owner is
495 * running, it is likely to release the lock soon.
497 * The mutex spinners are queued up using MCS lock so that only one
498 * spinner can compete for the mutex. However, if mutex spinning isn't
499 * going to happen, there is no point in going through the lock/unlock
502 * Returns true when the lock was taken, otherwise false, indicating
503 * that we need to jump to the slowpath and sleep.
505 * The waiter flag is set to true if the spinner is a waiter in the wait
506 * queue. The waiter-spinner will spin on the lock directly and concurrently
507 * with the spinner at the head of the OSQ, if present, until the owner is
510 static __always_inline bool
511 mutex_optimistic_spin(struct mutex *lock, struct ww_acquire_ctx *ww_ctx,
512 const bool use_ww_ctx, struct mutex_waiter *waiter)
516 * The purpose of the mutex_can_spin_on_owner() function is
517 * to eliminate the overhead of osq_lock() and osq_unlock()
518 * in case spinning isn't possible. As a waiter-spinner
519 * is not going to take OSQ lock anyway, there is no need
520 * to call mutex_can_spin_on_owner().
522 if (!mutex_can_spin_on_owner(lock))
526 * In order to avoid a stampede of mutex spinners trying to
527 * acquire the mutex all at once, the spinners need to take a
528 * MCS (queued) lock first before spinning on the owner field.
530 if (!osq_lock(&lock->osq))
535 struct task_struct *owner;
537 /* Try to acquire the mutex... */
538 owner = __mutex_trylock_or_owner(lock);
543 * There's an owner, wait for it to either
544 * release the lock or go to sleep.
546 if (!mutex_spin_on_owner(lock, owner, ww_ctx, waiter))
550 * The cpu_relax() call is a compiler barrier which forces
551 * everything in this loop to be re-loaded. We don't need
552 * memory barriers as we'll eventually observe the right
553 * values at the cost of a few extra spins.
559 osq_unlock(&lock->osq);
566 osq_unlock(&lock->osq);
570 * If we fell out of the spin path because of need_resched(),
571 * reschedule now, before we try-lock the mutex. This avoids getting
572 * scheduled out right after we obtained the mutex.
574 if (need_resched()) {
576 * We _should_ have TASK_RUNNING here, but just in case
577 * we do not, make it so, otherwise we might get stuck.
579 __set_current_state(TASK_RUNNING);
580 schedule_preempt_disabled();
586 static __always_inline bool
587 mutex_optimistic_spin(struct mutex *lock, struct ww_acquire_ctx *ww_ctx,
588 const bool use_ww_ctx, struct mutex_waiter *waiter)
594 static noinline void __sched __mutex_unlock_slowpath(struct mutex *lock, unsigned long ip);
597 * mutex_unlock - release the mutex
598 * @lock: the mutex to be released
600 * Unlock a mutex that has been locked by this task previously.
602 * This function must not be used in interrupt context. Unlocking
603 * of a not locked mutex is not allowed.
605 * This function is similar to (but not equivalent to) up().
607 void __sched mutex_unlock(struct mutex *lock)
609 #ifndef CONFIG_DEBUG_LOCK_ALLOC
610 if (__mutex_unlock_fast(lock))
613 __mutex_unlock_slowpath(lock, _RET_IP_);
615 EXPORT_SYMBOL(mutex_unlock);
618 * ww_mutex_unlock - release the w/w mutex
619 * @lock: the mutex to be released
621 * Unlock a mutex that has been locked by this task previously with any of the
622 * ww_mutex_lock* functions (with or without an acquire context). It is
623 * forbidden to release the locks after releasing the acquire context.
625 * This function must not be used in interrupt context. Unlocking
626 * of a unlocked mutex is not allowed.
628 void __sched ww_mutex_unlock(struct ww_mutex *lock)
631 * The unlocking fastpath is the 0->1 transition from 'locked'
632 * into 'unlocked' state:
635 #ifdef CONFIG_DEBUG_MUTEXES
636 DEBUG_LOCKS_WARN_ON(!lock->ctx->acquired);
638 if (lock->ctx->acquired > 0)
639 lock->ctx->acquired--;
643 mutex_unlock(&lock->base);
645 EXPORT_SYMBOL(ww_mutex_unlock);
647 static inline int __sched
648 __ww_mutex_lock_check_stamp(struct mutex *lock, struct mutex_waiter *waiter,
649 struct ww_acquire_ctx *ctx)
651 struct ww_mutex *ww = container_of(lock, struct ww_mutex, base);
652 struct ww_acquire_ctx *hold_ctx = READ_ONCE(ww->ctx);
653 struct mutex_waiter *cur;
655 if (hold_ctx && __ww_ctx_stamp_after(ctx, hold_ctx))
659 * If there is a waiter in front of us that has a context, then its
660 * stamp is earlier than ours and we must back off.
663 list_for_each_entry_continue_reverse(cur, &lock->wait_list, list) {
671 #ifdef CONFIG_DEBUG_MUTEXES
672 DEBUG_LOCKS_WARN_ON(ctx->contending_lock);
673 ctx->contending_lock = ww;
678 static inline int __sched
679 __ww_mutex_add_waiter(struct mutex_waiter *waiter,
681 struct ww_acquire_ctx *ww_ctx)
683 struct mutex_waiter *cur;
684 struct list_head *pos;
687 list_add_tail(&waiter->list, &lock->wait_list);
692 * Add the waiter before the first waiter with a higher stamp.
693 * Waiters without a context are skipped to avoid starving
696 pos = &lock->wait_list;
697 list_for_each_entry_reverse(cur, &lock->wait_list, list) {
701 if (__ww_ctx_stamp_after(ww_ctx, cur->ww_ctx)) {
702 /* Back off immediately if necessary. */
703 if (ww_ctx->acquired > 0) {
704 #ifdef CONFIG_DEBUG_MUTEXES
707 ww = container_of(lock, struct ww_mutex, base);
708 DEBUG_LOCKS_WARN_ON(ww_ctx->contending_lock);
709 ww_ctx->contending_lock = ww;
720 * Wake up the waiter so that it gets a chance to back
723 if (cur->ww_ctx->acquired > 0) {
724 debug_mutex_wake_waiter(lock, cur);
725 wake_up_process(cur->task);
729 list_add_tail(&waiter->list, pos);
734 * Lock a mutex (possibly interruptible), slowpath:
736 static __always_inline int __sched
737 __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
738 struct lockdep_map *nest_lock, unsigned long ip,
739 struct ww_acquire_ctx *ww_ctx, const bool use_ww_ctx)
741 struct mutex_waiter waiter;
748 ww = container_of(lock, struct ww_mutex, base);
749 if (use_ww_ctx && ww_ctx) {
750 if (unlikely(ww_ctx == READ_ONCE(ww->ctx)))
755 mutex_acquire_nest(&lock->dep_map, subclass, 0, nest_lock, ip);
757 if (__mutex_trylock(lock) ||
758 mutex_optimistic_spin(lock, ww_ctx, use_ww_ctx, NULL)) {
759 /* got the lock, yay! */
760 lock_acquired(&lock->dep_map, ip);
761 if (use_ww_ctx && ww_ctx)
762 ww_mutex_set_context_fastpath(ww, ww_ctx);
767 spin_lock(&lock->wait_lock);
769 * After waiting to acquire the wait_lock, try again.
771 if (__mutex_trylock(lock)) {
772 if (use_ww_ctx && ww_ctx)
773 __ww_mutex_wakeup_for_backoff(lock, ww_ctx);
778 debug_mutex_lock_common(lock, &waiter);
779 debug_mutex_add_waiter(lock, &waiter, current);
781 lock_contended(&lock->dep_map, ip);
784 /* add waiting tasks to the end of the waitqueue (FIFO): */
785 list_add_tail(&waiter.list, &lock->wait_list);
787 #ifdef CONFIG_DEBUG_MUTEXES
788 waiter.ww_ctx = MUTEX_POISON_WW_CTX;
791 /* Add in stamp order, waking up waiters that must back off. */
792 ret = __ww_mutex_add_waiter(&waiter, lock, ww_ctx);
794 goto err_early_backoff;
796 waiter.ww_ctx = ww_ctx;
799 waiter.task = current;
801 if (__mutex_waiter_is_first(lock, &waiter))
802 __mutex_set_flag(lock, MUTEX_FLAG_WAITERS);
804 set_current_state(state);
807 * Once we hold wait_lock, we're serialized against
808 * mutex_unlock() handing the lock off to us, do a trylock
809 * before testing the error conditions to make sure we pick up
812 if (__mutex_trylock(lock))
816 * Check for signals and wound conditions while holding
817 * wait_lock. This ensures the lock cancellation is ordered
818 * against mutex_unlock() and wake-ups do not go missing.
820 if (unlikely(signal_pending_state(state, current))) {
825 if (use_ww_ctx && ww_ctx && ww_ctx->acquired > 0) {
826 ret = __ww_mutex_lock_check_stamp(lock, &waiter, ww_ctx);
831 spin_unlock(&lock->wait_lock);
832 schedule_preempt_disabled();
835 * ww_mutex needs to always recheck its position since its waiter
836 * list is not FIFO ordered.
838 if ((use_ww_ctx && ww_ctx) || !first) {
839 first = __mutex_waiter_is_first(lock, &waiter);
841 __mutex_set_flag(lock, MUTEX_FLAG_HANDOFF);
844 set_current_state(state);
846 * Here we order against unlock; we must either see it change
847 * state back to RUNNING and fall through the next schedule(),
848 * or we must see its unlock and acquire.
850 if (__mutex_trylock(lock) ||
851 (first && mutex_optimistic_spin(lock, ww_ctx, use_ww_ctx, &waiter)))
854 spin_lock(&lock->wait_lock);
856 spin_lock(&lock->wait_lock);
858 __set_current_state(TASK_RUNNING);
860 mutex_remove_waiter(lock, &waiter, current);
861 if (likely(list_empty(&lock->wait_list)))
862 __mutex_clear_flag(lock, MUTEX_FLAGS);
864 debug_mutex_free_waiter(&waiter);
867 /* got the lock - cleanup and rejoice! */
868 lock_acquired(&lock->dep_map, ip);
870 if (use_ww_ctx && ww_ctx)
871 ww_mutex_set_context_slowpath(ww, ww_ctx);
873 spin_unlock(&lock->wait_lock);
878 __set_current_state(TASK_RUNNING);
879 mutex_remove_waiter(lock, &waiter, current);
881 spin_unlock(&lock->wait_lock);
882 debug_mutex_free_waiter(&waiter);
883 mutex_release(&lock->dep_map, 1, ip);
889 __mutex_lock(struct mutex *lock, long state, unsigned int subclass,
890 struct lockdep_map *nest_lock, unsigned long ip)
892 return __mutex_lock_common(lock, state, subclass, nest_lock, ip, NULL, false);
896 __ww_mutex_lock(struct mutex *lock, long state, unsigned int subclass,
897 struct lockdep_map *nest_lock, unsigned long ip,
898 struct ww_acquire_ctx *ww_ctx)
900 return __mutex_lock_common(lock, state, subclass, nest_lock, ip, ww_ctx, true);
903 #ifdef CONFIG_DEBUG_LOCK_ALLOC
905 mutex_lock_nested(struct mutex *lock, unsigned int subclass)
907 __mutex_lock(lock, TASK_UNINTERRUPTIBLE, subclass, NULL, _RET_IP_);
910 EXPORT_SYMBOL_GPL(mutex_lock_nested);
913 _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest)
915 __mutex_lock(lock, TASK_UNINTERRUPTIBLE, 0, nest, _RET_IP_);
917 EXPORT_SYMBOL_GPL(_mutex_lock_nest_lock);
920 mutex_lock_killable_nested(struct mutex *lock, unsigned int subclass)
922 return __mutex_lock(lock, TASK_KILLABLE, subclass, NULL, _RET_IP_);
924 EXPORT_SYMBOL_GPL(mutex_lock_killable_nested);
927 mutex_lock_interruptible_nested(struct mutex *lock, unsigned int subclass)
929 return __mutex_lock(lock, TASK_INTERRUPTIBLE, subclass, NULL, _RET_IP_);
931 EXPORT_SYMBOL_GPL(mutex_lock_interruptible_nested);
934 mutex_lock_io_nested(struct mutex *lock, unsigned int subclass)
940 token = io_schedule_prepare();
941 __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE,
942 subclass, NULL, _RET_IP_, NULL, 0);
943 io_schedule_finish(token);
945 EXPORT_SYMBOL_GPL(mutex_lock_io_nested);
948 ww_mutex_deadlock_injection(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
950 #ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH
953 if (ctx->deadlock_inject_countdown-- == 0) {
954 tmp = ctx->deadlock_inject_interval;
955 if (tmp > UINT_MAX/4)
958 tmp = tmp*2 + tmp + tmp/2;
960 ctx->deadlock_inject_interval = tmp;
961 ctx->deadlock_inject_countdown = tmp;
962 ctx->contending_lock = lock;
964 ww_mutex_unlock(lock);
974 ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
979 ret = __ww_mutex_lock(&lock->base, TASK_UNINTERRUPTIBLE,
980 0, ctx ? &ctx->dep_map : NULL, _RET_IP_,
982 if (!ret && ctx && ctx->acquired > 1)
983 return ww_mutex_deadlock_injection(lock, ctx);
987 EXPORT_SYMBOL_GPL(ww_mutex_lock);
990 ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
995 ret = __ww_mutex_lock(&lock->base, TASK_INTERRUPTIBLE,
996 0, ctx ? &ctx->dep_map : NULL, _RET_IP_,
999 if (!ret && ctx && ctx->acquired > 1)
1000 return ww_mutex_deadlock_injection(lock, ctx);
1004 EXPORT_SYMBOL_GPL(ww_mutex_lock_interruptible);
1009 * Release the lock, slowpath:
1011 static noinline void __sched __mutex_unlock_slowpath(struct mutex *lock, unsigned long ip)
1013 struct task_struct *next = NULL;
1014 DEFINE_WAKE_Q(wake_q);
1015 unsigned long owner;
1017 mutex_release(&lock->dep_map, 1, ip);
1020 * Release the lock before (potentially) taking the spinlock such that
1021 * other contenders can get on with things ASAP.
1023 * Except when HANDOFF, in that case we must not clear the owner field,
1024 * but instead set it to the top waiter.
1026 owner = atomic_long_read(&lock->owner);
1030 #ifdef CONFIG_DEBUG_MUTEXES
1031 DEBUG_LOCKS_WARN_ON(__owner_task(owner) != current);
1032 DEBUG_LOCKS_WARN_ON(owner & MUTEX_FLAG_PICKUP);
1035 if (owner & MUTEX_FLAG_HANDOFF)
1038 old = atomic_long_cmpxchg_release(&lock->owner, owner,
1039 __owner_flags(owner));
1041 if (owner & MUTEX_FLAG_WAITERS)
1050 spin_lock(&lock->wait_lock);
1051 debug_mutex_unlock(lock);
1052 if (!list_empty(&lock->wait_list)) {
1053 /* get the first entry from the wait-list: */
1054 struct mutex_waiter *waiter =
1055 list_first_entry(&lock->wait_list,
1056 struct mutex_waiter, list);
1058 next = waiter->task;
1060 debug_mutex_wake_waiter(lock, waiter);
1061 wake_q_add(&wake_q, next);
1064 if (owner & MUTEX_FLAG_HANDOFF)
1065 __mutex_handoff(lock, next);
1067 spin_unlock(&lock->wait_lock);
1072 #ifndef CONFIG_DEBUG_LOCK_ALLOC
1074 * Here come the less common (and hence less performance-critical) APIs:
1075 * mutex_lock_interruptible() and mutex_trylock().
1077 static noinline int __sched
1078 __mutex_lock_killable_slowpath(struct mutex *lock);
1080 static noinline int __sched
1081 __mutex_lock_interruptible_slowpath(struct mutex *lock);
1084 * mutex_lock_interruptible - acquire the mutex, interruptible
1085 * @lock: the mutex to be acquired
1087 * Lock the mutex like mutex_lock(), and return 0 if the mutex has
1088 * been acquired or sleep until the mutex becomes available. If a
1089 * signal arrives while waiting for the lock then this function
1092 * This function is similar to (but not equivalent to) down_interruptible().
1094 int __sched mutex_lock_interruptible(struct mutex *lock)
1098 if (__mutex_trylock_fast(lock))
1101 return __mutex_lock_interruptible_slowpath(lock);
1104 EXPORT_SYMBOL(mutex_lock_interruptible);
1106 int __sched mutex_lock_killable(struct mutex *lock)
1110 if (__mutex_trylock_fast(lock))
1113 return __mutex_lock_killable_slowpath(lock);
1115 EXPORT_SYMBOL(mutex_lock_killable);
1117 void __sched mutex_lock_io(struct mutex *lock)
1121 token = io_schedule_prepare();
1123 io_schedule_finish(token);
1125 EXPORT_SYMBOL_GPL(mutex_lock_io);
1127 static noinline void __sched
1128 __mutex_lock_slowpath(struct mutex *lock)
1130 __mutex_lock(lock, TASK_UNINTERRUPTIBLE, 0, NULL, _RET_IP_);
1133 static noinline int __sched
1134 __mutex_lock_killable_slowpath(struct mutex *lock)
1136 return __mutex_lock(lock, TASK_KILLABLE, 0, NULL, _RET_IP_);
1139 static noinline int __sched
1140 __mutex_lock_interruptible_slowpath(struct mutex *lock)
1142 return __mutex_lock(lock, TASK_INTERRUPTIBLE, 0, NULL, _RET_IP_);
1145 static noinline int __sched
1146 __ww_mutex_lock_slowpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
1148 return __ww_mutex_lock(&lock->base, TASK_UNINTERRUPTIBLE, 0, NULL,
1152 static noinline int __sched
1153 __ww_mutex_lock_interruptible_slowpath(struct ww_mutex *lock,
1154 struct ww_acquire_ctx *ctx)
1156 return __ww_mutex_lock(&lock->base, TASK_INTERRUPTIBLE, 0, NULL,
1163 * mutex_trylock - try to acquire the mutex, without waiting
1164 * @lock: the mutex to be acquired
1166 * Try to acquire the mutex atomically. Returns 1 if the mutex
1167 * has been acquired successfully, and 0 on contention.
1169 * NOTE: this function follows the spin_trylock() convention, so
1170 * it is negated from the down_trylock() return values! Be careful
1171 * about this when converting semaphore users to mutexes.
1173 * This function must not be used in interrupt context. The
1174 * mutex must be released by the same task that acquired it.
1176 int __sched mutex_trylock(struct mutex *lock)
1178 bool locked = __mutex_trylock(lock);
1181 mutex_acquire(&lock->dep_map, 0, 1, _RET_IP_);
1185 EXPORT_SYMBOL(mutex_trylock);
1187 #ifndef CONFIG_DEBUG_LOCK_ALLOC
1189 ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
1193 if (__mutex_trylock_fast(&lock->base)) {
1195 ww_mutex_set_context_fastpath(lock, ctx);
1199 return __ww_mutex_lock_slowpath(lock, ctx);
1201 EXPORT_SYMBOL(ww_mutex_lock);
1204 ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
1208 if (__mutex_trylock_fast(&lock->base)) {
1210 ww_mutex_set_context_fastpath(lock, ctx);
1214 return __ww_mutex_lock_interruptible_slowpath(lock, ctx);
1216 EXPORT_SYMBOL(ww_mutex_lock_interruptible);
1221 * atomic_dec_and_mutex_lock - return holding mutex if we dec to 0
1222 * @cnt: the atomic which we are to dec
1223 * @lock: the mutex to return holding if we dec to 0
1225 * return true and hold lock if we dec to 0, return false otherwise
1227 int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock)
1229 /* dec if we can't possibly hit 0 */
1230 if (atomic_add_unless(cnt, -1, 1))
1232 /* we might hit 0, so take the lock */
1234 if (!atomic_dec_and_test(cnt)) {
1235 /* when we actually did the dec, we didn't hit 0 */
1239 /* we hit 0, and we hold the lock */
1242 EXPORT_SYMBOL(atomic_dec_and_mutex_lock);