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/mutex-design.txt.
20 #include <linux/mutex.h>
21 #include <linux/ww_mutex.h>
22 #include <linux/sched.h>
23 #include <linux/sched/rt.h>
24 #include <linux/export.h>
25 #include <linux/spinlock.h>
26 #include <linux/interrupt.h>
27 #include <linux/debug_locks.h>
30 * In the DEBUG case we are using the "NULL fastpath" for mutexes,
31 * which forces all calls into the slowpath:
33 #ifdef CONFIG_DEBUG_MUTEXES
34 # include "mutex-debug.h"
35 # include <asm-generic/mutex-null.h>
38 # include <asm/mutex.h>
42 * A negative mutex count indicates that waiters are sleeping waiting for the
45 #define MUTEX_SHOW_NO_WAITER(mutex) (atomic_read(&(mutex)->count) >= 0)
48 __mutex_init(struct mutex
*lock
, const char *name
, struct lock_class_key
*key
)
50 atomic_set(&lock
->count
, 1);
51 spin_lock_init(&lock
->wait_lock
);
52 INIT_LIST_HEAD(&lock
->wait_list
);
53 mutex_clear_owner(lock
);
54 #ifdef CONFIG_MUTEX_SPIN_ON_OWNER
55 lock
->spin_mlock
= NULL
;
58 debug_mutex_init(lock
, name
, key
);
61 EXPORT_SYMBOL(__mutex_init
);
63 #ifndef CONFIG_DEBUG_LOCK_ALLOC
65 * We split the mutex lock/unlock logic into separate fastpath and
66 * slowpath functions, to reduce the register pressure on the fastpath.
67 * We also put the fastpath first in the kernel image, to make sure the
68 * branch is predicted by the CPU as default-untaken.
70 static __used noinline
void __sched
71 __mutex_lock_slowpath(atomic_t
*lock_count
);
74 * mutex_lock - acquire the mutex
75 * @lock: the mutex to be acquired
77 * Lock the mutex exclusively for this task. If the mutex is not
78 * available right now, it will sleep until it can get it.
80 * The mutex must later on be released by the same task that
81 * acquired it. Recursive locking is not allowed. The task
82 * may not exit without first unlocking the mutex. Also, kernel
83 * memory where the mutex resides mutex must not be freed with
84 * the mutex still locked. The mutex must first be initialized
85 * (or statically defined) before it can be locked. memset()-ing
86 * the mutex to 0 is not allowed.
88 * ( The CONFIG_DEBUG_MUTEXES .config option turns on debugging
89 * checks that will enforce the restrictions and will also do
90 * deadlock debugging. )
92 * This function is similar to (but not equivalent to) down().
94 void __sched
mutex_lock(struct mutex
*lock
)
98 * The locking fastpath is the 1->0 transition from
99 * 'unlocked' into 'locked' state.
101 __mutex_fastpath_lock(&lock
->count
, __mutex_lock_slowpath
);
102 mutex_set_owner(lock
);
105 EXPORT_SYMBOL(mutex_lock
);
108 #ifdef CONFIG_MUTEX_SPIN_ON_OWNER
110 * In order to avoid a stampede of mutex spinners from acquiring the mutex
111 * more or less simultaneously, the spinners need to acquire a MCS lock
112 * first before spinning on the owner field.
114 * We don't inline mspin_lock() so that perf can correctly account for the
115 * time spent in this lock function.
118 struct mspin_node
*next
;
119 int locked
; /* 1 if lock acquired */
121 #define MLOCK(mutex) ((struct mspin_node **)&((mutex)->spin_mlock))
124 void mspin_lock(struct mspin_node
**lock
, struct mspin_node
*node
)
126 struct mspin_node
*prev
;
132 prev
= xchg(lock
, node
);
133 if (likely(prev
== NULL
)) {
138 ACCESS_ONCE(prev
->next
) = node
;
140 /* Wait until the lock holder passes the lock down */
141 while (!ACCESS_ONCE(node
->locked
))
142 arch_mutex_cpu_relax();
145 static void mspin_unlock(struct mspin_node
**lock
, struct mspin_node
*node
)
147 struct mspin_node
*next
= ACCESS_ONCE(node
->next
);
151 * Release the lock by setting it to NULL
153 if (cmpxchg(lock
, node
, NULL
) == node
)
155 /* Wait until the next pointer is set */
156 while (!(next
= ACCESS_ONCE(node
->next
)))
157 arch_mutex_cpu_relax();
159 ACCESS_ONCE(next
->locked
) = 1;
164 * Mutex spinning code migrated from kernel/sched/core.c
167 static inline bool owner_running(struct mutex
*lock
, struct task_struct
*owner
)
169 if (lock
->owner
!= owner
)
173 * Ensure we emit the owner->on_cpu, dereference _after_ checking
174 * lock->owner still matches owner, if that fails, owner might
175 * point to free()d memory, if it still matches, the rcu_read_lock()
176 * ensures the memory stays valid.
180 return owner
->on_cpu
;
184 * Look out! "owner" is an entirely speculative pointer
185 * access and not reliable.
188 int mutex_spin_on_owner(struct mutex
*lock
, struct task_struct
*owner
)
191 while (owner_running(lock
, owner
)) {
195 arch_mutex_cpu_relax();
200 * We break out the loop above on need_resched() and when the
201 * owner changed, which is a sign for heavy contention. Return
202 * success only when lock->owner is NULL.
204 return lock
->owner
== NULL
;
208 * Initial check for entering the mutex spinning loop
210 static inline int mutex_can_spin_on_owner(struct mutex
*lock
)
212 struct task_struct
*owner
;
216 owner
= ACCESS_ONCE(lock
->owner
);
218 retval
= owner
->on_cpu
;
221 * if lock->owner is not set, the mutex owner may have just acquired
222 * it and not set the owner yet or the mutex has been released.
228 static __used noinline
void __sched
__mutex_unlock_slowpath(atomic_t
*lock_count
);
231 * mutex_unlock - release the mutex
232 * @lock: the mutex to be released
234 * Unlock a mutex that has been locked by this task previously.
236 * This function must not be used in interrupt context. Unlocking
237 * of a not locked mutex is not allowed.
239 * This function is similar to (but not equivalent to) up().
241 void __sched
mutex_unlock(struct mutex
*lock
)
244 * The unlocking fastpath is the 0->1 transition from 'locked'
245 * into 'unlocked' state:
247 #ifndef CONFIG_DEBUG_MUTEXES
249 * When debugging is enabled we must not clear the owner before time,
250 * the slow path will always be taken, and that clears the owner field
251 * after verifying that it was indeed current.
253 mutex_clear_owner(lock
);
255 __mutex_fastpath_unlock(&lock
->count
, __mutex_unlock_slowpath
);
258 EXPORT_SYMBOL(mutex_unlock
);
261 * ww_mutex_unlock - release the w/w mutex
262 * @lock: the mutex to be released
264 * Unlock a mutex that has been locked by this task previously with any of the
265 * ww_mutex_lock* functions (with or without an acquire context). It is
266 * forbidden to release the locks after releasing the acquire context.
268 * This function must not be used in interrupt context. Unlocking
269 * of a unlocked mutex is not allowed.
271 void __sched
ww_mutex_unlock(struct ww_mutex
*lock
)
274 * The unlocking fastpath is the 0->1 transition from 'locked'
275 * into 'unlocked' state:
278 #ifdef CONFIG_DEBUG_MUTEXES
279 DEBUG_LOCKS_WARN_ON(!lock
->ctx
->acquired
);
281 if (lock
->ctx
->acquired
> 0)
282 lock
->ctx
->acquired
--;
286 #ifndef CONFIG_DEBUG_MUTEXES
288 * When debugging is enabled we must not clear the owner before time,
289 * the slow path will always be taken, and that clears the owner field
290 * after verifying that it was indeed current.
292 mutex_clear_owner(&lock
->base
);
294 __mutex_fastpath_unlock(&lock
->base
.count
, __mutex_unlock_slowpath
);
296 EXPORT_SYMBOL(ww_mutex_unlock
);
298 static inline int __sched
299 __mutex_lock_check_stamp(struct mutex
*lock
, struct ww_acquire_ctx
*ctx
)
301 struct ww_mutex
*ww
= container_of(lock
, struct ww_mutex
, base
);
302 struct ww_acquire_ctx
*hold_ctx
= ACCESS_ONCE(ww
->ctx
);
307 if (unlikely(ctx
== hold_ctx
))
310 if (ctx
->stamp
- hold_ctx
->stamp
<= LONG_MAX
&&
311 (ctx
->stamp
!= hold_ctx
->stamp
|| ctx
> hold_ctx
)) {
312 #ifdef CONFIG_DEBUG_MUTEXES
313 DEBUG_LOCKS_WARN_ON(ctx
->contending_lock
);
314 ctx
->contending_lock
= ww
;
322 static __always_inline
void ww_mutex_lock_acquired(struct ww_mutex
*ww
,
323 struct ww_acquire_ctx
*ww_ctx
)
325 #ifdef CONFIG_DEBUG_MUTEXES
327 * If this WARN_ON triggers, you used ww_mutex_lock to acquire,
328 * but released with a normal mutex_unlock in this call.
330 * This should never happen, always use ww_mutex_unlock.
332 DEBUG_LOCKS_WARN_ON(ww
->ctx
);
335 * Not quite done after calling ww_acquire_done() ?
337 DEBUG_LOCKS_WARN_ON(ww_ctx
->done_acquire
);
339 if (ww_ctx
->contending_lock
) {
341 * After -EDEADLK you tried to
342 * acquire a different ww_mutex? Bad!
344 DEBUG_LOCKS_WARN_ON(ww_ctx
->contending_lock
!= ww
);
347 * You called ww_mutex_lock after receiving -EDEADLK,
348 * but 'forgot' to unlock everything else first?
350 DEBUG_LOCKS_WARN_ON(ww_ctx
->acquired
> 0);
351 ww_ctx
->contending_lock
= NULL
;
355 * Naughty, using a different class will lead to undefined behavior!
357 DEBUG_LOCKS_WARN_ON(ww_ctx
->ww_class
!= ww
->ww_class
);
363 * after acquiring lock with fastpath or when we lost out in contested
364 * slowpath, set ctx and wake up any waiters so they can recheck.
366 * This function is never called when CONFIG_DEBUG_LOCK_ALLOC is set,
367 * as the fastpath and opportunistic spinning are disabled in that case.
369 static __always_inline
void
370 ww_mutex_set_context_fastpath(struct ww_mutex
*lock
,
371 struct ww_acquire_ctx
*ctx
)
374 struct mutex_waiter
*cur
;
376 ww_mutex_lock_acquired(lock
, ctx
);
381 * The lock->ctx update should be visible on all cores before
382 * the atomic read is done, otherwise contended waiters might be
383 * missed. The contended waiters will either see ww_ctx == NULL
384 * and keep spinning, or it will acquire wait_lock, add itself
385 * to waiter list and sleep.
390 * Check if lock is contended, if not there is nobody to wake up
392 if (likely(atomic_read(&lock
->base
.count
) == 0))
396 * Uh oh, we raced in fastpath, wake up everyone in this case,
397 * so they can see the new lock->ctx.
399 spin_lock_mutex(&lock
->base
.wait_lock
, flags
);
400 list_for_each_entry(cur
, &lock
->base
.wait_list
, list
) {
401 debug_mutex_wake_waiter(&lock
->base
, cur
);
402 wake_up_process(cur
->task
);
404 spin_unlock_mutex(&lock
->base
.wait_lock
, flags
);
408 * Lock a mutex (possibly interruptible), slowpath:
410 static __always_inline
int __sched
411 __mutex_lock_common(struct mutex
*lock
, long state
, unsigned int subclass
,
412 struct lockdep_map
*nest_lock
, unsigned long ip
,
413 struct ww_acquire_ctx
*ww_ctx
)
415 struct task_struct
*task
= current
;
416 struct mutex_waiter waiter
;
421 mutex_acquire_nest(&lock
->dep_map
, subclass
, 0, nest_lock
, ip
);
423 #ifdef CONFIG_MUTEX_SPIN_ON_OWNER
425 * Optimistic spinning.
427 * We try to spin for acquisition when we find that there are no
428 * pending waiters and the lock owner is currently running on a
431 * The rationale is that if the lock owner is running, it is likely to
432 * release the lock soon.
434 * Since this needs the lock owner, and this mutex implementation
435 * doesn't track the owner atomically in the lock field, we need to
436 * track it non-atomically.
438 * We can't do this for DEBUG_MUTEXES because that relies on wait_lock
439 * to serialize everything.
441 * The mutex spinners are queued up using MCS lock so that only one
442 * spinner can compete for the mutex. However, if mutex spinning isn't
443 * going to happen, there is no point in going through the lock/unlock
446 if (!mutex_can_spin_on_owner(lock
))
450 struct task_struct
*owner
;
451 struct mspin_node node
;
453 if (!__builtin_constant_p(ww_ctx
== NULL
) && ww_ctx
->acquired
> 0) {
456 ww
= container_of(lock
, struct ww_mutex
, base
);
458 * If ww->ctx is set the contents are undefined, only
459 * by acquiring wait_lock there is a guarantee that
460 * they are not invalid when reading.
462 * As such, when deadlock detection needs to be
463 * performed the optimistic spinning cannot be done.
465 if (ACCESS_ONCE(ww
->ctx
))
470 * If there's an owner, wait for it to either
471 * release the lock or go to sleep.
473 mspin_lock(MLOCK(lock
), &node
);
474 owner
= ACCESS_ONCE(lock
->owner
);
475 if (owner
&& !mutex_spin_on_owner(lock
, owner
)) {
476 mspin_unlock(MLOCK(lock
), &node
);
480 if ((atomic_read(&lock
->count
) == 1) &&
481 (atomic_cmpxchg(&lock
->count
, 1, 0) == 1)) {
482 lock_acquired(&lock
->dep_map
, ip
);
483 if (!__builtin_constant_p(ww_ctx
== NULL
)) {
485 ww
= container_of(lock
, struct ww_mutex
, base
);
487 ww_mutex_set_context_fastpath(ww
, ww_ctx
);
490 mutex_set_owner(lock
);
491 mspin_unlock(MLOCK(lock
), &node
);
495 mspin_unlock(MLOCK(lock
), &node
);
498 * When there's no owner, we might have preempted between the
499 * owner acquiring the lock and setting the owner field. If
500 * we're an RT task that will live-lock because we won't let
501 * the owner complete.
503 if (!owner
&& (need_resched() || rt_task(task
)))
507 * The cpu_relax() call is a compiler barrier which forces
508 * everything in this loop to be re-loaded. We don't need
509 * memory barriers as we'll eventually observe the right
510 * values at the cost of a few extra spins.
512 arch_mutex_cpu_relax();
516 spin_lock_mutex(&lock
->wait_lock
, flags
);
518 debug_mutex_lock_common(lock
, &waiter
);
519 debug_mutex_add_waiter(lock
, &waiter
, task_thread_info(task
));
521 /* add waiting tasks to the end of the waitqueue (FIFO): */
522 list_add_tail(&waiter
.list
, &lock
->wait_list
);
525 if (MUTEX_SHOW_NO_WAITER(lock
) && (atomic_xchg(&lock
->count
, -1) == 1))
528 lock_contended(&lock
->dep_map
, ip
);
532 * Lets try to take the lock again - this is needed even if
533 * we get here for the first time (shortly after failing to
534 * acquire the lock), to make sure that we get a wakeup once
535 * it's unlocked. Later on, if we sleep, this is the
536 * operation that gives us the lock. We xchg it to -1, so
537 * that when we release the lock, we properly wake up the
540 if (MUTEX_SHOW_NO_WAITER(lock
) &&
541 (atomic_xchg(&lock
->count
, -1) == 1))
545 * got a signal? (This code gets eliminated in the
546 * TASK_UNINTERRUPTIBLE case.)
548 if (unlikely(signal_pending_state(state
, task
))) {
553 if (!__builtin_constant_p(ww_ctx
== NULL
) && ww_ctx
->acquired
> 0) {
554 ret
= __mutex_lock_check_stamp(lock
, ww_ctx
);
559 __set_task_state(task
, state
);
561 /* didn't get the lock, go to sleep: */
562 spin_unlock_mutex(&lock
->wait_lock
, flags
);
563 schedule_preempt_disabled();
564 spin_lock_mutex(&lock
->wait_lock
, flags
);
568 lock_acquired(&lock
->dep_map
, ip
);
569 /* got the lock - rejoice! */
570 mutex_remove_waiter(lock
, &waiter
, current_thread_info());
571 mutex_set_owner(lock
);
573 if (!__builtin_constant_p(ww_ctx
== NULL
)) {
574 struct ww_mutex
*ww
= container_of(lock
,
577 struct mutex_waiter
*cur
;
580 * This branch gets optimized out for the common case,
581 * and is only important for ww_mutex_lock.
584 ww_mutex_lock_acquired(ww
, ww_ctx
);
588 * Give any possible sleeping processes the chance to wake up,
589 * so they can recheck if they have to back off.
591 list_for_each_entry(cur
, &lock
->wait_list
, list
) {
592 debug_mutex_wake_waiter(lock
, cur
);
593 wake_up_process(cur
->task
);
597 /* set it to 0 if there are no waiters left: */
598 if (likely(list_empty(&lock
->wait_list
)))
599 atomic_set(&lock
->count
, 0);
601 spin_unlock_mutex(&lock
->wait_lock
, flags
);
603 debug_mutex_free_waiter(&waiter
);
609 mutex_remove_waiter(lock
, &waiter
, task_thread_info(task
));
610 spin_unlock_mutex(&lock
->wait_lock
, flags
);
611 debug_mutex_free_waiter(&waiter
);
612 mutex_release(&lock
->dep_map
, 1, ip
);
617 #ifdef CONFIG_DEBUG_LOCK_ALLOC
619 mutex_lock_nested(struct mutex
*lock
, unsigned int subclass
)
622 __mutex_lock_common(lock
, TASK_UNINTERRUPTIBLE
,
623 subclass
, NULL
, _RET_IP_
, NULL
);
626 EXPORT_SYMBOL_GPL(mutex_lock_nested
);
629 _mutex_lock_nest_lock(struct mutex
*lock
, struct lockdep_map
*nest
)
632 __mutex_lock_common(lock
, TASK_UNINTERRUPTIBLE
,
633 0, nest
, _RET_IP_
, NULL
);
636 EXPORT_SYMBOL_GPL(_mutex_lock_nest_lock
);
639 mutex_lock_killable_nested(struct mutex
*lock
, unsigned int subclass
)
642 return __mutex_lock_common(lock
, TASK_KILLABLE
,
643 subclass
, NULL
, _RET_IP_
, NULL
);
645 EXPORT_SYMBOL_GPL(mutex_lock_killable_nested
);
648 mutex_lock_interruptible_nested(struct mutex
*lock
, unsigned int subclass
)
651 return __mutex_lock_common(lock
, TASK_INTERRUPTIBLE
,
652 subclass
, NULL
, _RET_IP_
, NULL
);
655 EXPORT_SYMBOL_GPL(mutex_lock_interruptible_nested
);
658 ww_mutex_deadlock_injection(struct ww_mutex
*lock
, struct ww_acquire_ctx
*ctx
)
660 #ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH
663 if (ctx
->deadlock_inject_countdown
-- == 0) {
664 tmp
= ctx
->deadlock_inject_interval
;
665 if (tmp
> UINT_MAX
/4)
668 tmp
= tmp
*2 + tmp
+ tmp
/2;
670 ctx
->deadlock_inject_interval
= tmp
;
671 ctx
->deadlock_inject_countdown
= tmp
;
672 ctx
->contending_lock
= lock
;
674 ww_mutex_unlock(lock
);
684 __ww_mutex_lock(struct ww_mutex
*lock
, struct ww_acquire_ctx
*ctx
)
689 ret
= __mutex_lock_common(&lock
->base
, TASK_UNINTERRUPTIBLE
,
690 0, &ctx
->dep_map
, _RET_IP_
, ctx
);
691 if (!ret
&& ctx
->acquired
> 0)
692 return ww_mutex_deadlock_injection(lock
, ctx
);
696 EXPORT_SYMBOL_GPL(__ww_mutex_lock
);
699 __ww_mutex_lock_interruptible(struct ww_mutex
*lock
, struct ww_acquire_ctx
*ctx
)
704 ret
= __mutex_lock_common(&lock
->base
, TASK_INTERRUPTIBLE
,
705 0, &ctx
->dep_map
, _RET_IP_
, ctx
);
707 if (!ret
&& ctx
->acquired
> 0)
708 return ww_mutex_deadlock_injection(lock
, ctx
);
712 EXPORT_SYMBOL_GPL(__ww_mutex_lock_interruptible
);
717 * Release the lock, slowpath:
720 __mutex_unlock_common_slowpath(atomic_t
*lock_count
, int nested
)
722 struct mutex
*lock
= container_of(lock_count
, struct mutex
, count
);
725 spin_lock_mutex(&lock
->wait_lock
, flags
);
726 mutex_release(&lock
->dep_map
, nested
, _RET_IP_
);
727 debug_mutex_unlock(lock
);
730 * some architectures leave the lock unlocked in the fastpath failure
731 * case, others need to leave it locked. In the later case we have to
734 if (__mutex_slowpath_needs_to_unlock())
735 atomic_set(&lock
->count
, 1);
737 if (!list_empty(&lock
->wait_list
)) {
738 /* get the first entry from the wait-list: */
739 struct mutex_waiter
*waiter
=
740 list_entry(lock
->wait_list
.next
,
741 struct mutex_waiter
, list
);
743 debug_mutex_wake_waiter(lock
, waiter
);
745 wake_up_process(waiter
->task
);
748 spin_unlock_mutex(&lock
->wait_lock
, flags
);
752 * Release the lock, slowpath:
754 static __used noinline
void
755 __mutex_unlock_slowpath(atomic_t
*lock_count
)
757 __mutex_unlock_common_slowpath(lock_count
, 1);
760 #ifndef CONFIG_DEBUG_LOCK_ALLOC
762 * Here come the less common (and hence less performance-critical) APIs:
763 * mutex_lock_interruptible() and mutex_trylock().
765 static noinline
int __sched
766 __mutex_lock_killable_slowpath(struct mutex
*lock
);
768 static noinline
int __sched
769 __mutex_lock_interruptible_slowpath(struct mutex
*lock
);
772 * mutex_lock_interruptible - acquire the mutex, interruptible
773 * @lock: the mutex to be acquired
775 * Lock the mutex like mutex_lock(), and return 0 if the mutex has
776 * been acquired or sleep until the mutex becomes available. If a
777 * signal arrives while waiting for the lock then this function
780 * This function is similar to (but not equivalent to) down_interruptible().
782 int __sched
mutex_lock_interruptible(struct mutex
*lock
)
787 ret
= __mutex_fastpath_lock_retval(&lock
->count
);
789 mutex_set_owner(lock
);
792 return __mutex_lock_interruptible_slowpath(lock
);
795 EXPORT_SYMBOL(mutex_lock_interruptible
);
797 int __sched
mutex_lock_killable(struct mutex
*lock
)
802 ret
= __mutex_fastpath_lock_retval(&lock
->count
);
804 mutex_set_owner(lock
);
807 return __mutex_lock_killable_slowpath(lock
);
809 EXPORT_SYMBOL(mutex_lock_killable
);
811 static __used noinline
void __sched
812 __mutex_lock_slowpath(atomic_t
*lock_count
)
814 struct mutex
*lock
= container_of(lock_count
, struct mutex
, count
);
816 __mutex_lock_common(lock
, TASK_UNINTERRUPTIBLE
, 0,
817 NULL
, _RET_IP_
, NULL
);
820 static noinline
int __sched
821 __mutex_lock_killable_slowpath(struct mutex
*lock
)
823 return __mutex_lock_common(lock
, TASK_KILLABLE
, 0,
824 NULL
, _RET_IP_
, NULL
);
827 static noinline
int __sched
828 __mutex_lock_interruptible_slowpath(struct mutex
*lock
)
830 return __mutex_lock_common(lock
, TASK_INTERRUPTIBLE
, 0,
831 NULL
, _RET_IP_
, NULL
);
834 static noinline
int __sched
835 __ww_mutex_lock_slowpath(struct ww_mutex
*lock
, struct ww_acquire_ctx
*ctx
)
837 return __mutex_lock_common(&lock
->base
, TASK_UNINTERRUPTIBLE
, 0,
838 NULL
, _RET_IP_
, ctx
);
841 static noinline
int __sched
842 __ww_mutex_lock_interruptible_slowpath(struct ww_mutex
*lock
,
843 struct ww_acquire_ctx
*ctx
)
845 return __mutex_lock_common(&lock
->base
, TASK_INTERRUPTIBLE
, 0,
846 NULL
, _RET_IP_
, ctx
);
852 * Spinlock based trylock, we take the spinlock and check whether we
855 static inline int __mutex_trylock_slowpath(atomic_t
*lock_count
)
857 struct mutex
*lock
= container_of(lock_count
, struct mutex
, count
);
861 spin_lock_mutex(&lock
->wait_lock
, flags
);
863 prev
= atomic_xchg(&lock
->count
, -1);
864 if (likely(prev
== 1)) {
865 mutex_set_owner(lock
);
866 mutex_acquire(&lock
->dep_map
, 0, 1, _RET_IP_
);
869 /* Set it back to 0 if there are no waiters: */
870 if (likely(list_empty(&lock
->wait_list
)))
871 atomic_set(&lock
->count
, 0);
873 spin_unlock_mutex(&lock
->wait_lock
, flags
);
879 * mutex_trylock - try to acquire the mutex, without waiting
880 * @lock: the mutex to be acquired
882 * Try to acquire the mutex atomically. Returns 1 if the mutex
883 * has been acquired successfully, and 0 on contention.
885 * NOTE: this function follows the spin_trylock() convention, so
886 * it is negated from the down_trylock() return values! Be careful
887 * about this when converting semaphore users to mutexes.
889 * This function must not be used in interrupt context. The
890 * mutex must be released by the same task that acquired it.
892 int __sched
mutex_trylock(struct mutex
*lock
)
896 ret
= __mutex_fastpath_trylock(&lock
->count
, __mutex_trylock_slowpath
);
898 mutex_set_owner(lock
);
902 EXPORT_SYMBOL(mutex_trylock
);
904 #ifndef CONFIG_DEBUG_LOCK_ALLOC
906 __ww_mutex_lock(struct ww_mutex
*lock
, struct ww_acquire_ctx
*ctx
)
912 ret
= __mutex_fastpath_lock_retval(&lock
->base
.count
);
915 ww_mutex_set_context_fastpath(lock
, ctx
);
916 mutex_set_owner(&lock
->base
);
918 ret
= __ww_mutex_lock_slowpath(lock
, ctx
);
921 EXPORT_SYMBOL(__ww_mutex_lock
);
924 __ww_mutex_lock_interruptible(struct ww_mutex
*lock
, struct ww_acquire_ctx
*ctx
)
930 ret
= __mutex_fastpath_lock_retval(&lock
->base
.count
);
933 ww_mutex_set_context_fastpath(lock
, ctx
);
934 mutex_set_owner(&lock
->base
);
936 ret
= __ww_mutex_lock_interruptible_slowpath(lock
, ctx
);
939 EXPORT_SYMBOL(__ww_mutex_lock_interruptible
);
944 * atomic_dec_and_mutex_lock - return holding mutex if we dec to 0
945 * @cnt: the atomic which we are to dec
946 * @lock: the mutex to return holding if we dec to 0
948 * return true and hold lock if we dec to 0, return false otherwise
950 int atomic_dec_and_mutex_lock(atomic_t
*cnt
, struct mutex
*lock
)
952 /* dec if we can't possibly hit 0 */
953 if (atomic_add_unless(cnt
, -1, 1))
955 /* we might hit 0, so take the lock */
957 if (!atomic_dec_and_test(cnt
)) {
958 /* when we actually did the dec, we didn't hit 0 */
962 /* we hit 0, and we hold the lock */
965 EXPORT_SYMBOL(atomic_dec_and_mutex_lock
);