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
);