1 // SPDX-License-Identifier: GPL-2.0-only
3 * kernel/locking/mutex.c
5 * Mutexes: blocking mutual exclusion locks
7 * Started by Ingo Molnar:
9 * Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
11 * Many thanks to Arjan van de Ven, Thomas Gleixner, Steven Rostedt and
12 * David Howells for suggestions and improvements.
14 * - Adaptive spinning for mutexes by Peter Zijlstra. (Ported to mainline
15 * from the -rt tree, where it was originally implemented for rtmutexes
16 * by Steven Rostedt, based on work by Gregory Haskins, Peter Morreale
19 * Also see Documentation/locking/mutex-design.rst.
21 #include <linux/mutex.h>
22 #include <linux/ww_mutex.h>
23 #include <linux/sched/signal.h>
24 #include <linux/sched/rt.h>
25 #include <linux/sched/wake_q.h>
26 #include <linux/sched/debug.h>
27 #include <linux/export.h>
28 #include <linux/spinlock.h>
29 #include <linux/interrupt.h>
30 #include <linux/debug_locks.h>
31 #include <linux/osq_lock.h>
33 #define CREATE_TRACE_POINTS
34 #include <trace/events/lock.h>
36 #ifndef CONFIG_PREEMPT_RT
39 #ifdef CONFIG_DEBUG_MUTEXES
40 # define MUTEX_WARN_ON(cond) DEBUG_LOCKS_WARN_ON(cond)
42 # define MUTEX_WARN_ON(cond)
46 __mutex_init(struct mutex *lock, const char *name, struct lock_class_key *key)
48 atomic_long_set(&lock->owner, 0);
49 raw_spin_lock_init(&lock->wait_lock);
50 INIT_LIST_HEAD(&lock->wait_list);
51 #ifdef CONFIG_MUTEX_SPIN_ON_OWNER
52 osq_lock_init(&lock->osq);
55 debug_mutex_init(lock, name, key);
57 EXPORT_SYMBOL(__mutex_init);
60 * @owner: contains: 'struct task_struct *' to the current lock owner,
61 * NULL means not owned. Since task_struct pointers are aligned at
62 * at least L1_CACHE_BYTES, we have low bits to store extra state.
64 * Bit0 indicates a non-empty waiter list; unlock must issue a wakeup.
65 * Bit1 indicates unlock needs to hand the lock to the top-waiter
66 * Bit2 indicates handoff has been done and we're waiting for pickup.
68 #define MUTEX_FLAG_WAITERS 0x01
69 #define MUTEX_FLAG_HANDOFF 0x02
70 #define MUTEX_FLAG_PICKUP 0x04
72 #define MUTEX_FLAGS 0x07
75 * Internal helper function; C doesn't allow us to hide it :/
77 * DO NOT USE (outside of mutex code).
79 static inline struct task_struct *__mutex_owner(struct mutex *lock)
81 return (struct task_struct *)(atomic_long_read(&lock->owner) & ~MUTEX_FLAGS);
84 static inline struct task_struct *__owner_task(unsigned long owner)
86 return (struct task_struct *)(owner & ~MUTEX_FLAGS);
89 bool mutex_is_locked(struct mutex *lock)
91 return __mutex_owner(lock) != NULL;
93 EXPORT_SYMBOL(mutex_is_locked);
95 static inline unsigned long __owner_flags(unsigned long owner)
97 return owner & MUTEX_FLAGS;
101 * Returns: __mutex_owner(lock) on failure or NULL on success.
103 static inline struct task_struct *__mutex_trylock_common(struct mutex *lock, bool handoff)
105 unsigned long owner, curr = (unsigned long)current;
107 owner = atomic_long_read(&lock->owner);
108 for (;;) { /* must loop, can race against a flag */
109 unsigned long flags = __owner_flags(owner);
110 unsigned long task = owner & ~MUTEX_FLAGS;
113 if (flags & MUTEX_FLAG_PICKUP) {
116 flags &= ~MUTEX_FLAG_PICKUP;
117 } else if (handoff) {
118 if (flags & MUTEX_FLAG_HANDOFF)
120 flags |= MUTEX_FLAG_HANDOFF;
125 MUTEX_WARN_ON(flags & (MUTEX_FLAG_HANDOFF | MUTEX_FLAG_PICKUP));
129 if (atomic_long_try_cmpxchg_acquire(&lock->owner, &owner, task | flags)) {
136 return __owner_task(owner);
140 * Trylock or set HANDOFF
142 static inline bool __mutex_trylock_or_handoff(struct mutex *lock, bool handoff)
144 return !__mutex_trylock_common(lock, handoff);
148 * Actual trylock that will work on any unlocked state.
150 static inline bool __mutex_trylock(struct mutex *lock)
152 return !__mutex_trylock_common(lock, false);
155 #ifndef CONFIG_DEBUG_LOCK_ALLOC
157 * Lockdep annotations are contained to the slow paths for simplicity.
158 * There is nothing that would stop spreading the lockdep annotations outwards
163 * Optimistic trylock that only works in the uncontended case. Make sure to
164 * follow with a __mutex_trylock() before failing.
166 static __always_inline bool __mutex_trylock_fast(struct mutex *lock)
168 unsigned long curr = (unsigned long)current;
169 unsigned long zero = 0UL;
171 if (atomic_long_try_cmpxchg_acquire(&lock->owner, &zero, curr))
177 static __always_inline bool __mutex_unlock_fast(struct mutex *lock)
179 unsigned long curr = (unsigned long)current;
181 return atomic_long_try_cmpxchg_release(&lock->owner, &curr, 0UL);
185 static inline void __mutex_set_flag(struct mutex *lock, unsigned long flag)
187 atomic_long_or(flag, &lock->owner);
190 static inline void __mutex_clear_flag(struct mutex *lock, unsigned long flag)
192 atomic_long_andnot(flag, &lock->owner);
195 static inline bool __mutex_waiter_is_first(struct mutex *lock, struct mutex_waiter *waiter)
197 return list_first_entry(&lock->wait_list, struct mutex_waiter, list) == waiter;
201 * Add @waiter to a given location in the lock wait_list and set the
202 * FLAG_WAITERS flag if it's the first waiter.
205 __mutex_add_waiter(struct mutex *lock, struct mutex_waiter *waiter,
206 struct list_head *list)
208 debug_mutex_add_waiter(lock, waiter, current);
210 list_add_tail(&waiter->list, list);
211 if (__mutex_waiter_is_first(lock, waiter))
212 __mutex_set_flag(lock, MUTEX_FLAG_WAITERS);
216 __mutex_remove_waiter(struct mutex *lock, struct mutex_waiter *waiter)
218 list_del(&waiter->list);
219 if (likely(list_empty(&lock->wait_list)))
220 __mutex_clear_flag(lock, MUTEX_FLAGS);
222 debug_mutex_remove_waiter(lock, waiter, current);
226 * Give up ownership to a specific task, when @task = NULL, this is equivalent
227 * to a regular unlock. Sets PICKUP on a handoff, clears HANDOFF, preserves
228 * WAITERS. Provides RELEASE semantics like a regular unlock, the
229 * __mutex_trylock() provides a matching ACQUIRE semantics for the handoff.
231 static void __mutex_handoff(struct mutex *lock, struct task_struct *task)
233 unsigned long owner = atomic_long_read(&lock->owner);
238 MUTEX_WARN_ON(__owner_task(owner) != current);
239 MUTEX_WARN_ON(owner & MUTEX_FLAG_PICKUP);
241 new = (owner & MUTEX_FLAG_WAITERS);
242 new |= (unsigned long)task;
244 new |= MUTEX_FLAG_PICKUP;
246 if (atomic_long_try_cmpxchg_release(&lock->owner, &owner, new))
251 #ifndef CONFIG_DEBUG_LOCK_ALLOC
253 * We split the mutex lock/unlock logic into separate fastpath and
254 * slowpath functions, to reduce the register pressure on the fastpath.
255 * We also put the fastpath first in the kernel image, to make sure the
256 * branch is predicted by the CPU as default-untaken.
258 static void __sched __mutex_lock_slowpath(struct mutex *lock);
261 * mutex_lock - acquire the mutex
262 * @lock: the mutex to be acquired
264 * Lock the mutex exclusively for this task. If the mutex is not
265 * available right now, it will sleep until it can get it.
267 * The mutex must later on be released by the same task that
268 * acquired it. Recursive locking is not allowed. The task
269 * may not exit without first unlocking the mutex. Also, kernel
270 * memory where the mutex resides must not be freed with
271 * the mutex still locked. The mutex must first be initialized
272 * (or statically defined) before it can be locked. memset()-ing
273 * the mutex to 0 is not allowed.
275 * (The CONFIG_DEBUG_MUTEXES .config option turns on debugging
276 * checks that will enforce the restrictions and will also do
277 * deadlock debugging)
279 * This function is similar to (but not equivalent to) down().
281 void __sched mutex_lock(struct mutex *lock)
285 if (!__mutex_trylock_fast(lock))
286 __mutex_lock_slowpath(lock);
288 EXPORT_SYMBOL(mutex_lock);
291 #include "ww_mutex.h"
293 #ifdef CONFIG_MUTEX_SPIN_ON_OWNER
296 * Trylock variant that returns the owning task on failure.
298 static inline struct task_struct *__mutex_trylock_or_owner(struct mutex *lock)
300 return __mutex_trylock_common(lock, false);
304 bool ww_mutex_spin_on_owner(struct mutex *lock, struct ww_acquire_ctx *ww_ctx,
305 struct mutex_waiter *waiter)
309 ww = container_of(lock, struct ww_mutex, base);
312 * If ww->ctx is set the contents are undefined, only
313 * by acquiring wait_lock there is a guarantee that
314 * they are not invalid when reading.
316 * As such, when deadlock detection needs to be
317 * performed the optimistic spinning cannot be done.
319 * Check this in every inner iteration because we may
320 * be racing against another thread's ww_mutex_lock.
322 if (ww_ctx->acquired > 0 && READ_ONCE(ww->ctx))
326 * If we aren't on the wait list yet, cancel the spin
327 * if there are waiters. We want to avoid stealing the
328 * lock from a waiter with an earlier stamp, since the
329 * other thread may already own a lock that we also
332 if (!waiter && (atomic_long_read(&lock->owner) & MUTEX_FLAG_WAITERS))
336 * Similarly, stop spinning if we are no longer the
339 if (waiter && !__mutex_waiter_is_first(lock, waiter))
346 * Look out! "owner" is an entirely speculative pointer access and not
349 * "noinline" so that this function shows up on perf profiles.
352 bool mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner,
353 struct ww_acquire_ctx *ww_ctx, struct mutex_waiter *waiter)
357 lockdep_assert_preemption_disabled();
359 while (__mutex_owner(lock) == owner) {
361 * Ensure we emit the owner->on_cpu, dereference _after_
362 * checking lock->owner still matches owner. And we already
363 * disabled preemption which is equal to the RCU read-side
364 * crital section in optimistic spinning code. Thus the
365 * task_strcut structure won't go away during the spinning
371 * Use vcpu_is_preempted to detect lock holder preemption issue.
373 if (!owner_on_cpu(owner) || need_resched()) {
378 if (ww_ctx && !ww_mutex_spin_on_owner(lock, ww_ctx, waiter)) {
390 * Initial check for entering the mutex spinning loop
392 static inline int mutex_can_spin_on_owner(struct mutex *lock)
394 struct task_struct *owner;
397 lockdep_assert_preemption_disabled();
403 * We already disabled preemption which is equal to the RCU read-side
404 * crital section in optimistic spinning code. Thus the task_strcut
405 * structure won't go away during the spinning period.
407 owner = __mutex_owner(lock);
409 retval = owner_on_cpu(owner);
412 * If lock->owner is not set, the mutex has been released. Return true
413 * such that we'll trylock in the spin path, which is a faster option
414 * than the blocking slow path.
420 * Optimistic spinning.
422 * We try to spin for acquisition when we find that the lock owner
423 * is currently running on a (different) CPU and while we don't
424 * need to reschedule. The rationale is that if the lock owner is
425 * running, it is likely to release the lock soon.
427 * The mutex spinners are queued up using MCS lock so that only one
428 * spinner can compete for the mutex. However, if mutex spinning isn't
429 * going to happen, there is no point in going through the lock/unlock
432 * Returns true when the lock was taken, otherwise false, indicating
433 * that we need to jump to the slowpath and sleep.
435 * The waiter flag is set to true if the spinner is a waiter in the wait
436 * queue. The waiter-spinner will spin on the lock directly and concurrently
437 * with the spinner at the head of the OSQ, if present, until the owner is
440 static __always_inline bool
441 mutex_optimistic_spin(struct mutex *lock, struct ww_acquire_ctx *ww_ctx,
442 struct mutex_waiter *waiter)
446 * The purpose of the mutex_can_spin_on_owner() function is
447 * to eliminate the overhead of osq_lock() and osq_unlock()
448 * in case spinning isn't possible. As a waiter-spinner
449 * is not going to take OSQ lock anyway, there is no need
450 * to call mutex_can_spin_on_owner().
452 if (!mutex_can_spin_on_owner(lock))
456 * In order to avoid a stampede of mutex spinners trying to
457 * acquire the mutex all at once, the spinners need to take a
458 * MCS (queued) lock first before spinning on the owner field.
460 if (!osq_lock(&lock->osq))
465 struct task_struct *owner;
467 /* Try to acquire the mutex... */
468 owner = __mutex_trylock_or_owner(lock);
473 * There's an owner, wait for it to either
474 * release the lock or go to sleep.
476 if (!mutex_spin_on_owner(lock, owner, ww_ctx, waiter))
480 * The cpu_relax() call is a compiler barrier which forces
481 * everything in this loop to be re-loaded. We don't need
482 * memory barriers as we'll eventually observe the right
483 * values at the cost of a few extra spins.
489 osq_unlock(&lock->osq);
496 osq_unlock(&lock->osq);
500 * If we fell out of the spin path because of need_resched(),
501 * reschedule now, before we try-lock the mutex. This avoids getting
502 * scheduled out right after we obtained the mutex.
504 if (need_resched()) {
506 * We _should_ have TASK_RUNNING here, but just in case
507 * we do not, make it so, otherwise we might get stuck.
509 __set_current_state(TASK_RUNNING);
510 schedule_preempt_disabled();
516 static __always_inline bool
517 mutex_optimistic_spin(struct mutex *lock, struct ww_acquire_ctx *ww_ctx,
518 struct mutex_waiter *waiter)
524 static noinline void __sched __mutex_unlock_slowpath(struct mutex *lock, unsigned long ip);
527 * mutex_unlock - release the mutex
528 * @lock: the mutex to be released
530 * Unlock a mutex that has been locked by this task previously.
532 * This function must not be used in interrupt context. Unlocking
533 * of a not locked mutex is not allowed.
535 * The caller must ensure that the mutex stays alive until this function has
536 * returned - mutex_unlock() can NOT directly be used to release an object such
537 * that another concurrent task can free it.
538 * Mutexes are different from spinlocks & refcounts in this aspect.
540 * This function is similar to (but not equivalent to) up().
542 void __sched mutex_unlock(struct mutex *lock)
544 #ifndef CONFIG_DEBUG_LOCK_ALLOC
545 if (__mutex_unlock_fast(lock))
548 __mutex_unlock_slowpath(lock, _RET_IP_);
550 EXPORT_SYMBOL(mutex_unlock);
553 * ww_mutex_unlock - release the w/w mutex
554 * @lock: the mutex to be released
556 * Unlock a mutex that has been locked by this task previously with any of the
557 * ww_mutex_lock* functions (with or without an acquire context). It is
558 * forbidden to release the locks after releasing the acquire context.
560 * This function must not be used in interrupt context. Unlocking
561 * of a unlocked mutex is not allowed.
563 void __sched ww_mutex_unlock(struct ww_mutex *lock)
565 __ww_mutex_unlock(lock);
566 mutex_unlock(&lock->base);
568 EXPORT_SYMBOL(ww_mutex_unlock);
571 * Lock a mutex (possibly interruptible), slowpath:
573 static __always_inline int __sched
574 __mutex_lock_common(struct mutex *lock, unsigned int state, unsigned int subclass,
575 struct lockdep_map *nest_lock, unsigned long ip,
576 struct ww_acquire_ctx *ww_ctx, const bool use_ww_ctx)
578 struct mutex_waiter waiter;
587 MUTEX_WARN_ON(lock->magic != lock);
589 ww = container_of(lock, struct ww_mutex, base);
591 if (unlikely(ww_ctx == READ_ONCE(ww->ctx)))
595 * Reset the wounded flag after a kill. No other process can
596 * race and wound us here since they can't have a valid owner
597 * pointer if we don't have any locks held.
599 if (ww_ctx->acquired == 0)
602 #ifdef CONFIG_DEBUG_LOCK_ALLOC
603 nest_lock = &ww_ctx->dep_map;
608 mutex_acquire_nest(&lock->dep_map, subclass, 0, nest_lock, ip);
610 trace_contention_begin(lock, LCB_F_MUTEX | LCB_F_SPIN);
611 if (__mutex_trylock(lock) ||
612 mutex_optimistic_spin(lock, ww_ctx, NULL)) {
613 /* got the lock, yay! */
614 lock_acquired(&lock->dep_map, ip);
616 ww_mutex_set_context_fastpath(ww, ww_ctx);
617 trace_contention_end(lock, 0);
622 raw_spin_lock(&lock->wait_lock);
624 * After waiting to acquire the wait_lock, try again.
626 if (__mutex_trylock(lock)) {
628 __ww_mutex_check_waiters(lock, ww_ctx);
633 debug_mutex_lock_common(lock, &waiter);
634 waiter.task = current;
636 waiter.ww_ctx = ww_ctx;
638 lock_contended(&lock->dep_map, ip);
641 /* add waiting tasks to the end of the waitqueue (FIFO): */
642 __mutex_add_waiter(lock, &waiter, &lock->wait_list);
645 * Add in stamp order, waking up waiters that must kill
648 ret = __ww_mutex_add_waiter(&waiter, lock, ww_ctx);
653 set_current_state(state);
654 trace_contention_begin(lock, LCB_F_MUTEX);
659 * Once we hold wait_lock, we're serialized against
660 * mutex_unlock() handing the lock off to us, do a trylock
661 * before testing the error conditions to make sure we pick up
664 if (__mutex_trylock(lock))
668 * Check for signals and kill conditions while holding
669 * wait_lock. This ensures the lock cancellation is ordered
670 * against mutex_unlock() and wake-ups do not go missing.
672 if (signal_pending_state(state, current)) {
678 ret = __ww_mutex_check_kill(lock, &waiter, ww_ctx);
683 raw_spin_unlock(&lock->wait_lock);
684 schedule_preempt_disabled();
686 first = __mutex_waiter_is_first(lock, &waiter);
688 set_current_state(state);
690 * Here we order against unlock; we must either see it change
691 * state back to RUNNING and fall through the next schedule(),
692 * or we must see its unlock and acquire.
694 if (__mutex_trylock_or_handoff(lock, first))
698 trace_contention_begin(lock, LCB_F_MUTEX | LCB_F_SPIN);
699 if (mutex_optimistic_spin(lock, ww_ctx, &waiter))
701 trace_contention_begin(lock, LCB_F_MUTEX);
704 raw_spin_lock(&lock->wait_lock);
706 raw_spin_lock(&lock->wait_lock);
708 __set_current_state(TASK_RUNNING);
712 * Wound-Wait; we stole the lock (!first_waiter), check the
713 * waiters as anyone might want to wound us.
715 if (!ww_ctx->is_wait_die &&
716 !__mutex_waiter_is_first(lock, &waiter))
717 __ww_mutex_check_waiters(lock, ww_ctx);
720 __mutex_remove_waiter(lock, &waiter);
722 debug_mutex_free_waiter(&waiter);
725 /* got the lock - cleanup and rejoice! */
726 lock_acquired(&lock->dep_map, ip);
727 trace_contention_end(lock, 0);
730 ww_mutex_lock_acquired(ww, ww_ctx);
732 raw_spin_unlock(&lock->wait_lock);
737 __set_current_state(TASK_RUNNING);
738 __mutex_remove_waiter(lock, &waiter);
740 trace_contention_end(lock, ret);
741 raw_spin_unlock(&lock->wait_lock);
742 debug_mutex_free_waiter(&waiter);
743 mutex_release(&lock->dep_map, ip);
749 __mutex_lock(struct mutex *lock, unsigned int state, unsigned int subclass,
750 struct lockdep_map *nest_lock, unsigned long ip)
752 return __mutex_lock_common(lock, state, subclass, nest_lock, ip, NULL, false);
756 __ww_mutex_lock(struct mutex *lock, unsigned int state, unsigned int subclass,
757 unsigned long ip, struct ww_acquire_ctx *ww_ctx)
759 return __mutex_lock_common(lock, state, subclass, NULL, ip, ww_ctx, true);
763 * ww_mutex_trylock - tries to acquire the w/w mutex with optional acquire context
765 * @ww_ctx: optional w/w acquire context
767 * Trylocks a mutex with the optional acquire context; no deadlock detection is
768 * possible. Returns 1 if the mutex has been acquired successfully, 0 otherwise.
770 * Unlike ww_mutex_lock, no deadlock handling is performed. However, if a @ctx is
771 * specified, -EALREADY handling may happen in calls to ww_mutex_trylock.
773 * A mutex acquired with this function must be released with ww_mutex_unlock.
775 int ww_mutex_trylock(struct ww_mutex *ww, struct ww_acquire_ctx *ww_ctx)
778 return mutex_trylock(&ww->base);
780 MUTEX_WARN_ON(ww->base.magic != &ww->base);
783 * Reset the wounded flag after a kill. No other process can
784 * race and wound us here, since they can't have a valid owner
785 * pointer if we don't have any locks held.
787 if (ww_ctx->acquired == 0)
790 if (__mutex_trylock(&ww->base)) {
791 ww_mutex_set_context_fastpath(ww, ww_ctx);
792 mutex_acquire_nest(&ww->base.dep_map, 0, 1, &ww_ctx->dep_map, _RET_IP_);
798 EXPORT_SYMBOL(ww_mutex_trylock);
800 #ifdef CONFIG_DEBUG_LOCK_ALLOC
802 mutex_lock_nested(struct mutex *lock, unsigned int subclass)
804 __mutex_lock(lock, TASK_UNINTERRUPTIBLE, subclass, NULL, _RET_IP_);
807 EXPORT_SYMBOL_GPL(mutex_lock_nested);
810 _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest)
812 __mutex_lock(lock, TASK_UNINTERRUPTIBLE, 0, nest, _RET_IP_);
814 EXPORT_SYMBOL_GPL(_mutex_lock_nest_lock);
817 mutex_lock_killable_nested(struct mutex *lock, unsigned int subclass)
819 return __mutex_lock(lock, TASK_KILLABLE, subclass, NULL, _RET_IP_);
821 EXPORT_SYMBOL_GPL(mutex_lock_killable_nested);
824 mutex_lock_interruptible_nested(struct mutex *lock, unsigned int subclass)
826 return __mutex_lock(lock, TASK_INTERRUPTIBLE, subclass, NULL, _RET_IP_);
828 EXPORT_SYMBOL_GPL(mutex_lock_interruptible_nested);
831 mutex_lock_io_nested(struct mutex *lock, unsigned int subclass)
837 token = io_schedule_prepare();
838 __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE,
839 subclass, NULL, _RET_IP_, NULL, 0);
840 io_schedule_finish(token);
842 EXPORT_SYMBOL_GPL(mutex_lock_io_nested);
845 ww_mutex_deadlock_injection(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
847 #ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH
850 if (ctx->deadlock_inject_countdown-- == 0) {
851 tmp = ctx->deadlock_inject_interval;
852 if (tmp > UINT_MAX/4)
855 tmp = tmp*2 + tmp + tmp/2;
857 ctx->deadlock_inject_interval = tmp;
858 ctx->deadlock_inject_countdown = tmp;
859 ctx->contending_lock = lock;
861 ww_mutex_unlock(lock);
871 ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
876 ret = __ww_mutex_lock(&lock->base, TASK_UNINTERRUPTIBLE,
878 if (!ret && ctx && ctx->acquired > 1)
879 return ww_mutex_deadlock_injection(lock, ctx);
883 EXPORT_SYMBOL_GPL(ww_mutex_lock);
886 ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
891 ret = __ww_mutex_lock(&lock->base, TASK_INTERRUPTIBLE,
894 if (!ret && ctx && ctx->acquired > 1)
895 return ww_mutex_deadlock_injection(lock, ctx);
899 EXPORT_SYMBOL_GPL(ww_mutex_lock_interruptible);
904 * Release the lock, slowpath:
906 static noinline void __sched __mutex_unlock_slowpath(struct mutex *lock, unsigned long ip)
908 struct task_struct *next = NULL;
909 DEFINE_WAKE_Q(wake_q);
912 mutex_release(&lock->dep_map, ip);
915 * Release the lock before (potentially) taking the spinlock such that
916 * other contenders can get on with things ASAP.
918 * Except when HANDOFF, in that case we must not clear the owner field,
919 * but instead set it to the top waiter.
921 owner = atomic_long_read(&lock->owner);
923 MUTEX_WARN_ON(__owner_task(owner) != current);
924 MUTEX_WARN_ON(owner & MUTEX_FLAG_PICKUP);
926 if (owner & MUTEX_FLAG_HANDOFF)
929 if (atomic_long_try_cmpxchg_release(&lock->owner, &owner, __owner_flags(owner))) {
930 if (owner & MUTEX_FLAG_WAITERS)
937 raw_spin_lock(&lock->wait_lock);
938 debug_mutex_unlock(lock);
939 if (!list_empty(&lock->wait_list)) {
940 /* get the first entry from the wait-list: */
941 struct mutex_waiter *waiter =
942 list_first_entry(&lock->wait_list,
943 struct mutex_waiter, list);
947 debug_mutex_wake_waiter(lock, waiter);
948 wake_q_add(&wake_q, next);
951 if (owner & MUTEX_FLAG_HANDOFF)
952 __mutex_handoff(lock, next);
954 raw_spin_unlock(&lock->wait_lock);
959 #ifndef CONFIG_DEBUG_LOCK_ALLOC
961 * Here come the less common (and hence less performance-critical) APIs:
962 * mutex_lock_interruptible() and mutex_trylock().
964 static noinline int __sched
965 __mutex_lock_killable_slowpath(struct mutex *lock);
967 static noinline int __sched
968 __mutex_lock_interruptible_slowpath(struct mutex *lock);
971 * mutex_lock_interruptible() - Acquire the mutex, interruptible by signals.
972 * @lock: The mutex to be acquired.
974 * Lock the mutex like mutex_lock(). If a signal is delivered while the
975 * process is sleeping, this function will return without acquiring the
978 * Context: Process context.
979 * Return: 0 if the lock was successfully acquired or %-EINTR if a
982 int __sched mutex_lock_interruptible(struct mutex *lock)
986 if (__mutex_trylock_fast(lock))
989 return __mutex_lock_interruptible_slowpath(lock);
992 EXPORT_SYMBOL(mutex_lock_interruptible);
995 * mutex_lock_killable() - Acquire the mutex, interruptible by fatal signals.
996 * @lock: The mutex to be acquired.
998 * Lock the mutex like mutex_lock(). If a signal which will be fatal to
999 * the current process is delivered while the process is sleeping, this
1000 * function will return without acquiring the mutex.
1002 * Context: Process context.
1003 * Return: 0 if the lock was successfully acquired or %-EINTR if a
1004 * fatal signal arrived.
1006 int __sched mutex_lock_killable(struct mutex *lock)
1010 if (__mutex_trylock_fast(lock))
1013 return __mutex_lock_killable_slowpath(lock);
1015 EXPORT_SYMBOL(mutex_lock_killable);
1018 * mutex_lock_io() - Acquire the mutex and mark the process as waiting for I/O
1019 * @lock: The mutex to be acquired.
1021 * Lock the mutex like mutex_lock(). While the task is waiting for this
1022 * mutex, it will be accounted as being in the IO wait state by the
1025 * Context: Process context.
1027 void __sched mutex_lock_io(struct mutex *lock)
1031 token = io_schedule_prepare();
1033 io_schedule_finish(token);
1035 EXPORT_SYMBOL_GPL(mutex_lock_io);
1037 static noinline void __sched
1038 __mutex_lock_slowpath(struct mutex *lock)
1040 __mutex_lock(lock, TASK_UNINTERRUPTIBLE, 0, NULL, _RET_IP_);
1043 static noinline int __sched
1044 __mutex_lock_killable_slowpath(struct mutex *lock)
1046 return __mutex_lock(lock, TASK_KILLABLE, 0, NULL, _RET_IP_);
1049 static noinline int __sched
1050 __mutex_lock_interruptible_slowpath(struct mutex *lock)
1052 return __mutex_lock(lock, TASK_INTERRUPTIBLE, 0, NULL, _RET_IP_);
1055 static noinline int __sched
1056 __ww_mutex_lock_slowpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
1058 return __ww_mutex_lock(&lock->base, TASK_UNINTERRUPTIBLE, 0,
1062 static noinline int __sched
1063 __ww_mutex_lock_interruptible_slowpath(struct ww_mutex *lock,
1064 struct ww_acquire_ctx *ctx)
1066 return __ww_mutex_lock(&lock->base, TASK_INTERRUPTIBLE, 0,
1073 * mutex_trylock - try to acquire the mutex, without waiting
1074 * @lock: the mutex to be acquired
1076 * Try to acquire the mutex atomically. Returns 1 if the mutex
1077 * has been acquired successfully, and 0 on contention.
1079 * NOTE: this function follows the spin_trylock() convention, so
1080 * it is negated from the down_trylock() return values! Be careful
1081 * about this when converting semaphore users to mutexes.
1083 * This function must not be used in interrupt context. The
1084 * mutex must be released by the same task that acquired it.
1086 int __sched mutex_trylock(struct mutex *lock)
1090 MUTEX_WARN_ON(lock->magic != lock);
1092 locked = __mutex_trylock(lock);
1094 mutex_acquire(&lock->dep_map, 0, 1, _RET_IP_);
1098 EXPORT_SYMBOL(mutex_trylock);
1100 #ifndef CONFIG_DEBUG_LOCK_ALLOC
1102 ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
1106 if (__mutex_trylock_fast(&lock->base)) {
1108 ww_mutex_set_context_fastpath(lock, ctx);
1112 return __ww_mutex_lock_slowpath(lock, ctx);
1114 EXPORT_SYMBOL(ww_mutex_lock);
1117 ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
1121 if (__mutex_trylock_fast(&lock->base)) {
1123 ww_mutex_set_context_fastpath(lock, ctx);
1127 return __ww_mutex_lock_interruptible_slowpath(lock, ctx);
1129 EXPORT_SYMBOL(ww_mutex_lock_interruptible);
1131 #endif /* !CONFIG_DEBUG_LOCK_ALLOC */
1132 #endif /* !CONFIG_PREEMPT_RT */
1134 EXPORT_TRACEPOINT_SYMBOL_GPL(contention_begin);
1135 EXPORT_TRACEPOINT_SYMBOL_GPL(contention_end);
1138 * atomic_dec_and_mutex_lock - return holding mutex if we dec to 0
1139 * @cnt: the atomic which we are to dec
1140 * @lock: the mutex to return holding if we dec to 0
1142 * return true and hold lock if we dec to 0, return false otherwise
1144 int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock)
1146 /* dec if we can't possibly hit 0 */
1147 if (atomic_add_unless(cnt, -1, 1))
1149 /* we might hit 0, so take the lock */
1151 if (!atomic_dec_and_test(cnt)) {
1152 /* when we actually did the dec, we didn't hit 0 */
1156 /* we hit 0, and we hold the lock */
1159 EXPORT_SYMBOL(atomic_dec_and_mutex_lock);