1 // SPDX-License-Identifier: GPL-2.0-only
11  * Many thanks to Arjan van de Ven, Thomas Gleixner, Steven Rostedt and
14  *  - Adaptive spinning for mutexes by Peter Zijlstra. (Ported to mainline
15  *    from the -rt tree, where it was originally implemented for rtmutexes
19  * Also see Documentation/locking/mutex-design.rst.
48 	atomic_long_set(&lock->owner, 0);  in __mutex_init()
49 	raw_spin_lock_init(&lock->wait_lock);  in __mutex_init()
50 	INIT_LIST_HEAD(&lock->wait_list);  in __mutex_init()
52 	osq_lock_init(&lock->osq);  in __mutex_init()
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
81 	return (struct task_struct *)(atomic_long_read(&lock->owner) & ~MUTEX_FLAGS);  in __mutex_owner()
107 	owner = atomic_long_read(&lock->owner);  in __mutex_trylock_common()
129 		if (atomic_long_try_cmpxchg_acquire(&lock->owner, &owner, task | flags)) {  in __mutex_trylock_common()
171 	if (atomic_long_try_cmpxchg_acquire(&lock->owner, &zero, curr))  in __mutex_trylock_fast()
181 	return atomic_long_try_cmpxchg_release(&lock->owner, &curr, 0UL);  in __mutex_unlock_fast()
187 	atomic_long_or(flag, &lock->owner);  in __mutex_set_flag()
192 	atomic_long_andnot(flag, &lock->owner);  in __mutex_clear_flag()
197 	return list_first_entry(&lock->wait_list, struct mutex_waiter, list) == waiter;  in __mutex_waiter_is_first()
210 	list_add_tail(&waiter->list, list);  in __mutex_add_waiter()
218 	list_del(&waiter->list);  in __mutex_remove_waiter()
219 	if (likely(list_empty(&lock->wait_list)))  in __mutex_remove_waiter()
233 	unsigned long owner = atomic_long_read(&lock->owner);  in __mutex_handoff()
246 		if (atomic_long_try_cmpxchg_release(&lock->owner, &owner, new))  in __mutex_handoff()
256  * branch is predicted by the CPU as default-untaken.
261  * mutex_lock - acquire the mutex
272  * (or statically defined) before it can be locked. memset()-ing
312 	 * If ww->ctx is set the contents are undefined, only  in ww_mutex_spin_on_owner()
322 	if (ww_ctx->acquired > 0 && READ_ONCE(ww->ctx))  in ww_mutex_spin_on_owner()
332 	if (!waiter && (atomic_long_read(&lock->owner) & MUTEX_FLAG_WAITERS))  in ww_mutex_spin_on_owner()
361 		 * Ensure we emit the owner->on_cpu, dereference _after_  in mutex_spin_on_owner()
362 		 * checking lock->owner still matches owner. And we already  in mutex_spin_on_owner()
363 		 * disabled preemption which is equal to the RCU read-side  in mutex_spin_on_owner()
403 	 * We already disabled preemption which is equal to the RCU read-side  in mutex_can_spin_on_owner()
412 	 * If lock->owner is not set, the mutex has been released. Return true  in mutex_can_spin_on_owner()
436  * queue. The waiter-spinner will spin on the lock directly and concurrently
448 		 * in case spinning isn't possible. As a waiter-spinner  in mutex_optimistic_spin()
460 		if (!osq_lock(&lock->osq))  in mutex_optimistic_spin()
481 		 * everything in this loop to be re-loaded. We don't need  in mutex_optimistic_spin()
489 		osq_unlock(&lock->osq);  in mutex_optimistic_spin()
496 		osq_unlock(&lock->osq);  in mutex_optimistic_spin()
501 	 * reschedule now, before we try-lock the mutex. This avoids getting  in mutex_optimistic_spin()
527  * mutex_unlock - release the mutex
536  * returned - mutex_unlock() can NOT directly be used to release an object such
553  * ww_mutex_unlock - release the w/w mutex
566 	mutex_unlock(&lock->base);  in ww_mutex_unlock()
587 	MUTEX_WARN_ON(lock->magic != lock);  in __mutex_lock_common()
591 		if (unlikely(ww_ctx == READ_ONCE(ww->ctx)))  in __mutex_lock_common()
592 			return -EALREADY;  in __mutex_lock_common()
599 		if (ww_ctx->acquired == 0)  in __mutex_lock_common()
600 			ww_ctx->wounded = 0;  in __mutex_lock_common()
603 		nest_lock = &ww_ctx->dep_map;  in __mutex_lock_common()
608 	mutex_acquire_nest(&lock->dep_map, subclass, 0, nest_lock, ip);  in __mutex_lock_common()
614 		lock_acquired(&lock->dep_map, ip);  in __mutex_lock_common()
622 	raw_spin_lock(&lock->wait_lock);  in __mutex_lock_common()
638 	lock_contended(&lock->dep_map, ip);  in __mutex_lock_common()
642 		__mutex_add_waiter(lock, &waiter, &lock->wait_list);  in __mutex_lock_common()
659 		 * Once we hold wait_lock, we're serialized against  in __mutex_lock_common()
670 		 * against mutex_unlock() and wake-ups do not go missing.  in __mutex_lock_common()
673 			ret = -EINTR;  in __mutex_lock_common()
683 		raw_spin_unlock(&lock->wait_lock);  in __mutex_lock_common()
704 		raw_spin_lock(&lock->wait_lock);  in __mutex_lock_common()
706 	raw_spin_lock(&lock->wait_lock);  in __mutex_lock_common()
712 		 * Wound-Wait; we stole the lock (!first_waiter), check the  in __mutex_lock_common()
715 		if (!ww_ctx->is_wait_die &&  in __mutex_lock_common()
725 	/* got the lock - cleanup and rejoice! */  in __mutex_lock_common()
726 	lock_acquired(&lock->dep_map, ip);  in __mutex_lock_common()
732 	raw_spin_unlock(&lock->wait_lock);  in __mutex_lock_common()
741 	raw_spin_unlock(&lock->wait_lock);  in __mutex_lock_common()
743 	mutex_release(&lock->dep_map, ip);  in __mutex_lock_common()
763  * ww_mutex_trylock - tries to acquire the w/w mutex with optional acquire context
771  * specified, -EALREADY handling may happen in calls to ww_mutex_trylock.
778 		return mutex_trylock(&ww->base);  in ww_mutex_trylock()
780 	MUTEX_WARN_ON(ww->base.magic != &ww->base);  in ww_mutex_trylock()
787 	if (ww_ctx->acquired == 0)  in ww_mutex_trylock()
788 		ww_ctx->wounded = 0;  in ww_mutex_trylock()
790 	if (__mutex_trylock(&ww->base)) {  in ww_mutex_trylock()
792 		mutex_acquire_nest(&ww->base.dep_map, 0, 1, &ww_ctx->dep_map, _RET_IP_);  in ww_mutex_trylock()
850 	if (ctx->deadlock_inject_countdown-- == 0) {  in ww_mutex_deadlock_injection()
851 		tmp = ctx->deadlock_inject_interval;  in ww_mutex_deadlock_injection()
857 		ctx->deadlock_inject_interval = tmp;  in ww_mutex_deadlock_injection()
858 		ctx->deadlock_inject_countdown = tmp;  in ww_mutex_deadlock_injection()
859 		ctx->contending_lock = lock;  in ww_mutex_deadlock_injection()
863 		return -EDEADLK;  in ww_mutex_deadlock_injection()
876 	ret =  __ww_mutex_lock(&lock->base, TASK_UNINTERRUPTIBLE,  in ww_mutex_lock()
878 	if (!ret && ctx && ctx->acquired > 1)  in ww_mutex_lock()
891 	ret = __ww_mutex_lock(&lock->base, TASK_INTERRUPTIBLE,  in ww_mutex_lock_interruptible()
894 	if (!ret && ctx && ctx->acquired > 1)  in ww_mutex_lock_interruptible()
912 	mutex_release(&lock->dep_map, ip);  in __mutex_unlock_slowpath()
921 	owner = atomic_long_read(&lock->owner);  in __mutex_unlock_slowpath()
929 		if (atomic_long_try_cmpxchg_release(&lock->owner, &owner, __owner_flags(owner))) {  in __mutex_unlock_slowpath()
937 	raw_spin_lock(&lock->wait_lock);  in __mutex_unlock_slowpath()
939 	if (!list_empty(&lock->wait_list)) {  in __mutex_unlock_slowpath()
940 		/* get the first entry from the wait-list: */  in __mutex_unlock_slowpath()
942 			list_first_entry(&lock->wait_list,  in __mutex_unlock_slowpath()
945 		next = waiter->task;  in __mutex_unlock_slowpath()
954 	raw_spin_unlock(&lock->wait_lock);  in __mutex_unlock_slowpath()
961  * Here come the less common (and hence less performance-critical) APIs:
971  * mutex_lock_interruptible() - Acquire the mutex, interruptible by signals.
979  * Return: 0 if the lock was successfully acquired or %-EINTR if a
995  * mutex_lock_killable() - Acquire the mutex, interruptible by fatal signals.
1003  * Return: 0 if the lock was successfully acquired or %-EINTR if a
1018  * mutex_lock_io() - Acquire the mutex and mark the process as waiting for I/O
1058 	return __ww_mutex_lock(&lock->base, TASK_UNINTERRUPTIBLE, 0,  in __ww_mutex_lock_slowpath()
1066 	return __ww_mutex_lock(&lock->base, TASK_INTERRUPTIBLE, 0,  in __ww_mutex_lock_interruptible_slowpath()
1073  * mutex_trylock - try to acquire the mutex, without waiting
1090 	MUTEX_WARN_ON(lock->magic != lock);  in mutex_trylock()
1094 		mutex_acquire(&lock->dep_map, 0, 1, _RET_IP_);  in mutex_trylock()
1106 	if (__mutex_trylock_fast(&lock->base)) {  in ww_mutex_lock()
1121 	if (__mutex_trylock_fast(&lock->base)) {  in ww_mutex_lock_interruptible()
1138  * atomic_dec_and_mutex_lock - return holding mutex if we dec to 0
1147 	if (atomic_add_unless(cnt, -1, 1))  in atomic_dec_and_mutex_lock()