2 * RT-Mutexes: simple blocking mutual exclusion locks with PI support
4 * started by Ingo Molnar and Thomas Gleixner.
6 * Copyright (C) 2004-2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
7 * Copyright (C) 2005-2006 Timesys Corp., Thomas Gleixner <tglx@timesys.com>
8 * Copyright (C) 2005 Kihon Technologies Inc., Steven Rostedt
9 * Copyright (C) 2006 Esben Nielsen
11 * See Documentation/rt-mutex-design.txt for details.
13 #include <linux/spinlock.h>
14 #include <linux/module.h>
15 #include <linux/sched.h>
16 #include <linux/timer.h>
18 #include "rtmutex_common.h"
20 #ifdef CONFIG_DEBUG_RT_MUTEXES
21 # include "rtmutex-debug.h"
27 * lock->owner state tracking:
29 * lock->owner holds the task_struct pointer of the owner. Bit 0 and 1
30 * are used to keep track of the "owner is pending" and "lock has
34 * NULL 0 0 lock is free (fast acquire possible)
35 * NULL 0 1 invalid state
36 * NULL 1 0 Transitional State*
37 * NULL 1 1 invalid state
38 * taskpointer 0 0 lock is held (fast release possible)
39 * taskpointer 0 1 task is pending owner
40 * taskpointer 1 0 lock is held and has waiters
41 * taskpointer 1 1 task is pending owner and lock has more waiters
43 * Pending ownership is assigned to the top (highest priority)
44 * waiter of the lock, when the lock is released. The thread is woken
45 * up and can now take the lock. Until the lock is taken (bit 0
46 * cleared) a competing higher priority thread can steal the lock
47 * which puts the woken up thread back on the waiters list.
49 * The fast atomic compare exchange based acquire and release is only
50 * possible when bit 0 and 1 of lock->owner are 0.
52 * (*) There's a small time where the owner can be NULL and the
53 * "lock has waiters" bit is set. This can happen when grabbing the lock.
54 * To prevent a cmpxchg of the owner releasing the lock, we need to set this
55 * bit before looking at the lock, hence the reason this is a transitional
60 rt_mutex_set_owner(struct rt_mutex *lock, struct task_struct *owner,
63 unsigned long val = (unsigned long)owner | mask;
65 if (rt_mutex_has_waiters(lock))
66 val |= RT_MUTEX_HAS_WAITERS;
68 lock->owner = (struct task_struct *)val;
71 static inline void clear_rt_mutex_waiters(struct rt_mutex *lock)
73 lock->owner = (struct task_struct *)
74 ((unsigned long)lock->owner & ~RT_MUTEX_HAS_WAITERS);
77 static void fixup_rt_mutex_waiters(struct rt_mutex *lock)
79 if (!rt_mutex_has_waiters(lock))
80 clear_rt_mutex_waiters(lock);
84 * Calculate task priority from the waiter list priority
86 * Return task->normal_prio when the waiter list is empty or when
87 * the waiter is not allowed to do priority boosting
89 int rt_mutex_getprio(struct task_struct *task)
91 if (likely(!task_has_pi_waiters(task)))
92 return task->normal_prio;
94 return min(task_top_pi_waiter(task)->pi_list_entry.prio,
99 * Adjust the priority of a task, after its pi_waiters got modified.
101 * This can be both boosting and unboosting. task->pi_lock must be held.
103 void __rt_mutex_adjust_prio(struct task_struct *task)
105 int prio = rt_mutex_getprio(task);
107 if (task->prio != prio)
108 rt_mutex_setprio(task, prio);
112 * Adjust task priority (undo boosting). Called from the exit path of
113 * rt_mutex_slowunlock() and rt_mutex_slowlock().
115 * (Note: We do this outside of the protection of lock->wait_lock to
116 * allow the lock to be taken while or before we readjust the priority
117 * of task. We do not use the spin_xx_mutex() variants here as we are
118 * outside of the debug path.)
120 static void rt_mutex_adjust_prio(struct task_struct *task)
124 spin_lock_irqsave(&task->pi_lock, flags);
125 __rt_mutex_adjust_prio(task);
126 spin_unlock_irqrestore(&task->pi_lock, flags);
130 * Max number of times we'll walk the boosting chain:
132 int max_lock_depth = 1024;
135 * Adjust the priority chain. Also used for deadlock detection.
136 * Decreases task's usage by one - may thus free the task.
137 * Returns 0 or -EDEADLK.
139 int rt_mutex_adjust_prio_chain(struct task_struct *task,
141 struct rt_mutex *orig_lock,
142 struct rt_mutex_waiter *orig_waiter,
143 struct task_struct *top_task)
145 struct rt_mutex *lock;
146 struct rt_mutex_waiter *waiter, *top_waiter = orig_waiter;
147 int detect_deadlock, ret = 0, depth = 0;
150 detect_deadlock = debug_rt_mutex_detect_deadlock(orig_waiter,
154 * The (de)boosting is a step by step approach with a lot of
155 * pitfalls. We want this to be preemptible and we want hold a
156 * maximum of two locks per step. So we have to check
157 * carefully whether things change under us.
160 if (++depth > max_lock_depth) {
164 * Print this only once. If the admin changes the limit,
165 * print a new message when reaching the limit again.
167 if (prev_max != max_lock_depth) {
168 prev_max = max_lock_depth;
169 printk(KERN_WARNING "Maximum lock depth %d reached "
170 "task: %s (%d)\n", max_lock_depth,
171 top_task->comm, top_task->pid);
173 put_task_struct(task);
175 return deadlock_detect ? -EDEADLK : 0;
179 * Task can not go away as we did a get_task() before !
181 spin_lock_irqsave(&task->pi_lock, flags);
183 waiter = task->pi_blocked_on;
185 * Check whether the end of the boosting chain has been
186 * reached or the state of the chain has changed while we
189 if (!waiter || !waiter->task)
192 if (top_waiter && (!task_has_pi_waiters(task) ||
193 top_waiter != task_top_pi_waiter(task)))
197 * When deadlock detection is off then we check, if further
198 * priority adjustment is necessary.
200 if (!detect_deadlock && waiter->list_entry.prio == task->prio)
204 if (!spin_trylock(&lock->wait_lock)) {
205 spin_unlock_irqrestore(&task->pi_lock, flags);
210 /* Deadlock detection */
211 if (lock == orig_lock || rt_mutex_owner(lock) == top_task) {
212 debug_rt_mutex_deadlock(deadlock_detect, orig_waiter, lock);
213 spin_unlock(&lock->wait_lock);
214 ret = deadlock_detect ? -EDEADLK : 0;
218 top_waiter = rt_mutex_top_waiter(lock);
220 /* Requeue the waiter */
221 plist_del(&waiter->list_entry, &lock->wait_list);
222 waiter->list_entry.prio = task->prio;
223 plist_add(&waiter->list_entry, &lock->wait_list);
225 /* Release the task */
226 spin_unlock_irqrestore(&task->pi_lock, flags);
227 put_task_struct(task);
229 /* Grab the next task */
230 task = rt_mutex_owner(lock);
231 get_task_struct(task);
232 spin_lock_irqsave(&task->pi_lock, flags);
234 if (waiter == rt_mutex_top_waiter(lock)) {
235 /* Boost the owner */
236 plist_del(&top_waiter->pi_list_entry, &task->pi_waiters);
237 waiter->pi_list_entry.prio = waiter->list_entry.prio;
238 plist_add(&waiter->pi_list_entry, &task->pi_waiters);
239 __rt_mutex_adjust_prio(task);
241 } else if (top_waiter == waiter) {
242 /* Deboost the owner */
243 plist_del(&waiter->pi_list_entry, &task->pi_waiters);
244 waiter = rt_mutex_top_waiter(lock);
245 waiter->pi_list_entry.prio = waiter->list_entry.prio;
246 plist_add(&waiter->pi_list_entry, &task->pi_waiters);
247 __rt_mutex_adjust_prio(task);
250 spin_unlock_irqrestore(&task->pi_lock, flags);
252 top_waiter = rt_mutex_top_waiter(lock);
253 spin_unlock(&lock->wait_lock);
255 if (!detect_deadlock && waiter != top_waiter)
261 spin_unlock_irqrestore(&task->pi_lock, flags);
263 put_task_struct(task);
269 * Optimization: check if we can steal the lock from the
270 * assigned pending owner [which might not have taken the
273 static inline int try_to_steal_lock(struct rt_mutex *lock)
275 struct task_struct *pendowner = rt_mutex_owner(lock);
276 struct rt_mutex_waiter *next;
279 if (!rt_mutex_owner_pending(lock))
282 if (pendowner == current)
285 spin_lock_irqsave(&pendowner->pi_lock, flags);
286 if (current->prio >= pendowner->prio) {
287 spin_unlock_irqrestore(&pendowner->pi_lock, flags);
292 * Check if a waiter is enqueued on the pending owners
293 * pi_waiters list. Remove it and readjust pending owners
296 if (likely(!rt_mutex_has_waiters(lock))) {
297 spin_unlock_irqrestore(&pendowner->pi_lock, flags);
301 /* No chain handling, pending owner is not blocked on anything: */
302 next = rt_mutex_top_waiter(lock);
303 plist_del(&next->pi_list_entry, &pendowner->pi_waiters);
304 __rt_mutex_adjust_prio(pendowner);
305 spin_unlock_irqrestore(&pendowner->pi_lock, flags);
308 * We are going to steal the lock and a waiter was
309 * enqueued on the pending owners pi_waiters queue. So
310 * we have to enqueue this waiter into
311 * current->pi_waiters list. This covers the case,
312 * where current is boosted because it holds another
313 * lock and gets unboosted because the booster is
314 * interrupted, so we would delay a waiter with higher
315 * priority as current->normal_prio.
317 * Note: in the rare case of a SCHED_OTHER task changing
318 * its priority and thus stealing the lock, next->task
321 if (likely(next->task != current)) {
322 spin_lock_irqsave(¤t->pi_lock, flags);
323 plist_add(&next->pi_list_entry, ¤t->pi_waiters);
324 __rt_mutex_adjust_prio(current);
325 spin_unlock_irqrestore(¤t->pi_lock, flags);
331 * Try to take an rt-mutex
334 * - when the lock has a real owner
335 * - when a different pending owner exists and has higher priority than current
337 * Must be called with lock->wait_lock held.
339 static int try_to_take_rt_mutex(struct rt_mutex *lock)
342 * We have to be careful here if the atomic speedups are
343 * enabled, such that, when
344 * - no other waiter is on the lock
345 * - the lock has been released since we did the cmpxchg
346 * the lock can be released or taken while we are doing the
347 * checks and marking the lock with RT_MUTEX_HAS_WAITERS.
349 * The atomic acquire/release aware variant of
350 * mark_rt_mutex_waiters uses a cmpxchg loop. After setting
351 * the WAITERS bit, the atomic release / acquire can not
352 * happen anymore and lock->wait_lock protects us from the
355 * Note, that this might set lock->owner =
356 * RT_MUTEX_HAS_WAITERS in the case the lock is not contended
357 * any more. This is fixed up when we take the ownership.
358 * This is the transitional state explained at the top of this file.
360 mark_rt_mutex_waiters(lock);
362 if (rt_mutex_owner(lock) && !try_to_steal_lock(lock))
365 /* We got the lock. */
366 debug_rt_mutex_lock(lock);
368 rt_mutex_set_owner(lock, current, 0);
370 rt_mutex_deadlock_account_lock(lock, current);
376 * Task blocks on lock.
378 * Prepare waiter and propagate pi chain
380 * This must be called with lock->wait_lock held.
382 static int task_blocks_on_rt_mutex(struct rt_mutex *lock,
383 struct rt_mutex_waiter *waiter,
386 struct task_struct *owner = rt_mutex_owner(lock);
387 struct rt_mutex_waiter *top_waiter = waiter;
389 int chain_walk = 0, res;
391 spin_lock_irqsave(¤t->pi_lock, flags);
392 __rt_mutex_adjust_prio(current);
393 waiter->task = current;
395 plist_node_init(&waiter->list_entry, current->prio);
396 plist_node_init(&waiter->pi_list_entry, current->prio);
398 /* Get the top priority waiter on the lock */
399 if (rt_mutex_has_waiters(lock))
400 top_waiter = rt_mutex_top_waiter(lock);
401 plist_add(&waiter->list_entry, &lock->wait_list);
403 current->pi_blocked_on = waiter;
405 spin_unlock_irqrestore(¤t->pi_lock, flags);
407 if (waiter == rt_mutex_top_waiter(lock)) {
408 spin_lock_irqsave(&owner->pi_lock, flags);
409 plist_del(&top_waiter->pi_list_entry, &owner->pi_waiters);
410 plist_add(&waiter->pi_list_entry, &owner->pi_waiters);
412 __rt_mutex_adjust_prio(owner);
413 if (owner->pi_blocked_on)
415 spin_unlock_irqrestore(&owner->pi_lock, flags);
417 else if (debug_rt_mutex_detect_deadlock(waiter, detect_deadlock))
424 * The owner can't disappear while holding a lock,
425 * so the owner struct is protected by wait_lock.
426 * Gets dropped in rt_mutex_adjust_prio_chain()!
428 get_task_struct(owner);
430 spin_unlock(&lock->wait_lock);
432 res = rt_mutex_adjust_prio_chain(owner, detect_deadlock, lock, waiter,
435 spin_lock(&lock->wait_lock);
441 * Wake up the next waiter on the lock.
443 * Remove the top waiter from the current tasks waiter list and from
444 * the lock waiter list. Set it as pending owner. Then wake it up.
446 * Called with lock->wait_lock held.
448 static void wakeup_next_waiter(struct rt_mutex *lock)
450 struct rt_mutex_waiter *waiter;
451 struct task_struct *pendowner;
454 spin_lock_irqsave(¤t->pi_lock, flags);
456 waiter = rt_mutex_top_waiter(lock);
457 plist_del(&waiter->list_entry, &lock->wait_list);
460 * Remove it from current->pi_waiters. We do not adjust a
461 * possible priority boost right now. We execute wakeup in the
462 * boosted mode and go back to normal after releasing
465 plist_del(&waiter->pi_list_entry, ¤t->pi_waiters);
466 pendowner = waiter->task;
469 rt_mutex_set_owner(lock, pendowner, RT_MUTEX_OWNER_PENDING);
471 spin_unlock_irqrestore(¤t->pi_lock, flags);
474 * Clear the pi_blocked_on variable and enqueue a possible
475 * waiter into the pi_waiters list of the pending owner. This
476 * prevents that in case the pending owner gets unboosted a
477 * waiter with higher priority than pending-owner->normal_prio
478 * is blocked on the unboosted (pending) owner.
480 spin_lock_irqsave(&pendowner->pi_lock, flags);
482 WARN_ON(!pendowner->pi_blocked_on);
483 WARN_ON(pendowner->pi_blocked_on != waiter);
484 WARN_ON(pendowner->pi_blocked_on->lock != lock);
486 pendowner->pi_blocked_on = NULL;
488 if (rt_mutex_has_waiters(lock)) {
489 struct rt_mutex_waiter *next;
491 next = rt_mutex_top_waiter(lock);
492 plist_add(&next->pi_list_entry, &pendowner->pi_waiters);
494 spin_unlock_irqrestore(&pendowner->pi_lock, flags);
496 wake_up_process(pendowner);
500 * Remove a waiter from a lock
502 * Must be called with lock->wait_lock held
504 void remove_waiter(struct rt_mutex *lock,
505 struct rt_mutex_waiter *waiter)
507 int first = (waiter == rt_mutex_top_waiter(lock));
508 struct task_struct *owner = rt_mutex_owner(lock);
512 spin_lock_irqsave(¤t->pi_lock, flags);
513 plist_del(&waiter->list_entry, &lock->wait_list);
515 current->pi_blocked_on = NULL;
516 spin_unlock_irqrestore(¤t->pi_lock, flags);
518 if (first && owner != current) {
520 spin_lock_irqsave(&owner->pi_lock, flags);
522 plist_del(&waiter->pi_list_entry, &owner->pi_waiters);
524 if (rt_mutex_has_waiters(lock)) {
525 struct rt_mutex_waiter *next;
527 next = rt_mutex_top_waiter(lock);
528 plist_add(&next->pi_list_entry, &owner->pi_waiters);
530 __rt_mutex_adjust_prio(owner);
532 if (owner->pi_blocked_on)
535 spin_unlock_irqrestore(&owner->pi_lock, flags);
538 WARN_ON(!plist_node_empty(&waiter->pi_list_entry));
543 /* gets dropped in rt_mutex_adjust_prio_chain()! */
544 get_task_struct(owner);
546 spin_unlock(&lock->wait_lock);
548 rt_mutex_adjust_prio_chain(owner, 0, lock, NULL, current);
550 spin_lock(&lock->wait_lock);
554 * Recheck the pi chain, in case we got a priority setting
556 * Called from sched_setscheduler
558 void rt_mutex_adjust_pi(struct task_struct *task)
560 struct rt_mutex_waiter *waiter;
563 spin_lock_irqsave(&task->pi_lock, flags);
565 waiter = task->pi_blocked_on;
566 if (!waiter || waiter->list_entry.prio == task->prio) {
567 spin_unlock_irqrestore(&task->pi_lock, flags);
571 spin_unlock_irqrestore(&task->pi_lock, flags);
573 /* gets dropped in rt_mutex_adjust_prio_chain()! */
574 get_task_struct(task);
575 rt_mutex_adjust_prio_chain(task, 0, NULL, NULL, task);
579 * Slow path lock function:
582 rt_mutex_slowlock(struct rt_mutex *lock, int state,
583 struct hrtimer_sleeper *timeout,
586 struct rt_mutex_waiter waiter;
589 debug_rt_mutex_init_waiter(&waiter);
592 spin_lock(&lock->wait_lock);
594 /* Try to acquire the lock again: */
595 if (try_to_take_rt_mutex(lock)) {
596 spin_unlock(&lock->wait_lock);
600 set_current_state(state);
602 /* Setup the timer, when timeout != NULL */
603 if (unlikely(timeout))
604 hrtimer_start(&timeout->timer, timeout->timer.expires,
608 /* Try to acquire the lock: */
609 if (try_to_take_rt_mutex(lock))
613 * TASK_INTERRUPTIBLE checks for signals and
614 * timeout. Ignored otherwise.
616 if (unlikely(state == TASK_INTERRUPTIBLE)) {
617 /* Signal pending? */
618 if (signal_pending(current))
620 if (timeout && !timeout->task)
627 * waiter.task is NULL the first time we come here and
628 * when we have been woken up by the previous owner
629 * but the lock got stolen by a higher prio task.
632 ret = task_blocks_on_rt_mutex(lock, &waiter,
635 * If we got woken up by the owner then start loop
636 * all over without going into schedule to try
637 * to get the lock now:
639 if (unlikely(!waiter.task)) {
641 * Reset the return value. We might
642 * have returned with -EDEADLK and the
643 * owner released the lock while we
644 * were walking the pi chain.
653 spin_unlock(&lock->wait_lock);
655 debug_rt_mutex_print_deadlock(&waiter);
658 schedule_rt_mutex(lock);
660 spin_lock(&lock->wait_lock);
661 set_current_state(state);
664 set_current_state(TASK_RUNNING);
666 if (unlikely(waiter.task))
667 remove_waiter(lock, &waiter);
670 * try_to_take_rt_mutex() sets the waiter bit
671 * unconditionally. We might have to fix that up.
673 fixup_rt_mutex_waiters(lock);
675 spin_unlock(&lock->wait_lock);
677 /* Remove pending timer: */
678 if (unlikely(timeout))
679 hrtimer_cancel(&timeout->timer);
682 * Readjust priority, when we did not get the lock. We might
683 * have been the pending owner and boosted. Since we did not
684 * take the lock, the PI boost has to go.
687 rt_mutex_adjust_prio(current);
689 debug_rt_mutex_free_waiter(&waiter);
695 * Slow path try-lock function:
698 rt_mutex_slowtrylock(struct rt_mutex *lock)
702 spin_lock(&lock->wait_lock);
704 if (likely(rt_mutex_owner(lock) != current)) {
706 ret = try_to_take_rt_mutex(lock);
708 * try_to_take_rt_mutex() sets the lock waiters
709 * bit unconditionally. Clean this up.
711 fixup_rt_mutex_waiters(lock);
714 spin_unlock(&lock->wait_lock);
720 * Slow path to release a rt-mutex:
723 rt_mutex_slowunlock(struct rt_mutex *lock)
725 spin_lock(&lock->wait_lock);
727 debug_rt_mutex_unlock(lock);
729 rt_mutex_deadlock_account_unlock(current);
731 if (!rt_mutex_has_waiters(lock)) {
733 spin_unlock(&lock->wait_lock);
737 wakeup_next_waiter(lock);
739 spin_unlock(&lock->wait_lock);
741 /* Undo pi boosting if necessary: */
742 rt_mutex_adjust_prio(current);
746 * debug aware fast / slowpath lock,trylock,unlock
748 * The atomic acquire/release ops are compiled away, when either the
749 * architecture does not support cmpxchg or when debugging is enabled.
752 rt_mutex_fastlock(struct rt_mutex *lock, int state,
754 int (*slowfn)(struct rt_mutex *lock, int state,
755 struct hrtimer_sleeper *timeout,
756 int detect_deadlock))
758 if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) {
759 rt_mutex_deadlock_account_lock(lock, current);
762 return slowfn(lock, state, NULL, detect_deadlock);
766 rt_mutex_timed_fastlock(struct rt_mutex *lock, int state,
767 struct hrtimer_sleeper *timeout, int detect_deadlock,
768 int (*slowfn)(struct rt_mutex *lock, int state,
769 struct hrtimer_sleeper *timeout,
770 int detect_deadlock))
772 if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) {
773 rt_mutex_deadlock_account_lock(lock, current);
776 return slowfn(lock, state, timeout, detect_deadlock);
780 rt_mutex_fasttrylock(struct rt_mutex *lock,
781 int (*slowfn)(struct rt_mutex *lock))
783 if (likely(rt_mutex_cmpxchg(lock, NULL, current))) {
784 rt_mutex_deadlock_account_lock(lock, current);
791 rt_mutex_fastunlock(struct rt_mutex *lock,
792 void (*slowfn)(struct rt_mutex *lock))
794 if (likely(rt_mutex_cmpxchg(lock, current, NULL)))
795 rt_mutex_deadlock_account_unlock(current);
801 * rt_mutex_lock - lock a rt_mutex
803 * @lock: the rt_mutex to be locked
805 void __sched rt_mutex_lock(struct rt_mutex *lock)
809 rt_mutex_fastlock(lock, TASK_UNINTERRUPTIBLE, 0, rt_mutex_slowlock);
811 EXPORT_SYMBOL_GPL(rt_mutex_lock);
814 * rt_mutex_lock_interruptible - lock a rt_mutex interruptible
816 * @lock: the rt_mutex to be locked
817 * @detect_deadlock: deadlock detection on/off
821 * -EINTR when interrupted by a signal
822 * -EDEADLK when the lock would deadlock (when deadlock detection is on)
824 int __sched rt_mutex_lock_interruptible(struct rt_mutex *lock,
829 return rt_mutex_fastlock(lock, TASK_INTERRUPTIBLE,
830 detect_deadlock, rt_mutex_slowlock);
832 EXPORT_SYMBOL_GPL(rt_mutex_lock_interruptible);
835 * rt_mutex_lock_interruptible_ktime - lock a rt_mutex interruptible
836 * the timeout structure is provided
839 * @lock: the rt_mutex to be locked
840 * @timeout: timeout structure or NULL (no timeout)
841 * @detect_deadlock: deadlock detection on/off
845 * -EINTR when interrupted by a signal
846 * -ETIMEOUT when the timeout expired
847 * -EDEADLK when the lock would deadlock (when deadlock detection is on)
850 rt_mutex_timed_lock(struct rt_mutex *lock, struct hrtimer_sleeper *timeout,
855 return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout,
856 detect_deadlock, rt_mutex_slowlock);
858 EXPORT_SYMBOL_GPL(rt_mutex_timed_lock);
861 * rt_mutex_trylock - try to lock a rt_mutex
863 * @lock: the rt_mutex to be locked
865 * Returns 1 on success and 0 on contention
867 int __sched rt_mutex_trylock(struct rt_mutex *lock)
869 return rt_mutex_fasttrylock(lock, rt_mutex_slowtrylock);
871 EXPORT_SYMBOL_GPL(rt_mutex_trylock);
874 * rt_mutex_unlock - unlock a rt_mutex
876 * @lock: the rt_mutex to be unlocked
878 void __sched rt_mutex_unlock(struct rt_mutex *lock)
880 rt_mutex_fastunlock(lock, rt_mutex_slowunlock);
882 EXPORT_SYMBOL_GPL(rt_mutex_unlock);
885 * rt_mutex_destroy - mark a mutex unusable
886 * @lock: the mutex to be destroyed
888 * This function marks the mutex uninitialized, and any subsequent
889 * use of the mutex is forbidden. The mutex must not be locked when
890 * this function is called.
892 void rt_mutex_destroy(struct rt_mutex *lock)
894 WARN_ON(rt_mutex_is_locked(lock));
895 #ifdef CONFIG_DEBUG_RT_MUTEXES
900 EXPORT_SYMBOL_GPL(rt_mutex_destroy);
903 * __rt_mutex_init - initialize the rt lock
905 * @lock: the rt lock to be initialized
907 * Initialize the rt lock to unlocked state.
909 * Initializing of a locked rt lock is not allowed
911 void __rt_mutex_init(struct rt_mutex *lock, const char *name)
914 spin_lock_init(&lock->wait_lock);
915 plist_head_init(&lock->wait_list, &lock->wait_lock);
917 debug_rt_mutex_init(lock, name);
919 EXPORT_SYMBOL_GPL(__rt_mutex_init);
922 * rt_mutex_init_proxy_locked - initialize and lock a rt_mutex on behalf of a
925 * @lock: the rt_mutex to be locked
926 * @proxy_owner:the task to set as owner
928 * No locking. Caller has to do serializing itself
929 * Special API call for PI-futex support
931 void rt_mutex_init_proxy_locked(struct rt_mutex *lock,
932 struct task_struct *proxy_owner)
934 __rt_mutex_init(lock, NULL);
935 debug_rt_mutex_proxy_lock(lock, proxy_owner);
936 rt_mutex_set_owner(lock, proxy_owner, 0);
937 rt_mutex_deadlock_account_lock(lock, proxy_owner);
941 * rt_mutex_proxy_unlock - release a lock on behalf of owner
943 * @lock: the rt_mutex to be locked
945 * No locking. Caller has to do serializing itself
946 * Special API call for PI-futex support
948 void rt_mutex_proxy_unlock(struct rt_mutex *lock,
949 struct task_struct *proxy_owner)
951 debug_rt_mutex_proxy_unlock(lock);
952 rt_mutex_set_owner(lock, NULL, 0);
953 rt_mutex_deadlock_account_unlock(proxy_owner);
957 * rt_mutex_next_owner - return the next owner of the lock
959 * @lock: the rt lock query
961 * Returns the next owner of the lock or NULL
963 * Caller has to serialize against other accessors to the lock
966 * Special API call for PI-futex support
968 struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock)
970 if (!rt_mutex_has_waiters(lock))
973 return rt_mutex_top_waiter(lock)->task;