Merge branch 'merge' of git://git.kernel.org/pub/scm/linux/kernel/git/paulus/powerpc
[linux-2.6/lfs.git] / kernel / rtmutex.c
blob6522ae5b14a2ad7aca5cde919c3a5f1d305c6fd6
1 /*
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"
21 * lock->owner state tracking:
23 * lock->owner holds the task_struct pointer of the owner. Bit 0 and 1
24 * are used to keep track of the "owner is pending" and "lock has
25 * waiters" state.
27 * owner bit1 bit0
28 * NULL 0 0 lock is free (fast acquire possible)
29 * NULL 0 1 invalid state
30 * NULL 1 0 Transitional State*
31 * NULL 1 1 invalid state
32 * taskpointer 0 0 lock is held (fast release possible)
33 * taskpointer 0 1 task is pending owner
34 * taskpointer 1 0 lock is held and has waiters
35 * taskpointer 1 1 task is pending owner and lock has more waiters
37 * Pending ownership is assigned to the top (highest priority)
38 * waiter of the lock, when the lock is released. The thread is woken
39 * up and can now take the lock. Until the lock is taken (bit 0
40 * cleared) a competing higher priority thread can steal the lock
41 * which puts the woken up thread back on the waiters list.
43 * The fast atomic compare exchange based acquire and release is only
44 * possible when bit 0 and 1 of lock->owner are 0.
46 * (*) There's a small time where the owner can be NULL and the
47 * "lock has waiters" bit is set. This can happen when grabbing the lock.
48 * To prevent a cmpxchg of the owner releasing the lock, we need to set this
49 * bit before looking at the lock, hence the reason this is a transitional
50 * state.
53 static void
54 rt_mutex_set_owner(struct rt_mutex *lock, struct task_struct *owner,
55 unsigned long mask)
57 unsigned long val = (unsigned long)owner | mask;
59 if (rt_mutex_has_waiters(lock))
60 val |= RT_MUTEX_HAS_WAITERS;
62 lock->owner = (struct task_struct *)val;
65 static inline void clear_rt_mutex_waiters(struct rt_mutex *lock)
67 lock->owner = (struct task_struct *)
68 ((unsigned long)lock->owner & ~RT_MUTEX_HAS_WAITERS);
71 static void fixup_rt_mutex_waiters(struct rt_mutex *lock)
73 if (!rt_mutex_has_waiters(lock))
74 clear_rt_mutex_waiters(lock);
78 * We can speed up the acquire/release, if the architecture
79 * supports cmpxchg and if there's no debugging state to be set up
81 #if defined(__HAVE_ARCH_CMPXCHG) && !defined(CONFIG_DEBUG_RT_MUTEXES)
82 # define rt_mutex_cmpxchg(l,c,n) (cmpxchg(&l->owner, c, n) == c)
83 static inline void mark_rt_mutex_waiters(struct rt_mutex *lock)
85 unsigned long owner, *p = (unsigned long *) &lock->owner;
87 do {
88 owner = *p;
89 } while (cmpxchg(p, owner, owner | RT_MUTEX_HAS_WAITERS) != owner);
91 #else
92 # define rt_mutex_cmpxchg(l,c,n) (0)
93 static inline void mark_rt_mutex_waiters(struct rt_mutex *lock)
95 lock->owner = (struct task_struct *)
96 ((unsigned long)lock->owner | RT_MUTEX_HAS_WAITERS);
98 #endif
101 * Calculate task priority from the waiter list priority
103 * Return task->normal_prio when the waiter list is empty or when
104 * the waiter is not allowed to do priority boosting
106 int rt_mutex_getprio(struct task_struct *task)
108 if (likely(!task_has_pi_waiters(task)))
109 return task->normal_prio;
111 return min(task_top_pi_waiter(task)->pi_list_entry.prio,
112 task->normal_prio);
116 * Adjust the priority of a task, after its pi_waiters got modified.
118 * This can be both boosting and unboosting. task->pi_lock must be held.
120 static void __rt_mutex_adjust_prio(struct task_struct *task)
122 int prio = rt_mutex_getprio(task);
124 if (task->prio != prio)
125 rt_mutex_setprio(task, prio);
129 * Adjust task priority (undo boosting). Called from the exit path of
130 * rt_mutex_slowunlock() and rt_mutex_slowlock().
132 * (Note: We do this outside of the protection of lock->wait_lock to
133 * allow the lock to be taken while or before we readjust the priority
134 * of task. We do not use the spin_xx_mutex() variants here as we are
135 * outside of the debug path.)
137 static void rt_mutex_adjust_prio(struct task_struct *task)
139 unsigned long flags;
141 spin_lock_irqsave(&task->pi_lock, flags);
142 __rt_mutex_adjust_prio(task);
143 spin_unlock_irqrestore(&task->pi_lock, flags);
147 * Max number of times we'll walk the boosting chain:
149 int max_lock_depth = 1024;
152 * Adjust the priority chain. Also used for deadlock detection.
153 * Decreases task's usage by one - may thus free the task.
154 * Returns 0 or -EDEADLK.
156 static int rt_mutex_adjust_prio_chain(struct task_struct *task,
157 int deadlock_detect,
158 struct rt_mutex *orig_lock,
159 struct rt_mutex_waiter *orig_waiter,
160 struct task_struct *top_task)
162 struct rt_mutex *lock;
163 struct rt_mutex_waiter *waiter, *top_waiter = orig_waiter;
164 int detect_deadlock, ret = 0, depth = 0;
165 unsigned long flags;
167 detect_deadlock = debug_rt_mutex_detect_deadlock(orig_waiter,
168 deadlock_detect);
171 * The (de)boosting is a step by step approach with a lot of
172 * pitfalls. We want this to be preemptible and we want hold a
173 * maximum of two locks per step. So we have to check
174 * carefully whether things change under us.
176 again:
177 if (++depth > max_lock_depth) {
178 static int prev_max;
181 * Print this only once. If the admin changes the limit,
182 * print a new message when reaching the limit again.
184 if (prev_max != max_lock_depth) {
185 prev_max = max_lock_depth;
186 printk(KERN_WARNING "Maximum lock depth %d reached "
187 "task: %s (%d)\n", max_lock_depth,
188 top_task->comm, task_pid_nr(top_task));
190 put_task_struct(task);
192 return deadlock_detect ? -EDEADLK : 0;
194 retry:
196 * Task can not go away as we did a get_task() before !
198 spin_lock_irqsave(&task->pi_lock, flags);
200 waiter = task->pi_blocked_on;
202 * Check whether the end of the boosting chain has been
203 * reached or the state of the chain has changed while we
204 * dropped the locks.
206 if (!waiter || !waiter->task)
207 goto out_unlock_pi;
210 * Check the orig_waiter state. After we dropped the locks,
211 * the previous owner of the lock might have released the lock
212 * and made us the pending owner:
214 if (orig_waiter && !orig_waiter->task)
215 goto out_unlock_pi;
218 * Drop out, when the task has no waiters. Note,
219 * top_waiter can be NULL, when we are in the deboosting
220 * mode!
222 if (top_waiter && (!task_has_pi_waiters(task) ||
223 top_waiter != task_top_pi_waiter(task)))
224 goto out_unlock_pi;
227 * When deadlock detection is off then we check, if further
228 * priority adjustment is necessary.
230 if (!detect_deadlock && waiter->list_entry.prio == task->prio)
231 goto out_unlock_pi;
233 lock = waiter->lock;
234 if (!spin_trylock(&lock->wait_lock)) {
235 spin_unlock_irqrestore(&task->pi_lock, flags);
236 cpu_relax();
237 goto retry;
240 /* Deadlock detection */
241 if (lock == orig_lock || rt_mutex_owner(lock) == top_task) {
242 debug_rt_mutex_deadlock(deadlock_detect, orig_waiter, lock);
243 spin_unlock(&lock->wait_lock);
244 ret = deadlock_detect ? -EDEADLK : 0;
245 goto out_unlock_pi;
248 top_waiter = rt_mutex_top_waiter(lock);
250 /* Requeue the waiter */
251 plist_del(&waiter->list_entry, &lock->wait_list);
252 waiter->list_entry.prio = task->prio;
253 plist_add(&waiter->list_entry, &lock->wait_list);
255 /* Release the task */
256 spin_unlock_irqrestore(&task->pi_lock, flags);
257 put_task_struct(task);
259 /* Grab the next task */
260 task = rt_mutex_owner(lock);
261 get_task_struct(task);
262 spin_lock_irqsave(&task->pi_lock, flags);
264 if (waiter == rt_mutex_top_waiter(lock)) {
265 /* Boost the owner */
266 plist_del(&top_waiter->pi_list_entry, &task->pi_waiters);
267 waiter->pi_list_entry.prio = waiter->list_entry.prio;
268 plist_add(&waiter->pi_list_entry, &task->pi_waiters);
269 __rt_mutex_adjust_prio(task);
271 } else if (top_waiter == waiter) {
272 /* Deboost the owner */
273 plist_del(&waiter->pi_list_entry, &task->pi_waiters);
274 waiter = rt_mutex_top_waiter(lock);
275 waiter->pi_list_entry.prio = waiter->list_entry.prio;
276 plist_add(&waiter->pi_list_entry, &task->pi_waiters);
277 __rt_mutex_adjust_prio(task);
280 spin_unlock_irqrestore(&task->pi_lock, flags);
282 top_waiter = rt_mutex_top_waiter(lock);
283 spin_unlock(&lock->wait_lock);
285 if (!detect_deadlock && waiter != top_waiter)
286 goto out_put_task;
288 goto again;
290 out_unlock_pi:
291 spin_unlock_irqrestore(&task->pi_lock, flags);
292 out_put_task:
293 put_task_struct(task);
295 return ret;
299 * Optimization: check if we can steal the lock from the
300 * assigned pending owner [which might not have taken the
301 * lock yet]:
303 static inline int try_to_steal_lock(struct rt_mutex *lock)
305 struct task_struct *pendowner = rt_mutex_owner(lock);
306 struct rt_mutex_waiter *next;
307 unsigned long flags;
309 if (!rt_mutex_owner_pending(lock))
310 return 0;
312 if (pendowner == current)
313 return 1;
315 spin_lock_irqsave(&pendowner->pi_lock, flags);
316 if (current->prio >= pendowner->prio) {
317 spin_unlock_irqrestore(&pendowner->pi_lock, flags);
318 return 0;
322 * Check if a waiter is enqueued on the pending owners
323 * pi_waiters list. Remove it and readjust pending owners
324 * priority.
326 if (likely(!rt_mutex_has_waiters(lock))) {
327 spin_unlock_irqrestore(&pendowner->pi_lock, flags);
328 return 1;
331 /* No chain handling, pending owner is not blocked on anything: */
332 next = rt_mutex_top_waiter(lock);
333 plist_del(&next->pi_list_entry, &pendowner->pi_waiters);
334 __rt_mutex_adjust_prio(pendowner);
335 spin_unlock_irqrestore(&pendowner->pi_lock, flags);
338 * We are going to steal the lock and a waiter was
339 * enqueued on the pending owners pi_waiters queue. So
340 * we have to enqueue this waiter into
341 * current->pi_waiters list. This covers the case,
342 * where current is boosted because it holds another
343 * lock and gets unboosted because the booster is
344 * interrupted, so we would delay a waiter with higher
345 * priority as current->normal_prio.
347 * Note: in the rare case of a SCHED_OTHER task changing
348 * its priority and thus stealing the lock, next->task
349 * might be current:
351 if (likely(next->task != current)) {
352 spin_lock_irqsave(&current->pi_lock, flags);
353 plist_add(&next->pi_list_entry, &current->pi_waiters);
354 __rt_mutex_adjust_prio(current);
355 spin_unlock_irqrestore(&current->pi_lock, flags);
357 return 1;
361 * Try to take an rt-mutex
363 * This fails
364 * - when the lock has a real owner
365 * - when a different pending owner exists and has higher priority than current
367 * Must be called with lock->wait_lock held.
369 static int try_to_take_rt_mutex(struct rt_mutex *lock)
372 * We have to be careful here if the atomic speedups are
373 * enabled, such that, when
374 * - no other waiter is on the lock
375 * - the lock has been released since we did the cmpxchg
376 * the lock can be released or taken while we are doing the
377 * checks and marking the lock with RT_MUTEX_HAS_WAITERS.
379 * The atomic acquire/release aware variant of
380 * mark_rt_mutex_waiters uses a cmpxchg loop. After setting
381 * the WAITERS bit, the atomic release / acquire can not
382 * happen anymore and lock->wait_lock protects us from the
383 * non-atomic case.
385 * Note, that this might set lock->owner =
386 * RT_MUTEX_HAS_WAITERS in the case the lock is not contended
387 * any more. This is fixed up when we take the ownership.
388 * This is the transitional state explained at the top of this file.
390 mark_rt_mutex_waiters(lock);
392 if (rt_mutex_owner(lock) && !try_to_steal_lock(lock))
393 return 0;
395 /* We got the lock. */
396 debug_rt_mutex_lock(lock);
398 rt_mutex_set_owner(lock, current, 0);
400 rt_mutex_deadlock_account_lock(lock, current);
402 return 1;
406 * Task blocks on lock.
408 * Prepare waiter and propagate pi chain
410 * This must be called with lock->wait_lock held.
412 static int task_blocks_on_rt_mutex(struct rt_mutex *lock,
413 struct rt_mutex_waiter *waiter,
414 int detect_deadlock)
416 struct task_struct *owner = rt_mutex_owner(lock);
417 struct rt_mutex_waiter *top_waiter = waiter;
418 unsigned long flags;
419 int chain_walk = 0, res;
421 spin_lock_irqsave(&current->pi_lock, flags);
422 __rt_mutex_adjust_prio(current);
423 waiter->task = current;
424 waiter->lock = lock;
425 plist_node_init(&waiter->list_entry, current->prio);
426 plist_node_init(&waiter->pi_list_entry, current->prio);
428 /* Get the top priority waiter on the lock */
429 if (rt_mutex_has_waiters(lock))
430 top_waiter = rt_mutex_top_waiter(lock);
431 plist_add(&waiter->list_entry, &lock->wait_list);
433 current->pi_blocked_on = waiter;
435 spin_unlock_irqrestore(&current->pi_lock, flags);
437 if (waiter == rt_mutex_top_waiter(lock)) {
438 spin_lock_irqsave(&owner->pi_lock, flags);
439 plist_del(&top_waiter->pi_list_entry, &owner->pi_waiters);
440 plist_add(&waiter->pi_list_entry, &owner->pi_waiters);
442 __rt_mutex_adjust_prio(owner);
443 if (owner->pi_blocked_on)
444 chain_walk = 1;
445 spin_unlock_irqrestore(&owner->pi_lock, flags);
447 else if (debug_rt_mutex_detect_deadlock(waiter, detect_deadlock))
448 chain_walk = 1;
450 if (!chain_walk)
451 return 0;
454 * The owner can't disappear while holding a lock,
455 * so the owner struct is protected by wait_lock.
456 * Gets dropped in rt_mutex_adjust_prio_chain()!
458 get_task_struct(owner);
460 spin_unlock(&lock->wait_lock);
462 res = rt_mutex_adjust_prio_chain(owner, detect_deadlock, lock, waiter,
463 current);
465 spin_lock(&lock->wait_lock);
467 return res;
471 * Wake up the next waiter on the lock.
473 * Remove the top waiter from the current tasks waiter list and from
474 * the lock waiter list. Set it as pending owner. Then wake it up.
476 * Called with lock->wait_lock held.
478 static void wakeup_next_waiter(struct rt_mutex *lock)
480 struct rt_mutex_waiter *waiter;
481 struct task_struct *pendowner;
482 unsigned long flags;
484 spin_lock_irqsave(&current->pi_lock, flags);
486 waiter = rt_mutex_top_waiter(lock);
487 plist_del(&waiter->list_entry, &lock->wait_list);
490 * Remove it from current->pi_waiters. We do not adjust a
491 * possible priority boost right now. We execute wakeup in the
492 * boosted mode and go back to normal after releasing
493 * lock->wait_lock.
495 plist_del(&waiter->pi_list_entry, &current->pi_waiters);
496 pendowner = waiter->task;
497 waiter->task = NULL;
499 rt_mutex_set_owner(lock, pendowner, RT_MUTEX_OWNER_PENDING);
501 spin_unlock_irqrestore(&current->pi_lock, flags);
504 * Clear the pi_blocked_on variable and enqueue a possible
505 * waiter into the pi_waiters list of the pending owner. This
506 * prevents that in case the pending owner gets unboosted a
507 * waiter with higher priority than pending-owner->normal_prio
508 * is blocked on the unboosted (pending) owner.
510 spin_lock_irqsave(&pendowner->pi_lock, flags);
512 WARN_ON(!pendowner->pi_blocked_on);
513 WARN_ON(pendowner->pi_blocked_on != waiter);
514 WARN_ON(pendowner->pi_blocked_on->lock != lock);
516 pendowner->pi_blocked_on = NULL;
518 if (rt_mutex_has_waiters(lock)) {
519 struct rt_mutex_waiter *next;
521 next = rt_mutex_top_waiter(lock);
522 plist_add(&next->pi_list_entry, &pendowner->pi_waiters);
524 spin_unlock_irqrestore(&pendowner->pi_lock, flags);
526 wake_up_process(pendowner);
530 * Remove a waiter from a lock
532 * Must be called with lock->wait_lock held
534 static void remove_waiter(struct rt_mutex *lock,
535 struct rt_mutex_waiter *waiter)
537 int first = (waiter == rt_mutex_top_waiter(lock));
538 struct task_struct *owner = rt_mutex_owner(lock);
539 unsigned long flags;
540 int chain_walk = 0;
542 spin_lock_irqsave(&current->pi_lock, flags);
543 plist_del(&waiter->list_entry, &lock->wait_list);
544 waiter->task = NULL;
545 current->pi_blocked_on = NULL;
546 spin_unlock_irqrestore(&current->pi_lock, flags);
548 if (first && owner != current) {
550 spin_lock_irqsave(&owner->pi_lock, flags);
552 plist_del(&waiter->pi_list_entry, &owner->pi_waiters);
554 if (rt_mutex_has_waiters(lock)) {
555 struct rt_mutex_waiter *next;
557 next = rt_mutex_top_waiter(lock);
558 plist_add(&next->pi_list_entry, &owner->pi_waiters);
560 __rt_mutex_adjust_prio(owner);
562 if (owner->pi_blocked_on)
563 chain_walk = 1;
565 spin_unlock_irqrestore(&owner->pi_lock, flags);
568 WARN_ON(!plist_node_empty(&waiter->pi_list_entry));
570 if (!chain_walk)
571 return;
573 /* gets dropped in rt_mutex_adjust_prio_chain()! */
574 get_task_struct(owner);
576 spin_unlock(&lock->wait_lock);
578 rt_mutex_adjust_prio_chain(owner, 0, lock, NULL, current);
580 spin_lock(&lock->wait_lock);
584 * Recheck the pi chain, in case we got a priority setting
586 * Called from sched_setscheduler
588 void rt_mutex_adjust_pi(struct task_struct *task)
590 struct rt_mutex_waiter *waiter;
591 unsigned long flags;
593 spin_lock_irqsave(&task->pi_lock, flags);
595 waiter = task->pi_blocked_on;
596 if (!waiter || waiter->list_entry.prio == task->prio) {
597 spin_unlock_irqrestore(&task->pi_lock, flags);
598 return;
601 spin_unlock_irqrestore(&task->pi_lock, flags);
603 /* gets dropped in rt_mutex_adjust_prio_chain()! */
604 get_task_struct(task);
605 rt_mutex_adjust_prio_chain(task, 0, NULL, NULL, task);
609 * Slow path lock function:
611 static int __sched
612 rt_mutex_slowlock(struct rt_mutex *lock, int state,
613 struct hrtimer_sleeper *timeout,
614 int detect_deadlock)
616 struct rt_mutex_waiter waiter;
617 int ret = 0;
619 debug_rt_mutex_init_waiter(&waiter);
620 waiter.task = NULL;
622 spin_lock(&lock->wait_lock);
624 /* Try to acquire the lock again: */
625 if (try_to_take_rt_mutex(lock)) {
626 spin_unlock(&lock->wait_lock);
627 return 0;
630 set_current_state(state);
632 /* Setup the timer, when timeout != NULL */
633 if (unlikely(timeout)) {
634 hrtimer_start(&timeout->timer, timeout->timer.expires,
635 HRTIMER_MODE_ABS);
636 if (!hrtimer_active(&timeout->timer))
637 timeout->task = NULL;
640 for (;;) {
641 /* Try to acquire the lock: */
642 if (try_to_take_rt_mutex(lock))
643 break;
646 * TASK_INTERRUPTIBLE checks for signals and
647 * timeout. Ignored otherwise.
649 if (unlikely(state == TASK_INTERRUPTIBLE)) {
650 /* Signal pending? */
651 if (signal_pending(current))
652 ret = -EINTR;
653 if (timeout && !timeout->task)
654 ret = -ETIMEDOUT;
655 if (ret)
656 break;
660 * waiter.task is NULL the first time we come here and
661 * when we have been woken up by the previous owner
662 * but the lock got stolen by a higher prio task.
664 if (!waiter.task) {
665 ret = task_blocks_on_rt_mutex(lock, &waiter,
666 detect_deadlock);
668 * If we got woken up by the owner then start loop
669 * all over without going into schedule to try
670 * to get the lock now:
672 if (unlikely(!waiter.task)) {
674 * Reset the return value. We might
675 * have returned with -EDEADLK and the
676 * owner released the lock while we
677 * were walking the pi chain.
679 ret = 0;
680 continue;
682 if (unlikely(ret))
683 break;
686 spin_unlock(&lock->wait_lock);
688 debug_rt_mutex_print_deadlock(&waiter);
690 if (waiter.task)
691 schedule_rt_mutex(lock);
693 spin_lock(&lock->wait_lock);
694 set_current_state(state);
697 set_current_state(TASK_RUNNING);
699 if (unlikely(waiter.task))
700 remove_waiter(lock, &waiter);
703 * try_to_take_rt_mutex() sets the waiter bit
704 * unconditionally. We might have to fix that up.
706 fixup_rt_mutex_waiters(lock);
708 spin_unlock(&lock->wait_lock);
710 /* Remove pending timer: */
711 if (unlikely(timeout))
712 hrtimer_cancel(&timeout->timer);
715 * Readjust priority, when we did not get the lock. We might
716 * have been the pending owner and boosted. Since we did not
717 * take the lock, the PI boost has to go.
719 if (unlikely(ret))
720 rt_mutex_adjust_prio(current);
722 debug_rt_mutex_free_waiter(&waiter);
724 return ret;
728 * Slow path try-lock function:
730 static inline int
731 rt_mutex_slowtrylock(struct rt_mutex *lock)
733 int ret = 0;
735 spin_lock(&lock->wait_lock);
737 if (likely(rt_mutex_owner(lock) != current)) {
739 ret = try_to_take_rt_mutex(lock);
741 * try_to_take_rt_mutex() sets the lock waiters
742 * bit unconditionally. Clean this up.
744 fixup_rt_mutex_waiters(lock);
747 spin_unlock(&lock->wait_lock);
749 return ret;
753 * Slow path to release a rt-mutex:
755 static void __sched
756 rt_mutex_slowunlock(struct rt_mutex *lock)
758 spin_lock(&lock->wait_lock);
760 debug_rt_mutex_unlock(lock);
762 rt_mutex_deadlock_account_unlock(current);
764 if (!rt_mutex_has_waiters(lock)) {
765 lock->owner = NULL;
766 spin_unlock(&lock->wait_lock);
767 return;
770 wakeup_next_waiter(lock);
772 spin_unlock(&lock->wait_lock);
774 /* Undo pi boosting if necessary: */
775 rt_mutex_adjust_prio(current);
779 * debug aware fast / slowpath lock,trylock,unlock
781 * The atomic acquire/release ops are compiled away, when either the
782 * architecture does not support cmpxchg or when debugging is enabled.
784 static inline int
785 rt_mutex_fastlock(struct rt_mutex *lock, int state,
786 int detect_deadlock,
787 int (*slowfn)(struct rt_mutex *lock, int state,
788 struct hrtimer_sleeper *timeout,
789 int detect_deadlock))
791 if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) {
792 rt_mutex_deadlock_account_lock(lock, current);
793 return 0;
794 } else
795 return slowfn(lock, state, NULL, detect_deadlock);
798 static inline int
799 rt_mutex_timed_fastlock(struct rt_mutex *lock, int state,
800 struct hrtimer_sleeper *timeout, int detect_deadlock,
801 int (*slowfn)(struct rt_mutex *lock, int state,
802 struct hrtimer_sleeper *timeout,
803 int detect_deadlock))
805 if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) {
806 rt_mutex_deadlock_account_lock(lock, current);
807 return 0;
808 } else
809 return slowfn(lock, state, timeout, detect_deadlock);
812 static inline int
813 rt_mutex_fasttrylock(struct rt_mutex *lock,
814 int (*slowfn)(struct rt_mutex *lock))
816 if (likely(rt_mutex_cmpxchg(lock, NULL, current))) {
817 rt_mutex_deadlock_account_lock(lock, current);
818 return 1;
820 return slowfn(lock);
823 static inline void
824 rt_mutex_fastunlock(struct rt_mutex *lock,
825 void (*slowfn)(struct rt_mutex *lock))
827 if (likely(rt_mutex_cmpxchg(lock, current, NULL)))
828 rt_mutex_deadlock_account_unlock(current);
829 else
830 slowfn(lock);
834 * rt_mutex_lock - lock a rt_mutex
836 * @lock: the rt_mutex to be locked
838 void __sched rt_mutex_lock(struct rt_mutex *lock)
840 might_sleep();
842 rt_mutex_fastlock(lock, TASK_UNINTERRUPTIBLE, 0, rt_mutex_slowlock);
844 EXPORT_SYMBOL_GPL(rt_mutex_lock);
847 * rt_mutex_lock_interruptible - lock a rt_mutex interruptible
849 * @lock: the rt_mutex to be locked
850 * @detect_deadlock: deadlock detection on/off
852 * Returns:
853 * 0 on success
854 * -EINTR when interrupted by a signal
855 * -EDEADLK when the lock would deadlock (when deadlock detection is on)
857 int __sched rt_mutex_lock_interruptible(struct rt_mutex *lock,
858 int detect_deadlock)
860 might_sleep();
862 return rt_mutex_fastlock(lock, TASK_INTERRUPTIBLE,
863 detect_deadlock, rt_mutex_slowlock);
865 EXPORT_SYMBOL_GPL(rt_mutex_lock_interruptible);
868 * rt_mutex_lock_interruptible_ktime - lock a rt_mutex interruptible
869 * the timeout structure is provided
870 * by the caller
872 * @lock: the rt_mutex to be locked
873 * @timeout: timeout structure or NULL (no timeout)
874 * @detect_deadlock: deadlock detection on/off
876 * Returns:
877 * 0 on success
878 * -EINTR when interrupted by a signal
879 * -ETIMEOUT when the timeout expired
880 * -EDEADLK when the lock would deadlock (when deadlock detection is on)
883 rt_mutex_timed_lock(struct rt_mutex *lock, struct hrtimer_sleeper *timeout,
884 int detect_deadlock)
886 might_sleep();
888 return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout,
889 detect_deadlock, rt_mutex_slowlock);
891 EXPORT_SYMBOL_GPL(rt_mutex_timed_lock);
894 * rt_mutex_trylock - try to lock a rt_mutex
896 * @lock: the rt_mutex to be locked
898 * Returns 1 on success and 0 on contention
900 int __sched rt_mutex_trylock(struct rt_mutex *lock)
902 return rt_mutex_fasttrylock(lock, rt_mutex_slowtrylock);
904 EXPORT_SYMBOL_GPL(rt_mutex_trylock);
907 * rt_mutex_unlock - unlock a rt_mutex
909 * @lock: the rt_mutex to be unlocked
911 void __sched rt_mutex_unlock(struct rt_mutex *lock)
913 rt_mutex_fastunlock(lock, rt_mutex_slowunlock);
915 EXPORT_SYMBOL_GPL(rt_mutex_unlock);
917 /***
918 * rt_mutex_destroy - mark a mutex unusable
919 * @lock: the mutex to be destroyed
921 * This function marks the mutex uninitialized, and any subsequent
922 * use of the mutex is forbidden. The mutex must not be locked when
923 * this function is called.
925 void rt_mutex_destroy(struct rt_mutex *lock)
927 WARN_ON(rt_mutex_is_locked(lock));
928 #ifdef CONFIG_DEBUG_RT_MUTEXES
929 lock->magic = NULL;
930 #endif
933 EXPORT_SYMBOL_GPL(rt_mutex_destroy);
936 * __rt_mutex_init - initialize the rt lock
938 * @lock: the rt lock to be initialized
940 * Initialize the rt lock to unlocked state.
942 * Initializing of a locked rt lock is not allowed
944 void __rt_mutex_init(struct rt_mutex *lock, const char *name)
946 lock->owner = NULL;
947 spin_lock_init(&lock->wait_lock);
948 plist_head_init(&lock->wait_list, &lock->wait_lock);
950 debug_rt_mutex_init(lock, name);
952 EXPORT_SYMBOL_GPL(__rt_mutex_init);
955 * rt_mutex_init_proxy_locked - initialize and lock a rt_mutex on behalf of a
956 * proxy owner
958 * @lock: the rt_mutex to be locked
959 * @proxy_owner:the task to set as owner
961 * No locking. Caller has to do serializing itself
962 * Special API call for PI-futex support
964 void rt_mutex_init_proxy_locked(struct rt_mutex *lock,
965 struct task_struct *proxy_owner)
967 __rt_mutex_init(lock, NULL);
968 debug_rt_mutex_proxy_lock(lock, proxy_owner);
969 rt_mutex_set_owner(lock, proxy_owner, 0);
970 rt_mutex_deadlock_account_lock(lock, proxy_owner);
974 * rt_mutex_proxy_unlock - release a lock on behalf of owner
976 * @lock: the rt_mutex to be locked
978 * No locking. Caller has to do serializing itself
979 * Special API call for PI-futex support
981 void rt_mutex_proxy_unlock(struct rt_mutex *lock,
982 struct task_struct *proxy_owner)
984 debug_rt_mutex_proxy_unlock(lock);
985 rt_mutex_set_owner(lock, NULL, 0);
986 rt_mutex_deadlock_account_unlock(proxy_owner);
990 * rt_mutex_next_owner - return the next owner of the lock
992 * @lock: the rt lock query
994 * Returns the next owner of the lock or NULL
996 * Caller has to serialize against other accessors to the lock
997 * itself.
999 * Special API call for PI-futex support
1001 struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock)
1003 if (!rt_mutex_has_waiters(lock))
1004 return NULL;
1006 return rt_mutex_top_waiter(lock)->task;