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/export.h>
15 #include <linux/sched.h>
16 #include <linux/sched/rt.h>
17 #include <linux/timer.h>
19 #include "rtmutex_common.h"
22 * lock->owner state tracking:
24 * lock->owner holds the task_struct pointer of the owner. Bit 0
25 * is used to keep track of the "lock has waiters" state.
28 * NULL 0 lock is free (fast acquire possible)
29 * NULL 1 lock is free and has waiters and the top waiter
30 * is going to take the lock*
31 * taskpointer 0 lock is held (fast release possible)
32 * taskpointer 1 lock is held and has waiters**
34 * The fast atomic compare exchange based acquire and release is only
35 * possible when bit 0 of lock->owner is 0.
37 * (*) It also can be a transitional state when grabbing the lock
38 * with ->wait_lock is held. To prevent any fast path cmpxchg to the lock,
39 * we need to set the bit0 before looking at the lock, and the owner may be
40 * NULL in this small time, hence this can be a transitional state.
42 * (**) There is a small time when bit 0 is set but there are no
43 * waiters. This can happen when grabbing the lock in the slow path.
44 * To prevent a cmpxchg of the owner releasing the lock, we need to
45 * set this bit before looking at the lock.
49 rt_mutex_set_owner(struct rt_mutex
*lock
, struct task_struct
*owner
)
51 unsigned long val
= (unsigned long)owner
;
53 if (rt_mutex_has_waiters(lock
))
54 val
|= RT_MUTEX_HAS_WAITERS
;
56 lock
->owner
= (struct task_struct
*)val
;
59 static inline void clear_rt_mutex_waiters(struct rt_mutex
*lock
)
61 lock
->owner
= (struct task_struct
*)
62 ((unsigned long)lock
->owner
& ~RT_MUTEX_HAS_WAITERS
);
65 static void fixup_rt_mutex_waiters(struct rt_mutex
*lock
)
67 if (!rt_mutex_has_waiters(lock
))
68 clear_rt_mutex_waiters(lock
);
72 * We can speed up the acquire/release, if the architecture
73 * supports cmpxchg and if there's no debugging state to be set up
75 #if defined(__HAVE_ARCH_CMPXCHG) && !defined(CONFIG_DEBUG_RT_MUTEXES)
76 # define rt_mutex_cmpxchg(l,c,n) (cmpxchg(&l->owner, c, n) == c)
77 static inline void mark_rt_mutex_waiters(struct rt_mutex
*lock
)
79 unsigned long owner
, *p
= (unsigned long *) &lock
->owner
;
83 } while (cmpxchg(p
, owner
, owner
| RT_MUTEX_HAS_WAITERS
) != owner
);
86 # define rt_mutex_cmpxchg(l,c,n) (0)
87 static inline void mark_rt_mutex_waiters(struct rt_mutex
*lock
)
89 lock
->owner
= (struct task_struct
*)
90 ((unsigned long)lock
->owner
| RT_MUTEX_HAS_WAITERS
);
95 * Calculate task priority from the waiter list priority
97 * Return task->normal_prio when the waiter list is empty or when
98 * the waiter is not allowed to do priority boosting
100 int rt_mutex_getprio(struct task_struct
*task
)
102 if (likely(!task_has_pi_waiters(task
)))
103 return task
->normal_prio
;
105 return min(task_top_pi_waiter(task
)->pi_list_entry
.prio
,
110 * Adjust the priority of a task, after its pi_waiters got modified.
112 * This can be both boosting and unboosting. task->pi_lock must be held.
114 static void __rt_mutex_adjust_prio(struct task_struct
*task
)
116 int prio
= rt_mutex_getprio(task
);
118 if (task
->prio
!= prio
)
119 rt_mutex_setprio(task
, prio
);
123 * Adjust task priority (undo boosting). Called from the exit path of
124 * rt_mutex_slowunlock() and rt_mutex_slowlock().
126 * (Note: We do this outside of the protection of lock->wait_lock to
127 * allow the lock to be taken while or before we readjust the priority
128 * of task. We do not use the spin_xx_mutex() variants here as we are
129 * outside of the debug path.)
131 static void rt_mutex_adjust_prio(struct task_struct
*task
)
135 raw_spin_lock_irqsave(&task
->pi_lock
, flags
);
136 __rt_mutex_adjust_prio(task
);
137 raw_spin_unlock_irqrestore(&task
->pi_lock
, flags
);
141 * Max number of times we'll walk the boosting chain:
143 int max_lock_depth
= 1024;
145 static inline struct rt_mutex
*task_blocked_on_lock(struct task_struct
*p
)
147 return p
->pi_blocked_on
? p
->pi_blocked_on
->lock
: NULL
;
151 * Adjust the priority chain. Also used for deadlock detection.
152 * Decreases task's usage by one - may thus free the task.
153 * Returns 0 or -EDEADLK.
155 static int rt_mutex_adjust_prio_chain(struct task_struct
*task
,
157 struct rt_mutex
*orig_lock
,
158 struct rt_mutex
*next_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;
167 detect_deadlock
= debug_rt_mutex_detect_deadlock(orig_waiter
,
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.
177 if (++depth
> max_lock_depth
) {
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;
196 * Task can not go away as we did a get_task() before !
198 raw_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
210 * Check the orig_waiter state. After we dropped the locks,
211 * the previous owner of the lock might have released the lock.
213 if (orig_waiter
&& !rt_mutex_owner(orig_lock
))
217 * We dropped all locks after taking a refcount on @task, so
218 * the task might have moved on in the lock chain or even left
219 * the chain completely and blocks now on an unrelated lock or
222 * We stored the lock on which @task was blocked in @next_lock,
223 * so we can detect the chain change.
225 if (next_lock
!= waiter
->lock
)
229 * Drop out, when the task has no waiters. Note,
230 * top_waiter can be NULL, when we are in the deboosting
234 if (!task_has_pi_waiters(task
))
237 * If deadlock detection is off, we stop here if we
238 * are not the top pi waiter of the task.
240 if (!detect_deadlock
&& top_waiter
!= task_top_pi_waiter(task
))
245 * When deadlock detection is off then we check, if further
246 * priority adjustment is necessary.
248 if (!detect_deadlock
&& waiter
->list_entry
.prio
== task
->prio
)
252 if (!raw_spin_trylock(&lock
->wait_lock
)) {
253 raw_spin_unlock_irqrestore(&task
->pi_lock
, flags
);
259 * Deadlock detection. If the lock is the same as the original
260 * lock which caused us to walk the lock chain or if the
261 * current lock is owned by the task which initiated the chain
262 * walk, we detected a deadlock.
264 if (lock
== orig_lock
|| rt_mutex_owner(lock
) == top_task
) {
265 debug_rt_mutex_deadlock(deadlock_detect
, orig_waiter
, lock
);
266 raw_spin_unlock(&lock
->wait_lock
);
267 ret
= deadlock_detect
? -EDEADLK
: 0;
271 top_waiter
= rt_mutex_top_waiter(lock
);
273 /* Requeue the waiter */
274 plist_del(&waiter
->list_entry
, &lock
->wait_list
);
275 waiter
->list_entry
.prio
= task
->prio
;
276 plist_add(&waiter
->list_entry
, &lock
->wait_list
);
278 /* Release the task */
279 raw_spin_unlock_irqrestore(&task
->pi_lock
, flags
);
280 if (!rt_mutex_owner(lock
)) {
282 * If the requeue above changed the top waiter, then we need
283 * to wake the new top waiter up to try to get the lock.
286 if (top_waiter
!= rt_mutex_top_waiter(lock
))
287 wake_up_process(rt_mutex_top_waiter(lock
)->task
);
288 raw_spin_unlock(&lock
->wait_lock
);
291 put_task_struct(task
);
293 /* Grab the next task */
294 task
= rt_mutex_owner(lock
);
295 get_task_struct(task
);
296 raw_spin_lock_irqsave(&task
->pi_lock
, flags
);
298 if (waiter
== rt_mutex_top_waiter(lock
)) {
299 /* Boost the owner */
300 plist_del(&top_waiter
->pi_list_entry
, &task
->pi_waiters
);
301 waiter
->pi_list_entry
.prio
= waiter
->list_entry
.prio
;
302 plist_add(&waiter
->pi_list_entry
, &task
->pi_waiters
);
303 __rt_mutex_adjust_prio(task
);
305 } else if (top_waiter
== waiter
) {
306 /* Deboost the owner */
307 plist_del(&waiter
->pi_list_entry
, &task
->pi_waiters
);
308 waiter
= rt_mutex_top_waiter(lock
);
309 waiter
->pi_list_entry
.prio
= waiter
->list_entry
.prio
;
310 plist_add(&waiter
->pi_list_entry
, &task
->pi_waiters
);
311 __rt_mutex_adjust_prio(task
);
315 * Check whether the task which owns the current lock is pi
316 * blocked itself. If yes we store a pointer to the lock for
317 * the lock chain change detection above. After we dropped
318 * task->pi_lock next_lock cannot be dereferenced anymore.
320 next_lock
= task_blocked_on_lock(task
);
322 raw_spin_unlock_irqrestore(&task
->pi_lock
, flags
);
324 top_waiter
= rt_mutex_top_waiter(lock
);
325 raw_spin_unlock(&lock
->wait_lock
);
328 * We reached the end of the lock chain. Stop right here. No
329 * point to go back just to figure that out.
334 if (!detect_deadlock
&& waiter
!= top_waiter
)
340 raw_spin_unlock_irqrestore(&task
->pi_lock
, flags
);
342 put_task_struct(task
);
348 * Try to take an rt-mutex
350 * Must be called with lock->wait_lock held.
352 * @lock: the lock to be acquired.
353 * @task: the task which wants to acquire the lock
354 * @waiter: the waiter that is queued to the lock's wait list. (could be NULL)
356 static int try_to_take_rt_mutex(struct rt_mutex
*lock
, struct task_struct
*task
,
357 struct rt_mutex_waiter
*waiter
)
360 * We have to be careful here if the atomic speedups are
361 * enabled, such that, when
362 * - no other waiter is on the lock
363 * - the lock has been released since we did the cmpxchg
364 * the lock can be released or taken while we are doing the
365 * checks and marking the lock with RT_MUTEX_HAS_WAITERS.
367 * The atomic acquire/release aware variant of
368 * mark_rt_mutex_waiters uses a cmpxchg loop. After setting
369 * the WAITERS bit, the atomic release / acquire can not
370 * happen anymore and lock->wait_lock protects us from the
373 * Note, that this might set lock->owner =
374 * RT_MUTEX_HAS_WAITERS in the case the lock is not contended
375 * any more. This is fixed up when we take the ownership.
376 * This is the transitional state explained at the top of this file.
378 mark_rt_mutex_waiters(lock
);
380 if (rt_mutex_owner(lock
))
384 * It will get the lock because of one of these conditions:
385 * 1) there is no waiter
386 * 2) higher priority than waiters
387 * 3) it is top waiter
389 if (rt_mutex_has_waiters(lock
)) {
390 if (task
->prio
>= rt_mutex_top_waiter(lock
)->list_entry
.prio
) {
391 if (!waiter
|| waiter
!= rt_mutex_top_waiter(lock
))
396 if (waiter
|| rt_mutex_has_waiters(lock
)) {
398 struct rt_mutex_waiter
*top
;
400 raw_spin_lock_irqsave(&task
->pi_lock
, flags
);
402 /* remove the queued waiter. */
404 plist_del(&waiter
->list_entry
, &lock
->wait_list
);
405 task
->pi_blocked_on
= NULL
;
409 * We have to enqueue the top waiter(if it exists) into
410 * task->pi_waiters list.
412 if (rt_mutex_has_waiters(lock
)) {
413 top
= rt_mutex_top_waiter(lock
);
414 top
->pi_list_entry
.prio
= top
->list_entry
.prio
;
415 plist_add(&top
->pi_list_entry
, &task
->pi_waiters
);
417 raw_spin_unlock_irqrestore(&task
->pi_lock
, flags
);
420 /* We got the lock. */
421 debug_rt_mutex_lock(lock
);
423 rt_mutex_set_owner(lock
, task
);
425 rt_mutex_deadlock_account_lock(lock
, task
);
431 * Task blocks on lock.
433 * Prepare waiter and propagate pi chain
435 * This must be called with lock->wait_lock held.
437 static int task_blocks_on_rt_mutex(struct rt_mutex
*lock
,
438 struct rt_mutex_waiter
*waiter
,
439 struct task_struct
*task
,
442 struct task_struct
*owner
= rt_mutex_owner(lock
);
443 struct rt_mutex_waiter
*top_waiter
= waiter
;
444 struct rt_mutex
*next_lock
;
445 int chain_walk
= 0, res
;
449 * Early deadlock detection. We really don't want the task to
450 * enqueue on itself just to untangle the mess later. It's not
451 * only an optimization. We drop the locks, so another waiter
452 * can come in before the chain walk detects the deadlock. So
453 * the other will detect the deadlock and return -EDEADLOCK,
454 * which is wrong, as the other waiter is not in a deadlock
457 if (detect_deadlock
&& owner
== task
)
460 raw_spin_lock_irqsave(&task
->pi_lock
, flags
);
461 __rt_mutex_adjust_prio(task
);
464 plist_node_init(&waiter
->list_entry
, task
->prio
);
465 plist_node_init(&waiter
->pi_list_entry
, task
->prio
);
467 /* Get the top priority waiter on the lock */
468 if (rt_mutex_has_waiters(lock
))
469 top_waiter
= rt_mutex_top_waiter(lock
);
470 plist_add(&waiter
->list_entry
, &lock
->wait_list
);
472 task
->pi_blocked_on
= waiter
;
474 raw_spin_unlock_irqrestore(&task
->pi_lock
, flags
);
479 raw_spin_lock_irqsave(&owner
->pi_lock
, flags
);
480 if (waiter
== rt_mutex_top_waiter(lock
)) {
481 plist_del(&top_waiter
->pi_list_entry
, &owner
->pi_waiters
);
482 plist_add(&waiter
->pi_list_entry
, &owner
->pi_waiters
);
484 __rt_mutex_adjust_prio(owner
);
485 if (owner
->pi_blocked_on
)
487 } else if (debug_rt_mutex_detect_deadlock(waiter
, detect_deadlock
)) {
491 /* Store the lock on which owner is blocked or NULL */
492 next_lock
= task_blocked_on_lock(owner
);
494 raw_spin_unlock_irqrestore(&owner
->pi_lock
, flags
);
496 * Even if full deadlock detection is on, if the owner is not
497 * blocked itself, we can avoid finding this out in the chain
500 if (!chain_walk
|| !next_lock
)
504 * The owner can't disappear while holding a lock,
505 * so the owner struct is protected by wait_lock.
506 * Gets dropped in rt_mutex_adjust_prio_chain()!
508 get_task_struct(owner
);
510 raw_spin_unlock(&lock
->wait_lock
);
512 res
= rt_mutex_adjust_prio_chain(owner
, detect_deadlock
, lock
,
513 next_lock
, waiter
, task
);
515 raw_spin_lock(&lock
->wait_lock
);
521 * Wake up the next waiter on the lock.
523 * Remove the top waiter from the current tasks waiter list and wake it up.
525 * Called with lock->wait_lock held.
527 static void wakeup_next_waiter(struct rt_mutex
*lock
)
529 struct rt_mutex_waiter
*waiter
;
532 raw_spin_lock_irqsave(¤t
->pi_lock
, flags
);
534 waiter
= rt_mutex_top_waiter(lock
);
537 * Remove it from current->pi_waiters. We do not adjust a
538 * possible priority boost right now. We execute wakeup in the
539 * boosted mode and go back to normal after releasing
542 plist_del(&waiter
->pi_list_entry
, ¤t
->pi_waiters
);
544 rt_mutex_set_owner(lock
, NULL
);
546 raw_spin_unlock_irqrestore(¤t
->pi_lock
, flags
);
548 wake_up_process(waiter
->task
);
552 * Remove a waiter from a lock and give up
554 * Must be called with lock->wait_lock held and
555 * have just failed to try_to_take_rt_mutex().
557 static void remove_waiter(struct rt_mutex
*lock
,
558 struct rt_mutex_waiter
*waiter
)
560 int first
= (waiter
== rt_mutex_top_waiter(lock
));
561 struct task_struct
*owner
= rt_mutex_owner(lock
);
562 struct rt_mutex
*next_lock
= NULL
;
565 raw_spin_lock_irqsave(¤t
->pi_lock
, flags
);
566 plist_del(&waiter
->list_entry
, &lock
->wait_list
);
567 current
->pi_blocked_on
= NULL
;
568 raw_spin_unlock_irqrestore(¤t
->pi_lock
, flags
);
575 raw_spin_lock_irqsave(&owner
->pi_lock
, flags
);
577 plist_del(&waiter
->pi_list_entry
, &owner
->pi_waiters
);
579 if (rt_mutex_has_waiters(lock
)) {
580 struct rt_mutex_waiter
*next
;
582 next
= rt_mutex_top_waiter(lock
);
583 plist_add(&next
->pi_list_entry
, &owner
->pi_waiters
);
585 __rt_mutex_adjust_prio(owner
);
587 /* Store the lock on which owner is blocked or NULL */
588 next_lock
= task_blocked_on_lock(owner
);
590 raw_spin_unlock_irqrestore(&owner
->pi_lock
, flags
);
593 WARN_ON(!plist_node_empty(&waiter
->pi_list_entry
));
598 /* gets dropped in rt_mutex_adjust_prio_chain()! */
599 get_task_struct(owner
);
601 raw_spin_unlock(&lock
->wait_lock
);
603 rt_mutex_adjust_prio_chain(owner
, 0, lock
, next_lock
, NULL
, current
);
605 raw_spin_lock(&lock
->wait_lock
);
609 * Recheck the pi chain, in case we got a priority setting
611 * Called from sched_setscheduler
613 void rt_mutex_adjust_pi(struct task_struct
*task
)
615 struct rt_mutex_waiter
*waiter
;
616 struct rt_mutex
*next_lock
;
619 raw_spin_lock_irqsave(&task
->pi_lock
, flags
);
621 waiter
= task
->pi_blocked_on
;
622 if (!waiter
|| waiter
->list_entry
.prio
== task
->prio
) {
623 raw_spin_unlock_irqrestore(&task
->pi_lock
, flags
);
626 next_lock
= waiter
->lock
;
627 raw_spin_unlock_irqrestore(&task
->pi_lock
, flags
);
629 /* gets dropped in rt_mutex_adjust_prio_chain()! */
630 get_task_struct(task
);
632 rt_mutex_adjust_prio_chain(task
, 0, NULL
, next_lock
, NULL
, task
);
636 * __rt_mutex_slowlock() - Perform the wait-wake-try-to-take loop
637 * @lock: the rt_mutex to take
638 * @state: the state the task should block in (TASK_INTERRUPTIBLE
639 * or TASK_UNINTERRUPTIBLE)
640 * @timeout: the pre-initialized and started timer, or NULL for none
641 * @waiter: the pre-initialized rt_mutex_waiter
643 * lock->wait_lock must be held by the caller.
646 __rt_mutex_slowlock(struct rt_mutex
*lock
, int state
,
647 struct hrtimer_sleeper
*timeout
,
648 struct rt_mutex_waiter
*waiter
)
653 /* Try to acquire the lock: */
654 if (try_to_take_rt_mutex(lock
, current
, waiter
))
658 * TASK_INTERRUPTIBLE checks for signals and
659 * timeout. Ignored otherwise.
661 if (unlikely(state
== TASK_INTERRUPTIBLE
)) {
662 /* Signal pending? */
663 if (signal_pending(current
))
665 if (timeout
&& !timeout
->task
)
671 raw_spin_unlock(&lock
->wait_lock
);
673 debug_rt_mutex_print_deadlock(waiter
);
675 schedule_rt_mutex(lock
);
677 raw_spin_lock(&lock
->wait_lock
);
678 set_current_state(state
);
685 * Slow path lock function:
688 rt_mutex_slowlock(struct rt_mutex
*lock
, int state
,
689 struct hrtimer_sleeper
*timeout
,
692 struct rt_mutex_waiter waiter
;
695 debug_rt_mutex_init_waiter(&waiter
);
697 raw_spin_lock(&lock
->wait_lock
);
699 /* Try to acquire the lock again: */
700 if (try_to_take_rt_mutex(lock
, current
, NULL
)) {
701 raw_spin_unlock(&lock
->wait_lock
);
705 set_current_state(state
);
707 /* Setup the timer, when timeout != NULL */
708 if (unlikely(timeout
)) {
709 hrtimer_start_expires(&timeout
->timer
, HRTIMER_MODE_ABS
);
710 if (!hrtimer_active(&timeout
->timer
))
711 timeout
->task
= NULL
;
714 ret
= task_blocks_on_rt_mutex(lock
, &waiter
, current
, detect_deadlock
);
717 ret
= __rt_mutex_slowlock(lock
, state
, timeout
, &waiter
);
719 set_current_state(TASK_RUNNING
);
722 remove_waiter(lock
, &waiter
);
725 * try_to_take_rt_mutex() sets the waiter bit
726 * unconditionally. We might have to fix that up.
728 fixup_rt_mutex_waiters(lock
);
730 raw_spin_unlock(&lock
->wait_lock
);
732 /* Remove pending timer: */
733 if (unlikely(timeout
))
734 hrtimer_cancel(&timeout
->timer
);
736 debug_rt_mutex_free_waiter(&waiter
);
742 * Slow path try-lock function:
745 rt_mutex_slowtrylock(struct rt_mutex
*lock
)
749 raw_spin_lock(&lock
->wait_lock
);
751 if (likely(rt_mutex_owner(lock
) != current
)) {
753 ret
= try_to_take_rt_mutex(lock
, current
, NULL
);
755 * try_to_take_rt_mutex() sets the lock waiters
756 * bit unconditionally. Clean this up.
758 fixup_rt_mutex_waiters(lock
);
761 raw_spin_unlock(&lock
->wait_lock
);
767 * Slow path to release a rt-mutex:
770 rt_mutex_slowunlock(struct rt_mutex
*lock
)
772 raw_spin_lock(&lock
->wait_lock
);
774 debug_rt_mutex_unlock(lock
);
776 rt_mutex_deadlock_account_unlock(current
);
778 if (!rt_mutex_has_waiters(lock
)) {
780 raw_spin_unlock(&lock
->wait_lock
);
784 wakeup_next_waiter(lock
);
786 raw_spin_unlock(&lock
->wait_lock
);
788 /* Undo pi boosting if necessary: */
789 rt_mutex_adjust_prio(current
);
793 * debug aware fast / slowpath lock,trylock,unlock
795 * The atomic acquire/release ops are compiled away, when either the
796 * architecture does not support cmpxchg or when debugging is enabled.
799 rt_mutex_fastlock(struct rt_mutex
*lock
, int state
,
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
);
809 return slowfn(lock
, state
, NULL
, detect_deadlock
);
813 rt_mutex_timed_fastlock(struct rt_mutex
*lock
, int state
,
814 struct hrtimer_sleeper
*timeout
, int detect_deadlock
,
815 int (*slowfn
)(struct rt_mutex
*lock
, int state
,
816 struct hrtimer_sleeper
*timeout
,
817 int detect_deadlock
))
819 if (!detect_deadlock
&& likely(rt_mutex_cmpxchg(lock
, NULL
, current
))) {
820 rt_mutex_deadlock_account_lock(lock
, current
);
823 return slowfn(lock
, state
, timeout
, detect_deadlock
);
827 rt_mutex_fasttrylock(struct rt_mutex
*lock
,
828 int (*slowfn
)(struct rt_mutex
*lock
))
830 if (likely(rt_mutex_cmpxchg(lock
, NULL
, current
))) {
831 rt_mutex_deadlock_account_lock(lock
, current
);
838 rt_mutex_fastunlock(struct rt_mutex
*lock
,
839 void (*slowfn
)(struct rt_mutex
*lock
))
841 if (likely(rt_mutex_cmpxchg(lock
, current
, NULL
)))
842 rt_mutex_deadlock_account_unlock(current
);
848 * rt_mutex_lock - lock a rt_mutex
850 * @lock: the rt_mutex to be locked
852 void __sched
rt_mutex_lock(struct rt_mutex
*lock
)
856 rt_mutex_fastlock(lock
, TASK_UNINTERRUPTIBLE
, 0, rt_mutex_slowlock
);
858 EXPORT_SYMBOL_GPL(rt_mutex_lock
);
861 * rt_mutex_lock_interruptible - lock a rt_mutex interruptible
863 * @lock: the rt_mutex to be locked
864 * @detect_deadlock: deadlock detection on/off
868 * -EINTR when interrupted by a signal
869 * -EDEADLK when the lock would deadlock (when deadlock detection is on)
871 int __sched
rt_mutex_lock_interruptible(struct rt_mutex
*lock
,
876 return rt_mutex_fastlock(lock
, TASK_INTERRUPTIBLE
,
877 detect_deadlock
, rt_mutex_slowlock
);
879 EXPORT_SYMBOL_GPL(rt_mutex_lock_interruptible
);
882 * rt_mutex_timed_lock - lock a rt_mutex interruptible
883 * the timeout structure is provided
886 * @lock: the rt_mutex to be locked
887 * @timeout: timeout structure or NULL (no timeout)
888 * @detect_deadlock: deadlock detection on/off
892 * -EINTR when interrupted by a signal
893 * -ETIMEDOUT when the timeout expired
894 * -EDEADLK when the lock would deadlock (when deadlock detection is on)
897 rt_mutex_timed_lock(struct rt_mutex
*lock
, struct hrtimer_sleeper
*timeout
,
902 return rt_mutex_timed_fastlock(lock
, TASK_INTERRUPTIBLE
, timeout
,
903 detect_deadlock
, rt_mutex_slowlock
);
905 EXPORT_SYMBOL_GPL(rt_mutex_timed_lock
);
908 * rt_mutex_trylock - try to lock a rt_mutex
910 * @lock: the rt_mutex to be locked
912 * Returns 1 on success and 0 on contention
914 int __sched
rt_mutex_trylock(struct rt_mutex
*lock
)
916 return rt_mutex_fasttrylock(lock
, rt_mutex_slowtrylock
);
918 EXPORT_SYMBOL_GPL(rt_mutex_trylock
);
921 * rt_mutex_unlock - unlock a rt_mutex
923 * @lock: the rt_mutex to be unlocked
925 void __sched
rt_mutex_unlock(struct rt_mutex
*lock
)
927 rt_mutex_fastunlock(lock
, rt_mutex_slowunlock
);
929 EXPORT_SYMBOL_GPL(rt_mutex_unlock
);
932 * rt_mutex_destroy - mark a mutex unusable
933 * @lock: the mutex to be destroyed
935 * This function marks the mutex uninitialized, and any subsequent
936 * use of the mutex is forbidden. The mutex must not be locked when
937 * this function is called.
939 void rt_mutex_destroy(struct rt_mutex
*lock
)
941 WARN_ON(rt_mutex_is_locked(lock
));
942 #ifdef CONFIG_DEBUG_RT_MUTEXES
947 EXPORT_SYMBOL_GPL(rt_mutex_destroy
);
950 * __rt_mutex_init - initialize the rt lock
952 * @lock: the rt lock to be initialized
954 * Initialize the rt lock to unlocked state.
956 * Initializing of a locked rt lock is not allowed
958 void __rt_mutex_init(struct rt_mutex
*lock
, const char *name
)
961 raw_spin_lock_init(&lock
->wait_lock
);
962 plist_head_init(&lock
->wait_list
);
964 debug_rt_mutex_init(lock
, name
);
966 EXPORT_SYMBOL_GPL(__rt_mutex_init
);
969 * rt_mutex_init_proxy_locked - initialize and lock a rt_mutex on behalf of a
972 * @lock: the rt_mutex to be locked
973 * @proxy_owner:the task to set as owner
975 * No locking. Caller has to do serializing itself
976 * Special API call for PI-futex support
978 void rt_mutex_init_proxy_locked(struct rt_mutex
*lock
,
979 struct task_struct
*proxy_owner
)
981 __rt_mutex_init(lock
, NULL
);
982 debug_rt_mutex_proxy_lock(lock
, proxy_owner
);
983 rt_mutex_set_owner(lock
, proxy_owner
);
984 rt_mutex_deadlock_account_lock(lock
, proxy_owner
);
988 * rt_mutex_proxy_unlock - release a lock on behalf of owner
990 * @lock: the rt_mutex to be locked
992 * No locking. Caller has to do serializing itself
993 * Special API call for PI-futex support
995 void rt_mutex_proxy_unlock(struct rt_mutex
*lock
,
996 struct task_struct
*proxy_owner
)
998 debug_rt_mutex_proxy_unlock(lock
);
999 rt_mutex_set_owner(lock
, NULL
);
1000 rt_mutex_deadlock_account_unlock(proxy_owner
);
1004 * rt_mutex_start_proxy_lock() - Start lock acquisition for another task
1005 * @lock: the rt_mutex to take
1006 * @waiter: the pre-initialized rt_mutex_waiter
1007 * @task: the task to prepare
1008 * @detect_deadlock: perform deadlock detection (1) or not (0)
1011 * 0 - task blocked on lock
1012 * 1 - acquired the lock for task, caller should wake it up
1015 * Special API call for FUTEX_REQUEUE_PI support.
1017 int rt_mutex_start_proxy_lock(struct rt_mutex
*lock
,
1018 struct rt_mutex_waiter
*waiter
,
1019 struct task_struct
*task
, int detect_deadlock
)
1023 raw_spin_lock(&lock
->wait_lock
);
1025 if (try_to_take_rt_mutex(lock
, task
, NULL
)) {
1026 raw_spin_unlock(&lock
->wait_lock
);
1030 ret
= task_blocks_on_rt_mutex(lock
, waiter
, task
, detect_deadlock
);
1032 if (ret
&& !rt_mutex_owner(lock
)) {
1034 * Reset the return value. We might have
1035 * returned with -EDEADLK and the owner
1036 * released the lock while we were walking the
1037 * pi chain. Let the waiter sort it out.
1043 remove_waiter(lock
, waiter
);
1045 raw_spin_unlock(&lock
->wait_lock
);
1047 debug_rt_mutex_print_deadlock(waiter
);
1053 * rt_mutex_next_owner - return the next owner of the lock
1055 * @lock: the rt lock query
1057 * Returns the next owner of the lock or NULL
1059 * Caller has to serialize against other accessors to the lock
1062 * Special API call for PI-futex support
1064 struct task_struct
*rt_mutex_next_owner(struct rt_mutex
*lock
)
1066 if (!rt_mutex_has_waiters(lock
))
1069 return rt_mutex_top_waiter(lock
)->task
;
1073 * rt_mutex_finish_proxy_lock() - Complete lock acquisition
1074 * @lock: the rt_mutex we were woken on
1075 * @to: the timeout, null if none. hrtimer should already have
1077 * @waiter: the pre-initialized rt_mutex_waiter
1078 * @detect_deadlock: perform deadlock detection (1) or not (0)
1080 * Complete the lock acquisition started our behalf by another thread.
1084 * <0 - error, one of -EINTR, -ETIMEDOUT, or -EDEADLK
1086 * Special API call for PI-futex requeue support
1088 int rt_mutex_finish_proxy_lock(struct rt_mutex
*lock
,
1089 struct hrtimer_sleeper
*to
,
1090 struct rt_mutex_waiter
*waiter
,
1091 int detect_deadlock
)
1095 raw_spin_lock(&lock
->wait_lock
);
1097 set_current_state(TASK_INTERRUPTIBLE
);
1099 ret
= __rt_mutex_slowlock(lock
, TASK_INTERRUPTIBLE
, to
, waiter
);
1101 set_current_state(TASK_RUNNING
);
1104 remove_waiter(lock
, waiter
);
1107 * try_to_take_rt_mutex() sets the waiter bit unconditionally. We might
1108 * have to fix that up.
1110 fixup_rt_mutex_waiters(lock
);
1112 raw_spin_unlock(&lock
->wait_lock
);