projects/linux·blob v2.6.22-rc7 · refs

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1/*
2 * RT-Mutexes: simple blocking mutual exclusion locks with PI support
3 *
4 * started by Ingo Molnar and Thomas Gleixner.
5 *
6 * Copyright (C) 2004-2006 Red Hat, Inc., Ingo Molnar <[email protected]>
7 * Copyright (C) 2005-2006 Timesys Corp., Thomas Gleixner <[email protected]>
8 * Copyright (C) 2005 Kihon Technologies Inc., Steven Rostedt
9 * Copyright (C) 2006 Esben Nielsen
10 *
11 * See Documentation/rt-mutex-design.txt for details.
12 */
13#include <linux/spinlock.h>
14#include <linux/module.h>
15#include <linux/sched.h>
16#include <linux/timer.h>
17
18#include "rtmutex_common.h"
19
20#ifdef CONFIG_DEBUG_RT_MUTEXES
21# include "rtmutex-debug.h"
22#else
23# include "rtmutex.h"
24#endif
25
26/*
27 * lock->owner state tracking:
28 *
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
31 * waiters" state.
32 *
33 * owner bit1 bit0
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
42 *
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.
48 *
49 * The fast atomic compare exchange based acquire and release is only
50 * possible when bit 0 and 1 of lock->owner are 0.
51 *
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
56 * state.
57 */
58
59static void
60rt_mutex_set_owner(struct rt_mutex *lock, struct task_struct *owner,
61 unsigned long mask)
62{
63 unsigned long val = (unsigned long)owner | mask;
64
65 if (rt_mutex_has_waiters(lock))
66 val |= RT_MUTEX_HAS_WAITERS;
67
68 lock->owner = (struct task_struct *)val;
69}
70
71static inline void clear_rt_mutex_waiters(struct rt_mutex *lock)
72{
73 lock->owner = (struct task_struct *)
74 ((unsigned long)lock->owner & ~RT_MUTEX_HAS_WAITERS);
75}
76
77static void fixup_rt_mutex_waiters(struct rt_mutex *lock)
78{
79 if (!rt_mutex_has_waiters(lock))
80 clear_rt_mutex_waiters(lock);
81}
82
83/*
84 * We can speed up the acquire/release, if the architecture
85 * supports cmpxchg and if there's no debugging state to be set up
86 */
87#if defined(__HAVE_ARCH_CMPXCHG) && !defined(CONFIG_DEBUG_RT_MUTEXES)
88# define rt_mutex_cmpxchg(l,c,n) (cmpxchg(&l->owner, c, n) == c)
89static inline void mark_rt_mutex_waiters(struct rt_mutex *lock)
90{
91 unsigned long owner, *p = (unsigned long *) &lock->owner;
92
93 do {
94 owner = *p;
95 } while (cmpxchg(p, owner, owner | RT_MUTEX_HAS_WAITERS) != owner);
96}
97#else
98# define rt_mutex_cmpxchg(l,c,n) (0)
99static inline void mark_rt_mutex_waiters(struct rt_mutex *lock)
100{
101 lock->owner = (struct task_struct *)
102 ((unsigned long)lock->owner | RT_MUTEX_HAS_WAITERS);
103}
104#endif
105
106/*
107 * Calculate task priority from the waiter list priority
108 *
109 * Return task->normal_prio when the waiter list is empty or when
110 * the waiter is not allowed to do priority boosting
111 */
112int rt_mutex_getprio(struct task_struct *task)
113{
114 if (likely(!task_has_pi_waiters(task)))
115 return task->normal_prio;
116
117 return min(task_top_pi_waiter(task)->pi_list_entry.prio,
118 task->normal_prio);
119}
120
121/*
122 * Adjust the priority of a task, after its pi_waiters got modified.
123 *
124 * This can be both boosting and unboosting. task->pi_lock must be held.
125 */
126static void __rt_mutex_adjust_prio(struct task_struct *task)
127{
128 int prio = rt_mutex_getprio(task);
129
130 if (task->prio != prio)
131 rt_mutex_setprio(task, prio);
132}
133
134/*
135 * Adjust task priority (undo boosting). Called from the exit path of
136 * rt_mutex_slowunlock() and rt_mutex_slowlock().
137 *
138 * (Note: We do this outside of the protection of lock->wait_lock to
139 * allow the lock to be taken while or before we readjust the priority
140 * of task. We do not use the spin_xx_mutex() variants here as we are
141 * outside of the debug path.)
142 */
143static void rt_mutex_adjust_prio(struct task_struct *task)
144{
145 unsigned long flags;
146
147 spin_lock_irqsave(&task->pi_lock, flags);
148 __rt_mutex_adjust_prio(task);
149 spin_unlock_irqrestore(&task->pi_lock, flags);
150}
151
152/*
153 * Max number of times we'll walk the boosting chain:
154 */
155int max_lock_depth = 1024;
156
157/*
158 * Adjust the priority chain. Also used for deadlock detection.
159 * Decreases task's usage by one - may thus free the task.
160 * Returns 0 or -EDEADLK.
161 */
162static int rt_mutex_adjust_prio_chain(struct task_struct *task,
163 int deadlock_detect,
164 struct rt_mutex *orig_lock,
165 struct rt_mutex_waiter *orig_waiter,
166 struct task_struct *top_task)
167{
168 struct rt_mutex *lock;
169 struct rt_mutex_waiter *waiter, *top_waiter = orig_waiter;
170 int detect_deadlock, ret = 0, depth = 0;
171 unsigned long flags;
172
173 detect_deadlock = debug_rt_mutex_detect_deadlock(orig_waiter,
174 deadlock_detect);
175
176 /*
177 * The (de)boosting is a step by step approach with a lot of
178 * pitfalls. We want this to be preemptible and we want hold a
179 * maximum of two locks per step. So we have to check
180 * carefully whether things change under us.
181 */
182 again:
183 if (++depth > max_lock_depth) {
184 static int prev_max;
185
186 /*
187 * Print this only once. If the admin changes the limit,
188 * print a new message when reaching the limit again.
189 */
190 if (prev_max != max_lock_depth) {
191 prev_max = max_lock_depth;
192 printk(KERN_WARNING "Maximum lock depth %d reached "
193 "task: %s (%d)\n", max_lock_depth,
194 top_task->comm, top_task->pid);
195 }
196 put_task_struct(task);
197
198 return deadlock_detect ? -EDEADLK : 0;
199 }
200 retry:
201 /*
202 * Task can not go away as we did a get_task() before !
203 */
204 spin_lock_irqsave(&task->pi_lock, flags);
205
206 waiter = task->pi_blocked_on;
207 /*
208 * Check whether the end of the boosting chain has been
209 * reached or the state of the chain has changed while we
210 * dropped the locks.
211 */
212 if (!waiter || !waiter->task)
213 goto out_unlock_pi;
214
215 /*
216 * Check the orig_waiter state. After we dropped the locks,
217 * the previous owner of the lock might have released the lock
218 * and made us the pending owner:
219 */
220 if (orig_waiter && !orig_waiter->task)
221 goto out_unlock_pi;
222
223 /*
224 * Drop out, when the task has no waiters. Note,
225 * top_waiter can be NULL, when we are in the deboosting
226 * mode!
227 */
228 if (top_waiter && (!task_has_pi_waiters(task) ||
229 top_waiter != task_top_pi_waiter(task)))
230 goto out_unlock_pi;
231
232 /*
233 * When deadlock detection is off then we check, if further
234 * priority adjustment is necessary.
235 */
236 if (!detect_deadlock && waiter->list_entry.prio == task->prio)
237 goto out_unlock_pi;
238
239 lock = waiter->lock;
240 if (!spin_trylock(&lock->wait_lock)) {
241 spin_unlock_irqrestore(&task->pi_lock, flags);
242 cpu_relax();
243 goto retry;
244 }
245
246 /* Deadlock detection */
247 if (lock == orig_lock || rt_mutex_owner(lock) == top_task) {
248 debug_rt_mutex_deadlock(deadlock_detect, orig_waiter, lock);
249 spin_unlock(&lock->wait_lock);
250 ret = deadlock_detect ? -EDEADLK : 0;
251 goto out_unlock_pi;
252 }
253
254 top_waiter = rt_mutex_top_waiter(lock);
255
256 /* Requeue the waiter */
257 plist_del(&waiter->list_entry, &lock->wait_list);
258 waiter->list_entry.prio = task->prio;
259 plist_add(&waiter->list_entry, &lock->wait_list);
260
261 /* Release the task */
262 spin_unlock_irqrestore(&task->pi_lock, flags);
263 put_task_struct(task);
264
265 /* Grab the next task */
266 task = rt_mutex_owner(lock);
267 get_task_struct(task);
268 spin_lock_irqsave(&task->pi_lock, flags);
269
270 if (waiter == rt_mutex_top_waiter(lock)) {
271 /* Boost the owner */
272 plist_del(&top_waiter->pi_list_entry, &task->pi_waiters);
273 waiter->pi_list_entry.prio = waiter->list_entry.prio;
274 plist_add(&waiter->pi_list_entry, &task->pi_waiters);
275 __rt_mutex_adjust_prio(task);
276
277 } else if (top_waiter == waiter) {
278 /* Deboost the owner */
279 plist_del(&waiter->pi_list_entry, &task->pi_waiters);
280 waiter = rt_mutex_top_waiter(lock);
281 waiter->pi_list_entry.prio = waiter->list_entry.prio;
282 plist_add(&waiter->pi_list_entry, &task->pi_waiters);
283 __rt_mutex_adjust_prio(task);
284 }
285
286 spin_unlock_irqrestore(&task->pi_lock, flags);
287
288 top_waiter = rt_mutex_top_waiter(lock);
289 spin_unlock(&lock->wait_lock);
290
291 if (!detect_deadlock && waiter != top_waiter)
292 goto out_put_task;
293
294 goto again;
295
296 out_unlock_pi:
297 spin_unlock_irqrestore(&task->pi_lock, flags);
298 out_put_task:
299 put_task_struct(task);
300
301 return ret;
302}
303
304/*
305 * Optimization: check if we can steal the lock from the
306 * assigned pending owner [which might not have taken the
307 * lock yet]:
308 */
309static inline int try_to_steal_lock(struct rt_mutex *lock)
310{
311 struct task_struct *pendowner = rt_mutex_owner(lock);
312 struct rt_mutex_waiter *next;
313 unsigned long flags;
314
315 if (!rt_mutex_owner_pending(lock))
316 return 0;
317
318 if (pendowner == current)
319 return 1;
320
321 spin_lock_irqsave(&pendowner->pi_lock, flags);
322 if (current->prio >= pendowner->prio) {
323 spin_unlock_irqrestore(&pendowner->pi_lock, flags);
324 return 0;
325 }
326
327 /*
328 * Check if a waiter is enqueued on the pending owners
329 * pi_waiters list. Remove it and readjust pending owners
330 * priority.
331 */
332 if (likely(!rt_mutex_has_waiters(lock))) {
333 spin_unlock_irqrestore(&pendowner->pi_lock, flags);
334 return 1;
335 }
336
337 /* No chain handling, pending owner is not blocked on anything: */
338 next = rt_mutex_top_waiter(lock);
339 plist_del(&next->pi_list_entry, &pendowner->pi_waiters);
340 __rt_mutex_adjust_prio(pendowner);
341 spin_unlock_irqrestore(&pendowner->pi_lock, flags);
342
343 /*
344 * We are going to steal the lock and a waiter was
345 * enqueued on the pending owners pi_waiters queue. So
346 * we have to enqueue this waiter into
347 * current->pi_waiters list. This covers the case,
348 * where current is boosted because it holds another
349 * lock and gets unboosted because the booster is
350 * interrupted, so we would delay a waiter with higher
351 * priority as current->normal_prio.
352 *
353 * Note: in the rare case of a SCHED_OTHER task changing
354 * its priority and thus stealing the lock, next->task
355 * might be current:
356 */
357 if (likely(next->task != current)) {
358 spin_lock_irqsave(&current->pi_lock, flags);
359 plist_add(&next->pi_list_entry, &current->pi_waiters);
360 __rt_mutex_adjust_prio(current);
361 spin_unlock_irqrestore(&current->pi_lock, flags);
362 }
363 return 1;
364}
365
366/*
367 * Try to take an rt-mutex
368 *
369 * This fails
370 * - when the lock has a real owner
371 * - when a different pending owner exists and has higher priority than current
372 *
373 * Must be called with lock->wait_lock held.
374 */
375static int try_to_take_rt_mutex(struct rt_mutex *lock)
376{
377 /*
378 * We have to be careful here if the atomic speedups are
379 * enabled, such that, when
380 * - no other waiter is on the lock
381 * - the lock has been released since we did the cmpxchg
382 * the lock can be released or taken while we are doing the
383 * checks and marking the lock with RT_MUTEX_HAS_WAITERS.
384 *
385 * The atomic acquire/release aware variant of
386 * mark_rt_mutex_waiters uses a cmpxchg loop. After setting
387 * the WAITERS bit, the atomic release / acquire can not
388 * happen anymore and lock->wait_lock protects us from the
389 * non-atomic case.
390 *
391 * Note, that this might set lock->owner =
392 * RT_MUTEX_HAS_WAITERS in the case the lock is not contended
393 * any more. This is fixed up when we take the ownership.
394 * This is the transitional state explained at the top of this file.
395 */
396 mark_rt_mutex_waiters(lock);
397
398 if (rt_mutex_owner(lock) && !try_to_steal_lock(lock))
399 return 0;
400
401 /* We got the lock. */
402 debug_rt_mutex_lock(lock);
403
404 rt_mutex_set_owner(lock, current, 0);
405
406 rt_mutex_deadlock_account_lock(lock, current);
407
408 return 1;
409}
410
411/*
412 * Task blocks on lock.
413 *
414 * Prepare waiter and propagate pi chain
415 *
416 * This must be called with lock->wait_lock held.
417 */
418static int task_blocks_on_rt_mutex(struct rt_mutex *lock,
419 struct rt_mutex_waiter *waiter,
420 int detect_deadlock)
421{
422 struct task_struct *owner = rt_mutex_owner(lock);
423 struct rt_mutex_waiter *top_waiter = waiter;
424 unsigned long flags;
425 int chain_walk = 0, res;
426
427 spin_lock_irqsave(&current->pi_lock, flags);
428 __rt_mutex_adjust_prio(current);
429 waiter->task = current;
430 waiter->lock = lock;
431 plist_node_init(&waiter->list_entry, current->prio);
432 plist_node_init(&waiter->pi_list_entry, current->prio);
433
434 /* Get the top priority waiter on the lock */
435 if (rt_mutex_has_waiters(lock))
436 top_waiter = rt_mutex_top_waiter(lock);
437 plist_add(&waiter->list_entry, &lock->wait_list);
438
439 current->pi_blocked_on = waiter;
440
441 spin_unlock_irqrestore(&current->pi_lock, flags);
442
443 if (waiter == rt_mutex_top_waiter(lock)) {
444 spin_lock_irqsave(&owner->pi_lock, flags);
445 plist_del(&top_waiter->pi_list_entry, &owner->pi_waiters);
446 plist_add(&waiter->pi_list_entry, &owner->pi_waiters);
447
448 __rt_mutex_adjust_prio(owner);
449 if (owner->pi_blocked_on)
450 chain_walk = 1;
451 spin_unlock_irqrestore(&owner->pi_lock, flags);
452 }
453 else if (debug_rt_mutex_detect_deadlock(waiter, detect_deadlock))
454 chain_walk = 1;
455
456 if (!chain_walk)
457 return 0;
458
459 /*
460 * The owner can't disappear while holding a lock,
461 * so the owner struct is protected by wait_lock.
462 * Gets dropped in rt_mutex_adjust_prio_chain()!
463 */
464 get_task_struct(owner);
465
466 spin_unlock(&lock->wait_lock);
467
468 res = rt_mutex_adjust_prio_chain(owner, detect_deadlock, lock, waiter,
469 current);
470
471 spin_lock(&lock->wait_lock);
472
473 return res;
474}
475
476/*
477 * Wake up the next waiter on the lock.
478 *
479 * Remove the top waiter from the current tasks waiter list and from
480 * the lock waiter list. Set it as pending owner. Then wake it up.
481 *
482 * Called with lock->wait_lock held.
483 */
484static void wakeup_next_waiter(struct rt_mutex *lock)
485{
486 struct rt_mutex_waiter *waiter;
487 struct task_struct *pendowner;
488 unsigned long flags;
489
490 spin_lock_irqsave(&current->pi_lock, flags);
491
492 waiter = rt_mutex_top_waiter(lock);
493 plist_del(&waiter->list_entry, &lock->wait_list);
494
495 /*
496 * Remove it from current->pi_waiters. We do not adjust a
497 * possible priority boost right now. We execute wakeup in the
498 * boosted mode and go back to normal after releasing
499 * lock->wait_lock.
500 */
501 plist_del(&waiter->pi_list_entry, &current->pi_waiters);
502 pendowner = waiter->task;
503 waiter->task = NULL;
504
505 rt_mutex_set_owner(lock, pendowner, RT_MUTEX_OWNER_PENDING);
506
507 spin_unlock_irqrestore(&current->pi_lock, flags);
508
509 /*
510 * Clear the pi_blocked_on variable and enqueue a possible
511 * waiter into the pi_waiters list of the pending owner. This
512 * prevents that in case the pending owner gets unboosted a
513 * waiter with higher priority than pending-owner->normal_prio
514 * is blocked on the unboosted (pending) owner.
515 */
516 spin_lock_irqsave(&pendowner->pi_lock, flags);
517
518 WARN_ON(!pendowner->pi_blocked_on);
519 WARN_ON(pendowner->pi_blocked_on != waiter);
520 WARN_ON(pendowner->pi_blocked_on->lock != lock);
521
522 pendowner->pi_blocked_on = NULL;
523
524 if (rt_mutex_has_waiters(lock)) {
525 struct rt_mutex_waiter *next;
526
527 next = rt_mutex_top_waiter(lock);
528 plist_add(&next->pi_list_entry, &pendowner->pi_waiters);
529 }
530 spin_unlock_irqrestore(&pendowner->pi_lock, flags);
531
532 wake_up_process(pendowner);
533}
534
535/*
536 * Remove a waiter from a lock
537 *
538 * Must be called with lock->wait_lock held
539 */
540static void remove_waiter(struct rt_mutex *lock,
541 struct rt_mutex_waiter *waiter)
542{
543 int first = (waiter == rt_mutex_top_waiter(lock));
544 struct task_struct *owner = rt_mutex_owner(lock);
545 unsigned long flags;
546 int chain_walk = 0;
547
548 spin_lock_irqsave(&current->pi_lock, flags);
549 plist_del(&waiter->list_entry, &lock->wait_list);
550 waiter->task = NULL;
551 current->pi_blocked_on = NULL;
552 spin_unlock_irqrestore(&current->pi_lock, flags);
553
554 if (first && owner != current) {
555
556 spin_lock_irqsave(&owner->pi_lock, flags);
557
558 plist_del(&waiter->pi_list_entry, &owner->pi_waiters);
559
560 if (rt_mutex_has_waiters(lock)) {
561 struct rt_mutex_waiter *next;
562
563 next = rt_mutex_top_waiter(lock);
564 plist_add(&next->pi_list_entry, &owner->pi_waiters);
565 }
566 __rt_mutex_adjust_prio(owner);
567
568 if (owner->pi_blocked_on)
569 chain_walk = 1;
570
571 spin_unlock_irqrestore(&owner->pi_lock, flags);
572 }
573
574 WARN_ON(!plist_node_empty(&waiter->pi_list_entry));
575
576 if (!chain_walk)
577 return;
578
579 /* gets dropped in rt_mutex_adjust_prio_chain()! */
580 get_task_struct(owner);
581
582 spin_unlock(&lock->wait_lock);
583
584 rt_mutex_adjust_prio_chain(owner, 0, lock, NULL, current);
585
586 spin_lock(&lock->wait_lock);
587}
588
589/*
590 * Recheck the pi chain, in case we got a priority setting
591 *
592 * Called from sched_setscheduler
593 */
594void rt_mutex_adjust_pi(struct task_struct *task)
595{
596 struct rt_mutex_waiter *waiter;
597 unsigned long flags;
598
599 spin_lock_irqsave(&task->pi_lock, flags);
600
601 waiter = task->pi_blocked_on;
602 if (!waiter || waiter->list_entry.prio == task->prio) {
603 spin_unlock_irqrestore(&task->pi_lock, flags);
604 return;
605 }
606
607 spin_unlock_irqrestore(&task->pi_lock, flags);
608
609 /* gets dropped in rt_mutex_adjust_prio_chain()! */
610 get_task_struct(task);
611 rt_mutex_adjust_prio_chain(task, 0, NULL, NULL, task);
612}
613
614/*
615 * Slow path lock function:
616 */
617static int __sched
618rt_mutex_slowlock(struct rt_mutex *lock, int state,
619 struct hrtimer_sleeper *timeout,
620 int detect_deadlock)
621{
622 struct rt_mutex_waiter waiter;
623 int ret = 0;
624
625 debug_rt_mutex_init_waiter(&waiter);
626 waiter.task = NULL;
627
628 spin_lock(&lock->wait_lock);
629
630 /* Try to acquire the lock again: */
631 if (try_to_take_rt_mutex(lock)) {
632 spin_unlock(&lock->wait_lock);
633 return 0;
634 }
635
636 set_current_state(state);
637
638 /* Setup the timer, when timeout != NULL */
639 if (unlikely(timeout))
640 hrtimer_start(&timeout->timer, timeout->timer.expires,
641 HRTIMER_MODE_ABS);
642
643 for (;;) {
644 /* Try to acquire the lock: */
645 if (try_to_take_rt_mutex(lock))
646 break;
647
648 /*
649 * TASK_INTERRUPTIBLE checks for signals and
650 * timeout. Ignored otherwise.
651 */
652 if (unlikely(state == TASK_INTERRUPTIBLE)) {
653 /* Signal pending? */
654 if (signal_pending(current))
655 ret = -EINTR;
656 if (timeout && !timeout->task)
657 ret = -ETIMEDOUT;
658 if (ret)
659 break;
660 }
661
662 /*
663 * waiter.task is NULL the first time we come here and
664 * when we have been woken up by the previous owner
665 * but the lock got stolen by a higher prio task.
666 */
667 if (!waiter.task) {
668 ret = task_blocks_on_rt_mutex(lock, &waiter,
669 detect_deadlock);
670 /*
671 * If we got woken up by the owner then start loop
672 * all over without going into schedule to try
673 * to get the lock now:
674 */
675 if (unlikely(!waiter.task)) {
676 /*
677 * Reset the return value. We might
678 * have returned with -EDEADLK and the
679 * owner released the lock while we
680 * were walking the pi chain.
681 */
682 ret = 0;
683 continue;
684 }
685 if (unlikely(ret))
686 break;
687 }
688
689 spin_unlock(&lock->wait_lock);
690
691 debug_rt_mutex_print_deadlock(&waiter);
692
693 if (waiter.task)
694 schedule_rt_mutex(lock);
695
696 spin_lock(&lock->wait_lock);
697 set_current_state(state);
698 }
699
700 set_current_state(TASK_RUNNING);
701
702 if (unlikely(waiter.task))
703 remove_waiter(lock, &waiter);
704
705 /*
706 * try_to_take_rt_mutex() sets the waiter bit
707 * unconditionally. We might have to fix that up.
708 */
709 fixup_rt_mutex_waiters(lock);
710
711 spin_unlock(&lock->wait_lock);
712
713 /* Remove pending timer: */
714 if (unlikely(timeout))
715 hrtimer_cancel(&timeout->timer);
716
717 /*
718 * Readjust priority, when we did not get the lock. We might
719 * have been the pending owner and boosted. Since we did not
720 * take the lock, the PI boost has to go.
721 */
722 if (unlikely(ret))
723 rt_mutex_adjust_prio(current);
724
725 debug_rt_mutex_free_waiter(&waiter);
726
727 return ret;
728}
729
730/*
731 * Slow path try-lock function:
732 */
733static inline int
734rt_mutex_slowtrylock(struct rt_mutex *lock)
735{
736 int ret = 0;
737
738 spin_lock(&lock->wait_lock);
739
740 if (likely(rt_mutex_owner(lock) != current)) {
741
742 ret = try_to_take_rt_mutex(lock);
743 /*
744 * try_to_take_rt_mutex() sets the lock waiters
745 * bit unconditionally. Clean this up.
746 */
747 fixup_rt_mutex_waiters(lock);
748 }
749
750 spin_unlock(&lock->wait_lock);
751
752 return ret;
753}
754
755/*
756 * Slow path to release a rt-mutex:
757 */
758static void __sched
759rt_mutex_slowunlock(struct rt_mutex *lock)
760{
761 spin_lock(&lock->wait_lock);
762
763 debug_rt_mutex_unlock(lock);
764
765 rt_mutex_deadlock_account_unlock(current);
766
767 if (!rt_mutex_has_waiters(lock)) {
768 lock->owner = NULL;
769 spin_unlock(&lock->wait_lock);
770 return;
771 }
772
773 wakeup_next_waiter(lock);
774
775 spin_unlock(&lock->wait_lock);
776
777 /* Undo pi boosting if necessary: */
778 rt_mutex_adjust_prio(current);
779}
780
781/*
782 * debug aware fast / slowpath lock,trylock,unlock
783 *
784 * The atomic acquire/release ops are compiled away, when either the
785 * architecture does not support cmpxchg or when debugging is enabled.
786 */
787static inline int
788rt_mutex_fastlock(struct rt_mutex *lock, int state,
789 int detect_deadlock,
790 int (*slowfn)(struct rt_mutex *lock, int state,
791 struct hrtimer_sleeper *timeout,
792 int detect_deadlock))
793{
794 if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) {
795 rt_mutex_deadlock_account_lock(lock, current);
796 return 0;
797 } else
798 return slowfn(lock, state, NULL, detect_deadlock);
799}
800
801static inline int
802rt_mutex_timed_fastlock(struct rt_mutex *lock, int state,
803 struct hrtimer_sleeper *timeout, int detect_deadlock,
804 int (*slowfn)(struct rt_mutex *lock, int state,
805 struct hrtimer_sleeper *timeout,
806 int detect_deadlock))
807{
808 if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) {
809 rt_mutex_deadlock_account_lock(lock, current);
810 return 0;
811 } else
812 return slowfn(lock, state, timeout, detect_deadlock);
813}
814
815static inline int
816rt_mutex_fasttrylock(struct rt_mutex *lock,
817 int (*slowfn)(struct rt_mutex *lock))
818{
819 if (likely(rt_mutex_cmpxchg(lock, NULL, current))) {
820 rt_mutex_deadlock_account_lock(lock, current);
821 return 1;
822 }
823 return slowfn(lock);
824}
825
826static inline void
827rt_mutex_fastunlock(struct rt_mutex *lock,
828 void (*slowfn)(struct rt_mutex *lock))
829{
830 if (likely(rt_mutex_cmpxchg(lock, current, NULL)))
831 rt_mutex_deadlock_account_unlock(current);
832 else
833 slowfn(lock);
834}
835
836/**
837 * rt_mutex_lock - lock a rt_mutex
838 *
839 * @lock: the rt_mutex to be locked
840 */
841void __sched rt_mutex_lock(struct rt_mutex *lock)
842{
843 might_sleep();
844
845 rt_mutex_fastlock(lock, TASK_UNINTERRUPTIBLE, 0, rt_mutex_slowlock);
846}
847EXPORT_SYMBOL_GPL(rt_mutex_lock);
848
849/**
850 * rt_mutex_lock_interruptible - lock a rt_mutex interruptible
851 *
852 * @lock: the rt_mutex to be locked
853 * @detect_deadlock: deadlock detection on/off
854 *
855 * Returns:
856 * 0 on success
857 * -EINTR when interrupted by a signal
858 * -EDEADLK when the lock would deadlock (when deadlock detection is on)
859 */
860int __sched rt_mutex_lock_interruptible(struct rt_mutex *lock,
861 int detect_deadlock)
862{
863 might_sleep();
864
865 return rt_mutex_fastlock(lock, TASK_INTERRUPTIBLE,
866 detect_deadlock, rt_mutex_slowlock);
867}
868EXPORT_SYMBOL_GPL(rt_mutex_lock_interruptible);
869
870/**
871 * rt_mutex_lock_interruptible_ktime - lock a rt_mutex interruptible
872 * the timeout structure is provided
873 * by the caller
874 *
875 * @lock: the rt_mutex to be locked
876 * @timeout: timeout structure or NULL (no timeout)
877 * @detect_deadlock: deadlock detection on/off
878 *
879 * Returns:
880 * 0 on success
881 * -EINTR when interrupted by a signal
882 * -ETIMEOUT when the timeout expired
883 * -EDEADLK when the lock would deadlock (when deadlock detection is on)
884 */
885int
886rt_mutex_timed_lock(struct rt_mutex *lock, struct hrtimer_sleeper *timeout,
887 int detect_deadlock)
888{
889 might_sleep();
890
891 return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout,
892 detect_deadlock, rt_mutex_slowlock);
893}
894EXPORT_SYMBOL_GPL(rt_mutex_timed_lock);
895
896/**
897 * rt_mutex_trylock - try to lock a rt_mutex
898 *
899 * @lock: the rt_mutex to be locked
900 *
901 * Returns 1 on success and 0 on contention
902 */
903int __sched rt_mutex_trylock(struct rt_mutex *lock)
904{
905 return rt_mutex_fasttrylock(lock, rt_mutex_slowtrylock);
906}
907EXPORT_SYMBOL_GPL(rt_mutex_trylock);
908
909/**
910 * rt_mutex_unlock - unlock a rt_mutex
911 *
912 * @lock: the rt_mutex to be unlocked
913 */
914void __sched rt_mutex_unlock(struct rt_mutex *lock)
915{
916 rt_mutex_fastunlock(lock, rt_mutex_slowunlock);
917}
918EXPORT_SYMBOL_GPL(rt_mutex_unlock);
919
920/***
921 * rt_mutex_destroy - mark a mutex unusable
922 * @lock: the mutex to be destroyed
923 *
924 * This function marks the mutex uninitialized, and any subsequent
925 * use of the mutex is forbidden. The mutex must not be locked when
926 * this function is called.
927 */
928void rt_mutex_destroy(struct rt_mutex *lock)
929{
930 WARN_ON(rt_mutex_is_locked(lock));
931#ifdef CONFIG_DEBUG_RT_MUTEXES
932 lock->magic = NULL;
933#endif
934}
935
936EXPORT_SYMBOL_GPL(rt_mutex_destroy);
937
938/**
939 * __rt_mutex_init - initialize the rt lock
940 *
941 * @lock: the rt lock to be initialized
942 *
943 * Initialize the rt lock to unlocked state.
944 *
945 * Initializing of a locked rt lock is not allowed
946 */
947void __rt_mutex_init(struct rt_mutex *lock, const char *name)
948{
949 lock->owner = NULL;
950 spin_lock_init(&lock->wait_lock);
951 plist_head_init(&lock->wait_list, &lock->wait_lock);
952
953 debug_rt_mutex_init(lock, name);
954}
955EXPORT_SYMBOL_GPL(__rt_mutex_init);
956
957/**
958 * rt_mutex_init_proxy_locked - initialize and lock a rt_mutex on behalf of a
959 * proxy owner
960 *
961 * @lock: the rt_mutex to be locked
962 * @proxy_owner:the task to set as owner
963 *
964 * No locking. Caller has to do serializing itself
965 * Special API call for PI-futex support
966 */
967void rt_mutex_init_proxy_locked(struct rt_mutex *lock,
968 struct task_struct *proxy_owner)
969{
970 __rt_mutex_init(lock, NULL);
971 debug_rt_mutex_proxy_lock(lock, proxy_owner);
972 rt_mutex_set_owner(lock, proxy_owner, 0);
973 rt_mutex_deadlock_account_lock(lock, proxy_owner);
974}
975
976/**
977 * rt_mutex_proxy_unlock - release a lock on behalf of owner
978 *
979 * @lock: the rt_mutex to be locked
980 *
981 * No locking. Caller has to do serializing itself
982 * Special API call for PI-futex support
983 */
984void rt_mutex_proxy_unlock(struct rt_mutex *lock,
985 struct task_struct *proxy_owner)
986{
987 debug_rt_mutex_proxy_unlock(lock);
988 rt_mutex_set_owner(lock, NULL, 0);
989 rt_mutex_deadlock_account_unlock(proxy_owner);
990}
991
992/**
993 * rt_mutex_next_owner - return the next owner of the lock
994 *
995 * @lock: the rt lock query
996 *
997 * Returns the next owner of the lock or NULL
998 *
999 * Caller has to serialize against other accessors to the lock
1000 * itself.
1001 *
1002 * Special API call for PI-futex support
1003 */
1004struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock)
1005{
1006 if (!rt_mutex_has_waiters(lock))
1007 return NULL;
1008
1009 return rt_mutex_top_waiter(lock)->task;
1010}