ia64/linux-2.6.18-xen.hg

view kernel/rtmutex.c @ 912:dd42cdb0ab89

[IA64] Build blktap2 driver by default in x86 builds.

add CONFIG_XEN_BLKDEV_TAP2=y to buildconfigs/linux-defconfig_xen_ia64.

Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
author Isaku Yamahata <yamahata@valinux.co.jp>
date Mon Jun 29 12:09:16 2009 +0900 (2009-06-29)
parents 831230e53067
children
line source
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 <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
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>
18 #include "rtmutex_common.h"
20 #ifdef CONFIG_DEBUG_RT_MUTEXES
21 # include "rtmutex-debug.h"
22 #else
23 # include "rtmutex.h"
24 #endif
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 */
59 static void
60 rt_mutex_set_owner(struct rt_mutex *lock, struct task_struct *owner,
61 unsigned long mask)
62 {
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;
69 }
71 static 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 }
77 static void fixup_rt_mutex_waiters(struct rt_mutex *lock)
78 {
79 if (!rt_mutex_has_waiters(lock))
80 clear_rt_mutex_waiters(lock);
81 }
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)
89 static inline void mark_rt_mutex_waiters(struct rt_mutex *lock)
90 {
91 unsigned long owner, *p = (unsigned long *) &lock->owner;
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)
99 static 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
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 */
112 int rt_mutex_getprio(struct task_struct *task)
113 {
114 if (likely(!task_has_pi_waiters(task)))
115 return task->normal_prio;
117 return min(task_top_pi_waiter(task)->pi_list_entry.prio,
118 task->normal_prio);
119 }
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 */
126 static void __rt_mutex_adjust_prio(struct task_struct *task)
127 {
128 int prio = rt_mutex_getprio(task);
130 if (task->prio != prio)
131 rt_mutex_setprio(task, prio);
132 }
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 */
143 static void rt_mutex_adjust_prio(struct task_struct *task)
144 {
145 unsigned long flags;
147 spin_lock_irqsave(&task->pi_lock, flags);
148 __rt_mutex_adjust_prio(task);
149 spin_unlock_irqrestore(&task->pi_lock, flags);
150 }
152 /*
153 * Max number of times we'll walk the boosting chain:
154 */
155 int max_lock_depth = 1024;
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 */
162 static 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;
173 detect_deadlock = debug_rt_mutex_detect_deadlock(orig_waiter,
174 deadlock_detect);
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;
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);
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);
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;
215 if (top_waiter && (!task_has_pi_waiters(task) ||
216 top_waiter != task_top_pi_waiter(task)))
217 goto out_unlock_pi;
219 /*
220 * When deadlock detection is off then we check, if further
221 * priority adjustment is necessary.
222 */
223 if (!detect_deadlock && waiter->list_entry.prio == task->prio)
224 goto out_unlock_pi;
226 lock = waiter->lock;
227 if (!spin_trylock(&lock->wait_lock)) {
228 spin_unlock_irqrestore(&task->pi_lock, flags);
229 cpu_relax();
230 goto retry;
231 }
233 /* Deadlock detection */
234 if (lock == orig_lock || rt_mutex_owner(lock) == top_task) {
235 debug_rt_mutex_deadlock(deadlock_detect, orig_waiter, lock);
236 spin_unlock(&lock->wait_lock);
237 ret = deadlock_detect ? -EDEADLK : 0;
238 goto out_unlock_pi;
239 }
241 top_waiter = rt_mutex_top_waiter(lock);
243 /* Requeue the waiter */
244 plist_del(&waiter->list_entry, &lock->wait_list);
245 waiter->list_entry.prio = task->prio;
246 plist_add(&waiter->list_entry, &lock->wait_list);
248 /* Release the task */
249 spin_unlock_irqrestore(&task->pi_lock, flags);
250 put_task_struct(task);
252 /* Grab the next task */
253 task = rt_mutex_owner(lock);
254 spin_lock_irqsave(&task->pi_lock, flags);
256 if (waiter == rt_mutex_top_waiter(lock)) {
257 /* Boost the owner */
258 plist_del(&top_waiter->pi_list_entry, &task->pi_waiters);
259 waiter->pi_list_entry.prio = waiter->list_entry.prio;
260 plist_add(&waiter->pi_list_entry, &task->pi_waiters);
261 __rt_mutex_adjust_prio(task);
263 } else if (top_waiter == waiter) {
264 /* Deboost the owner */
265 plist_del(&waiter->pi_list_entry, &task->pi_waiters);
266 waiter = rt_mutex_top_waiter(lock);
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);
270 }
272 get_task_struct(task);
273 spin_unlock_irqrestore(&task->pi_lock, flags);
275 top_waiter = rt_mutex_top_waiter(lock);
276 spin_unlock(&lock->wait_lock);
278 if (!detect_deadlock && waiter != top_waiter)
279 goto out_put_task;
281 goto again;
283 out_unlock_pi:
284 spin_unlock_irqrestore(&task->pi_lock, flags);
285 out_put_task:
286 put_task_struct(task);
288 return ret;
289 }
291 /*
292 * Optimization: check if we can steal the lock from the
293 * assigned pending owner [which might not have taken the
294 * lock yet]:
295 */
296 static inline int try_to_steal_lock(struct rt_mutex *lock)
297 {
298 struct task_struct *pendowner = rt_mutex_owner(lock);
299 struct rt_mutex_waiter *next;
300 unsigned long flags;
302 if (!rt_mutex_owner_pending(lock))
303 return 0;
305 if (pendowner == current)
306 return 1;
308 spin_lock_irqsave(&pendowner->pi_lock, flags);
309 if (current->prio >= pendowner->prio) {
310 spin_unlock_irqrestore(&pendowner->pi_lock, flags);
311 return 0;
312 }
314 /*
315 * Check if a waiter is enqueued on the pending owners
316 * pi_waiters list. Remove it and readjust pending owners
317 * priority.
318 */
319 if (likely(!rt_mutex_has_waiters(lock))) {
320 spin_unlock_irqrestore(&pendowner->pi_lock, flags);
321 return 1;
322 }
324 /* No chain handling, pending owner is not blocked on anything: */
325 next = rt_mutex_top_waiter(lock);
326 plist_del(&next->pi_list_entry, &pendowner->pi_waiters);
327 __rt_mutex_adjust_prio(pendowner);
328 spin_unlock_irqrestore(&pendowner->pi_lock, flags);
330 /*
331 * We are going to steal the lock and a waiter was
332 * enqueued on the pending owners pi_waiters queue. So
333 * we have to enqueue this waiter into
334 * current->pi_waiters list. This covers the case,
335 * where current is boosted because it holds another
336 * lock and gets unboosted because the booster is
337 * interrupted, so we would delay a waiter with higher
338 * priority as current->normal_prio.
339 *
340 * Note: in the rare case of a SCHED_OTHER task changing
341 * its priority and thus stealing the lock, next->task
342 * might be current:
343 */
344 if (likely(next->task != current)) {
345 spin_lock_irqsave(&current->pi_lock, flags);
346 plist_add(&next->pi_list_entry, &current->pi_waiters);
347 __rt_mutex_adjust_prio(current);
348 spin_unlock_irqrestore(&current->pi_lock, flags);
349 }
350 return 1;
351 }
353 /*
354 * Try to take an rt-mutex
355 *
356 * This fails
357 * - when the lock has a real owner
358 * - when a different pending owner exists and has higher priority than current
359 *
360 * Must be called with lock->wait_lock held.
361 */
362 static int try_to_take_rt_mutex(struct rt_mutex *lock)
363 {
364 /*
365 * We have to be careful here if the atomic speedups are
366 * enabled, such that, when
367 * - no other waiter is on the lock
368 * - the lock has been released since we did the cmpxchg
369 * the lock can be released or taken while we are doing the
370 * checks and marking the lock with RT_MUTEX_HAS_WAITERS.
371 *
372 * The atomic acquire/release aware variant of
373 * mark_rt_mutex_waiters uses a cmpxchg loop. After setting
374 * the WAITERS bit, the atomic release / acquire can not
375 * happen anymore and lock->wait_lock protects us from the
376 * non-atomic case.
377 *
378 * Note, that this might set lock->owner =
379 * RT_MUTEX_HAS_WAITERS in the case the lock is not contended
380 * any more. This is fixed up when we take the ownership.
381 * This is the transitional state explained at the top of this file.
382 */
383 mark_rt_mutex_waiters(lock);
385 if (rt_mutex_owner(lock) && !try_to_steal_lock(lock))
386 return 0;
388 /* We got the lock. */
389 debug_rt_mutex_lock(lock);
391 rt_mutex_set_owner(lock, current, 0);
393 rt_mutex_deadlock_account_lock(lock, current);
395 return 1;
396 }
398 /*
399 * Task blocks on lock.
400 *
401 * Prepare waiter and propagate pi chain
402 *
403 * This must be called with lock->wait_lock held.
404 */
405 static int task_blocks_on_rt_mutex(struct rt_mutex *lock,
406 struct rt_mutex_waiter *waiter,
407 int detect_deadlock)
408 {
409 struct task_struct *owner = rt_mutex_owner(lock);
410 struct rt_mutex_waiter *top_waiter = waiter;
411 unsigned long flags;
412 int boost = 0, res;
414 spin_lock_irqsave(&current->pi_lock, flags);
415 __rt_mutex_adjust_prio(current);
416 waiter->task = current;
417 waiter->lock = lock;
418 plist_node_init(&waiter->list_entry, current->prio);
419 plist_node_init(&waiter->pi_list_entry, current->prio);
421 /* Get the top priority waiter on the lock */
422 if (rt_mutex_has_waiters(lock))
423 top_waiter = rt_mutex_top_waiter(lock);
424 plist_add(&waiter->list_entry, &lock->wait_list);
426 current->pi_blocked_on = waiter;
428 spin_unlock_irqrestore(&current->pi_lock, flags);
430 if (waiter == rt_mutex_top_waiter(lock)) {
431 spin_lock_irqsave(&owner->pi_lock, flags);
432 plist_del(&top_waiter->pi_list_entry, &owner->pi_waiters);
433 plist_add(&waiter->pi_list_entry, &owner->pi_waiters);
435 __rt_mutex_adjust_prio(owner);
436 if (owner->pi_blocked_on) {
437 boost = 1;
438 /* gets dropped in rt_mutex_adjust_prio_chain()! */
439 get_task_struct(owner);
440 }
441 spin_unlock_irqrestore(&owner->pi_lock, flags);
442 }
443 else if (debug_rt_mutex_detect_deadlock(waiter, detect_deadlock)) {
444 spin_lock_irqsave(&owner->pi_lock, flags);
445 if (owner->pi_blocked_on) {
446 boost = 1;
447 /* gets dropped in rt_mutex_adjust_prio_chain()! */
448 get_task_struct(owner);
449 }
450 spin_unlock_irqrestore(&owner->pi_lock, flags);
451 }
452 if (!boost)
453 return 0;
455 spin_unlock(&lock->wait_lock);
457 res = rt_mutex_adjust_prio_chain(owner, detect_deadlock, lock, waiter,
458 current);
460 spin_lock(&lock->wait_lock);
462 return res;
463 }
465 /*
466 * Wake up the next waiter on the lock.
467 *
468 * Remove the top waiter from the current tasks waiter list and from
469 * the lock waiter list. Set it as pending owner. Then wake it up.
470 *
471 * Called with lock->wait_lock held.
472 */
473 static void wakeup_next_waiter(struct rt_mutex *lock)
474 {
475 struct rt_mutex_waiter *waiter;
476 struct task_struct *pendowner;
477 unsigned long flags;
479 spin_lock_irqsave(&current->pi_lock, flags);
481 waiter = rt_mutex_top_waiter(lock);
482 plist_del(&waiter->list_entry, &lock->wait_list);
484 /*
485 * Remove it from current->pi_waiters. We do not adjust a
486 * possible priority boost right now. We execute wakeup in the
487 * boosted mode and go back to normal after releasing
488 * lock->wait_lock.
489 */
490 plist_del(&waiter->pi_list_entry, &current->pi_waiters);
491 pendowner = waiter->task;
492 waiter->task = NULL;
494 rt_mutex_set_owner(lock, pendowner, RT_MUTEX_OWNER_PENDING);
496 spin_unlock_irqrestore(&current->pi_lock, flags);
498 /*
499 * Clear the pi_blocked_on variable and enqueue a possible
500 * waiter into the pi_waiters list of the pending owner. This
501 * prevents that in case the pending owner gets unboosted a
502 * waiter with higher priority than pending-owner->normal_prio
503 * is blocked on the unboosted (pending) owner.
504 */
505 spin_lock_irqsave(&pendowner->pi_lock, flags);
507 WARN_ON(!pendowner->pi_blocked_on);
508 WARN_ON(pendowner->pi_blocked_on != waiter);
509 WARN_ON(pendowner->pi_blocked_on->lock != lock);
511 pendowner->pi_blocked_on = NULL;
513 if (rt_mutex_has_waiters(lock)) {
514 struct rt_mutex_waiter *next;
516 next = rt_mutex_top_waiter(lock);
517 plist_add(&next->pi_list_entry, &pendowner->pi_waiters);
518 }
519 spin_unlock_irqrestore(&pendowner->pi_lock, flags);
521 wake_up_process(pendowner);
522 }
524 /*
525 * Remove a waiter from a lock
526 *
527 * Must be called with lock->wait_lock held
528 */
529 static void remove_waiter(struct rt_mutex *lock,
530 struct rt_mutex_waiter *waiter)
531 {
532 int first = (waiter == rt_mutex_top_waiter(lock));
533 struct task_struct *owner = rt_mutex_owner(lock);
534 unsigned long flags;
535 int boost = 0;
537 spin_lock_irqsave(&current->pi_lock, flags);
538 plist_del(&waiter->list_entry, &lock->wait_list);
539 waiter->task = NULL;
540 current->pi_blocked_on = NULL;
541 spin_unlock_irqrestore(&current->pi_lock, flags);
543 if (first && owner != current) {
545 spin_lock_irqsave(&owner->pi_lock, flags);
547 plist_del(&waiter->pi_list_entry, &owner->pi_waiters);
549 if (rt_mutex_has_waiters(lock)) {
550 struct rt_mutex_waiter *next;
552 next = rt_mutex_top_waiter(lock);
553 plist_add(&next->pi_list_entry, &owner->pi_waiters);
554 }
555 __rt_mutex_adjust_prio(owner);
557 if (owner->pi_blocked_on) {
558 boost = 1;
559 /* gets dropped in rt_mutex_adjust_prio_chain()! */
560 get_task_struct(owner);
561 }
562 spin_unlock_irqrestore(&owner->pi_lock, flags);
563 }
565 WARN_ON(!plist_node_empty(&waiter->pi_list_entry));
567 if (!boost)
568 return;
570 spin_unlock(&lock->wait_lock);
572 rt_mutex_adjust_prio_chain(owner, 0, lock, NULL, current);
574 spin_lock(&lock->wait_lock);
575 }
577 /*
578 * Recheck the pi chain, in case we got a priority setting
579 *
580 * Called from sched_setscheduler
581 */
582 void rt_mutex_adjust_pi(struct task_struct *task)
583 {
584 struct rt_mutex_waiter *waiter;
585 unsigned long flags;
587 spin_lock_irqsave(&task->pi_lock, flags);
589 waiter = task->pi_blocked_on;
590 if (!waiter || waiter->list_entry.prio == task->prio) {
591 spin_unlock_irqrestore(&task->pi_lock, flags);
592 return;
593 }
595 /* gets dropped in rt_mutex_adjust_prio_chain()! */
596 get_task_struct(task);
597 spin_unlock_irqrestore(&task->pi_lock, flags);
599 rt_mutex_adjust_prio_chain(task, 0, NULL, NULL, task);
600 }
602 /*
603 * Slow path lock function:
604 */
605 static int __sched
606 rt_mutex_slowlock(struct rt_mutex *lock, int state,
607 struct hrtimer_sleeper *timeout,
608 int detect_deadlock)
609 {
610 struct rt_mutex_waiter waiter;
611 int ret = 0;
613 debug_rt_mutex_init_waiter(&waiter);
614 waiter.task = NULL;
616 spin_lock(&lock->wait_lock);
618 /* Try to acquire the lock again: */
619 if (try_to_take_rt_mutex(lock)) {
620 spin_unlock(&lock->wait_lock);
621 return 0;
622 }
624 set_current_state(state);
626 /* Setup the timer, when timeout != NULL */
627 if (unlikely(timeout))
628 hrtimer_start(&timeout->timer, timeout->timer.expires,
629 HRTIMER_ABS);
631 for (;;) {
632 /* Try to acquire the lock: */
633 if (try_to_take_rt_mutex(lock))
634 break;
636 /*
637 * TASK_INTERRUPTIBLE checks for signals and
638 * timeout. Ignored otherwise.
639 */
640 if (unlikely(state == TASK_INTERRUPTIBLE)) {
641 /* Signal pending? */
642 if (signal_pending(current))
643 ret = -EINTR;
644 if (timeout && !timeout->task)
645 ret = -ETIMEDOUT;
646 if (ret)
647 break;
648 }
650 /*
651 * waiter.task is NULL the first time we come here and
652 * when we have been woken up by the previous owner
653 * but the lock got stolen by a higher prio task.
654 */
655 if (!waiter.task) {
656 ret = task_blocks_on_rt_mutex(lock, &waiter,
657 detect_deadlock);
658 /*
659 * If we got woken up by the owner then start loop
660 * all over without going into schedule to try
661 * to get the lock now:
662 */
663 if (unlikely(!waiter.task))
664 continue;
666 if (unlikely(ret))
667 break;
668 }
670 spin_unlock(&lock->wait_lock);
672 debug_rt_mutex_print_deadlock(&waiter);
674 if (waiter.task)
675 schedule_rt_mutex(lock);
677 spin_lock(&lock->wait_lock);
678 set_current_state(state);
679 }
681 set_current_state(TASK_RUNNING);
683 if (unlikely(waiter.task))
684 remove_waiter(lock, &waiter);
686 /*
687 * try_to_take_rt_mutex() sets the waiter bit
688 * unconditionally. We might have to fix that up.
689 */
690 fixup_rt_mutex_waiters(lock);
692 spin_unlock(&lock->wait_lock);
694 /* Remove pending timer: */
695 if (unlikely(timeout))
696 hrtimer_cancel(&timeout->timer);
698 /*
699 * Readjust priority, when we did not get the lock. We might
700 * have been the pending owner and boosted. Since we did not
701 * take the lock, the PI boost has to go.
702 */
703 if (unlikely(ret))
704 rt_mutex_adjust_prio(current);
706 debug_rt_mutex_free_waiter(&waiter);
708 return ret;
709 }
711 /*
712 * Slow path try-lock function:
713 */
714 static inline int
715 rt_mutex_slowtrylock(struct rt_mutex *lock)
716 {
717 int ret = 0;
719 spin_lock(&lock->wait_lock);
721 if (likely(rt_mutex_owner(lock) != current)) {
723 ret = try_to_take_rt_mutex(lock);
724 /*
725 * try_to_take_rt_mutex() sets the lock waiters
726 * bit unconditionally. Clean this up.
727 */
728 fixup_rt_mutex_waiters(lock);
729 }
731 spin_unlock(&lock->wait_lock);
733 return ret;
734 }
736 /*
737 * Slow path to release a rt-mutex:
738 */
739 static void __sched
740 rt_mutex_slowunlock(struct rt_mutex *lock)
741 {
742 spin_lock(&lock->wait_lock);
744 debug_rt_mutex_unlock(lock);
746 rt_mutex_deadlock_account_unlock(current);
748 if (!rt_mutex_has_waiters(lock)) {
749 lock->owner = NULL;
750 spin_unlock(&lock->wait_lock);
751 return;
752 }
754 wakeup_next_waiter(lock);
756 spin_unlock(&lock->wait_lock);
758 /* Undo pi boosting if necessary: */
759 rt_mutex_adjust_prio(current);
760 }
762 /*
763 * debug aware fast / slowpath lock,trylock,unlock
764 *
765 * The atomic acquire/release ops are compiled away, when either the
766 * architecture does not support cmpxchg or when debugging is enabled.
767 */
768 static inline int
769 rt_mutex_fastlock(struct rt_mutex *lock, int state,
770 int detect_deadlock,
771 int (*slowfn)(struct rt_mutex *lock, int state,
772 struct hrtimer_sleeper *timeout,
773 int detect_deadlock))
774 {
775 if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) {
776 rt_mutex_deadlock_account_lock(lock, current);
777 return 0;
778 } else
779 return slowfn(lock, state, NULL, detect_deadlock);
780 }
782 static inline int
783 rt_mutex_timed_fastlock(struct rt_mutex *lock, int state,
784 struct hrtimer_sleeper *timeout, int detect_deadlock,
785 int (*slowfn)(struct rt_mutex *lock, int state,
786 struct hrtimer_sleeper *timeout,
787 int detect_deadlock))
788 {
789 if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) {
790 rt_mutex_deadlock_account_lock(lock, current);
791 return 0;
792 } else
793 return slowfn(lock, state, timeout, detect_deadlock);
794 }
796 static inline int
797 rt_mutex_fasttrylock(struct rt_mutex *lock,
798 int (*slowfn)(struct rt_mutex *lock))
799 {
800 if (likely(rt_mutex_cmpxchg(lock, NULL, current))) {
801 rt_mutex_deadlock_account_lock(lock, current);
802 return 1;
803 }
804 return slowfn(lock);
805 }
807 static inline void
808 rt_mutex_fastunlock(struct rt_mutex *lock,
809 void (*slowfn)(struct rt_mutex *lock))
810 {
811 if (likely(rt_mutex_cmpxchg(lock, current, NULL)))
812 rt_mutex_deadlock_account_unlock(current);
813 else
814 slowfn(lock);
815 }
817 /**
818 * rt_mutex_lock - lock a rt_mutex
819 *
820 * @lock: the rt_mutex to be locked
821 */
822 void __sched rt_mutex_lock(struct rt_mutex *lock)
823 {
824 might_sleep();
826 rt_mutex_fastlock(lock, TASK_UNINTERRUPTIBLE, 0, rt_mutex_slowlock);
827 }
828 EXPORT_SYMBOL_GPL(rt_mutex_lock);
830 /**
831 * rt_mutex_lock_interruptible - lock a rt_mutex interruptible
832 *
833 * @lock: the rt_mutex to be locked
834 * @detect_deadlock: deadlock detection on/off
835 *
836 * Returns:
837 * 0 on success
838 * -EINTR when interrupted by a signal
839 * -EDEADLK when the lock would deadlock (when deadlock detection is on)
840 */
841 int __sched rt_mutex_lock_interruptible(struct rt_mutex *lock,
842 int detect_deadlock)
843 {
844 might_sleep();
846 return rt_mutex_fastlock(lock, TASK_INTERRUPTIBLE,
847 detect_deadlock, rt_mutex_slowlock);
848 }
849 EXPORT_SYMBOL_GPL(rt_mutex_lock_interruptible);
851 /**
852 * rt_mutex_lock_interruptible_ktime - lock a rt_mutex interruptible
853 * the timeout structure is provided
854 * by the caller
855 *
856 * @lock: the rt_mutex to be locked
857 * @timeout: timeout structure or NULL (no timeout)
858 * @detect_deadlock: deadlock detection on/off
859 *
860 * Returns:
861 * 0 on success
862 * -EINTR when interrupted by a signal
863 * -ETIMEOUT when the timeout expired
864 * -EDEADLK when the lock would deadlock (when deadlock detection is on)
865 */
866 int
867 rt_mutex_timed_lock(struct rt_mutex *lock, struct hrtimer_sleeper *timeout,
868 int detect_deadlock)
869 {
870 might_sleep();
872 return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout,
873 detect_deadlock, rt_mutex_slowlock);
874 }
875 EXPORT_SYMBOL_GPL(rt_mutex_timed_lock);
877 /**
878 * rt_mutex_trylock - try to lock a rt_mutex
879 *
880 * @lock: the rt_mutex to be locked
881 *
882 * Returns 1 on success and 0 on contention
883 */
884 int __sched rt_mutex_trylock(struct rt_mutex *lock)
885 {
886 return rt_mutex_fasttrylock(lock, rt_mutex_slowtrylock);
887 }
888 EXPORT_SYMBOL_GPL(rt_mutex_trylock);
890 /**
891 * rt_mutex_unlock - unlock a rt_mutex
892 *
893 * @lock: the rt_mutex to be unlocked
894 */
895 void __sched rt_mutex_unlock(struct rt_mutex *lock)
896 {
897 rt_mutex_fastunlock(lock, rt_mutex_slowunlock);
898 }
899 EXPORT_SYMBOL_GPL(rt_mutex_unlock);
901 /***
902 * rt_mutex_destroy - mark a mutex unusable
903 * @lock: the mutex to be destroyed
904 *
905 * This function marks the mutex uninitialized, and any subsequent
906 * use of the mutex is forbidden. The mutex must not be locked when
907 * this function is called.
908 */
909 void rt_mutex_destroy(struct rt_mutex *lock)
910 {
911 WARN_ON(rt_mutex_is_locked(lock));
912 #ifdef CONFIG_DEBUG_RT_MUTEXES
913 lock->magic = NULL;
914 #endif
915 }
917 EXPORT_SYMBOL_GPL(rt_mutex_destroy);
919 /**
920 * __rt_mutex_init - initialize the rt lock
921 *
922 * @lock: the rt lock to be initialized
923 *
924 * Initialize the rt lock to unlocked state.
925 *
926 * Initializing of a locked rt lock is not allowed
927 */
928 void __rt_mutex_init(struct rt_mutex *lock, const char *name)
929 {
930 lock->owner = NULL;
931 spin_lock_init(&lock->wait_lock);
932 plist_head_init(&lock->wait_list, &lock->wait_lock);
934 debug_rt_mutex_init(lock, name);
935 }
936 EXPORT_SYMBOL_GPL(__rt_mutex_init);
938 /**
939 * rt_mutex_init_proxy_locked - initialize and lock a rt_mutex on behalf of a
940 * proxy owner
941 *
942 * @lock: the rt_mutex to be locked
943 * @proxy_owner:the task to set as owner
944 *
945 * No locking. Caller has to do serializing itself
946 * Special API call for PI-futex support
947 */
948 void rt_mutex_init_proxy_locked(struct rt_mutex *lock,
949 struct task_struct *proxy_owner)
950 {
951 __rt_mutex_init(lock, NULL);
952 debug_rt_mutex_proxy_lock(lock, proxy_owner);
953 rt_mutex_set_owner(lock, proxy_owner, 0);
954 rt_mutex_deadlock_account_lock(lock, proxy_owner);
955 }
957 /**
958 * rt_mutex_proxy_unlock - release a lock on behalf of owner
959 *
960 * @lock: the rt_mutex to be locked
961 *
962 * No locking. Caller has to do serializing itself
963 * Special API call for PI-futex support
964 */
965 void rt_mutex_proxy_unlock(struct rt_mutex *lock,
966 struct task_struct *proxy_owner)
967 {
968 debug_rt_mutex_proxy_unlock(lock);
969 rt_mutex_set_owner(lock, NULL, 0);
970 rt_mutex_deadlock_account_unlock(proxy_owner);
971 }
973 /**
974 * rt_mutex_next_owner - return the next owner of the lock
975 *
976 * @lock: the rt lock query
977 *
978 * Returns the next owner of the lock or NULL
979 *
980 * Caller has to serialize against other accessors to the lock
981 * itself.
982 *
983 * Special API call for PI-futex support
984 */
985 struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock)
986 {
987 if (!rt_mutex_has_waiters(lock))
988 return NULL;
990 return rt_mutex_top_waiter(lock)->task;
991 }