bitmap, irq: add smp_affinity_list interface to /proc/irq
[linux-2.6.git] / kernel / rtmutex.c
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>
17
18 #include "rtmutex_common.h"
19
20 /*
21  * lock->owner state tracking:
22  *
23  * lock->owner holds the task_struct pointer of the owner. Bit 0
24  * is used to keep track of the "lock has waiters" state.
25  *
26  * owner        bit0
27  * NULL         0       lock is free (fast acquire possible)
28  * NULL         1       lock is free and has waiters and the top waiter
29  *                              is going to take the lock*
30  * taskpointer  0       lock is held (fast release possible)
31  * taskpointer  1       lock is held and has waiters**
32  *
33  * The fast atomic compare exchange based acquire and release is only
34  * possible when bit 0 of lock->owner is 0.
35  *
36  * (*) It also can be a transitional state when grabbing the lock
37  * with ->wait_lock is held. To prevent any fast path cmpxchg to the lock,
38  * we need to set the bit0 before looking at the lock, and the owner may be
39  * NULL in this small time, hence this can be a transitional state.
40  *
41  * (**) There is a small time when bit 0 is set but there are no
42  * waiters. This can happen when grabbing the lock in the slow path.
43  * To prevent a cmpxchg of the owner releasing the lock, we need to
44  * set this bit before looking at the lock.
45  */
46
47 static void
48 rt_mutex_set_owner(struct rt_mutex *lock, struct task_struct *owner)
49 {
50         unsigned long val = (unsigned long)owner;
51
52         if (rt_mutex_has_waiters(lock))
53                 val |= RT_MUTEX_HAS_WAITERS;
54
55         lock->owner = (struct task_struct *)val;
56 }
57
58 static inline void clear_rt_mutex_waiters(struct rt_mutex *lock)
59 {
60         lock->owner = (struct task_struct *)
61                         ((unsigned long)lock->owner & ~RT_MUTEX_HAS_WAITERS);
62 }
63
64 static void fixup_rt_mutex_waiters(struct rt_mutex *lock)
65 {
66         if (!rt_mutex_has_waiters(lock))
67                 clear_rt_mutex_waiters(lock);
68 }
69
70 /*
71  * We can speed up the acquire/release, if the architecture
72  * supports cmpxchg and if there's no debugging state to be set up
73  */
74 #if defined(__HAVE_ARCH_CMPXCHG) && !defined(CONFIG_DEBUG_RT_MUTEXES)
75 # define rt_mutex_cmpxchg(l,c,n)        (cmpxchg(&l->owner, c, n) == c)
76 static inline void mark_rt_mutex_waiters(struct rt_mutex *lock)
77 {
78         unsigned long owner, *p = (unsigned long *) &lock->owner;
79
80         do {
81                 owner = *p;
82         } while (cmpxchg(p, owner, owner | RT_MUTEX_HAS_WAITERS) != owner);
83 }
84 #else
85 # define rt_mutex_cmpxchg(l,c,n)        (0)
86 static inline void mark_rt_mutex_waiters(struct rt_mutex *lock)
87 {
88         lock->owner = (struct task_struct *)
89                         ((unsigned long)lock->owner | RT_MUTEX_HAS_WAITERS);
90 }
91 #endif
92
93 /*
94  * Calculate task priority from the waiter list priority
95  *
96  * Return task->normal_prio when the waiter list is empty or when
97  * the waiter is not allowed to do priority boosting
98  */
99 int rt_mutex_getprio(struct task_struct *task)
100 {
101         if (likely(!task_has_pi_waiters(task)))
102                 return task->normal_prio;
103
104         return min(task_top_pi_waiter(task)->pi_list_entry.prio,
105                    task->normal_prio);
106 }
107
108 /*
109  * Adjust the priority of a task, after its pi_waiters got modified.
110  *
111  * This can be both boosting and unboosting. task->pi_lock must be held.
112  */
113 static void __rt_mutex_adjust_prio(struct task_struct *task)
114 {
115         int prio = rt_mutex_getprio(task);
116
117         if (task->prio != prio)
118                 rt_mutex_setprio(task, prio);
119 }
120
121 /*
122  * Adjust task priority (undo boosting). Called from the exit path of
123  * rt_mutex_slowunlock() and rt_mutex_slowlock().
124  *
125  * (Note: We do this outside of the protection of lock->wait_lock to
126  * allow the lock to be taken while or before we readjust the priority
127  * of task. We do not use the spin_xx_mutex() variants here as we are
128  * outside of the debug path.)
129  */
130 static void rt_mutex_adjust_prio(struct task_struct *task)
131 {
132         unsigned long flags;
133
134         raw_spin_lock_irqsave(&task->pi_lock, flags);
135         __rt_mutex_adjust_prio(task);
136         raw_spin_unlock_irqrestore(&task->pi_lock, flags);
137 }
138
139 /*
140  * Max number of times we'll walk the boosting chain:
141  */
142 int max_lock_depth = 1024;
143
144 /*
145  * Adjust the priority chain. Also used for deadlock detection.
146  * Decreases task's usage by one - may thus free the task.
147  * Returns 0 or -EDEADLK.
148  */
149 static int rt_mutex_adjust_prio_chain(struct task_struct *task,
150                                       int deadlock_detect,
151                                       struct rt_mutex *orig_lock,
152                                       struct rt_mutex_waiter *orig_waiter,
153                                       struct task_struct *top_task)
154 {
155         struct rt_mutex *lock;
156         struct rt_mutex_waiter *waiter, *top_waiter = orig_waiter;
157         int detect_deadlock, ret = 0, depth = 0;
158         unsigned long flags;
159
160         detect_deadlock = debug_rt_mutex_detect_deadlock(orig_waiter,
161                                                          deadlock_detect);
162
163         /*
164          * The (de)boosting is a step by step approach with a lot of
165          * pitfalls. We want this to be preemptible and we want hold a
166          * maximum of two locks per step. So we have to check
167          * carefully whether things change under us.
168          */
169  again:
170         if (++depth > max_lock_depth) {
171                 static int prev_max;
172
173                 /*
174                  * Print this only once. If the admin changes the limit,
175                  * print a new message when reaching the limit again.
176                  */
177                 if (prev_max != max_lock_depth) {
178                         prev_max = max_lock_depth;
179                         printk(KERN_WARNING "Maximum lock depth %d reached "
180                                "task: %s (%d)\n", max_lock_depth,
181                                top_task->comm, task_pid_nr(top_task));
182                 }
183                 put_task_struct(task);
184
185                 return deadlock_detect ? -EDEADLK : 0;
186         }
187  retry:
188         /*
189          * Task can not go away as we did a get_task() before !
190          */
191         raw_spin_lock_irqsave(&task->pi_lock, flags);
192
193         waiter = task->pi_blocked_on;
194         /*
195          * Check whether the end of the boosting chain has been
196          * reached or the state of the chain has changed while we
197          * dropped the locks.
198          */
199         if (!waiter)
200                 goto out_unlock_pi;
201
202         /*
203          * Check the orig_waiter state. After we dropped the locks,
204          * the previous owner of the lock might have released the lock.
205          */
206         if (orig_waiter && !rt_mutex_owner(orig_lock))
207                 goto out_unlock_pi;
208
209         /*
210          * Drop out, when the task has no waiters. Note,
211          * top_waiter can be NULL, when we are in the deboosting
212          * mode!
213          */
214         if (top_waiter && (!task_has_pi_waiters(task) ||
215                            top_waiter != task_top_pi_waiter(task)))
216                 goto out_unlock_pi;
217
218         /*
219          * When deadlock detection is off then we check, if further
220          * priority adjustment is necessary.
221          */
222         if (!detect_deadlock && waiter->list_entry.prio == task->prio)
223                 goto out_unlock_pi;
224
225         lock = waiter->lock;
226         if (!raw_spin_trylock(&lock->wait_lock)) {
227                 raw_spin_unlock_irqrestore(&task->pi_lock, flags);
228                 cpu_relax();
229                 goto retry;
230         }
231
232         /* Deadlock detection */
233         if (lock == orig_lock || rt_mutex_owner(lock) == top_task) {
234                 debug_rt_mutex_deadlock(deadlock_detect, orig_waiter, lock);
235                 raw_spin_unlock(&lock->wait_lock);
236                 ret = deadlock_detect ? -EDEADLK : 0;
237                 goto out_unlock_pi;
238         }
239
240         top_waiter = rt_mutex_top_waiter(lock);
241
242         /* Requeue the waiter */
243         plist_del(&waiter->list_entry, &lock->wait_list);
244         waiter->list_entry.prio = task->prio;
245         plist_add(&waiter->list_entry, &lock->wait_list);
246
247         /* Release the task */
248         raw_spin_unlock_irqrestore(&task->pi_lock, flags);
249         if (!rt_mutex_owner(lock)) {
250                 /*
251                  * If the requeue above changed the top waiter, then we need
252                  * to wake the new top waiter up to try to get the lock.
253                  */
254
255                 if (top_waiter != rt_mutex_top_waiter(lock))
256                         wake_up_process(rt_mutex_top_waiter(lock)->task);
257                 raw_spin_unlock(&lock->wait_lock);
258                 goto out_put_task;
259         }
260         put_task_struct(task);
261
262         /* Grab the next task */
263         task = rt_mutex_owner(lock);
264         get_task_struct(task);
265         raw_spin_lock_irqsave(&task->pi_lock, flags);
266
267         if (waiter == rt_mutex_top_waiter(lock)) {
268                 /* Boost the owner */
269                 plist_del(&top_waiter->pi_list_entry, &task->pi_waiters);
270                 waiter->pi_list_entry.prio = waiter->list_entry.prio;
271                 plist_add(&waiter->pi_list_entry, &task->pi_waiters);
272                 __rt_mutex_adjust_prio(task);
273
274         } else if (top_waiter == waiter) {
275                 /* Deboost the owner */
276                 plist_del(&waiter->pi_list_entry, &task->pi_waiters);
277                 waiter = rt_mutex_top_waiter(lock);
278                 waiter->pi_list_entry.prio = waiter->list_entry.prio;
279                 plist_add(&waiter->pi_list_entry, &task->pi_waiters);
280                 __rt_mutex_adjust_prio(task);
281         }
282
283         raw_spin_unlock_irqrestore(&task->pi_lock, flags);
284
285         top_waiter = rt_mutex_top_waiter(lock);
286         raw_spin_unlock(&lock->wait_lock);
287
288         if (!detect_deadlock && waiter != top_waiter)
289                 goto out_put_task;
290
291         goto again;
292
293  out_unlock_pi:
294         raw_spin_unlock_irqrestore(&task->pi_lock, flags);
295  out_put_task:
296         put_task_struct(task);
297
298         return ret;
299 }
300
301 /*
302  * Try to take an rt-mutex
303  *
304  * Must be called with lock->wait_lock held.
305  *
306  * @lock:   the lock to be acquired.
307  * @task:   the task which wants to acquire the lock
308  * @waiter: the waiter that is queued to the lock's wait list. (could be NULL)
309  */
310 static int try_to_take_rt_mutex(struct rt_mutex *lock, struct task_struct *task,
311                 struct rt_mutex_waiter *waiter)
312 {
313         /*
314          * We have to be careful here if the atomic speedups are
315          * enabled, such that, when
316          *  - no other waiter is on the lock
317          *  - the lock has been released since we did the cmpxchg
318          * the lock can be released or taken while we are doing the
319          * checks and marking the lock with RT_MUTEX_HAS_WAITERS.
320          *
321          * The atomic acquire/release aware variant of
322          * mark_rt_mutex_waiters uses a cmpxchg loop. After setting
323          * the WAITERS bit, the atomic release / acquire can not
324          * happen anymore and lock->wait_lock protects us from the
325          * non-atomic case.
326          *
327          * Note, that this might set lock->owner =
328          * RT_MUTEX_HAS_WAITERS in the case the lock is not contended
329          * any more. This is fixed up when we take the ownership.
330          * This is the transitional state explained at the top of this file.
331          */
332         mark_rt_mutex_waiters(lock);
333
334         if (rt_mutex_owner(lock))
335                 return 0;
336
337         /*
338          * It will get the lock because of one of these conditions:
339          * 1) there is no waiter
340          * 2) higher priority than waiters
341          * 3) it is top waiter
342          */
343         if (rt_mutex_has_waiters(lock)) {
344                 if (task->prio >= rt_mutex_top_waiter(lock)->list_entry.prio) {
345                         if (!waiter || waiter != rt_mutex_top_waiter(lock))
346                                 return 0;
347                 }
348         }
349
350         if (waiter || rt_mutex_has_waiters(lock)) {
351                 unsigned long flags;
352                 struct rt_mutex_waiter *top;
353
354                 raw_spin_lock_irqsave(&task->pi_lock, flags);
355
356                 /* remove the queued waiter. */
357                 if (waiter) {
358                         plist_del(&waiter->list_entry, &lock->wait_list);
359                         task->pi_blocked_on = NULL;
360                 }
361
362                 /*
363                  * We have to enqueue the top waiter(if it exists) into
364                  * task->pi_waiters list.
365                  */
366                 if (rt_mutex_has_waiters(lock)) {
367                         top = rt_mutex_top_waiter(lock);
368                         top->pi_list_entry.prio = top->list_entry.prio;
369                         plist_add(&top->pi_list_entry, &task->pi_waiters);
370                 }
371                 raw_spin_unlock_irqrestore(&task->pi_lock, flags);
372         }
373
374         /* We got the lock. */
375         debug_rt_mutex_lock(lock);
376
377         rt_mutex_set_owner(lock, task);
378
379         rt_mutex_deadlock_account_lock(lock, task);
380
381         return 1;
382 }
383
384 /*
385  * Task blocks on lock.
386  *
387  * Prepare waiter and propagate pi chain
388  *
389  * This must be called with lock->wait_lock held.
390  */
391 static int task_blocks_on_rt_mutex(struct rt_mutex *lock,
392                                    struct rt_mutex_waiter *waiter,
393                                    struct task_struct *task,
394                                    int detect_deadlock)
395 {
396         struct task_struct *owner = rt_mutex_owner(lock);
397         struct rt_mutex_waiter *top_waiter = waiter;
398         unsigned long flags;
399         int chain_walk = 0, res;
400
401         raw_spin_lock_irqsave(&task->pi_lock, flags);
402         __rt_mutex_adjust_prio(task);
403         waiter->task = task;
404         waiter->lock = lock;
405         plist_node_init(&waiter->list_entry, task->prio);
406         plist_node_init(&waiter->pi_list_entry, task->prio);
407
408         /* Get the top priority waiter on the lock */
409         if (rt_mutex_has_waiters(lock))
410                 top_waiter = rt_mutex_top_waiter(lock);
411         plist_add(&waiter->list_entry, &lock->wait_list);
412
413         task->pi_blocked_on = waiter;
414
415         raw_spin_unlock_irqrestore(&task->pi_lock, flags);
416
417         if (!owner)
418                 return 0;
419
420         if (waiter == rt_mutex_top_waiter(lock)) {
421                 raw_spin_lock_irqsave(&owner->pi_lock, flags);
422                 plist_del(&top_waiter->pi_list_entry, &owner->pi_waiters);
423                 plist_add(&waiter->pi_list_entry, &owner->pi_waiters);
424
425                 __rt_mutex_adjust_prio(owner);
426                 if (owner->pi_blocked_on)
427                         chain_walk = 1;
428                 raw_spin_unlock_irqrestore(&owner->pi_lock, flags);
429         }
430         else if (debug_rt_mutex_detect_deadlock(waiter, detect_deadlock))
431                 chain_walk = 1;
432
433         if (!chain_walk)
434                 return 0;
435
436         /*
437          * The owner can't disappear while holding a lock,
438          * so the owner struct is protected by wait_lock.
439          * Gets dropped in rt_mutex_adjust_prio_chain()!
440          */
441         get_task_struct(owner);
442
443         raw_spin_unlock(&lock->wait_lock);
444
445         res = rt_mutex_adjust_prio_chain(owner, detect_deadlock, lock, waiter,
446                                          task);
447
448         raw_spin_lock(&lock->wait_lock);
449
450         return res;
451 }
452
453 /*
454  * Wake up the next waiter on the lock.
455  *
456  * Remove the top waiter from the current tasks waiter list and wake it up.
457  *
458  * Called with lock->wait_lock held.
459  */
460 static void wakeup_next_waiter(struct rt_mutex *lock)
461 {
462         struct rt_mutex_waiter *waiter;
463         unsigned long flags;
464
465         raw_spin_lock_irqsave(&current->pi_lock, flags);
466
467         waiter = rt_mutex_top_waiter(lock);
468
469         /*
470          * Remove it from current->pi_waiters. We do not adjust a
471          * possible priority boost right now. We execute wakeup in the
472          * boosted mode and go back to normal after releasing
473          * lock->wait_lock.
474          */
475         plist_del(&waiter->pi_list_entry, &current->pi_waiters);
476
477         rt_mutex_set_owner(lock, NULL);
478
479         raw_spin_unlock_irqrestore(&current->pi_lock, flags);
480
481         wake_up_process(waiter->task);
482 }
483
484 /*
485  * Remove a waiter from a lock and give up
486  *
487  * Must be called with lock->wait_lock held and
488  * have just failed to try_to_take_rt_mutex().
489  */
490 static void remove_waiter(struct rt_mutex *lock,
491                           struct rt_mutex_waiter *waiter)
492 {
493         int first = (waiter == rt_mutex_top_waiter(lock));
494         struct task_struct *owner = rt_mutex_owner(lock);
495         unsigned long flags;
496         int chain_walk = 0;
497
498         raw_spin_lock_irqsave(&current->pi_lock, flags);
499         plist_del(&waiter->list_entry, &lock->wait_list);
500         current->pi_blocked_on = NULL;
501         raw_spin_unlock_irqrestore(&current->pi_lock, flags);
502
503         if (!owner)
504                 return;
505
506         if (first) {
507
508                 raw_spin_lock_irqsave(&owner->pi_lock, flags);
509
510                 plist_del(&waiter->pi_list_entry, &owner->pi_waiters);
511
512                 if (rt_mutex_has_waiters(lock)) {
513                         struct rt_mutex_waiter *next;
514
515                         next = rt_mutex_top_waiter(lock);
516                         plist_add(&next->pi_list_entry, &owner->pi_waiters);
517                 }
518                 __rt_mutex_adjust_prio(owner);
519
520                 if (owner->pi_blocked_on)
521                         chain_walk = 1;
522
523                 raw_spin_unlock_irqrestore(&owner->pi_lock, flags);
524         }
525
526         WARN_ON(!plist_node_empty(&waiter->pi_list_entry));
527
528         if (!chain_walk)
529                 return;
530
531         /* gets dropped in rt_mutex_adjust_prio_chain()! */
532         get_task_struct(owner);
533
534         raw_spin_unlock(&lock->wait_lock);
535
536         rt_mutex_adjust_prio_chain(owner, 0, lock, NULL, current);
537
538         raw_spin_lock(&lock->wait_lock);
539 }
540
541 /*
542  * Recheck the pi chain, in case we got a priority setting
543  *
544  * Called from sched_setscheduler
545  */
546 void rt_mutex_adjust_pi(struct task_struct *task)
547 {
548         struct rt_mutex_waiter *waiter;
549         unsigned long flags;
550
551         raw_spin_lock_irqsave(&task->pi_lock, flags);
552
553         waiter = task->pi_blocked_on;
554         if (!waiter || waiter->list_entry.prio == task->prio) {
555                 raw_spin_unlock_irqrestore(&task->pi_lock, flags);
556                 return;
557         }
558
559         raw_spin_unlock_irqrestore(&task->pi_lock, flags);
560
561         /* gets dropped in rt_mutex_adjust_prio_chain()! */
562         get_task_struct(task);
563         rt_mutex_adjust_prio_chain(task, 0, NULL, NULL, task);
564 }
565
566 /**
567  * __rt_mutex_slowlock() - Perform the wait-wake-try-to-take loop
568  * @lock:                the rt_mutex to take
569  * @state:               the state the task should block in (TASK_INTERRUPTIBLE
570  *                       or TASK_UNINTERRUPTIBLE)
571  * @timeout:             the pre-initialized and started timer, or NULL for none
572  * @waiter:              the pre-initialized rt_mutex_waiter
573  *
574  * lock->wait_lock must be held by the caller.
575  */
576 static int __sched
577 __rt_mutex_slowlock(struct rt_mutex *lock, int state,
578                     struct hrtimer_sleeper *timeout,
579                     struct rt_mutex_waiter *waiter)
580 {
581         int ret = 0;
582
583         for (;;) {
584                 /* Try to acquire the lock: */
585                 if (try_to_take_rt_mutex(lock, current, waiter))
586                         break;
587
588                 /*
589                  * TASK_INTERRUPTIBLE checks for signals and
590                  * timeout. Ignored otherwise.
591                  */
592                 if (unlikely(state == TASK_INTERRUPTIBLE)) {
593                         /* Signal pending? */
594                         if (signal_pending(current))
595                                 ret = -EINTR;
596                         if (timeout && !timeout->task)
597                                 ret = -ETIMEDOUT;
598                         if (ret)
599                                 break;
600                 }
601
602                 raw_spin_unlock(&lock->wait_lock);
603
604                 debug_rt_mutex_print_deadlock(waiter);
605
606                 schedule_rt_mutex(lock);
607
608                 raw_spin_lock(&lock->wait_lock);
609                 set_current_state(state);
610         }
611
612         return ret;
613 }
614
615 /*
616  * Slow path lock function:
617  */
618 static int __sched
619 rt_mutex_slowlock(struct rt_mutex *lock, int state,
620                   struct hrtimer_sleeper *timeout,
621                   int detect_deadlock)
622 {
623         struct rt_mutex_waiter waiter;
624         int ret = 0;
625
626         debug_rt_mutex_init_waiter(&waiter);
627
628         raw_spin_lock(&lock->wait_lock);
629
630         /* Try to acquire the lock again: */
631         if (try_to_take_rt_mutex(lock, current, NULL)) {
632                 raw_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_expires(&timeout->timer, HRTIMER_MODE_ABS);
641                 if (!hrtimer_active(&timeout->timer))
642                         timeout->task = NULL;
643         }
644
645         ret = task_blocks_on_rt_mutex(lock, &waiter, current, detect_deadlock);
646
647         if (likely(!ret))
648                 ret = __rt_mutex_slowlock(lock, state, timeout, &waiter);
649
650         set_current_state(TASK_RUNNING);
651
652         if (unlikely(ret))
653                 remove_waiter(lock, &waiter);
654
655         /*
656          * try_to_take_rt_mutex() sets the waiter bit
657          * unconditionally. We might have to fix that up.
658          */
659         fixup_rt_mutex_waiters(lock);
660
661         raw_spin_unlock(&lock->wait_lock);
662
663         /* Remove pending timer: */
664         if (unlikely(timeout))
665                 hrtimer_cancel(&timeout->timer);
666
667         debug_rt_mutex_free_waiter(&waiter);
668
669         return ret;
670 }
671
672 /*
673  * Slow path try-lock function:
674  */
675 static inline int
676 rt_mutex_slowtrylock(struct rt_mutex *lock)
677 {
678         int ret = 0;
679
680         raw_spin_lock(&lock->wait_lock);
681
682         if (likely(rt_mutex_owner(lock) != current)) {
683
684                 ret = try_to_take_rt_mutex(lock, current, NULL);
685                 /*
686                  * try_to_take_rt_mutex() sets the lock waiters
687                  * bit unconditionally. Clean this up.
688                  */
689                 fixup_rt_mutex_waiters(lock);
690         }
691
692         raw_spin_unlock(&lock->wait_lock);
693
694         return ret;
695 }
696
697 /*
698  * Slow path to release a rt-mutex:
699  */
700 static void __sched
701 rt_mutex_slowunlock(struct rt_mutex *lock)
702 {
703         raw_spin_lock(&lock->wait_lock);
704
705         debug_rt_mutex_unlock(lock);
706
707         rt_mutex_deadlock_account_unlock(current);
708
709         if (!rt_mutex_has_waiters(lock)) {
710                 lock->owner = NULL;
711                 raw_spin_unlock(&lock->wait_lock);
712                 return;
713         }
714
715         wakeup_next_waiter(lock);
716
717         raw_spin_unlock(&lock->wait_lock);
718
719         /* Undo pi boosting if necessary: */
720         rt_mutex_adjust_prio(current);
721 }
722
723 /*
724  * debug aware fast / slowpath lock,trylock,unlock
725  *
726  * The atomic acquire/release ops are compiled away, when either the
727  * architecture does not support cmpxchg or when debugging is enabled.
728  */
729 static inline int
730 rt_mutex_fastlock(struct rt_mutex *lock, int state,
731                   int detect_deadlock,
732                   int (*slowfn)(struct rt_mutex *lock, int state,
733                                 struct hrtimer_sleeper *timeout,
734                                 int detect_deadlock))
735 {
736         if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) {
737                 rt_mutex_deadlock_account_lock(lock, current);
738                 return 0;
739         } else
740                 return slowfn(lock, state, NULL, detect_deadlock);
741 }
742
743 static inline int
744 rt_mutex_timed_fastlock(struct rt_mutex *lock, int state,
745                         struct hrtimer_sleeper *timeout, int detect_deadlock,
746                         int (*slowfn)(struct rt_mutex *lock, int state,
747                                       struct hrtimer_sleeper *timeout,
748                                       int detect_deadlock))
749 {
750         if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) {
751                 rt_mutex_deadlock_account_lock(lock, current);
752                 return 0;
753         } else
754                 return slowfn(lock, state, timeout, detect_deadlock);
755 }
756
757 static inline int
758 rt_mutex_fasttrylock(struct rt_mutex *lock,
759                      int (*slowfn)(struct rt_mutex *lock))
760 {
761         if (likely(rt_mutex_cmpxchg(lock, NULL, current))) {
762                 rt_mutex_deadlock_account_lock(lock, current);
763                 return 1;
764         }
765         return slowfn(lock);
766 }
767
768 static inline void
769 rt_mutex_fastunlock(struct rt_mutex *lock,
770                     void (*slowfn)(struct rt_mutex *lock))
771 {
772         if (likely(rt_mutex_cmpxchg(lock, current, NULL)))
773                 rt_mutex_deadlock_account_unlock(current);
774         else
775                 slowfn(lock);
776 }
777
778 /**
779  * rt_mutex_lock - lock a rt_mutex
780  *
781  * @lock: the rt_mutex to be locked
782  */
783 void __sched rt_mutex_lock(struct rt_mutex *lock)
784 {
785         might_sleep();
786
787         rt_mutex_fastlock(lock, TASK_UNINTERRUPTIBLE, 0, rt_mutex_slowlock);
788 }
789 EXPORT_SYMBOL_GPL(rt_mutex_lock);
790
791 /**
792  * rt_mutex_lock_interruptible - lock a rt_mutex interruptible
793  *
794  * @lock:               the rt_mutex to be locked
795  * @detect_deadlock:    deadlock detection on/off
796  *
797  * Returns:
798  *  0           on success
799  * -EINTR       when interrupted by a signal
800  * -EDEADLK     when the lock would deadlock (when deadlock detection is on)
801  */
802 int __sched rt_mutex_lock_interruptible(struct rt_mutex *lock,
803                                                  int detect_deadlock)
804 {
805         might_sleep();
806
807         return rt_mutex_fastlock(lock, TASK_INTERRUPTIBLE,
808                                  detect_deadlock, rt_mutex_slowlock);
809 }
810 EXPORT_SYMBOL_GPL(rt_mutex_lock_interruptible);
811
812 /**
813  * rt_mutex_timed_lock - lock a rt_mutex interruptible
814  *                      the timeout structure is provided
815  *                      by the caller
816  *
817  * @lock:               the rt_mutex to be locked
818  * @timeout:            timeout structure or NULL (no timeout)
819  * @detect_deadlock:    deadlock detection on/off
820  *
821  * Returns:
822  *  0           on success
823  * -EINTR       when interrupted by a signal
824  * -ETIMEDOUT   when the timeout expired
825  * -EDEADLK     when the lock would deadlock (when deadlock detection is on)
826  */
827 int
828 rt_mutex_timed_lock(struct rt_mutex *lock, struct hrtimer_sleeper *timeout,
829                     int detect_deadlock)
830 {
831         might_sleep();
832
833         return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout,
834                                        detect_deadlock, rt_mutex_slowlock);
835 }
836 EXPORT_SYMBOL_GPL(rt_mutex_timed_lock);
837
838 /**
839  * rt_mutex_trylock - try to lock a rt_mutex
840  *
841  * @lock:       the rt_mutex to be locked
842  *
843  * Returns 1 on success and 0 on contention
844  */
845 int __sched rt_mutex_trylock(struct rt_mutex *lock)
846 {
847         return rt_mutex_fasttrylock(lock, rt_mutex_slowtrylock);
848 }
849 EXPORT_SYMBOL_GPL(rt_mutex_trylock);
850
851 /**
852  * rt_mutex_unlock - unlock a rt_mutex
853  *
854  * @lock: the rt_mutex to be unlocked
855  */
856 void __sched rt_mutex_unlock(struct rt_mutex *lock)
857 {
858         rt_mutex_fastunlock(lock, rt_mutex_slowunlock);
859 }
860 EXPORT_SYMBOL_GPL(rt_mutex_unlock);
861
862 /**
863  * rt_mutex_destroy - mark a mutex unusable
864  * @lock: the mutex to be destroyed
865  *
866  * This function marks the mutex uninitialized, and any subsequent
867  * use of the mutex is forbidden. The mutex must not be locked when
868  * this function is called.
869  */
870 void rt_mutex_destroy(struct rt_mutex *lock)
871 {
872         WARN_ON(rt_mutex_is_locked(lock));
873 #ifdef CONFIG_DEBUG_RT_MUTEXES
874         lock->magic = NULL;
875 #endif
876 }
877
878 EXPORT_SYMBOL_GPL(rt_mutex_destroy);
879
880 /**
881  * __rt_mutex_init - initialize the rt lock
882  *
883  * @lock: the rt lock to be initialized
884  *
885  * Initialize the rt lock to unlocked state.
886  *
887  * Initializing of a locked rt lock is not allowed
888  */
889 void __rt_mutex_init(struct rt_mutex *lock, const char *name)
890 {
891         lock->owner = NULL;
892         raw_spin_lock_init(&lock->wait_lock);
893         plist_head_init_raw(&lock->wait_list, &lock->wait_lock);
894
895         debug_rt_mutex_init(lock, name);
896 }
897 EXPORT_SYMBOL_GPL(__rt_mutex_init);
898
899 /**
900  * rt_mutex_init_proxy_locked - initialize and lock a rt_mutex on behalf of a
901  *                              proxy owner
902  *
903  * @lock:       the rt_mutex to be locked
904  * @proxy_owner:the task to set as owner
905  *
906  * No locking. Caller has to do serializing itself
907  * Special API call for PI-futex support
908  */
909 void rt_mutex_init_proxy_locked(struct rt_mutex *lock,
910                                 struct task_struct *proxy_owner)
911 {
912         __rt_mutex_init(lock, NULL);
913         debug_rt_mutex_proxy_lock(lock, proxy_owner);
914         rt_mutex_set_owner(lock, proxy_owner);
915         rt_mutex_deadlock_account_lock(lock, proxy_owner);
916 }
917
918 /**
919  * rt_mutex_proxy_unlock - release a lock on behalf of owner
920  *
921  * @lock:       the rt_mutex to be locked
922  *
923  * No locking. Caller has to do serializing itself
924  * Special API call for PI-futex support
925  */
926 void rt_mutex_proxy_unlock(struct rt_mutex *lock,
927                            struct task_struct *proxy_owner)
928 {
929         debug_rt_mutex_proxy_unlock(lock);
930         rt_mutex_set_owner(lock, NULL);
931         rt_mutex_deadlock_account_unlock(proxy_owner);
932 }
933
934 /**
935  * rt_mutex_start_proxy_lock() - Start lock acquisition for another task
936  * @lock:               the rt_mutex to take
937  * @waiter:             the pre-initialized rt_mutex_waiter
938  * @task:               the task to prepare
939  * @detect_deadlock:    perform deadlock detection (1) or not (0)
940  *
941  * Returns:
942  *  0 - task blocked on lock
943  *  1 - acquired the lock for task, caller should wake it up
944  * <0 - error
945  *
946  * Special API call for FUTEX_REQUEUE_PI support.
947  */
948 int rt_mutex_start_proxy_lock(struct rt_mutex *lock,
949                               struct rt_mutex_waiter *waiter,
950                               struct task_struct *task, int detect_deadlock)
951 {
952         int ret;
953
954         raw_spin_lock(&lock->wait_lock);
955
956         if (try_to_take_rt_mutex(lock, task, NULL)) {
957                 raw_spin_unlock(&lock->wait_lock);
958                 return 1;
959         }
960
961         ret = task_blocks_on_rt_mutex(lock, waiter, task, detect_deadlock);
962
963         if (ret && !rt_mutex_owner(lock)) {
964                 /*
965                  * Reset the return value. We might have
966                  * returned with -EDEADLK and the owner
967                  * released the lock while we were walking the
968                  * pi chain.  Let the waiter sort it out.
969                  */
970                 ret = 0;
971         }
972
973         if (unlikely(ret))
974                 remove_waiter(lock, waiter);
975
976         raw_spin_unlock(&lock->wait_lock);
977
978         debug_rt_mutex_print_deadlock(waiter);
979
980         return ret;
981 }
982
983 /**
984  * rt_mutex_next_owner - return the next owner of the lock
985  *
986  * @lock: the rt lock query
987  *
988  * Returns the next owner of the lock or NULL
989  *
990  * Caller has to serialize against other accessors to the lock
991  * itself.
992  *
993  * Special API call for PI-futex support
994  */
995 struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock)
996 {
997         if (!rt_mutex_has_waiters(lock))
998                 return NULL;
999
1000         return rt_mutex_top_waiter(lock)->task;
1001 }
1002
1003 /**
1004  * rt_mutex_finish_proxy_lock() - Complete lock acquisition
1005  * @lock:               the rt_mutex we were woken on
1006  * @to:                 the timeout, null if none. hrtimer should already have
1007  *                      been started.
1008  * @waiter:             the pre-initialized rt_mutex_waiter
1009  * @detect_deadlock:    perform deadlock detection (1) or not (0)
1010  *
1011  * Complete the lock acquisition started our behalf by another thread.
1012  *
1013  * Returns:
1014  *  0 - success
1015  * <0 - error, one of -EINTR, -ETIMEDOUT, or -EDEADLK
1016  *
1017  * Special API call for PI-futex requeue support
1018  */
1019 int rt_mutex_finish_proxy_lock(struct rt_mutex *lock,
1020                                struct hrtimer_sleeper *to,
1021                                struct rt_mutex_waiter *waiter,
1022                                int detect_deadlock)
1023 {
1024         int ret;
1025
1026         raw_spin_lock(&lock->wait_lock);
1027
1028         set_current_state(TASK_INTERRUPTIBLE);
1029
1030         ret = __rt_mutex_slowlock(lock, TASK_INTERRUPTIBLE, to, waiter);
1031
1032         set_current_state(TASK_RUNNING);
1033
1034         if (unlikely(ret))
1035                 remove_waiter(lock, waiter);
1036
1037         /*
1038          * try_to_take_rt_mutex() sets the waiter bit unconditionally. We might
1039          * have to fix that up.
1040          */
1041         fixup_rt_mutex_waiters(lock);
1042
1043         raw_spin_unlock(&lock->wait_lock);
1044
1045         return ret;
1046 }