Merge branch 'for-3.11' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq
[platform/adaptation/renesas_rcar/renesas_kernel.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/export.h>
15 #include <linux/sched.h>
16 #include <linux/sched/rt.h>
17 #include <linux/timer.h>
18
19 #include "rtmutex_common.h"
20
21 /*
22  * lock->owner state tracking:
23  *
24  * lock->owner holds the task_struct pointer of the owner. Bit 0
25  * is used to keep track of the "lock has waiters" state.
26  *
27  * owner        bit0
28  * NULL         0       lock is free (fast acquire possible)
29  * NULL         1       lock is free and has waiters and the top waiter
30  *                              is going to take the lock*
31  * taskpointer  0       lock is held (fast release possible)
32  * taskpointer  1       lock is held and has waiters**
33  *
34  * The fast atomic compare exchange based acquire and release is only
35  * possible when bit 0 of lock->owner is 0.
36  *
37  * (*) It also can be a transitional state when grabbing the lock
38  * with ->wait_lock is held. To prevent any fast path cmpxchg to the lock,
39  * we need to set the bit0 before looking at the lock, and the owner may be
40  * NULL in this small time, hence this can be a transitional state.
41  *
42  * (**) There is a small time when bit 0 is set but there are no
43  * waiters. This can happen when grabbing the lock in the slow path.
44  * To prevent a cmpxchg of the owner releasing the lock, we need to
45  * set this bit before looking at the lock.
46  */
47
48 static void
49 rt_mutex_set_owner(struct rt_mutex *lock, struct task_struct *owner)
50 {
51         unsigned long val = (unsigned long)owner;
52
53         if (rt_mutex_has_waiters(lock))
54                 val |= RT_MUTEX_HAS_WAITERS;
55
56         lock->owner = (struct task_struct *)val;
57 }
58
59 static inline void clear_rt_mutex_waiters(struct rt_mutex *lock)
60 {
61         lock->owner = (struct task_struct *)
62                         ((unsigned long)lock->owner & ~RT_MUTEX_HAS_WAITERS);
63 }
64
65 static void fixup_rt_mutex_waiters(struct rt_mutex *lock)
66 {
67         if (!rt_mutex_has_waiters(lock))
68                 clear_rt_mutex_waiters(lock);
69 }
70
71 /*
72  * We can speed up the acquire/release, if the architecture
73  * supports cmpxchg and if there's no debugging state to be set up
74  */
75 #if defined(__HAVE_ARCH_CMPXCHG) && !defined(CONFIG_DEBUG_RT_MUTEXES)
76 # define rt_mutex_cmpxchg(l,c,n)        (cmpxchg(&l->owner, c, n) == c)
77 static inline void mark_rt_mutex_waiters(struct rt_mutex *lock)
78 {
79         unsigned long owner, *p = (unsigned long *) &lock->owner;
80
81         do {
82                 owner = *p;
83         } while (cmpxchg(p, owner, owner | RT_MUTEX_HAS_WAITERS) != owner);
84 }
85 #else
86 # define rt_mutex_cmpxchg(l,c,n)        (0)
87 static inline void mark_rt_mutex_waiters(struct rt_mutex *lock)
88 {
89         lock->owner = (struct task_struct *)
90                         ((unsigned long)lock->owner | RT_MUTEX_HAS_WAITERS);
91 }
92 #endif
93
94 /*
95  * Calculate task priority from the waiter list priority
96  *
97  * Return task->normal_prio when the waiter list is empty or when
98  * the waiter is not allowed to do priority boosting
99  */
100 int rt_mutex_getprio(struct task_struct *task)
101 {
102         if (likely(!task_has_pi_waiters(task)))
103                 return task->normal_prio;
104
105         return min(task_top_pi_waiter(task)->pi_list_entry.prio,
106                    task->normal_prio);
107 }
108
109 /*
110  * Adjust the priority of a task, after its pi_waiters got modified.
111  *
112  * This can be both boosting and unboosting. task->pi_lock must be held.
113  */
114 static void __rt_mutex_adjust_prio(struct task_struct *task)
115 {
116         int prio = rt_mutex_getprio(task);
117
118         if (task->prio != prio)
119                 rt_mutex_setprio(task, prio);
120 }
121
122 /*
123  * Adjust task priority (undo boosting). Called from the exit path of
124  * rt_mutex_slowunlock() and rt_mutex_slowlock().
125  *
126  * (Note: We do this outside of the protection of lock->wait_lock to
127  * allow the lock to be taken while or before we readjust the priority
128  * of task. We do not use the spin_xx_mutex() variants here as we are
129  * outside of the debug path.)
130  */
131 static void rt_mutex_adjust_prio(struct task_struct *task)
132 {
133         unsigned long flags;
134
135         raw_spin_lock_irqsave(&task->pi_lock, flags);
136         __rt_mutex_adjust_prio(task);
137         raw_spin_unlock_irqrestore(&task->pi_lock, flags);
138 }
139
140 /*
141  * Max number of times we'll walk the boosting chain:
142  */
143 int max_lock_depth = 1024;
144
145 /*
146  * Adjust the priority chain. Also used for deadlock detection.
147  * Decreases task's usage by one - may thus free the task.
148  *
149  * @task: the task owning the mutex (owner) for which a chain walk is probably
150  *        needed
151  * @deadlock_detect: do we have to carry out deadlock detection?
152  * @orig_lock: the mutex (can be NULL if we are walking the chain to recheck
153  *             things for a task that has just got its priority adjusted, and
154  *             is waiting on a mutex)
155  * @orig_waiter: rt_mutex_waiter struct for the task that has just donated
156  *               its priority to the mutex owner (can be NULL in the case
157  *               depicted above or if the top waiter is gone away and we are
158  *               actually deboosting the owner)
159  * @top_task: the current top waiter
160  *
161  * Returns 0 or -EDEADLK.
162  */
163 static int rt_mutex_adjust_prio_chain(struct task_struct *task,
164                                       int deadlock_detect,
165                                       struct rt_mutex *orig_lock,
166                                       struct rt_mutex_waiter *orig_waiter,
167                                       struct task_struct *top_task)
168 {
169         struct rt_mutex *lock;
170         struct rt_mutex_waiter *waiter, *top_waiter = orig_waiter;
171         int detect_deadlock, ret = 0, depth = 0;
172         unsigned long flags;
173
174         detect_deadlock = debug_rt_mutex_detect_deadlock(orig_waiter,
175                                                          deadlock_detect);
176
177         /*
178          * The (de)boosting is a step by step approach with a lot of
179          * pitfalls. We want this to be preemptible and we want hold a
180          * maximum of two locks per step. So we have to check
181          * carefully whether things change under us.
182          */
183  again:
184         if (++depth > max_lock_depth) {
185                 static int prev_max;
186
187                 /*
188                  * Print this only once. If the admin changes the limit,
189                  * print a new message when reaching the limit again.
190                  */
191                 if (prev_max != max_lock_depth) {
192                         prev_max = max_lock_depth;
193                         printk(KERN_WARNING "Maximum lock depth %d reached "
194                                "task: %s (%d)\n", max_lock_depth,
195                                top_task->comm, task_pid_nr(top_task));
196                 }
197                 put_task_struct(task);
198
199                 return deadlock_detect ? -EDEADLK : 0;
200         }
201  retry:
202         /*
203          * Task can not go away as we did a get_task() before !
204          */
205         raw_spin_lock_irqsave(&task->pi_lock, flags);
206
207         waiter = task->pi_blocked_on;
208         /*
209          * Check whether the end of the boosting chain has been
210          * reached or the state of the chain has changed while we
211          * dropped the locks.
212          */
213         if (!waiter)
214                 goto out_unlock_pi;
215
216         /*
217          * Check the orig_waiter state. After we dropped the locks,
218          * the previous owner of the lock might have released the lock.
219          */
220         if (orig_waiter && !rt_mutex_owner(orig_lock))
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 (!raw_spin_trylock(&lock->wait_lock)) {
241                 raw_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                 raw_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         raw_spin_unlock_irqrestore(&task->pi_lock, flags);
263         if (!rt_mutex_owner(lock)) {
264                 /*
265                  * If the requeue above changed the top waiter, then we need
266                  * to wake the new top waiter up to try to get the lock.
267                  */
268
269                 if (top_waiter != rt_mutex_top_waiter(lock))
270                         wake_up_process(rt_mutex_top_waiter(lock)->task);
271                 raw_spin_unlock(&lock->wait_lock);
272                 goto out_put_task;
273         }
274         put_task_struct(task);
275
276         /* Grab the next task */
277         task = rt_mutex_owner(lock);
278         get_task_struct(task);
279         raw_spin_lock_irqsave(&task->pi_lock, flags);
280
281         if (waiter == rt_mutex_top_waiter(lock)) {
282                 /* Boost the owner */
283                 plist_del(&top_waiter->pi_list_entry, &task->pi_waiters);
284                 waiter->pi_list_entry.prio = waiter->list_entry.prio;
285                 plist_add(&waiter->pi_list_entry, &task->pi_waiters);
286                 __rt_mutex_adjust_prio(task);
287
288         } else if (top_waiter == waiter) {
289                 /* Deboost the owner */
290                 plist_del(&waiter->pi_list_entry, &task->pi_waiters);
291                 waiter = rt_mutex_top_waiter(lock);
292                 waiter->pi_list_entry.prio = waiter->list_entry.prio;
293                 plist_add(&waiter->pi_list_entry, &task->pi_waiters);
294                 __rt_mutex_adjust_prio(task);
295         }
296
297         raw_spin_unlock_irqrestore(&task->pi_lock, flags);
298
299         top_waiter = rt_mutex_top_waiter(lock);
300         raw_spin_unlock(&lock->wait_lock);
301
302         if (!detect_deadlock && waiter != top_waiter)
303                 goto out_put_task;
304
305         goto again;
306
307  out_unlock_pi:
308         raw_spin_unlock_irqrestore(&task->pi_lock, flags);
309  out_put_task:
310         put_task_struct(task);
311
312         return ret;
313 }
314
315 /*
316  * Try to take an rt-mutex
317  *
318  * Must be called with lock->wait_lock held.
319  *
320  * @lock:   the lock to be acquired.
321  * @task:   the task which wants to acquire the lock
322  * @waiter: the waiter that is queued to the lock's wait list. (could be NULL)
323  */
324 static int try_to_take_rt_mutex(struct rt_mutex *lock, struct task_struct *task,
325                 struct rt_mutex_waiter *waiter)
326 {
327         /*
328          * We have to be careful here if the atomic speedups are
329          * enabled, such that, when
330          *  - no other waiter is on the lock
331          *  - the lock has been released since we did the cmpxchg
332          * the lock can be released or taken while we are doing the
333          * checks and marking the lock with RT_MUTEX_HAS_WAITERS.
334          *
335          * The atomic acquire/release aware variant of
336          * mark_rt_mutex_waiters uses a cmpxchg loop. After setting
337          * the WAITERS bit, the atomic release / acquire can not
338          * happen anymore and lock->wait_lock protects us from the
339          * non-atomic case.
340          *
341          * Note, that this might set lock->owner =
342          * RT_MUTEX_HAS_WAITERS in the case the lock is not contended
343          * any more. This is fixed up when we take the ownership.
344          * This is the transitional state explained at the top of this file.
345          */
346         mark_rt_mutex_waiters(lock);
347
348         if (rt_mutex_owner(lock))
349                 return 0;
350
351         /*
352          * It will get the lock because of one of these conditions:
353          * 1) there is no waiter
354          * 2) higher priority than waiters
355          * 3) it is top waiter
356          */
357         if (rt_mutex_has_waiters(lock)) {
358                 if (task->prio >= rt_mutex_top_waiter(lock)->list_entry.prio) {
359                         if (!waiter || waiter != rt_mutex_top_waiter(lock))
360                                 return 0;
361                 }
362         }
363
364         if (waiter || rt_mutex_has_waiters(lock)) {
365                 unsigned long flags;
366                 struct rt_mutex_waiter *top;
367
368                 raw_spin_lock_irqsave(&task->pi_lock, flags);
369
370                 /* remove the queued waiter. */
371                 if (waiter) {
372                         plist_del(&waiter->list_entry, &lock->wait_list);
373                         task->pi_blocked_on = NULL;
374                 }
375
376                 /*
377                  * We have to enqueue the top waiter(if it exists) into
378                  * task->pi_waiters list.
379                  */
380                 if (rt_mutex_has_waiters(lock)) {
381                         top = rt_mutex_top_waiter(lock);
382                         top->pi_list_entry.prio = top->list_entry.prio;
383                         plist_add(&top->pi_list_entry, &task->pi_waiters);
384                 }
385                 raw_spin_unlock_irqrestore(&task->pi_lock, flags);
386         }
387
388         /* We got the lock. */
389         debug_rt_mutex_lock(lock);
390
391         rt_mutex_set_owner(lock, task);
392
393         rt_mutex_deadlock_account_lock(lock, task);
394
395         return 1;
396 }
397
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                                    struct task_struct *task,
408                                    int detect_deadlock)
409 {
410         struct task_struct *owner = rt_mutex_owner(lock);
411         struct rt_mutex_waiter *top_waiter = waiter;
412         unsigned long flags;
413         int chain_walk = 0, res;
414
415         raw_spin_lock_irqsave(&task->pi_lock, flags);
416         __rt_mutex_adjust_prio(task);
417         waiter->task = task;
418         waiter->lock = lock;
419         plist_node_init(&waiter->list_entry, task->prio);
420         plist_node_init(&waiter->pi_list_entry, task->prio);
421
422         /* Get the top priority waiter on the lock */
423         if (rt_mutex_has_waiters(lock))
424                 top_waiter = rt_mutex_top_waiter(lock);
425         plist_add(&waiter->list_entry, &lock->wait_list);
426
427         task->pi_blocked_on = waiter;
428
429         raw_spin_unlock_irqrestore(&task->pi_lock, flags);
430
431         if (!owner)
432                 return 0;
433
434         if (waiter == rt_mutex_top_waiter(lock)) {
435                 raw_spin_lock_irqsave(&owner->pi_lock, flags);
436                 plist_del(&top_waiter->pi_list_entry, &owner->pi_waiters);
437                 plist_add(&waiter->pi_list_entry, &owner->pi_waiters);
438
439                 __rt_mutex_adjust_prio(owner);
440                 if (owner->pi_blocked_on)
441                         chain_walk = 1;
442                 raw_spin_unlock_irqrestore(&owner->pi_lock, flags);
443         }
444         else if (debug_rt_mutex_detect_deadlock(waiter, detect_deadlock))
445                 chain_walk = 1;
446
447         if (!chain_walk)
448                 return 0;
449
450         /*
451          * The owner can't disappear while holding a lock,
452          * so the owner struct is protected by wait_lock.
453          * Gets dropped in rt_mutex_adjust_prio_chain()!
454          */
455         get_task_struct(owner);
456
457         raw_spin_unlock(&lock->wait_lock);
458
459         res = rt_mutex_adjust_prio_chain(owner, detect_deadlock, lock, waiter,
460                                          task);
461
462         raw_spin_lock(&lock->wait_lock);
463
464         return res;
465 }
466
467 /*
468  * Wake up the next waiter on the lock.
469  *
470  * Remove the top waiter from the current tasks waiter list and wake it up.
471  *
472  * Called with lock->wait_lock held.
473  */
474 static void wakeup_next_waiter(struct rt_mutex *lock)
475 {
476         struct rt_mutex_waiter *waiter;
477         unsigned long flags;
478
479         raw_spin_lock_irqsave(&current->pi_lock, flags);
480
481         waiter = rt_mutex_top_waiter(lock);
482
483         /*
484          * Remove it from current->pi_waiters. We do not adjust a
485          * possible priority boost right now. We execute wakeup in the
486          * boosted mode and go back to normal after releasing
487          * lock->wait_lock.
488          */
489         plist_del(&waiter->pi_list_entry, &current->pi_waiters);
490
491         rt_mutex_set_owner(lock, NULL);
492
493         raw_spin_unlock_irqrestore(&current->pi_lock, flags);
494
495         wake_up_process(waiter->task);
496 }
497
498 /*
499  * Remove a waiter from a lock and give up
500  *
501  * Must be called with lock->wait_lock held and
502  * have just failed to try_to_take_rt_mutex().
503  */
504 static void remove_waiter(struct rt_mutex *lock,
505                           struct rt_mutex_waiter *waiter)
506 {
507         int first = (waiter == rt_mutex_top_waiter(lock));
508         struct task_struct *owner = rt_mutex_owner(lock);
509         unsigned long flags;
510         int chain_walk = 0;
511
512         raw_spin_lock_irqsave(&current->pi_lock, flags);
513         plist_del(&waiter->list_entry, &lock->wait_list);
514         current->pi_blocked_on = NULL;
515         raw_spin_unlock_irqrestore(&current->pi_lock, flags);
516
517         if (!owner)
518                 return;
519
520         if (first) {
521
522                 raw_spin_lock_irqsave(&owner->pi_lock, flags);
523
524                 plist_del(&waiter->pi_list_entry, &owner->pi_waiters);
525
526                 if (rt_mutex_has_waiters(lock)) {
527                         struct rt_mutex_waiter *next;
528
529                         next = rt_mutex_top_waiter(lock);
530                         plist_add(&next->pi_list_entry, &owner->pi_waiters);
531                 }
532                 __rt_mutex_adjust_prio(owner);
533
534                 if (owner->pi_blocked_on)
535                         chain_walk = 1;
536
537                 raw_spin_unlock_irqrestore(&owner->pi_lock, flags);
538         }
539
540         WARN_ON(!plist_node_empty(&waiter->pi_list_entry));
541
542         if (!chain_walk)
543                 return;
544
545         /* gets dropped in rt_mutex_adjust_prio_chain()! */
546         get_task_struct(owner);
547
548         raw_spin_unlock(&lock->wait_lock);
549
550         rt_mutex_adjust_prio_chain(owner, 0, lock, NULL, current);
551
552         raw_spin_lock(&lock->wait_lock);
553 }
554
555 /*
556  * Recheck the pi chain, in case we got a priority setting
557  *
558  * Called from sched_setscheduler
559  */
560 void rt_mutex_adjust_pi(struct task_struct *task)
561 {
562         struct rt_mutex_waiter *waiter;
563         unsigned long flags;
564
565         raw_spin_lock_irqsave(&task->pi_lock, flags);
566
567         waiter = task->pi_blocked_on;
568         if (!waiter || waiter->list_entry.prio == task->prio) {
569                 raw_spin_unlock_irqrestore(&task->pi_lock, flags);
570                 return;
571         }
572
573         raw_spin_unlock_irqrestore(&task->pi_lock, flags);
574
575         /* gets dropped in rt_mutex_adjust_prio_chain()! */
576         get_task_struct(task);
577         rt_mutex_adjust_prio_chain(task, 0, NULL, NULL, task);
578 }
579
580 /**
581  * __rt_mutex_slowlock() - Perform the wait-wake-try-to-take loop
582  * @lock:                the rt_mutex to take
583  * @state:               the state the task should block in (TASK_INTERRUPTIBLE
584  *                       or TASK_UNINTERRUPTIBLE)
585  * @timeout:             the pre-initialized and started timer, or NULL for none
586  * @waiter:              the pre-initialized rt_mutex_waiter
587  *
588  * lock->wait_lock must be held by the caller.
589  */
590 static int __sched
591 __rt_mutex_slowlock(struct rt_mutex *lock, int state,
592                     struct hrtimer_sleeper *timeout,
593                     struct rt_mutex_waiter *waiter)
594 {
595         int ret = 0;
596
597         for (;;) {
598                 /* Try to acquire the lock: */
599                 if (try_to_take_rt_mutex(lock, current, waiter))
600                         break;
601
602                 /*
603                  * TASK_INTERRUPTIBLE checks for signals and
604                  * timeout. Ignored otherwise.
605                  */
606                 if (unlikely(state == TASK_INTERRUPTIBLE)) {
607                         /* Signal pending? */
608                         if (signal_pending(current))
609                                 ret = -EINTR;
610                         if (timeout && !timeout->task)
611                                 ret = -ETIMEDOUT;
612                         if (ret)
613                                 break;
614                 }
615
616                 raw_spin_unlock(&lock->wait_lock);
617
618                 debug_rt_mutex_print_deadlock(waiter);
619
620                 schedule_rt_mutex(lock);
621
622                 raw_spin_lock(&lock->wait_lock);
623                 set_current_state(state);
624         }
625
626         return ret;
627 }
628
629 /*
630  * Slow path lock function:
631  */
632 static int __sched
633 rt_mutex_slowlock(struct rt_mutex *lock, int state,
634                   struct hrtimer_sleeper *timeout,
635                   int detect_deadlock)
636 {
637         struct rt_mutex_waiter waiter;
638         int ret = 0;
639
640         debug_rt_mutex_init_waiter(&waiter);
641
642         raw_spin_lock(&lock->wait_lock);
643
644         /* Try to acquire the lock again: */
645         if (try_to_take_rt_mutex(lock, current, NULL)) {
646                 raw_spin_unlock(&lock->wait_lock);
647                 return 0;
648         }
649
650         set_current_state(state);
651
652         /* Setup the timer, when timeout != NULL */
653         if (unlikely(timeout)) {
654                 hrtimer_start_expires(&timeout->timer, HRTIMER_MODE_ABS);
655                 if (!hrtimer_active(&timeout->timer))
656                         timeout->task = NULL;
657         }
658
659         ret = task_blocks_on_rt_mutex(lock, &waiter, current, detect_deadlock);
660
661         if (likely(!ret))
662                 ret = __rt_mutex_slowlock(lock, state, timeout, &waiter);
663
664         set_current_state(TASK_RUNNING);
665
666         if (unlikely(ret))
667                 remove_waiter(lock, &waiter);
668
669         /*
670          * try_to_take_rt_mutex() sets the waiter bit
671          * unconditionally. We might have to fix that up.
672          */
673         fixup_rt_mutex_waiters(lock);
674
675         raw_spin_unlock(&lock->wait_lock);
676
677         /* Remove pending timer: */
678         if (unlikely(timeout))
679                 hrtimer_cancel(&timeout->timer);
680
681         debug_rt_mutex_free_waiter(&waiter);
682
683         return ret;
684 }
685
686 /*
687  * Slow path try-lock function:
688  */
689 static inline int
690 rt_mutex_slowtrylock(struct rt_mutex *lock)
691 {
692         int ret = 0;
693
694         raw_spin_lock(&lock->wait_lock);
695
696         if (likely(rt_mutex_owner(lock) != current)) {
697
698                 ret = try_to_take_rt_mutex(lock, current, NULL);
699                 /*
700                  * try_to_take_rt_mutex() sets the lock waiters
701                  * bit unconditionally. Clean this up.
702                  */
703                 fixup_rt_mutex_waiters(lock);
704         }
705
706         raw_spin_unlock(&lock->wait_lock);
707
708         return ret;
709 }
710
711 /*
712  * Slow path to release a rt-mutex:
713  */
714 static void __sched
715 rt_mutex_slowunlock(struct rt_mutex *lock)
716 {
717         raw_spin_lock(&lock->wait_lock);
718
719         debug_rt_mutex_unlock(lock);
720
721         rt_mutex_deadlock_account_unlock(current);
722
723         if (!rt_mutex_has_waiters(lock)) {
724                 lock->owner = NULL;
725                 raw_spin_unlock(&lock->wait_lock);
726                 return;
727         }
728
729         wakeup_next_waiter(lock);
730
731         raw_spin_unlock(&lock->wait_lock);
732
733         /* Undo pi boosting if necessary: */
734         rt_mutex_adjust_prio(current);
735 }
736
737 /*
738  * debug aware fast / slowpath lock,trylock,unlock
739  *
740  * The atomic acquire/release ops are compiled away, when either the
741  * architecture does not support cmpxchg or when debugging is enabled.
742  */
743 static inline int
744 rt_mutex_fastlock(struct rt_mutex *lock, int state,
745                   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, NULL, detect_deadlock);
755 }
756
757 static inline int
758 rt_mutex_timed_fastlock(struct rt_mutex *lock, int state,
759                         struct hrtimer_sleeper *timeout, int detect_deadlock,
760                         int (*slowfn)(struct rt_mutex *lock, int state,
761                                       struct hrtimer_sleeper *timeout,
762                                       int detect_deadlock))
763 {
764         if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) {
765                 rt_mutex_deadlock_account_lock(lock, current);
766                 return 0;
767         } else
768                 return slowfn(lock, state, timeout, detect_deadlock);
769 }
770
771 static inline int
772 rt_mutex_fasttrylock(struct rt_mutex *lock,
773                      int (*slowfn)(struct rt_mutex *lock))
774 {
775         if (likely(rt_mutex_cmpxchg(lock, NULL, current))) {
776                 rt_mutex_deadlock_account_lock(lock, current);
777                 return 1;
778         }
779         return slowfn(lock);
780 }
781
782 static inline void
783 rt_mutex_fastunlock(struct rt_mutex *lock,
784                     void (*slowfn)(struct rt_mutex *lock))
785 {
786         if (likely(rt_mutex_cmpxchg(lock, current, NULL)))
787                 rt_mutex_deadlock_account_unlock(current);
788         else
789                 slowfn(lock);
790 }
791
792 /**
793  * rt_mutex_lock - lock a rt_mutex
794  *
795  * @lock: the rt_mutex to be locked
796  */
797 void __sched rt_mutex_lock(struct rt_mutex *lock)
798 {
799         might_sleep();
800
801         rt_mutex_fastlock(lock, TASK_UNINTERRUPTIBLE, 0, rt_mutex_slowlock);
802 }
803 EXPORT_SYMBOL_GPL(rt_mutex_lock);
804
805 /**
806  * rt_mutex_lock_interruptible - lock a rt_mutex interruptible
807  *
808  * @lock:               the rt_mutex to be locked
809  * @detect_deadlock:    deadlock detection on/off
810  *
811  * Returns:
812  *  0           on success
813  * -EINTR       when interrupted by a signal
814  * -EDEADLK     when the lock would deadlock (when deadlock detection is on)
815  */
816 int __sched rt_mutex_lock_interruptible(struct rt_mutex *lock,
817                                                  int detect_deadlock)
818 {
819         might_sleep();
820
821         return rt_mutex_fastlock(lock, TASK_INTERRUPTIBLE,
822                                  detect_deadlock, rt_mutex_slowlock);
823 }
824 EXPORT_SYMBOL_GPL(rt_mutex_lock_interruptible);
825
826 /**
827  * rt_mutex_timed_lock - lock a rt_mutex interruptible
828  *                      the timeout structure is provided
829  *                      by the caller
830  *
831  * @lock:               the rt_mutex to be locked
832  * @timeout:            timeout structure or NULL (no timeout)
833  * @detect_deadlock:    deadlock detection on/off
834  *
835  * Returns:
836  *  0           on success
837  * -EINTR       when interrupted by a signal
838  * -ETIMEDOUT   when the timeout expired
839  * -EDEADLK     when the lock would deadlock (when deadlock detection is on)
840  */
841 int
842 rt_mutex_timed_lock(struct rt_mutex *lock, struct hrtimer_sleeper *timeout,
843                     int detect_deadlock)
844 {
845         might_sleep();
846
847         return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout,
848                                        detect_deadlock, rt_mutex_slowlock);
849 }
850 EXPORT_SYMBOL_GPL(rt_mutex_timed_lock);
851
852 /**
853  * rt_mutex_trylock - try to lock a rt_mutex
854  *
855  * @lock:       the rt_mutex to be locked
856  *
857  * Returns 1 on success and 0 on contention
858  */
859 int __sched rt_mutex_trylock(struct rt_mutex *lock)
860 {
861         return rt_mutex_fasttrylock(lock, rt_mutex_slowtrylock);
862 }
863 EXPORT_SYMBOL_GPL(rt_mutex_trylock);
864
865 /**
866  * rt_mutex_unlock - unlock a rt_mutex
867  *
868  * @lock: the rt_mutex to be unlocked
869  */
870 void __sched rt_mutex_unlock(struct rt_mutex *lock)
871 {
872         rt_mutex_fastunlock(lock, rt_mutex_slowunlock);
873 }
874 EXPORT_SYMBOL_GPL(rt_mutex_unlock);
875
876 /**
877  * rt_mutex_destroy - mark a mutex unusable
878  * @lock: the mutex to be destroyed
879  *
880  * This function marks the mutex uninitialized, and any subsequent
881  * use of the mutex is forbidden. The mutex must not be locked when
882  * this function is called.
883  */
884 void rt_mutex_destroy(struct rt_mutex *lock)
885 {
886         WARN_ON(rt_mutex_is_locked(lock));
887 #ifdef CONFIG_DEBUG_RT_MUTEXES
888         lock->magic = NULL;
889 #endif
890 }
891
892 EXPORT_SYMBOL_GPL(rt_mutex_destroy);
893
894 /**
895  * __rt_mutex_init - initialize the rt lock
896  *
897  * @lock: the rt lock to be initialized
898  *
899  * Initialize the rt lock to unlocked state.
900  *
901  * Initializing of a locked rt lock is not allowed
902  */
903 void __rt_mutex_init(struct rt_mutex *lock, const char *name)
904 {
905         lock->owner = NULL;
906         raw_spin_lock_init(&lock->wait_lock);
907         plist_head_init(&lock->wait_list);
908
909         debug_rt_mutex_init(lock, name);
910 }
911 EXPORT_SYMBOL_GPL(__rt_mutex_init);
912
913 /**
914  * rt_mutex_init_proxy_locked - initialize and lock a rt_mutex on behalf of a
915  *                              proxy owner
916  *
917  * @lock:       the rt_mutex to be locked
918  * @proxy_owner:the task to set as owner
919  *
920  * No locking. Caller has to do serializing itself
921  * Special API call for PI-futex support
922  */
923 void rt_mutex_init_proxy_locked(struct rt_mutex *lock,
924                                 struct task_struct *proxy_owner)
925 {
926         __rt_mutex_init(lock, NULL);
927         debug_rt_mutex_proxy_lock(lock, proxy_owner);
928         rt_mutex_set_owner(lock, proxy_owner);
929         rt_mutex_deadlock_account_lock(lock, proxy_owner);
930 }
931
932 /**
933  * rt_mutex_proxy_unlock - release a lock on behalf of owner
934  *
935  * @lock:       the rt_mutex to be locked
936  *
937  * No locking. Caller has to do serializing itself
938  * Special API call for PI-futex support
939  */
940 void rt_mutex_proxy_unlock(struct rt_mutex *lock,
941                            struct task_struct *proxy_owner)
942 {
943         debug_rt_mutex_proxy_unlock(lock);
944         rt_mutex_set_owner(lock, NULL);
945         rt_mutex_deadlock_account_unlock(proxy_owner);
946 }
947
948 /**
949  * rt_mutex_start_proxy_lock() - Start lock acquisition for another task
950  * @lock:               the rt_mutex to take
951  * @waiter:             the pre-initialized rt_mutex_waiter
952  * @task:               the task to prepare
953  * @detect_deadlock:    perform deadlock detection (1) or not (0)
954  *
955  * Returns:
956  *  0 - task blocked on lock
957  *  1 - acquired the lock for task, caller should wake it up
958  * <0 - error
959  *
960  * Special API call for FUTEX_REQUEUE_PI support.
961  */
962 int rt_mutex_start_proxy_lock(struct rt_mutex *lock,
963                               struct rt_mutex_waiter *waiter,
964                               struct task_struct *task, int detect_deadlock)
965 {
966         int ret;
967
968         raw_spin_lock(&lock->wait_lock);
969
970         if (try_to_take_rt_mutex(lock, task, NULL)) {
971                 raw_spin_unlock(&lock->wait_lock);
972                 return 1;
973         }
974
975         ret = task_blocks_on_rt_mutex(lock, waiter, task, detect_deadlock);
976
977         if (ret && !rt_mutex_owner(lock)) {
978                 /*
979                  * Reset the return value. We might have
980                  * returned with -EDEADLK and the owner
981                  * released the lock while we were walking the
982                  * pi chain.  Let the waiter sort it out.
983                  */
984                 ret = 0;
985         }
986
987         if (unlikely(ret))
988                 remove_waiter(lock, waiter);
989
990         raw_spin_unlock(&lock->wait_lock);
991
992         debug_rt_mutex_print_deadlock(waiter);
993
994         return ret;
995 }
996
997 /**
998  * rt_mutex_next_owner - return the next owner of the lock
999  *
1000  * @lock: the rt lock query
1001  *
1002  * Returns the next owner of the lock or NULL
1003  *
1004  * Caller has to serialize against other accessors to the lock
1005  * itself.
1006  *
1007  * Special API call for PI-futex support
1008  */
1009 struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock)
1010 {
1011         if (!rt_mutex_has_waiters(lock))
1012                 return NULL;
1013
1014         return rt_mutex_top_waiter(lock)->task;
1015 }
1016
1017 /**
1018  * rt_mutex_finish_proxy_lock() - Complete lock acquisition
1019  * @lock:               the rt_mutex we were woken on
1020  * @to:                 the timeout, null if none. hrtimer should already have
1021  *                      been started.
1022  * @waiter:             the pre-initialized rt_mutex_waiter
1023  * @detect_deadlock:    perform deadlock detection (1) or not (0)
1024  *
1025  * Complete the lock acquisition started our behalf by another thread.
1026  *
1027  * Returns:
1028  *  0 - success
1029  * <0 - error, one of -EINTR, -ETIMEDOUT, or -EDEADLK
1030  *
1031  * Special API call for PI-futex requeue support
1032  */
1033 int rt_mutex_finish_proxy_lock(struct rt_mutex *lock,
1034                                struct hrtimer_sleeper *to,
1035                                struct rt_mutex_waiter *waiter,
1036                                int detect_deadlock)
1037 {
1038         int ret;
1039
1040         raw_spin_lock(&lock->wait_lock);
1041
1042         set_current_state(TASK_INTERRUPTIBLE);
1043
1044         ret = __rt_mutex_slowlock(lock, TASK_INTERRUPTIBLE, to, waiter);
1045
1046         set_current_state(TASK_RUNNING);
1047
1048         if (unlikely(ret))
1049                 remove_waiter(lock, waiter);
1050
1051         /*
1052          * try_to_take_rt_mutex() sets the waiter bit unconditionally. We might
1053          * have to fix that up.
1054          */
1055         fixup_rt_mutex_waiters(lock);
1056
1057         raw_spin_unlock(&lock->wait_lock);
1058
1059         return ret;
1060 }