[PATCH] sched: cleanup, remove task_t, convert to struct task_struct
[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 #include <linux/spinlock.h>
12 #include <linux/module.h>
13 #include <linux/sched.h>
14 #include <linux/timer.h>
15
16 #include "rtmutex_common.h"
17
18 #ifdef CONFIG_DEBUG_RT_MUTEXES
19 # include "rtmutex-debug.h"
20 #else
21 # include "rtmutex.h"
22 #endif
23
24 /*
25  * lock->owner state tracking:
26  *
27  * lock->owner holds the task_struct pointer of the owner. Bit 0 and 1
28  * are used to keep track of the "owner is pending" and "lock has
29  * waiters" state.
30  *
31  * owner        bit1    bit0
32  * NULL         0       0       lock is free (fast acquire possible)
33  * NULL         0       1       invalid state
34  * NULL         1       0       Transitional State*
35  * NULL         1       1       invalid state
36  * taskpointer  0       0       lock is held (fast release possible)
37  * taskpointer  0       1       task is pending owner
38  * taskpointer  1       0       lock is held and has waiters
39  * taskpointer  1       1       task is pending owner and lock has more waiters
40  *
41  * Pending ownership is assigned to the top (highest priority)
42  * waiter of the lock, when the lock is released. The thread is woken
43  * up and can now take the lock. Until the lock is taken (bit 0
44  * cleared) a competing higher priority thread can steal the lock
45  * which puts the woken up thread back on the waiters list.
46  *
47  * The fast atomic compare exchange based acquire and release is only
48  * possible when bit 0 and 1 of lock->owner are 0.
49  *
50  * (*) There's a small time where the owner can be NULL and the
51  * "lock has waiters" bit is set.  This can happen when grabbing the lock.
52  * To prevent a cmpxchg of the owner releasing the lock, we need to set this
53  * bit before looking at the lock, hence the reason this is a transitional
54  * state.
55  */
56
57 static void
58 rt_mutex_set_owner(struct rt_mutex *lock, struct task_struct *owner,
59                    unsigned long mask)
60 {
61         unsigned long val = (unsigned long)owner | mask;
62
63         if (rt_mutex_has_waiters(lock))
64                 val |= RT_MUTEX_HAS_WAITERS;
65
66         lock->owner = (struct task_struct *)val;
67 }
68
69 static inline void clear_rt_mutex_waiters(struct rt_mutex *lock)
70 {
71         lock->owner = (struct task_struct *)
72                         ((unsigned long)lock->owner & ~RT_MUTEX_HAS_WAITERS);
73 }
74
75 static void fixup_rt_mutex_waiters(struct rt_mutex *lock)
76 {
77         if (!rt_mutex_has_waiters(lock))
78                 clear_rt_mutex_waiters(lock);
79 }
80
81 /*
82  * We can speed up the acquire/release, if the architecture
83  * supports cmpxchg and if there's no debugging state to be set up
84  */
85 #if defined(__HAVE_ARCH_CMPXCHG) && !defined(CONFIG_DEBUG_RT_MUTEXES)
86 # define rt_mutex_cmpxchg(l,c,n)        (cmpxchg(&l->owner, c, n) == c)
87 static inline void mark_rt_mutex_waiters(struct rt_mutex *lock)
88 {
89         unsigned long owner, *p = (unsigned long *) &lock->owner;
90
91         do {
92                 owner = *p;
93         } while (cmpxchg(p, owner, owner | RT_MUTEX_HAS_WAITERS) != owner);
94 }
95 #else
96 # define rt_mutex_cmpxchg(l,c,n)        (0)
97 static inline void mark_rt_mutex_waiters(struct rt_mutex *lock)
98 {
99         lock->owner = (struct task_struct *)
100                         ((unsigned long)lock->owner | RT_MUTEX_HAS_WAITERS);
101 }
102 #endif
103
104 /*
105  * Calculate task priority from the waiter list priority
106  *
107  * Return task->normal_prio when the waiter list is empty or when
108  * the waiter is not allowed to do priority boosting
109  */
110 int rt_mutex_getprio(struct task_struct *task)
111 {
112         if (likely(!task_has_pi_waiters(task)))
113                 return task->normal_prio;
114
115         return min(task_top_pi_waiter(task)->pi_list_entry.prio,
116                    task->normal_prio);
117 }
118
119 /*
120  * Adjust the priority of a task, after its pi_waiters got modified.
121  *
122  * This can be both boosting and unboosting. task->pi_lock must be held.
123  */
124 static void __rt_mutex_adjust_prio(struct task_struct *task)
125 {
126         int prio = rt_mutex_getprio(task);
127
128         if (task->prio != prio)
129                 rt_mutex_setprio(task, prio);
130 }
131
132 /*
133  * Adjust task priority (undo boosting). Called from the exit path of
134  * rt_mutex_slowunlock() and rt_mutex_slowlock().
135  *
136  * (Note: We do this outside of the protection of lock->wait_lock to
137  * allow the lock to be taken while or before we readjust the priority
138  * of task. We do not use the spin_xx_mutex() variants here as we are
139  * outside of the debug path.)
140  */
141 static void rt_mutex_adjust_prio(struct task_struct *task)
142 {
143         unsigned long flags;
144
145         spin_lock_irqsave(&task->pi_lock, flags);
146         __rt_mutex_adjust_prio(task);
147         spin_unlock_irqrestore(&task->pi_lock, flags);
148 }
149
150 /*
151  * Max number of times we'll walk the boosting chain:
152  */
153 int max_lock_depth = 1024;
154
155 /*
156  * Adjust the priority chain. Also used for deadlock detection.
157  * Decreases task's usage by one - may thus free the task.
158  * Returns 0 or -EDEADLK.
159  */
160 static int rt_mutex_adjust_prio_chain(struct task_struct *task,
161                                       int deadlock_detect,
162                                       struct rt_mutex *orig_lock,
163                                       struct rt_mutex_waiter *orig_waiter,
164                                       struct task_struct *top_task)
165 {
166         struct rt_mutex *lock;
167         struct rt_mutex_waiter *waiter, *top_waiter = orig_waiter;
168         int detect_deadlock, ret = 0, depth = 0;
169         unsigned long flags;
170
171         detect_deadlock = debug_rt_mutex_detect_deadlock(orig_waiter,
172                                                          deadlock_detect);
173
174         /*
175          * The (de)boosting is a step by step approach with a lot of
176          * pitfalls. We want this to be preemptible and we want hold a
177          * maximum of two locks per step. So we have to check
178          * carefully whether things change under us.
179          */
180  again:
181         if (++depth > max_lock_depth) {
182                 static int prev_max;
183
184                 /*
185                  * Print this only once. If the admin changes the limit,
186                  * print a new message when reaching the limit again.
187                  */
188                 if (prev_max != max_lock_depth) {
189                         prev_max = max_lock_depth;
190                         printk(KERN_WARNING "Maximum lock depth %d reached "
191                                "task: %s (%d)\n", max_lock_depth,
192                                top_task->comm, top_task->pid);
193                 }
194                 put_task_struct(task);
195
196                 return deadlock_detect ? -EDEADLK : 0;
197         }
198  retry:
199         /*
200          * Task can not go away as we did a get_task() before !
201          */
202         spin_lock_irqsave(&task->pi_lock, flags);
203
204         waiter = task->pi_blocked_on;
205         /*
206          * Check whether the end of the boosting chain has been
207          * reached or the state of the chain has changed while we
208          * dropped the locks.
209          */
210         if (!waiter || !waiter->task)
211                 goto out_unlock_pi;
212
213         if (top_waiter && (!task_has_pi_waiters(task) ||
214                            top_waiter != task_top_pi_waiter(task)))
215                 goto out_unlock_pi;
216
217         /*
218          * When deadlock detection is off then we check, if further
219          * priority adjustment is necessary.
220          */
221         if (!detect_deadlock && waiter->list_entry.prio == task->prio)
222                 goto out_unlock_pi;
223
224         lock = waiter->lock;
225         if (!spin_trylock(&lock->wait_lock)) {
226                 spin_unlock_irqrestore(&task->pi_lock, flags);
227                 cpu_relax();
228                 goto retry;
229         }
230
231         /* Deadlock detection */
232         if (lock == orig_lock || rt_mutex_owner(lock) == top_task) {
233                 debug_rt_mutex_deadlock(deadlock_detect, orig_waiter, lock);
234                 spin_unlock(&lock->wait_lock);
235                 ret = deadlock_detect ? -EDEADLK : 0;
236                 goto out_unlock_pi;
237         }
238
239         top_waiter = rt_mutex_top_waiter(lock);
240
241         /* Requeue the waiter */
242         plist_del(&waiter->list_entry, &lock->wait_list);
243         waiter->list_entry.prio = task->prio;
244         plist_add(&waiter->list_entry, &lock->wait_list);
245
246         /* Release the task */
247         spin_unlock_irqrestore(&task->pi_lock, flags);
248         put_task_struct(task);
249
250         /* Grab the next task */
251         task = rt_mutex_owner(lock);
252         spin_lock_irqsave(&task->pi_lock, flags);
253
254         if (waiter == rt_mutex_top_waiter(lock)) {
255                 /* Boost the owner */
256                 plist_del(&top_waiter->pi_list_entry, &task->pi_waiters);
257                 waiter->pi_list_entry.prio = waiter->list_entry.prio;
258                 plist_add(&waiter->pi_list_entry, &task->pi_waiters);
259                 __rt_mutex_adjust_prio(task);
260
261         } else if (top_waiter == waiter) {
262                 /* Deboost the owner */
263                 plist_del(&waiter->pi_list_entry, &task->pi_waiters);
264                 waiter = rt_mutex_top_waiter(lock);
265                 waiter->pi_list_entry.prio = waiter->list_entry.prio;
266                 plist_add(&waiter->pi_list_entry, &task->pi_waiters);
267                 __rt_mutex_adjust_prio(task);
268         }
269
270         get_task_struct(task);
271         spin_unlock_irqrestore(&task->pi_lock, flags);
272
273         top_waiter = rt_mutex_top_waiter(lock);
274         spin_unlock(&lock->wait_lock);
275
276         if (!detect_deadlock && waiter != top_waiter)
277                 goto out_put_task;
278
279         goto again;
280
281  out_unlock_pi:
282         spin_unlock_irqrestore(&task->pi_lock, flags);
283  out_put_task:
284         put_task_struct(task);
285
286         return ret;
287 }
288
289 /*
290  * Optimization: check if we can steal the lock from the
291  * assigned pending owner [which might not have taken the
292  * lock yet]:
293  */
294 static inline int try_to_steal_lock(struct rt_mutex *lock)
295 {
296         struct task_struct *pendowner = rt_mutex_owner(lock);
297         struct rt_mutex_waiter *next;
298         unsigned long flags;
299
300         if (!rt_mutex_owner_pending(lock))
301                 return 0;
302
303         if (pendowner == current)
304                 return 1;
305
306         spin_lock_irqsave(&pendowner->pi_lock, flags);
307         if (current->prio >= pendowner->prio) {
308                 spin_unlock_irqrestore(&pendowner->pi_lock, flags);
309                 return 0;
310         }
311
312         /*
313          * Check if a waiter is enqueued on the pending owners
314          * pi_waiters list. Remove it and readjust pending owners
315          * priority.
316          */
317         if (likely(!rt_mutex_has_waiters(lock))) {
318                 spin_unlock_irqrestore(&pendowner->pi_lock, flags);
319                 return 1;
320         }
321
322         /* No chain handling, pending owner is not blocked on anything: */
323         next = rt_mutex_top_waiter(lock);
324         plist_del(&next->pi_list_entry, &pendowner->pi_waiters);
325         __rt_mutex_adjust_prio(pendowner);
326         spin_unlock_irqrestore(&pendowner->pi_lock, flags);
327
328         /*
329          * We are going to steal the lock and a waiter was
330          * enqueued on the pending owners pi_waiters queue. So
331          * we have to enqueue this waiter into
332          * current->pi_waiters list. This covers the case,
333          * where current is boosted because it holds another
334          * lock and gets unboosted because the booster is
335          * interrupted, so we would delay a waiter with higher
336          * priority as current->normal_prio.
337          *
338          * Note: in the rare case of a SCHED_OTHER task changing
339          * its priority and thus stealing the lock, next->task
340          * might be current:
341          */
342         if (likely(next->task != current)) {
343                 spin_lock_irqsave(&current->pi_lock, flags);
344                 plist_add(&next->pi_list_entry, &current->pi_waiters);
345                 __rt_mutex_adjust_prio(current);
346                 spin_unlock_irqrestore(&current->pi_lock, flags);
347         }
348         return 1;
349 }
350
351 /*
352  * Try to take an rt-mutex
353  *
354  * This fails
355  * - when the lock has a real owner
356  * - when a different pending owner exists and has higher priority than current
357  *
358  * Must be called with lock->wait_lock held.
359  */
360 static int try_to_take_rt_mutex(struct rt_mutex *lock)
361 {
362         /*
363          * We have to be careful here if the atomic speedups are
364          * enabled, such that, when
365          *  - no other waiter is on the lock
366          *  - the lock has been released since we did the cmpxchg
367          * the lock can be released or taken while we are doing the
368          * checks and marking the lock with RT_MUTEX_HAS_WAITERS.
369          *
370          * The atomic acquire/release aware variant of
371          * mark_rt_mutex_waiters uses a cmpxchg loop. After setting
372          * the WAITERS bit, the atomic release / acquire can not
373          * happen anymore and lock->wait_lock protects us from the
374          * non-atomic case.
375          *
376          * Note, that this might set lock->owner =
377          * RT_MUTEX_HAS_WAITERS in the case the lock is not contended
378          * any more. This is fixed up when we take the ownership.
379          * This is the transitional state explained at the top of this file.
380          */
381         mark_rt_mutex_waiters(lock);
382
383         if (rt_mutex_owner(lock) && !try_to_steal_lock(lock))
384                 return 0;
385
386         /* We got the lock. */
387         debug_rt_mutex_lock(lock);
388
389         rt_mutex_set_owner(lock, current, 0);
390
391         rt_mutex_deadlock_account_lock(lock, current);
392
393         return 1;
394 }
395
396 /*
397  * Task blocks on lock.
398  *
399  * Prepare waiter and propagate pi chain
400  *
401  * This must be called with lock->wait_lock held.
402  */
403 static int task_blocks_on_rt_mutex(struct rt_mutex *lock,
404                                    struct rt_mutex_waiter *waiter,
405                                    int detect_deadlock)
406 {
407         struct task_struct *owner = rt_mutex_owner(lock);
408         struct rt_mutex_waiter *top_waiter = waiter;
409         unsigned long flags;
410         int boost = 0, res;
411
412         spin_lock_irqsave(&current->pi_lock, flags);
413         __rt_mutex_adjust_prio(current);
414         waiter->task = current;
415         waiter->lock = lock;
416         plist_node_init(&waiter->list_entry, current->prio);
417         plist_node_init(&waiter->pi_list_entry, current->prio);
418
419         /* Get the top priority waiter on the lock */
420         if (rt_mutex_has_waiters(lock))
421                 top_waiter = rt_mutex_top_waiter(lock);
422         plist_add(&waiter->list_entry, &lock->wait_list);
423
424         current->pi_blocked_on = waiter;
425
426         spin_unlock_irqrestore(&current->pi_lock, flags);
427
428         if (waiter == rt_mutex_top_waiter(lock)) {
429                 spin_lock_irqsave(&owner->pi_lock, flags);
430                 plist_del(&top_waiter->pi_list_entry, &owner->pi_waiters);
431                 plist_add(&waiter->pi_list_entry, &owner->pi_waiters);
432
433                 __rt_mutex_adjust_prio(owner);
434                 if (owner->pi_blocked_on) {
435                         boost = 1;
436                         /* gets dropped in rt_mutex_adjust_prio_chain()! */
437                         get_task_struct(owner);
438                 }
439                 spin_unlock_irqrestore(&owner->pi_lock, flags);
440         }
441         else if (debug_rt_mutex_detect_deadlock(waiter, detect_deadlock)) {
442                 spin_lock_irqsave(&owner->pi_lock, flags);
443                 if (owner->pi_blocked_on) {
444                         boost = 1;
445                         /* gets dropped in rt_mutex_adjust_prio_chain()! */
446                         get_task_struct(owner);
447                 }
448                 spin_unlock_irqrestore(&owner->pi_lock, flags);
449         }
450         if (!boost)
451                 return 0;
452
453         spin_unlock(&lock->wait_lock);
454
455         res = rt_mutex_adjust_prio_chain(owner, detect_deadlock, lock, waiter,
456                                          current);
457
458         spin_lock(&lock->wait_lock);
459
460         return res;
461 }
462
463 /*
464  * Wake up the next waiter on the lock.
465  *
466  * Remove the top waiter from the current tasks waiter list and from
467  * the lock waiter list. Set it as pending owner. Then wake it up.
468  *
469  * Called with lock->wait_lock held.
470  */
471 static void wakeup_next_waiter(struct rt_mutex *lock)
472 {
473         struct rt_mutex_waiter *waiter;
474         struct task_struct *pendowner;
475         unsigned long flags;
476
477         spin_lock_irqsave(&current->pi_lock, flags);
478
479         waiter = rt_mutex_top_waiter(lock);
480         plist_del(&waiter->list_entry, &lock->wait_list);
481
482         /*
483          * Remove it from current->pi_waiters. We do not adjust a
484          * possible priority boost right now. We execute wakeup in the
485          * boosted mode and go back to normal after releasing
486          * lock->wait_lock.
487          */
488         plist_del(&waiter->pi_list_entry, &current->pi_waiters);
489         pendowner = waiter->task;
490         waiter->task = NULL;
491
492         rt_mutex_set_owner(lock, pendowner, RT_MUTEX_OWNER_PENDING);
493
494         spin_unlock_irqrestore(&current->pi_lock, flags);
495
496         /*
497          * Clear the pi_blocked_on variable and enqueue a possible
498          * waiter into the pi_waiters list of the pending owner. This
499          * prevents that in case the pending owner gets unboosted a
500          * waiter with higher priority than pending-owner->normal_prio
501          * is blocked on the unboosted (pending) owner.
502          */
503         spin_lock_irqsave(&pendowner->pi_lock, flags);
504
505         WARN_ON(!pendowner->pi_blocked_on);
506         WARN_ON(pendowner->pi_blocked_on != waiter);
507         WARN_ON(pendowner->pi_blocked_on->lock != lock);
508
509         pendowner->pi_blocked_on = NULL;
510
511         if (rt_mutex_has_waiters(lock)) {
512                 struct rt_mutex_waiter *next;
513
514                 next = rt_mutex_top_waiter(lock);
515                 plist_add(&next->pi_list_entry, &pendowner->pi_waiters);
516         }
517         spin_unlock_irqrestore(&pendowner->pi_lock, flags);
518
519         wake_up_process(pendowner);
520 }
521
522 /*
523  * Remove a waiter from a lock
524  *
525  * Must be called with lock->wait_lock held
526  */
527 static void remove_waiter(struct rt_mutex *lock,
528                           struct rt_mutex_waiter *waiter)
529 {
530         int first = (waiter == rt_mutex_top_waiter(lock));
531         struct task_struct *owner = rt_mutex_owner(lock);
532         unsigned long flags;
533         int boost = 0;
534
535         spin_lock_irqsave(&current->pi_lock, flags);
536         plist_del(&waiter->list_entry, &lock->wait_list);
537         waiter->task = NULL;
538         current->pi_blocked_on = NULL;
539         spin_unlock_irqrestore(&current->pi_lock, flags);
540
541         if (first && owner != current) {
542
543                 spin_lock_irqsave(&owner->pi_lock, flags);
544
545                 plist_del(&waiter->pi_list_entry, &owner->pi_waiters);
546
547                 if (rt_mutex_has_waiters(lock)) {
548                         struct rt_mutex_waiter *next;
549
550                         next = rt_mutex_top_waiter(lock);
551                         plist_add(&next->pi_list_entry, &owner->pi_waiters);
552                 }
553                 __rt_mutex_adjust_prio(owner);
554
555                 if (owner->pi_blocked_on) {
556                         boost = 1;
557                         /* gets dropped in rt_mutex_adjust_prio_chain()! */
558                         get_task_struct(owner);
559                 }
560                 spin_unlock_irqrestore(&owner->pi_lock, flags);
561         }
562
563         WARN_ON(!plist_node_empty(&waiter->pi_list_entry));
564
565         if (!boost)
566                 return;
567
568         spin_unlock(&lock->wait_lock);
569
570         rt_mutex_adjust_prio_chain(owner, 0, lock, NULL, current);
571
572         spin_lock(&lock->wait_lock);
573 }
574
575 /*
576  * Recheck the pi chain, in case we got a priority setting
577  *
578  * Called from sched_setscheduler
579  */
580 void rt_mutex_adjust_pi(struct task_struct *task)
581 {
582         struct rt_mutex_waiter *waiter;
583         unsigned long flags;
584
585         spin_lock_irqsave(&task->pi_lock, flags);
586
587         waiter = task->pi_blocked_on;
588         if (!waiter || waiter->list_entry.prio == task->prio) {
589                 spin_unlock_irqrestore(&task->pi_lock, flags);
590                 return;
591         }
592
593         /* gets dropped in rt_mutex_adjust_prio_chain()! */
594         get_task_struct(task);
595         spin_unlock_irqrestore(&task->pi_lock, flags);
596
597         rt_mutex_adjust_prio_chain(task, 0, NULL, NULL, task);
598 }
599
600 /*
601  * Slow path lock function:
602  */
603 static int __sched
604 rt_mutex_slowlock(struct rt_mutex *lock, int state,
605                   struct hrtimer_sleeper *timeout,
606                   int detect_deadlock)
607 {
608         struct rt_mutex_waiter waiter;
609         int ret = 0;
610
611         debug_rt_mutex_init_waiter(&waiter);
612         waiter.task = NULL;
613
614         spin_lock(&lock->wait_lock);
615
616         /* Try to acquire the lock again: */
617         if (try_to_take_rt_mutex(lock)) {
618                 spin_unlock(&lock->wait_lock);
619                 return 0;
620         }
621
622         set_current_state(state);
623
624         /* Setup the timer, when timeout != NULL */
625         if (unlikely(timeout))
626                 hrtimer_start(&timeout->timer, timeout->timer.expires,
627                               HRTIMER_ABS);
628
629         for (;;) {
630                 /* Try to acquire the lock: */
631                 if (try_to_take_rt_mutex(lock))
632                         break;
633
634                 /*
635                  * TASK_INTERRUPTIBLE checks for signals and
636                  * timeout. Ignored otherwise.
637                  */
638                 if (unlikely(state == TASK_INTERRUPTIBLE)) {
639                         /* Signal pending? */
640                         if (signal_pending(current))
641                                 ret = -EINTR;
642                         if (timeout && !timeout->task)
643                                 ret = -ETIMEDOUT;
644                         if (ret)
645                                 break;
646                 }
647
648                 /*
649                  * waiter.task is NULL the first time we come here and
650                  * when we have been woken up by the previous owner
651                  * but the lock got stolen by a higher prio task.
652                  */
653                 if (!waiter.task) {
654                         ret = task_blocks_on_rt_mutex(lock, &waiter,
655                                                       detect_deadlock);
656                         /*
657                          * If we got woken up by the owner then start loop
658                          * all over without going into schedule to try
659                          * to get the lock now:
660                          */
661                         if (unlikely(!waiter.task))
662                                 continue;
663
664                         if (unlikely(ret))
665                                 break;
666                 }
667
668                 spin_unlock(&lock->wait_lock);
669
670                 debug_rt_mutex_print_deadlock(&waiter);
671
672                 if (waiter.task)
673                         schedule_rt_mutex(lock);
674
675                 spin_lock(&lock->wait_lock);
676                 set_current_state(state);
677         }
678
679         set_current_state(TASK_RUNNING);
680
681         if (unlikely(waiter.task))
682                 remove_waiter(lock, &waiter);
683
684         /*
685          * try_to_take_rt_mutex() sets the waiter bit
686          * unconditionally. We might have to fix that up.
687          */
688         fixup_rt_mutex_waiters(lock);
689
690         spin_unlock(&lock->wait_lock);
691
692         /* Remove pending timer: */
693         if (unlikely(timeout))
694                 hrtimer_cancel(&timeout->timer);
695
696         /*
697          * Readjust priority, when we did not get the lock. We might
698          * have been the pending owner and boosted. Since we did not
699          * take the lock, the PI boost has to go.
700          */
701         if (unlikely(ret))
702                 rt_mutex_adjust_prio(current);
703
704         debug_rt_mutex_free_waiter(&waiter);
705
706         return ret;
707 }
708
709 /*
710  * Slow path try-lock function:
711  */
712 static inline int
713 rt_mutex_slowtrylock(struct rt_mutex *lock)
714 {
715         int ret = 0;
716
717         spin_lock(&lock->wait_lock);
718
719         if (likely(rt_mutex_owner(lock) != current)) {
720
721                 ret = try_to_take_rt_mutex(lock);
722                 /*
723                  * try_to_take_rt_mutex() sets the lock waiters
724                  * bit unconditionally. Clean this up.
725                  */
726                 fixup_rt_mutex_waiters(lock);
727         }
728
729         spin_unlock(&lock->wait_lock);
730
731         return ret;
732 }
733
734 /*
735  * Slow path to release a rt-mutex:
736  */
737 static void __sched
738 rt_mutex_slowunlock(struct rt_mutex *lock)
739 {
740         spin_lock(&lock->wait_lock);
741
742         debug_rt_mutex_unlock(lock);
743
744         rt_mutex_deadlock_account_unlock(current);
745
746         if (!rt_mutex_has_waiters(lock)) {
747                 lock->owner = NULL;
748                 spin_unlock(&lock->wait_lock);
749                 return;
750         }
751
752         wakeup_next_waiter(lock);
753
754         spin_unlock(&lock->wait_lock);
755
756         /* Undo pi boosting if necessary: */
757         rt_mutex_adjust_prio(current);
758 }
759
760 /*
761  * debug aware fast / slowpath lock,trylock,unlock
762  *
763  * The atomic acquire/release ops are compiled away, when either the
764  * architecture does not support cmpxchg or when debugging is enabled.
765  */
766 static inline int
767 rt_mutex_fastlock(struct rt_mutex *lock, int state,
768                   int detect_deadlock,
769                   int (*slowfn)(struct rt_mutex *lock, int state,
770                                 struct hrtimer_sleeper *timeout,
771                                 int detect_deadlock))
772 {
773         if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) {
774                 rt_mutex_deadlock_account_lock(lock, current);
775                 return 0;
776         } else
777                 return slowfn(lock, state, NULL, detect_deadlock);
778 }
779
780 static inline int
781 rt_mutex_timed_fastlock(struct rt_mutex *lock, int state,
782                         struct hrtimer_sleeper *timeout, int detect_deadlock,
783                         int (*slowfn)(struct rt_mutex *lock, int state,
784                                       struct hrtimer_sleeper *timeout,
785                                       int detect_deadlock))
786 {
787         if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) {
788                 rt_mutex_deadlock_account_lock(lock, current);
789                 return 0;
790         } else
791                 return slowfn(lock, state, timeout, detect_deadlock);
792 }
793
794 static inline int
795 rt_mutex_fasttrylock(struct rt_mutex *lock,
796                      int (*slowfn)(struct rt_mutex *lock))
797 {
798         if (likely(rt_mutex_cmpxchg(lock, NULL, current))) {
799                 rt_mutex_deadlock_account_lock(lock, current);
800                 return 1;
801         }
802         return slowfn(lock);
803 }
804
805 static inline void
806 rt_mutex_fastunlock(struct rt_mutex *lock,
807                     void (*slowfn)(struct rt_mutex *lock))
808 {
809         if (likely(rt_mutex_cmpxchg(lock, current, NULL)))
810                 rt_mutex_deadlock_account_unlock(current);
811         else
812                 slowfn(lock);
813 }
814
815 /**
816  * rt_mutex_lock - lock a rt_mutex
817  *
818  * @lock: the rt_mutex to be locked
819  */
820 void __sched rt_mutex_lock(struct rt_mutex *lock)
821 {
822         might_sleep();
823
824         rt_mutex_fastlock(lock, TASK_UNINTERRUPTIBLE, 0, rt_mutex_slowlock);
825 }
826 EXPORT_SYMBOL_GPL(rt_mutex_lock);
827
828 /**
829  * rt_mutex_lock_interruptible - lock a rt_mutex interruptible
830  *
831  * @lock:               the rt_mutex to be locked
832  * @detect_deadlock:    deadlock detection on/off
833  *
834  * Returns:
835  *  0           on success
836  * -EINTR       when interrupted by a signal
837  * -EDEADLK     when the lock would deadlock (when deadlock detection is on)
838  */
839 int __sched rt_mutex_lock_interruptible(struct rt_mutex *lock,
840                                                  int detect_deadlock)
841 {
842         might_sleep();
843
844         return rt_mutex_fastlock(lock, TASK_INTERRUPTIBLE,
845                                  detect_deadlock, rt_mutex_slowlock);
846 }
847 EXPORT_SYMBOL_GPL(rt_mutex_lock_interruptible);
848
849 /**
850  * rt_mutex_lock_interruptible_ktime - lock a rt_mutex interruptible
851  *                                     the timeout structure is provided
852  *                                     by the caller
853  *
854  * @lock:               the rt_mutex to be locked
855  * @timeout:            timeout structure or NULL (no timeout)
856  * @detect_deadlock:    deadlock detection on/off
857  *
858  * Returns:
859  *  0           on success
860  * -EINTR       when interrupted by a signal
861  * -ETIMEOUT    when the timeout expired
862  * -EDEADLK     when the lock would deadlock (when deadlock detection is on)
863  */
864 int
865 rt_mutex_timed_lock(struct rt_mutex *lock, struct hrtimer_sleeper *timeout,
866                     int detect_deadlock)
867 {
868         might_sleep();
869
870         return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout,
871                                        detect_deadlock, rt_mutex_slowlock);
872 }
873 EXPORT_SYMBOL_GPL(rt_mutex_timed_lock);
874
875 /**
876  * rt_mutex_trylock - try to lock a rt_mutex
877  *
878  * @lock:       the rt_mutex to be locked
879  *
880  * Returns 1 on success and 0 on contention
881  */
882 int __sched rt_mutex_trylock(struct rt_mutex *lock)
883 {
884         return rt_mutex_fasttrylock(lock, rt_mutex_slowtrylock);
885 }
886 EXPORT_SYMBOL_GPL(rt_mutex_trylock);
887
888 /**
889  * rt_mutex_unlock - unlock a rt_mutex
890  *
891  * @lock: the rt_mutex to be unlocked
892  */
893 void __sched rt_mutex_unlock(struct rt_mutex *lock)
894 {
895         rt_mutex_fastunlock(lock, rt_mutex_slowunlock);
896 }
897 EXPORT_SYMBOL_GPL(rt_mutex_unlock);
898
899 /***
900  * rt_mutex_destroy - mark a mutex unusable
901  * @lock: the mutex to be destroyed
902  *
903  * This function marks the mutex uninitialized, and any subsequent
904  * use of the mutex is forbidden. The mutex must not be locked when
905  * this function is called.
906  */
907 void rt_mutex_destroy(struct rt_mutex *lock)
908 {
909         WARN_ON(rt_mutex_is_locked(lock));
910 #ifdef CONFIG_DEBUG_RT_MUTEXES
911         lock->magic = NULL;
912 #endif
913 }
914
915 EXPORT_SYMBOL_GPL(rt_mutex_destroy);
916
917 /**
918  * __rt_mutex_init - initialize the rt lock
919  *
920  * @lock: the rt lock to be initialized
921  *
922  * Initialize the rt lock to unlocked state.
923  *
924  * Initializing of a locked rt lock is not allowed
925  */
926 void __rt_mutex_init(struct rt_mutex *lock, const char *name)
927 {
928         lock->owner = NULL;
929         spin_lock_init(&lock->wait_lock);
930         plist_head_init(&lock->wait_list, &lock->wait_lock);
931
932         debug_rt_mutex_init(lock, name);
933 }
934 EXPORT_SYMBOL_GPL(__rt_mutex_init);
935
936 /**
937  * rt_mutex_init_proxy_locked - initialize and lock a rt_mutex on behalf of a
938  *                              proxy owner
939  *
940  * @lock:       the rt_mutex to be locked
941  * @proxy_owner:the task to set as owner
942  *
943  * No locking. Caller has to do serializing itself
944  * Special API call for PI-futex support
945  */
946 void rt_mutex_init_proxy_locked(struct rt_mutex *lock,
947                                 struct task_struct *proxy_owner)
948 {
949         __rt_mutex_init(lock, NULL);
950         debug_rt_mutex_proxy_lock(lock, proxy_owner);
951         rt_mutex_set_owner(lock, proxy_owner, 0);
952         rt_mutex_deadlock_account_lock(lock, proxy_owner);
953 }
954
955 /**
956  * rt_mutex_proxy_unlock - release a lock on behalf of owner
957  *
958  * @lock:       the rt_mutex to be locked
959  *
960  * No locking. Caller has to do serializing itself
961  * Special API call for PI-futex support
962  */
963 void rt_mutex_proxy_unlock(struct rt_mutex *lock,
964                            struct task_struct *proxy_owner)
965 {
966         debug_rt_mutex_proxy_unlock(lock);
967         rt_mutex_set_owner(lock, NULL, 0);
968         rt_mutex_deadlock_account_unlock(proxy_owner);
969 }
970
971 /**
972  * rt_mutex_next_owner - return the next owner of the lock
973  *
974  * @lock: the rt lock query
975  *
976  * Returns the next owner of the lock or NULL
977  *
978  * Caller has to serialize against other accessors to the lock
979  * itself.
980  *
981  * Special API call for PI-futex support
982  */
983 struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock)
984 {
985         if (!rt_mutex_has_waiters(lock))
986                 return NULL;
987
988         return rt_mutex_top_waiter(lock)->task;
989 }