Line data Source code
1 : // SPDX-License-Identifier: GPL-2.0-only
2 : /*
3 : * RT-Mutexes: simple blocking mutual exclusion locks with PI support
4 : *
5 : * started by Ingo Molnar and Thomas Gleixner.
6 : *
7 : * Copyright (C) 2004-2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
8 : * Copyright (C) 2005-2006 Timesys Corp., Thomas Gleixner <tglx@timesys.com>
9 : * Copyright (C) 2005 Kihon Technologies Inc., Steven Rostedt
10 : * Copyright (C) 2006 Esben Nielsen
11 : *
12 : * See Documentation/locking/rt-mutex-design.rst for details.
13 : */
14 : #include <linux/spinlock.h>
15 : #include <linux/export.h>
16 : #include <linux/sched/signal.h>
17 : #include <linux/sched/rt.h>
18 : #include <linux/sched/deadline.h>
19 : #include <linux/sched/wake_q.h>
20 : #include <linux/sched/debug.h>
21 : #include <linux/timer.h>
22 :
23 : #include "rtmutex_common.h"
24 :
25 : /*
26 : * lock->owner state tracking:
27 : *
28 : * lock->owner holds the task_struct pointer of the owner. Bit 0
29 : * is used to keep track of the "lock has waiters" state.
30 : *
31 : * owner bit0
32 : * NULL 0 lock is free (fast acquire possible)
33 : * NULL 1 lock is free and has waiters and the top waiter
34 : * is going to take the lock*
35 : * taskpointer 0 lock is held (fast release possible)
36 : * taskpointer 1 lock is held and has waiters**
37 : *
38 : * The fast atomic compare exchange based acquire and release is only
39 : * possible when bit 0 of lock->owner is 0.
40 : *
41 : * (*) It also can be a transitional state when grabbing the lock
42 : * with ->wait_lock is held. To prevent any fast path cmpxchg to the lock,
43 : * we need to set the bit0 before looking at the lock, and the owner may be
44 : * NULL in this small time, hence this can be a transitional state.
45 : *
46 : * (**) There is a small time when bit 0 is set but there are no
47 : * waiters. This can happen when grabbing the lock in the slow path.
48 : * To prevent a cmpxchg of the owner releasing the lock, we need to
49 : * set this bit before looking at the lock.
50 : */
51 :
52 : static void
53 0 : rt_mutex_set_owner(struct rt_mutex *lock, struct task_struct *owner)
54 : {
55 0 : unsigned long val = (unsigned long)owner;
56 :
57 0 : if (rt_mutex_has_waiters(lock))
58 0 : val |= RT_MUTEX_HAS_WAITERS;
59 :
60 0 : WRITE_ONCE(lock->owner, (struct task_struct *)val);
61 : }
62 :
63 : static inline void clear_rt_mutex_waiters(struct rt_mutex *lock)
64 : {
65 : lock->owner = (struct task_struct *)
66 : ((unsigned long)lock->owner & ~RT_MUTEX_HAS_WAITERS);
67 : }
68 :
69 0 : static void fixup_rt_mutex_waiters(struct rt_mutex *lock)
70 : {
71 0 : unsigned long owner, *p = (unsigned long *) &lock->owner;
72 :
73 0 : if (rt_mutex_has_waiters(lock))
74 : return;
75 :
76 : /*
77 : * The rbtree has no waiters enqueued, now make sure that the
78 : * lock->owner still has the waiters bit set, otherwise the
79 : * following can happen:
80 : *
81 : * CPU 0 CPU 1 CPU2
82 : * l->owner=T1
83 : * rt_mutex_lock(l)
84 : * lock(l->lock)
85 : * l->owner = T1 | HAS_WAITERS;
86 : * enqueue(T2)
87 : * boost()
88 : * unlock(l->lock)
89 : * block()
90 : *
91 : * rt_mutex_lock(l)
92 : * lock(l->lock)
93 : * l->owner = T1 | HAS_WAITERS;
94 : * enqueue(T3)
95 : * boost()
96 : * unlock(l->lock)
97 : * block()
98 : * signal(->T2) signal(->T3)
99 : * lock(l->lock)
100 : * dequeue(T2)
101 : * deboost()
102 : * unlock(l->lock)
103 : * lock(l->lock)
104 : * dequeue(T3)
105 : * ==> wait list is empty
106 : * deboost()
107 : * unlock(l->lock)
108 : * lock(l->lock)
109 : * fixup_rt_mutex_waiters()
110 : * if (wait_list_empty(l) {
111 : * l->owner = owner
112 : * owner = l->owner & ~HAS_WAITERS;
113 : * ==> l->owner = T1
114 : * }
115 : * lock(l->lock)
116 : * rt_mutex_unlock(l) fixup_rt_mutex_waiters()
117 : * if (wait_list_empty(l) {
118 : * owner = l->owner & ~HAS_WAITERS;
119 : * cmpxchg(l->owner, T1, NULL)
120 : * ===> Success (l->owner = NULL)
121 : *
122 : * l->owner = owner
123 : * ==> l->owner = T1
124 : * }
125 : *
126 : * With the check for the waiter bit in place T3 on CPU2 will not
127 : * overwrite. All tasks fiddling with the waiters bit are
128 : * serialized by l->lock, so nothing else can modify the waiters
129 : * bit. If the bit is set then nothing can change l->owner either
130 : * so the simple RMW is safe. The cmpxchg() will simply fail if it
131 : * happens in the middle of the RMW because the waiters bit is
132 : * still set.
133 : */
134 0 : owner = READ_ONCE(*p);
135 0 : if (owner & RT_MUTEX_HAS_WAITERS)
136 0 : WRITE_ONCE(*p, owner & ~RT_MUTEX_HAS_WAITERS);
137 : }
138 :
139 : /*
140 : * We can speed up the acquire/release, if there's no debugging state to be
141 : * set up.
142 : */
143 : #ifndef CONFIG_DEBUG_RT_MUTEXES
144 : # define rt_mutex_cmpxchg_acquire(l,c,n) (cmpxchg_acquire(&l->owner, c, n) == c)
145 : # define rt_mutex_cmpxchg_release(l,c,n) (cmpxchg_release(&l->owner, c, n) == c)
146 :
147 : /*
148 : * Callers must hold the ->wait_lock -- which is the whole purpose as we force
149 : * all future threads that attempt to [Rmw] the lock to the slowpath. As such
150 : * relaxed semantics suffice.
151 : */
152 : static inline void mark_rt_mutex_waiters(struct rt_mutex *lock)
153 : {
154 : unsigned long owner, *p = (unsigned long *) &lock->owner;
155 :
156 : do {
157 : owner = *p;
158 : } while (cmpxchg_relaxed(p, owner,
159 : owner | RT_MUTEX_HAS_WAITERS) != owner);
160 : }
161 :
162 : /*
163 : * Safe fastpath aware unlock:
164 : * 1) Clear the waiters bit
165 : * 2) Drop lock->wait_lock
166 : * 3) Try to unlock the lock with cmpxchg
167 : */
168 : static inline bool unlock_rt_mutex_safe(struct rt_mutex *lock,
169 : unsigned long flags)
170 : __releases(lock->wait_lock)
171 : {
172 : struct task_struct *owner = rt_mutex_owner(lock);
173 :
174 : clear_rt_mutex_waiters(lock);
175 : raw_spin_unlock_irqrestore(&lock->wait_lock, flags);
176 : /*
177 : * If a new waiter comes in between the unlock and the cmpxchg
178 : * we have two situations:
179 : *
180 : * unlock(wait_lock);
181 : * lock(wait_lock);
182 : * cmpxchg(p, owner, 0) == owner
183 : * mark_rt_mutex_waiters(lock);
184 : * acquire(lock);
185 : * or:
186 : *
187 : * unlock(wait_lock);
188 : * lock(wait_lock);
189 : * mark_rt_mutex_waiters(lock);
190 : *
191 : * cmpxchg(p, owner, 0) != owner
192 : * enqueue_waiter();
193 : * unlock(wait_lock);
194 : * lock(wait_lock);
195 : * wake waiter();
196 : * unlock(wait_lock);
197 : * lock(wait_lock);
198 : * acquire(lock);
199 : */
200 : return rt_mutex_cmpxchg_release(lock, owner, NULL);
201 : }
202 :
203 : #else
204 : # define rt_mutex_cmpxchg_acquire(l,c,n) (0)
205 : # define rt_mutex_cmpxchg_release(l,c,n) (0)
206 :
207 0 : static inline void mark_rt_mutex_waiters(struct rt_mutex *lock)
208 : {
209 0 : lock->owner = (struct task_struct *)
210 0 : ((unsigned long)lock->owner | RT_MUTEX_HAS_WAITERS);
211 : }
212 :
213 : /*
214 : * Simple slow path only version: lock->owner is protected by lock->wait_lock.
215 : */
216 0 : static inline bool unlock_rt_mutex_safe(struct rt_mutex *lock,
217 : unsigned long flags)
218 : __releases(lock->wait_lock)
219 : {
220 0 : lock->owner = NULL;
221 0 : raw_spin_unlock_irqrestore(&lock->wait_lock, flags);
222 0 : return true;
223 : }
224 : #endif
225 :
226 : /*
227 : * Only use with rt_mutex_waiter_{less,equal}()
228 : */
229 : #define task_to_waiter(p) \
230 : &(struct rt_mutex_waiter){ .prio = (p)->prio, .deadline = (p)->dl.deadline }
231 :
232 : static inline int
233 0 : rt_mutex_waiter_less(struct rt_mutex_waiter *left,
234 : struct rt_mutex_waiter *right)
235 : {
236 0 : if (left->prio < right->prio)
237 : return 1;
238 :
239 : /*
240 : * If both waiters have dl_prio(), we check the deadlines of the
241 : * associated tasks.
242 : * If left waiter has a dl_prio(), and we didn't return 1 above,
243 : * then right waiter has a dl_prio() too.
244 : */
245 0 : if (dl_prio(left->prio))
246 0 : return dl_time_before(left->deadline, right->deadline);
247 :
248 : return 0;
249 : }
250 :
251 : static inline int
252 0 : rt_mutex_waiter_equal(struct rt_mutex_waiter *left,
253 : struct rt_mutex_waiter *right)
254 : {
255 0 : if (left->prio != right->prio)
256 : return 0;
257 :
258 : /*
259 : * If both waiters have dl_prio(), we check the deadlines of the
260 : * associated tasks.
261 : * If left waiter has a dl_prio(), and we didn't return 0 above,
262 : * then right waiter has a dl_prio() too.
263 : */
264 0 : if (dl_prio(left->prio))
265 0 : return left->deadline == right->deadline;
266 :
267 : return 1;
268 : }
269 :
270 : #define __node_2_waiter(node) \
271 : rb_entry((node), struct rt_mutex_waiter, tree_entry)
272 :
273 0 : static inline bool __waiter_less(struct rb_node *a, const struct rb_node *b)
274 : {
275 0 : return rt_mutex_waiter_less(__node_2_waiter(a), __node_2_waiter(b));
276 : }
277 :
278 : static void
279 0 : rt_mutex_enqueue(struct rt_mutex *lock, struct rt_mutex_waiter *waiter)
280 : {
281 0 : rb_add_cached(&waiter->tree_entry, &lock->waiters, __waiter_less);
282 0 : }
283 :
284 : static void
285 0 : rt_mutex_dequeue(struct rt_mutex *lock, struct rt_mutex_waiter *waiter)
286 : {
287 0 : if (RB_EMPTY_NODE(&waiter->tree_entry))
288 : return;
289 :
290 0 : rb_erase_cached(&waiter->tree_entry, &lock->waiters);
291 0 : RB_CLEAR_NODE(&waiter->tree_entry);
292 : }
293 :
294 : #define __node_2_pi_waiter(node) \
295 : rb_entry((node), struct rt_mutex_waiter, pi_tree_entry)
296 :
297 0 : static inline bool __pi_waiter_less(struct rb_node *a, const struct rb_node *b)
298 : {
299 0 : return rt_mutex_waiter_less(__node_2_pi_waiter(a), __node_2_pi_waiter(b));
300 : }
301 :
302 : static void
303 0 : rt_mutex_enqueue_pi(struct task_struct *task, struct rt_mutex_waiter *waiter)
304 : {
305 0 : rb_add_cached(&waiter->pi_tree_entry, &task->pi_waiters, __pi_waiter_less);
306 0 : }
307 :
308 : static void
309 0 : rt_mutex_dequeue_pi(struct task_struct *task, struct rt_mutex_waiter *waiter)
310 : {
311 0 : if (RB_EMPTY_NODE(&waiter->pi_tree_entry))
312 : return;
313 :
314 0 : rb_erase_cached(&waiter->pi_tree_entry, &task->pi_waiters);
315 0 : RB_CLEAR_NODE(&waiter->pi_tree_entry);
316 : }
317 :
318 0 : static void rt_mutex_adjust_prio(struct task_struct *p)
319 : {
320 0 : struct task_struct *pi_task = NULL;
321 :
322 0 : lockdep_assert_held(&p->pi_lock);
323 :
324 0 : if (task_has_pi_waiters(p))
325 0 : pi_task = task_top_pi_waiter(p)->task;
326 :
327 0 : rt_mutex_setprio(p, pi_task);
328 0 : }
329 :
330 : /*
331 : * Deadlock detection is conditional:
332 : *
333 : * If CONFIG_DEBUG_RT_MUTEXES=n, deadlock detection is only conducted
334 : * if the detect argument is == RT_MUTEX_FULL_CHAINWALK.
335 : *
336 : * If CONFIG_DEBUG_RT_MUTEXES=y, deadlock detection is always
337 : * conducted independent of the detect argument.
338 : *
339 : * If the waiter argument is NULL this indicates the deboost path and
340 : * deadlock detection is disabled independent of the detect argument
341 : * and the config settings.
342 : */
343 0 : static bool rt_mutex_cond_detect_deadlock(struct rt_mutex_waiter *waiter,
344 : enum rtmutex_chainwalk chwalk)
345 : {
346 : /*
347 : * This is just a wrapper function for the following call,
348 : * because debug_rt_mutex_detect_deadlock() smells like a magic
349 : * debug feature and I wanted to keep the cond function in the
350 : * main source file along with the comments instead of having
351 : * two of the same in the headers.
352 : */
353 0 : return debug_rt_mutex_detect_deadlock(waiter, chwalk);
354 : }
355 :
356 : /*
357 : * Max number of times we'll walk the boosting chain:
358 : */
359 : int max_lock_depth = 1024;
360 :
361 0 : static inline struct rt_mutex *task_blocked_on_lock(struct task_struct *p)
362 : {
363 0 : return p->pi_blocked_on ? p->pi_blocked_on->lock : NULL;
364 : }
365 :
366 : /*
367 : * Adjust the priority chain. Also used for deadlock detection.
368 : * Decreases task's usage by one - may thus free the task.
369 : *
370 : * @task: the task owning the mutex (owner) for which a chain walk is
371 : * probably needed
372 : * @chwalk: do we have to carry out deadlock detection?
373 : * @orig_lock: the mutex (can be NULL if we are walking the chain to recheck
374 : * things for a task that has just got its priority adjusted, and
375 : * is waiting on a mutex)
376 : * @next_lock: the mutex on which the owner of @orig_lock was blocked before
377 : * we dropped its pi_lock. Is never dereferenced, only used for
378 : * comparison to detect lock chain changes.
379 : * @orig_waiter: rt_mutex_waiter struct for the task that has just donated
380 : * its priority to the mutex owner (can be NULL in the case
381 : * depicted above or if the top waiter is gone away and we are
382 : * actually deboosting the owner)
383 : * @top_task: the current top waiter
384 : *
385 : * Returns 0 or -EDEADLK.
386 : *
387 : * Chain walk basics and protection scope
388 : *
389 : * [R] refcount on task
390 : * [P] task->pi_lock held
391 : * [L] rtmutex->wait_lock held
392 : *
393 : * Step Description Protected by
394 : * function arguments:
395 : * @task [R]
396 : * @orig_lock if != NULL @top_task is blocked on it
397 : * @next_lock Unprotected. Cannot be
398 : * dereferenced. Only used for
399 : * comparison.
400 : * @orig_waiter if != NULL @top_task is blocked on it
401 : * @top_task current, or in case of proxy
402 : * locking protected by calling
403 : * code
404 : * again:
405 : * loop_sanity_check();
406 : * retry:
407 : * [1] lock(task->pi_lock); [R] acquire [P]
408 : * [2] waiter = task->pi_blocked_on; [P]
409 : * [3] check_exit_conditions_1(); [P]
410 : * [4] lock = waiter->lock; [P]
411 : * [5] if (!try_lock(lock->wait_lock)) { [P] try to acquire [L]
412 : * unlock(task->pi_lock); release [P]
413 : * goto retry;
414 : * }
415 : * [6] check_exit_conditions_2(); [P] + [L]
416 : * [7] requeue_lock_waiter(lock, waiter); [P] + [L]
417 : * [8] unlock(task->pi_lock); release [P]
418 : * put_task_struct(task); release [R]
419 : * [9] check_exit_conditions_3(); [L]
420 : * [10] task = owner(lock); [L]
421 : * get_task_struct(task); [L] acquire [R]
422 : * lock(task->pi_lock); [L] acquire [P]
423 : * [11] requeue_pi_waiter(tsk, waiters(lock));[P] + [L]
424 : * [12] check_exit_conditions_4(); [P] + [L]
425 : * [13] unlock(task->pi_lock); release [P]
426 : * unlock(lock->wait_lock); release [L]
427 : * goto again;
428 : */
429 0 : static int rt_mutex_adjust_prio_chain(struct task_struct *task,
430 : enum rtmutex_chainwalk chwalk,
431 : struct rt_mutex *orig_lock,
432 : struct rt_mutex *next_lock,
433 : struct rt_mutex_waiter *orig_waiter,
434 : struct task_struct *top_task)
435 : {
436 0 : struct rt_mutex_waiter *waiter, *top_waiter = orig_waiter;
437 0 : struct rt_mutex_waiter *prerequeue_top_waiter;
438 0 : int ret = 0, depth = 0;
439 0 : struct rt_mutex *lock;
440 0 : bool detect_deadlock;
441 0 : bool requeue = true;
442 :
443 0 : detect_deadlock = rt_mutex_cond_detect_deadlock(orig_waiter, chwalk);
444 :
445 : /*
446 : * The (de)boosting is a step by step approach with a lot of
447 : * pitfalls. We want this to be preemptible and we want hold a
448 : * maximum of two locks per step. So we have to check
449 : * carefully whether things change under us.
450 : */
451 : again:
452 : /*
453 : * We limit the lock chain length for each invocation.
454 : */
455 0 : if (++depth > max_lock_depth) {
456 0 : static int prev_max;
457 :
458 : /*
459 : * Print this only once. If the admin changes the limit,
460 : * print a new message when reaching the limit again.
461 : */
462 0 : if (prev_max != max_lock_depth) {
463 0 : prev_max = max_lock_depth;
464 0 : printk(KERN_WARNING "Maximum lock depth %d reached "
465 : "task: %s (%d)\n", max_lock_depth,
466 0 : top_task->comm, task_pid_nr(top_task));
467 : }
468 0 : put_task_struct(task);
469 :
470 0 : return -EDEADLK;
471 : }
472 :
473 : /*
474 : * We are fully preemptible here and only hold the refcount on
475 : * @task. So everything can have changed under us since the
476 : * caller or our own code below (goto retry/again) dropped all
477 : * locks.
478 : */
479 0 : retry:
480 : /*
481 : * [1] Task cannot go away as we did a get_task() before !
482 : */
483 0 : raw_spin_lock_irq(&task->pi_lock);
484 :
485 : /*
486 : * [2] Get the waiter on which @task is blocked on.
487 : */
488 0 : waiter = task->pi_blocked_on;
489 :
490 : /*
491 : * [3] check_exit_conditions_1() protected by task->pi_lock.
492 : */
493 :
494 : /*
495 : * Check whether the end of the boosting chain has been
496 : * reached or the state of the chain has changed while we
497 : * dropped the locks.
498 : */
499 0 : if (!waiter)
500 0 : goto out_unlock_pi;
501 :
502 : /*
503 : * Check the orig_waiter state. After we dropped the locks,
504 : * the previous owner of the lock might have released the lock.
505 : */
506 0 : if (orig_waiter && !rt_mutex_owner(orig_lock))
507 0 : goto out_unlock_pi;
508 :
509 : /*
510 : * We dropped all locks after taking a refcount on @task, so
511 : * the task might have moved on in the lock chain or even left
512 : * the chain completely and blocks now on an unrelated lock or
513 : * on @orig_lock.
514 : *
515 : * We stored the lock on which @task was blocked in @next_lock,
516 : * so we can detect the chain change.
517 : */
518 0 : if (next_lock != waiter->lock)
519 0 : goto out_unlock_pi;
520 :
521 : /*
522 : * Drop out, when the task has no waiters. Note,
523 : * top_waiter can be NULL, when we are in the deboosting
524 : * mode!
525 : */
526 0 : if (top_waiter) {
527 0 : if (!task_has_pi_waiters(task))
528 0 : goto out_unlock_pi;
529 : /*
530 : * If deadlock detection is off, we stop here if we
531 : * are not the top pi waiter of the task. If deadlock
532 : * detection is enabled we continue, but stop the
533 : * requeueing in the chain walk.
534 : */
535 0 : if (top_waiter != task_top_pi_waiter(task)) {
536 0 : if (!detect_deadlock)
537 0 : goto out_unlock_pi;
538 : else
539 : requeue = false;
540 : }
541 : }
542 :
543 : /*
544 : * If the waiter priority is the same as the task priority
545 : * then there is no further priority adjustment necessary. If
546 : * deadlock detection is off, we stop the chain walk. If its
547 : * enabled we continue, but stop the requeueing in the chain
548 : * walk.
549 : */
550 0 : if (rt_mutex_waiter_equal(waiter, task_to_waiter(task))) {
551 0 : if (!detect_deadlock)
552 0 : goto out_unlock_pi;
553 : else
554 : requeue = false;
555 : }
556 :
557 : /*
558 : * [4] Get the next lock
559 : */
560 0 : lock = waiter->lock;
561 : /*
562 : * [5] We need to trylock here as we are holding task->pi_lock,
563 : * which is the reverse lock order versus the other rtmutex
564 : * operations.
565 : */
566 0 : if (!raw_spin_trylock(&lock->wait_lock)) {
567 0 : raw_spin_unlock_irq(&task->pi_lock);
568 0 : cpu_relax();
569 0 : goto retry;
570 : }
571 :
572 : /*
573 : * [6] check_exit_conditions_2() protected by task->pi_lock and
574 : * lock->wait_lock.
575 : *
576 : * Deadlock detection. If the lock is the same as the original
577 : * lock which caused us to walk the lock chain or if the
578 : * current lock is owned by the task which initiated the chain
579 : * walk, we detected a deadlock.
580 : */
581 0 : if (lock == orig_lock || rt_mutex_owner(lock) == top_task) {
582 0 : debug_rt_mutex_deadlock(chwalk, orig_waiter, lock);
583 0 : raw_spin_unlock(&lock->wait_lock);
584 0 : ret = -EDEADLK;
585 0 : goto out_unlock_pi;
586 : }
587 :
588 : /*
589 : * If we just follow the lock chain for deadlock detection, no
590 : * need to do all the requeue operations. To avoid a truckload
591 : * of conditionals around the various places below, just do the
592 : * minimum chain walk checks.
593 : */
594 0 : if (!requeue) {
595 : /*
596 : * No requeue[7] here. Just release @task [8]
597 : */
598 0 : raw_spin_unlock(&task->pi_lock);
599 0 : put_task_struct(task);
600 :
601 : /*
602 : * [9] check_exit_conditions_3 protected by lock->wait_lock.
603 : * If there is no owner of the lock, end of chain.
604 : */
605 0 : if (!rt_mutex_owner(lock)) {
606 0 : raw_spin_unlock_irq(&lock->wait_lock);
607 0 : return 0;
608 : }
609 :
610 : /* [10] Grab the next task, i.e. owner of @lock */
611 0 : task = get_task_struct(rt_mutex_owner(lock));
612 0 : raw_spin_lock(&task->pi_lock);
613 :
614 : /*
615 : * No requeue [11] here. We just do deadlock detection.
616 : *
617 : * [12] Store whether owner is blocked
618 : * itself. Decision is made after dropping the locks
619 : */
620 0 : next_lock = task_blocked_on_lock(task);
621 : /*
622 : * Get the top waiter for the next iteration
623 : */
624 0 : top_waiter = rt_mutex_top_waiter(lock);
625 :
626 : /* [13] Drop locks */
627 0 : raw_spin_unlock(&task->pi_lock);
628 0 : raw_spin_unlock_irq(&lock->wait_lock);
629 :
630 : /* If owner is not blocked, end of chain. */
631 0 : if (!next_lock)
632 0 : goto out_put_task;
633 0 : goto again;
634 : }
635 :
636 : /*
637 : * Store the current top waiter before doing the requeue
638 : * operation on @lock. We need it for the boost/deboost
639 : * decision below.
640 : */
641 0 : prerequeue_top_waiter = rt_mutex_top_waiter(lock);
642 :
643 : /* [7] Requeue the waiter in the lock waiter tree. */
644 0 : rt_mutex_dequeue(lock, waiter);
645 :
646 : /*
647 : * Update the waiter prio fields now that we're dequeued.
648 : *
649 : * These values can have changed through either:
650 : *
651 : * sys_sched_set_scheduler() / sys_sched_setattr()
652 : *
653 : * or
654 : *
655 : * DL CBS enforcement advancing the effective deadline.
656 : *
657 : * Even though pi_waiters also uses these fields, and that tree is only
658 : * updated in [11], we can do this here, since we hold [L], which
659 : * serializes all pi_waiters access and rb_erase() does not care about
660 : * the values of the node being removed.
661 : */
662 0 : waiter->prio = task->prio;
663 0 : waiter->deadline = task->dl.deadline;
664 :
665 0 : rt_mutex_enqueue(lock, waiter);
666 :
667 : /* [8] Release the task */
668 0 : raw_spin_unlock(&task->pi_lock);
669 0 : put_task_struct(task);
670 :
671 : /*
672 : * [9] check_exit_conditions_3 protected by lock->wait_lock.
673 : *
674 : * We must abort the chain walk if there is no lock owner even
675 : * in the dead lock detection case, as we have nothing to
676 : * follow here. This is the end of the chain we are walking.
677 : */
678 0 : if (!rt_mutex_owner(lock)) {
679 : /*
680 : * If the requeue [7] above changed the top waiter,
681 : * then we need to wake the new top waiter up to try
682 : * to get the lock.
683 : */
684 0 : if (prerequeue_top_waiter != rt_mutex_top_waiter(lock))
685 0 : wake_up_process(rt_mutex_top_waiter(lock)->task);
686 0 : raw_spin_unlock_irq(&lock->wait_lock);
687 0 : return 0;
688 : }
689 :
690 : /* [10] Grab the next task, i.e. the owner of @lock */
691 0 : task = get_task_struct(rt_mutex_owner(lock));
692 0 : raw_spin_lock(&task->pi_lock);
693 :
694 : /* [11] requeue the pi waiters if necessary */
695 0 : if (waiter == rt_mutex_top_waiter(lock)) {
696 : /*
697 : * The waiter became the new top (highest priority)
698 : * waiter on the lock. Replace the previous top waiter
699 : * in the owner tasks pi waiters tree with this waiter
700 : * and adjust the priority of the owner.
701 : */
702 0 : rt_mutex_dequeue_pi(task, prerequeue_top_waiter);
703 0 : rt_mutex_enqueue_pi(task, waiter);
704 0 : rt_mutex_adjust_prio(task);
705 :
706 0 : } else if (prerequeue_top_waiter == waiter) {
707 : /*
708 : * The waiter was the top waiter on the lock, but is
709 : * no longer the top prority waiter. Replace waiter in
710 : * the owner tasks pi waiters tree with the new top
711 : * (highest priority) waiter and adjust the priority
712 : * of the owner.
713 : * The new top waiter is stored in @waiter so that
714 : * @waiter == @top_waiter evaluates to true below and
715 : * we continue to deboost the rest of the chain.
716 : */
717 0 : rt_mutex_dequeue_pi(task, waiter);
718 0 : waiter = rt_mutex_top_waiter(lock);
719 0 : rt_mutex_enqueue_pi(task, waiter);
720 0 : rt_mutex_adjust_prio(task);
721 : } else {
722 : /*
723 : * Nothing changed. No need to do any priority
724 : * adjustment.
725 : */
726 0 : }
727 :
728 : /*
729 : * [12] check_exit_conditions_4() protected by task->pi_lock
730 : * and lock->wait_lock. The actual decisions are made after we
731 : * dropped the locks.
732 : *
733 : * Check whether the task which owns the current lock is pi
734 : * blocked itself. If yes we store a pointer to the lock for
735 : * the lock chain change detection above. After we dropped
736 : * task->pi_lock next_lock cannot be dereferenced anymore.
737 : */
738 0 : next_lock = task_blocked_on_lock(task);
739 : /*
740 : * Store the top waiter of @lock for the end of chain walk
741 : * decision below.
742 : */
743 0 : top_waiter = rt_mutex_top_waiter(lock);
744 :
745 : /* [13] Drop the locks */
746 0 : raw_spin_unlock(&task->pi_lock);
747 0 : raw_spin_unlock_irq(&lock->wait_lock);
748 :
749 : /*
750 : * Make the actual exit decisions [12], based on the stored
751 : * values.
752 : *
753 : * We reached the end of the lock chain. Stop right here. No
754 : * point to go back just to figure that out.
755 : */
756 0 : if (!next_lock)
757 0 : goto out_put_task;
758 :
759 : /*
760 : * If the current waiter is not the top waiter on the lock,
761 : * then we can stop the chain walk here if we are not in full
762 : * deadlock detection mode.
763 : */
764 0 : if (!detect_deadlock && waiter != top_waiter)
765 0 : goto out_put_task;
766 :
767 0 : goto again;
768 :
769 0 : out_unlock_pi:
770 0 : raw_spin_unlock_irq(&task->pi_lock);
771 0 : out_put_task:
772 0 : put_task_struct(task);
773 :
774 0 : return ret;
775 : }
776 :
777 : /*
778 : * Try to take an rt-mutex
779 : *
780 : * Must be called with lock->wait_lock held and interrupts disabled
781 : *
782 : * @lock: The lock to be acquired.
783 : * @task: The task which wants to acquire the lock
784 : * @waiter: The waiter that is queued to the lock's wait tree if the
785 : * callsite called task_blocked_on_lock(), otherwise NULL
786 : */
787 0 : static int try_to_take_rt_mutex(struct rt_mutex *lock, struct task_struct *task,
788 : struct rt_mutex_waiter *waiter)
789 : {
790 0 : lockdep_assert_held(&lock->wait_lock);
791 :
792 : /*
793 : * Before testing whether we can acquire @lock, we set the
794 : * RT_MUTEX_HAS_WAITERS bit in @lock->owner. This forces all
795 : * other tasks which try to modify @lock into the slow path
796 : * and they serialize on @lock->wait_lock.
797 : *
798 : * The RT_MUTEX_HAS_WAITERS bit can have a transitional state
799 : * as explained at the top of this file if and only if:
800 : *
801 : * - There is a lock owner. The caller must fixup the
802 : * transient state if it does a trylock or leaves the lock
803 : * function due to a signal or timeout.
804 : *
805 : * - @task acquires the lock and there are no other
806 : * waiters. This is undone in rt_mutex_set_owner(@task) at
807 : * the end of this function.
808 : */
809 0 : mark_rt_mutex_waiters(lock);
810 :
811 : /*
812 : * If @lock has an owner, give up.
813 : */
814 0 : if (rt_mutex_owner(lock))
815 : return 0;
816 :
817 : /*
818 : * If @waiter != NULL, @task has already enqueued the waiter
819 : * into @lock waiter tree. If @waiter == NULL then this is a
820 : * trylock attempt.
821 : */
822 0 : if (waiter) {
823 : /*
824 : * If waiter is not the highest priority waiter of
825 : * @lock, give up.
826 : */
827 0 : if (waiter != rt_mutex_top_waiter(lock))
828 : return 0;
829 :
830 : /*
831 : * We can acquire the lock. Remove the waiter from the
832 : * lock waiters tree.
833 : */
834 0 : rt_mutex_dequeue(lock, waiter);
835 :
836 : } else {
837 : /*
838 : * If the lock has waiters already we check whether @task is
839 : * eligible to take over the lock.
840 : *
841 : * If there are no other waiters, @task can acquire
842 : * the lock. @task->pi_blocked_on is NULL, so it does
843 : * not need to be dequeued.
844 : */
845 0 : if (rt_mutex_has_waiters(lock)) {
846 : /*
847 : * If @task->prio is greater than or equal to
848 : * the top waiter priority (kernel view),
849 : * @task lost.
850 : */
851 0 : if (!rt_mutex_waiter_less(task_to_waiter(task),
852 : rt_mutex_top_waiter(lock)))
853 : return 0;
854 :
855 : /*
856 : * The current top waiter stays enqueued. We
857 : * don't have to change anything in the lock
858 : * waiters order.
859 : */
860 : } else {
861 : /*
862 : * No waiters. Take the lock without the
863 : * pi_lock dance.@task->pi_blocked_on is NULL
864 : * and we have no waiters to enqueue in @task
865 : * pi waiters tree.
866 : */
867 0 : goto takeit;
868 : }
869 : }
870 :
871 : /*
872 : * Clear @task->pi_blocked_on. Requires protection by
873 : * @task->pi_lock. Redundant operation for the @waiter == NULL
874 : * case, but conditionals are more expensive than a redundant
875 : * store.
876 : */
877 0 : raw_spin_lock(&task->pi_lock);
878 0 : task->pi_blocked_on = NULL;
879 : /*
880 : * Finish the lock acquisition. @task is the new owner. If
881 : * other waiters exist we have to insert the highest priority
882 : * waiter into @task->pi_waiters tree.
883 : */
884 0 : if (rt_mutex_has_waiters(lock))
885 0 : rt_mutex_enqueue_pi(task, rt_mutex_top_waiter(lock));
886 0 : raw_spin_unlock(&task->pi_lock);
887 :
888 0 : takeit:
889 : /* We got the lock. */
890 0 : debug_rt_mutex_lock(lock);
891 :
892 : /*
893 : * This either preserves the RT_MUTEX_HAS_WAITERS bit if there
894 : * are still waiters or clears it.
895 : */
896 0 : rt_mutex_set_owner(lock, task);
897 :
898 0 : return 1;
899 : }
900 :
901 : /*
902 : * Task blocks on lock.
903 : *
904 : * Prepare waiter and propagate pi chain
905 : *
906 : * This must be called with lock->wait_lock held and interrupts disabled
907 : */
908 0 : static int task_blocks_on_rt_mutex(struct rt_mutex *lock,
909 : struct rt_mutex_waiter *waiter,
910 : struct task_struct *task,
911 : enum rtmutex_chainwalk chwalk)
912 : {
913 0 : struct task_struct *owner = rt_mutex_owner(lock);
914 0 : struct rt_mutex_waiter *top_waiter = waiter;
915 0 : struct rt_mutex *next_lock;
916 0 : int chain_walk = 0, res;
917 :
918 0 : lockdep_assert_held(&lock->wait_lock);
919 :
920 : /*
921 : * Early deadlock detection. We really don't want the task to
922 : * enqueue on itself just to untangle the mess later. It's not
923 : * only an optimization. We drop the locks, so another waiter
924 : * can come in before the chain walk detects the deadlock. So
925 : * the other will detect the deadlock and return -EDEADLOCK,
926 : * which is wrong, as the other waiter is not in a deadlock
927 : * situation.
928 : */
929 0 : if (owner == task)
930 : return -EDEADLK;
931 :
932 0 : raw_spin_lock(&task->pi_lock);
933 0 : waiter->task = task;
934 0 : waiter->lock = lock;
935 0 : waiter->prio = task->prio;
936 0 : waiter->deadline = task->dl.deadline;
937 :
938 : /* Get the top priority waiter on the lock */
939 0 : if (rt_mutex_has_waiters(lock))
940 0 : top_waiter = rt_mutex_top_waiter(lock);
941 0 : rt_mutex_enqueue(lock, waiter);
942 :
943 0 : task->pi_blocked_on = waiter;
944 :
945 0 : raw_spin_unlock(&task->pi_lock);
946 :
947 0 : if (!owner)
948 : return 0;
949 :
950 0 : raw_spin_lock(&owner->pi_lock);
951 0 : if (waiter == rt_mutex_top_waiter(lock)) {
952 0 : rt_mutex_dequeue_pi(owner, top_waiter);
953 0 : rt_mutex_enqueue_pi(owner, waiter);
954 :
955 0 : rt_mutex_adjust_prio(owner);
956 0 : if (owner->pi_blocked_on)
957 0 : chain_walk = 1;
958 0 : } else if (rt_mutex_cond_detect_deadlock(waiter, chwalk)) {
959 0 : chain_walk = 1;
960 : }
961 :
962 : /* Store the lock on which owner is blocked or NULL */
963 0 : next_lock = task_blocked_on_lock(owner);
964 :
965 0 : raw_spin_unlock(&owner->pi_lock);
966 : /*
967 : * Even if full deadlock detection is on, if the owner is not
968 : * blocked itself, we can avoid finding this out in the chain
969 : * walk.
970 : */
971 0 : if (!chain_walk || !next_lock)
972 : return 0;
973 :
974 : /*
975 : * The owner can't disappear while holding a lock,
976 : * so the owner struct is protected by wait_lock.
977 : * Gets dropped in rt_mutex_adjust_prio_chain()!
978 : */
979 0 : get_task_struct(owner);
980 :
981 0 : raw_spin_unlock_irq(&lock->wait_lock);
982 :
983 0 : res = rt_mutex_adjust_prio_chain(owner, chwalk, lock,
984 : next_lock, waiter, task);
985 :
986 0 : raw_spin_lock_irq(&lock->wait_lock);
987 :
988 0 : return res;
989 : }
990 :
991 : /*
992 : * Remove the top waiter from the current tasks pi waiter tree and
993 : * queue it up.
994 : *
995 : * Called with lock->wait_lock held and interrupts disabled.
996 : */
997 0 : static void mark_wakeup_next_waiter(struct wake_q_head *wake_q,
998 : struct rt_mutex *lock)
999 : {
1000 0 : struct rt_mutex_waiter *waiter;
1001 :
1002 0 : raw_spin_lock(¤t->pi_lock);
1003 :
1004 0 : waiter = rt_mutex_top_waiter(lock);
1005 :
1006 : /*
1007 : * Remove it from current->pi_waiters and deboost.
1008 : *
1009 : * We must in fact deboost here in order to ensure we call
1010 : * rt_mutex_setprio() to update p->pi_top_task before the
1011 : * task unblocks.
1012 : */
1013 0 : rt_mutex_dequeue_pi(current, waiter);
1014 0 : rt_mutex_adjust_prio(current);
1015 :
1016 : /*
1017 : * As we are waking up the top waiter, and the waiter stays
1018 : * queued on the lock until it gets the lock, this lock
1019 : * obviously has waiters. Just set the bit here and this has
1020 : * the added benefit of forcing all new tasks into the
1021 : * slow path making sure no task of lower priority than
1022 : * the top waiter can steal this lock.
1023 : */
1024 0 : lock->owner = (void *) RT_MUTEX_HAS_WAITERS;
1025 :
1026 : /*
1027 : * We deboosted before waking the top waiter task such that we don't
1028 : * run two tasks with the 'same' priority (and ensure the
1029 : * p->pi_top_task pointer points to a blocked task). This however can
1030 : * lead to priority inversion if we would get preempted after the
1031 : * deboost but before waking our donor task, hence the preempt_disable()
1032 : * before unlock.
1033 : *
1034 : * Pairs with preempt_enable() in rt_mutex_postunlock();
1035 : */
1036 0 : preempt_disable();
1037 0 : wake_q_add(wake_q, waiter->task);
1038 0 : raw_spin_unlock(¤t->pi_lock);
1039 0 : }
1040 :
1041 : /*
1042 : * Remove a waiter from a lock and give up
1043 : *
1044 : * Must be called with lock->wait_lock held and interrupts disabled. I must
1045 : * have just failed to try_to_take_rt_mutex().
1046 : */
1047 0 : static void remove_waiter(struct rt_mutex *lock,
1048 : struct rt_mutex_waiter *waiter)
1049 : {
1050 0 : bool is_top_waiter = (waiter == rt_mutex_top_waiter(lock));
1051 0 : struct task_struct *owner = rt_mutex_owner(lock);
1052 0 : struct rt_mutex *next_lock;
1053 :
1054 0 : lockdep_assert_held(&lock->wait_lock);
1055 :
1056 0 : raw_spin_lock(¤t->pi_lock);
1057 0 : rt_mutex_dequeue(lock, waiter);
1058 0 : current->pi_blocked_on = NULL;
1059 0 : raw_spin_unlock(¤t->pi_lock);
1060 :
1061 : /*
1062 : * Only update priority if the waiter was the highest priority
1063 : * waiter of the lock and there is an owner to update.
1064 : */
1065 0 : if (!owner || !is_top_waiter)
1066 : return;
1067 :
1068 0 : raw_spin_lock(&owner->pi_lock);
1069 :
1070 0 : rt_mutex_dequeue_pi(owner, waiter);
1071 :
1072 0 : if (rt_mutex_has_waiters(lock))
1073 0 : rt_mutex_enqueue_pi(owner, rt_mutex_top_waiter(lock));
1074 :
1075 0 : rt_mutex_adjust_prio(owner);
1076 :
1077 : /* Store the lock on which owner is blocked or NULL */
1078 0 : next_lock = task_blocked_on_lock(owner);
1079 :
1080 0 : raw_spin_unlock(&owner->pi_lock);
1081 :
1082 : /*
1083 : * Don't walk the chain, if the owner task is not blocked
1084 : * itself.
1085 : */
1086 0 : if (!next_lock)
1087 : return;
1088 :
1089 : /* gets dropped in rt_mutex_adjust_prio_chain()! */
1090 0 : get_task_struct(owner);
1091 :
1092 0 : raw_spin_unlock_irq(&lock->wait_lock);
1093 :
1094 0 : rt_mutex_adjust_prio_chain(owner, RT_MUTEX_MIN_CHAINWALK, lock,
1095 : next_lock, NULL, current);
1096 :
1097 0 : raw_spin_lock_irq(&lock->wait_lock);
1098 : }
1099 :
1100 : /*
1101 : * Recheck the pi chain, in case we got a priority setting
1102 : *
1103 : * Called from sched_setscheduler
1104 : */
1105 4 : void rt_mutex_adjust_pi(struct task_struct *task)
1106 : {
1107 4 : struct rt_mutex_waiter *waiter;
1108 4 : struct rt_mutex *next_lock;
1109 4 : unsigned long flags;
1110 :
1111 4 : raw_spin_lock_irqsave(&task->pi_lock, flags);
1112 :
1113 4 : waiter = task->pi_blocked_on;
1114 4 : if (!waiter || rt_mutex_waiter_equal(waiter, task_to_waiter(task))) {
1115 4 : raw_spin_unlock_irqrestore(&task->pi_lock, flags);
1116 4 : return;
1117 : }
1118 0 : next_lock = waiter->lock;
1119 0 : raw_spin_unlock_irqrestore(&task->pi_lock, flags);
1120 :
1121 : /* gets dropped in rt_mutex_adjust_prio_chain()! */
1122 0 : get_task_struct(task);
1123 :
1124 0 : rt_mutex_adjust_prio_chain(task, RT_MUTEX_MIN_CHAINWALK, NULL,
1125 : next_lock, NULL, task);
1126 : }
1127 :
1128 0 : void rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
1129 : {
1130 0 : debug_rt_mutex_init_waiter(waiter);
1131 0 : RB_CLEAR_NODE(&waiter->pi_tree_entry);
1132 0 : RB_CLEAR_NODE(&waiter->tree_entry);
1133 0 : waiter->task = NULL;
1134 0 : }
1135 :
1136 : /**
1137 : * __rt_mutex_slowlock() - Perform the wait-wake-try-to-take loop
1138 : * @lock: the rt_mutex to take
1139 : * @state: the state the task should block in (TASK_INTERRUPTIBLE
1140 : * or TASK_UNINTERRUPTIBLE)
1141 : * @timeout: the pre-initialized and started timer, or NULL for none
1142 : * @waiter: the pre-initialized rt_mutex_waiter
1143 : *
1144 : * Must be called with lock->wait_lock held and interrupts disabled
1145 : */
1146 : static int __sched
1147 0 : __rt_mutex_slowlock(struct rt_mutex *lock, int state,
1148 : struct hrtimer_sleeper *timeout,
1149 : struct rt_mutex_waiter *waiter)
1150 : {
1151 0 : int ret = 0;
1152 :
1153 0 : for (;;) {
1154 : /* Try to acquire the lock: */
1155 0 : if (try_to_take_rt_mutex(lock, current, waiter))
1156 : break;
1157 :
1158 : /*
1159 : * TASK_INTERRUPTIBLE checks for signals and
1160 : * timeout. Ignored otherwise.
1161 : */
1162 0 : if (likely(state == TASK_INTERRUPTIBLE)) {
1163 : /* Signal pending? */
1164 0 : if (signal_pending(current))
1165 0 : ret = -EINTR;
1166 0 : if (timeout && !timeout->task)
1167 : ret = -ETIMEDOUT;
1168 0 : if (ret)
1169 : break;
1170 : }
1171 :
1172 0 : raw_spin_unlock_irq(&lock->wait_lock);
1173 :
1174 0 : debug_rt_mutex_print_deadlock(waiter);
1175 :
1176 0 : schedule();
1177 :
1178 0 : raw_spin_lock_irq(&lock->wait_lock);
1179 0 : set_current_state(state);
1180 : }
1181 :
1182 0 : __set_current_state(TASK_RUNNING);
1183 0 : return ret;
1184 : }
1185 :
1186 0 : static void rt_mutex_handle_deadlock(int res, int detect_deadlock,
1187 : struct rt_mutex_waiter *w)
1188 : {
1189 : /*
1190 : * If the result is not -EDEADLOCK or the caller requested
1191 : * deadlock detection, nothing to do here.
1192 : */
1193 0 : if (res != -EDEADLOCK || detect_deadlock)
1194 0 : return;
1195 :
1196 : /*
1197 : * Yell lowdly and stop the task right here.
1198 : */
1199 0 : rt_mutex_print_deadlock(w);
1200 0 : while (1) {
1201 0 : set_current_state(TASK_INTERRUPTIBLE);
1202 0 : schedule();
1203 : }
1204 : }
1205 :
1206 : /*
1207 : * Slow path lock function:
1208 : */
1209 : static int __sched
1210 0 : rt_mutex_slowlock(struct rt_mutex *lock, int state,
1211 : struct hrtimer_sleeper *timeout,
1212 : enum rtmutex_chainwalk chwalk)
1213 : {
1214 0 : struct rt_mutex_waiter waiter;
1215 0 : unsigned long flags;
1216 0 : int ret = 0;
1217 :
1218 0 : rt_mutex_init_waiter(&waiter);
1219 :
1220 : /*
1221 : * Technically we could use raw_spin_[un]lock_irq() here, but this can
1222 : * be called in early boot if the cmpxchg() fast path is disabled
1223 : * (debug, no architecture support). In this case we will acquire the
1224 : * rtmutex with lock->wait_lock held. But we cannot unconditionally
1225 : * enable interrupts in that early boot case. So we need to use the
1226 : * irqsave/restore variants.
1227 : */
1228 0 : raw_spin_lock_irqsave(&lock->wait_lock, flags);
1229 :
1230 : /* Try to acquire the lock again: */
1231 0 : if (try_to_take_rt_mutex(lock, current, NULL)) {
1232 0 : raw_spin_unlock_irqrestore(&lock->wait_lock, flags);
1233 0 : return 0;
1234 : }
1235 :
1236 0 : set_current_state(state);
1237 :
1238 : /* Setup the timer, when timeout != NULL */
1239 0 : if (unlikely(timeout))
1240 0 : hrtimer_start_expires(&timeout->timer, HRTIMER_MODE_ABS);
1241 :
1242 0 : ret = task_blocks_on_rt_mutex(lock, &waiter, current, chwalk);
1243 :
1244 0 : if (likely(!ret))
1245 : /* sleep on the mutex */
1246 0 : ret = __rt_mutex_slowlock(lock, state, timeout, &waiter);
1247 :
1248 0 : if (unlikely(ret)) {
1249 0 : __set_current_state(TASK_RUNNING);
1250 0 : remove_waiter(lock, &waiter);
1251 0 : rt_mutex_handle_deadlock(ret, chwalk, &waiter);
1252 : }
1253 :
1254 : /*
1255 : * try_to_take_rt_mutex() sets the waiter bit
1256 : * unconditionally. We might have to fix that up.
1257 : */
1258 0 : fixup_rt_mutex_waiters(lock);
1259 :
1260 0 : raw_spin_unlock_irqrestore(&lock->wait_lock, flags);
1261 :
1262 : /* Remove pending timer: */
1263 0 : if (unlikely(timeout))
1264 0 : hrtimer_cancel(&timeout->timer);
1265 :
1266 0 : debug_rt_mutex_free_waiter(&waiter);
1267 :
1268 0 : return ret;
1269 : }
1270 :
1271 0 : static inline int __rt_mutex_slowtrylock(struct rt_mutex *lock)
1272 : {
1273 0 : int ret = try_to_take_rt_mutex(lock, current, NULL);
1274 :
1275 : /*
1276 : * try_to_take_rt_mutex() sets the lock waiters bit
1277 : * unconditionally. Clean this up.
1278 : */
1279 0 : fixup_rt_mutex_waiters(lock);
1280 :
1281 0 : return ret;
1282 : }
1283 :
1284 : /*
1285 : * Slow path try-lock function:
1286 : */
1287 0 : static inline int rt_mutex_slowtrylock(struct rt_mutex *lock)
1288 : {
1289 0 : unsigned long flags;
1290 0 : int ret;
1291 :
1292 : /*
1293 : * If the lock already has an owner we fail to get the lock.
1294 : * This can be done without taking the @lock->wait_lock as
1295 : * it is only being read, and this is a trylock anyway.
1296 : */
1297 0 : if (rt_mutex_owner(lock))
1298 : return 0;
1299 :
1300 : /*
1301 : * The mutex has currently no owner. Lock the wait lock and try to
1302 : * acquire the lock. We use irqsave here to support early boot calls.
1303 : */
1304 0 : raw_spin_lock_irqsave(&lock->wait_lock, flags);
1305 :
1306 0 : ret = __rt_mutex_slowtrylock(lock);
1307 :
1308 0 : raw_spin_unlock_irqrestore(&lock->wait_lock, flags);
1309 :
1310 0 : return ret;
1311 : }
1312 :
1313 : /*
1314 : * Slow path to release a rt-mutex.
1315 : *
1316 : * Return whether the current task needs to call rt_mutex_postunlock().
1317 : */
1318 0 : static bool __sched rt_mutex_slowunlock(struct rt_mutex *lock,
1319 : struct wake_q_head *wake_q)
1320 : {
1321 0 : unsigned long flags;
1322 :
1323 : /* irqsave required to support early boot calls */
1324 0 : raw_spin_lock_irqsave(&lock->wait_lock, flags);
1325 :
1326 0 : debug_rt_mutex_unlock(lock);
1327 :
1328 : /*
1329 : * We must be careful here if the fast path is enabled. If we
1330 : * have no waiters queued we cannot set owner to NULL here
1331 : * because of:
1332 : *
1333 : * foo->lock->owner = NULL;
1334 : * rtmutex_lock(foo->lock); <- fast path
1335 : * free = atomic_dec_and_test(foo->refcnt);
1336 : * rtmutex_unlock(foo->lock); <- fast path
1337 : * if (free)
1338 : * kfree(foo);
1339 : * raw_spin_unlock(foo->lock->wait_lock);
1340 : *
1341 : * So for the fastpath enabled kernel:
1342 : *
1343 : * Nothing can set the waiters bit as long as we hold
1344 : * lock->wait_lock. So we do the following sequence:
1345 : *
1346 : * owner = rt_mutex_owner(lock);
1347 : * clear_rt_mutex_waiters(lock);
1348 : * raw_spin_unlock(&lock->wait_lock);
1349 : * if (cmpxchg(&lock->owner, owner, 0) == owner)
1350 : * return;
1351 : * goto retry;
1352 : *
1353 : * The fastpath disabled variant is simple as all access to
1354 : * lock->owner is serialized by lock->wait_lock:
1355 : *
1356 : * lock->owner = NULL;
1357 : * raw_spin_unlock(&lock->wait_lock);
1358 : */
1359 0 : while (!rt_mutex_has_waiters(lock)) {
1360 : /* Drops lock->wait_lock ! */
1361 0 : if (unlock_rt_mutex_safe(lock, flags) == true)
1362 0 : return false;
1363 : /* Relock the rtmutex and try again */
1364 0 : raw_spin_lock_irqsave(&lock->wait_lock, flags);
1365 : }
1366 :
1367 : /*
1368 : * The wakeup next waiter path does not suffer from the above
1369 : * race. See the comments there.
1370 : *
1371 : * Queue the next waiter for wakeup once we release the wait_lock.
1372 : */
1373 0 : mark_wakeup_next_waiter(wake_q, lock);
1374 0 : raw_spin_unlock_irqrestore(&lock->wait_lock, flags);
1375 :
1376 0 : return true; /* call rt_mutex_postunlock() */
1377 : }
1378 :
1379 : /*
1380 : * debug aware fast / slowpath lock,trylock,unlock
1381 : *
1382 : * The atomic acquire/release ops are compiled away, when either the
1383 : * architecture does not support cmpxchg or when debugging is enabled.
1384 : */
1385 : static inline int
1386 0 : rt_mutex_fastlock(struct rt_mutex *lock, int state,
1387 : int (*slowfn)(struct rt_mutex *lock, int state,
1388 : struct hrtimer_sleeper *timeout,
1389 : enum rtmutex_chainwalk chwalk))
1390 : {
1391 0 : if (likely(rt_mutex_cmpxchg_acquire(lock, NULL, current)))
1392 : return 0;
1393 :
1394 0 : return slowfn(lock, state, NULL, RT_MUTEX_MIN_CHAINWALK);
1395 : }
1396 :
1397 : static inline int
1398 0 : rt_mutex_timed_fastlock(struct rt_mutex *lock, int state,
1399 : struct hrtimer_sleeper *timeout,
1400 : enum rtmutex_chainwalk chwalk,
1401 : int (*slowfn)(struct rt_mutex *lock, int state,
1402 : struct hrtimer_sleeper *timeout,
1403 : enum rtmutex_chainwalk chwalk))
1404 : {
1405 0 : if (chwalk == RT_MUTEX_MIN_CHAINWALK &&
1406 : likely(rt_mutex_cmpxchg_acquire(lock, NULL, current)))
1407 : return 0;
1408 :
1409 0 : return slowfn(lock, state, timeout, chwalk);
1410 : }
1411 :
1412 : static inline int
1413 0 : rt_mutex_fasttrylock(struct rt_mutex *lock,
1414 : int (*slowfn)(struct rt_mutex *lock))
1415 : {
1416 0 : if (likely(rt_mutex_cmpxchg_acquire(lock, NULL, current)))
1417 : return 1;
1418 :
1419 0 : return slowfn(lock);
1420 : }
1421 :
1422 : /*
1423 : * Performs the wakeup of the top-waiter and re-enables preemption.
1424 : */
1425 0 : void rt_mutex_postunlock(struct wake_q_head *wake_q)
1426 : {
1427 0 : wake_up_q(wake_q);
1428 :
1429 : /* Pairs with preempt_disable() in rt_mutex_slowunlock() */
1430 0 : preempt_enable();
1431 0 : }
1432 :
1433 : static inline void
1434 0 : rt_mutex_fastunlock(struct rt_mutex *lock,
1435 : bool (*slowfn)(struct rt_mutex *lock,
1436 : struct wake_q_head *wqh))
1437 : {
1438 0 : DEFINE_WAKE_Q(wake_q);
1439 :
1440 0 : if (likely(rt_mutex_cmpxchg_release(lock, current, NULL)))
1441 : return;
1442 :
1443 0 : if (slowfn(lock, &wake_q))
1444 0 : rt_mutex_postunlock(&wake_q);
1445 : }
1446 :
1447 0 : static inline void __rt_mutex_lock(struct rt_mutex *lock, unsigned int subclass)
1448 : {
1449 0 : might_sleep();
1450 :
1451 0 : mutex_acquire(&lock->dep_map, subclass, 0, _RET_IP_);
1452 0 : rt_mutex_fastlock(lock, TASK_UNINTERRUPTIBLE, rt_mutex_slowlock);
1453 0 : }
1454 :
1455 : #ifdef CONFIG_DEBUG_LOCK_ALLOC
1456 : /**
1457 : * rt_mutex_lock_nested - lock a rt_mutex
1458 : *
1459 : * @lock: the rt_mutex to be locked
1460 : * @subclass: the lockdep subclass
1461 : */
1462 0 : void __sched rt_mutex_lock_nested(struct rt_mutex *lock, unsigned int subclass)
1463 : {
1464 0 : __rt_mutex_lock(lock, subclass);
1465 0 : }
1466 : EXPORT_SYMBOL_GPL(rt_mutex_lock_nested);
1467 :
1468 : #else /* !CONFIG_DEBUG_LOCK_ALLOC */
1469 :
1470 : /**
1471 : * rt_mutex_lock - lock a rt_mutex
1472 : *
1473 : * @lock: the rt_mutex to be locked
1474 : */
1475 : void __sched rt_mutex_lock(struct rt_mutex *lock)
1476 : {
1477 : __rt_mutex_lock(lock, 0);
1478 : }
1479 : EXPORT_SYMBOL_GPL(rt_mutex_lock);
1480 : #endif
1481 :
1482 : /**
1483 : * rt_mutex_lock_interruptible - lock a rt_mutex interruptible
1484 : *
1485 : * @lock: the rt_mutex to be locked
1486 : *
1487 : * Returns:
1488 : * 0 on success
1489 : * -EINTR when interrupted by a signal
1490 : */
1491 0 : int __sched rt_mutex_lock_interruptible(struct rt_mutex *lock)
1492 : {
1493 0 : int ret;
1494 :
1495 0 : might_sleep();
1496 :
1497 0 : mutex_acquire(&lock->dep_map, 0, 0, _RET_IP_);
1498 0 : ret = rt_mutex_fastlock(lock, TASK_INTERRUPTIBLE, rt_mutex_slowlock);
1499 0 : if (ret)
1500 0 : mutex_release(&lock->dep_map, _RET_IP_);
1501 :
1502 0 : return ret;
1503 : }
1504 : EXPORT_SYMBOL_GPL(rt_mutex_lock_interruptible);
1505 :
1506 : /*
1507 : * Futex variant, must not use fastpath.
1508 : */
1509 0 : int __sched rt_mutex_futex_trylock(struct rt_mutex *lock)
1510 : {
1511 0 : return rt_mutex_slowtrylock(lock);
1512 : }
1513 :
1514 0 : int __sched __rt_mutex_futex_trylock(struct rt_mutex *lock)
1515 : {
1516 0 : return __rt_mutex_slowtrylock(lock);
1517 : }
1518 :
1519 : /**
1520 : * rt_mutex_timed_lock - lock a rt_mutex interruptible
1521 : * the timeout structure is provided
1522 : * by the caller
1523 : *
1524 : * @lock: the rt_mutex to be locked
1525 : * @timeout: timeout structure or NULL (no timeout)
1526 : *
1527 : * Returns:
1528 : * 0 on success
1529 : * -EINTR when interrupted by a signal
1530 : * -ETIMEDOUT when the timeout expired
1531 : */
1532 : int
1533 0 : rt_mutex_timed_lock(struct rt_mutex *lock, struct hrtimer_sleeper *timeout)
1534 : {
1535 0 : int ret;
1536 :
1537 0 : might_sleep();
1538 :
1539 0 : mutex_acquire(&lock->dep_map, 0, 0, _RET_IP_);
1540 0 : ret = rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout,
1541 : RT_MUTEX_MIN_CHAINWALK,
1542 : rt_mutex_slowlock);
1543 0 : if (ret)
1544 0 : mutex_release(&lock->dep_map, _RET_IP_);
1545 :
1546 0 : return ret;
1547 : }
1548 : EXPORT_SYMBOL_GPL(rt_mutex_timed_lock);
1549 :
1550 : /**
1551 : * rt_mutex_trylock - try to lock a rt_mutex
1552 : *
1553 : * @lock: the rt_mutex to be locked
1554 : *
1555 : * This function can only be called in thread context. It's safe to
1556 : * call it from atomic regions, but not from hard interrupt or soft
1557 : * interrupt context.
1558 : *
1559 : * Returns 1 on success and 0 on contention
1560 : */
1561 0 : int __sched rt_mutex_trylock(struct rt_mutex *lock)
1562 : {
1563 0 : int ret;
1564 :
1565 0 : if (WARN_ON_ONCE(in_irq() || in_nmi() || in_serving_softirq()))
1566 : return 0;
1567 :
1568 0 : ret = rt_mutex_fasttrylock(lock, rt_mutex_slowtrylock);
1569 0 : if (ret)
1570 0 : mutex_acquire(&lock->dep_map, 0, 1, _RET_IP_);
1571 :
1572 : return ret;
1573 : }
1574 : EXPORT_SYMBOL_GPL(rt_mutex_trylock);
1575 :
1576 : /**
1577 : * rt_mutex_unlock - unlock a rt_mutex
1578 : *
1579 : * @lock: the rt_mutex to be unlocked
1580 : */
1581 0 : void __sched rt_mutex_unlock(struct rt_mutex *lock)
1582 : {
1583 0 : mutex_release(&lock->dep_map, _RET_IP_);
1584 0 : rt_mutex_fastunlock(lock, rt_mutex_slowunlock);
1585 0 : }
1586 : EXPORT_SYMBOL_GPL(rt_mutex_unlock);
1587 :
1588 : /**
1589 : * __rt_mutex_futex_unlock - Futex variant, that since futex variants
1590 : * do not use the fast-path, can be simple and will not need to retry.
1591 : *
1592 : * @lock: The rt_mutex to be unlocked
1593 : * @wake_q: The wake queue head from which to get the next lock waiter
1594 : */
1595 0 : bool __sched __rt_mutex_futex_unlock(struct rt_mutex *lock,
1596 : struct wake_q_head *wake_q)
1597 : {
1598 0 : lockdep_assert_held(&lock->wait_lock);
1599 :
1600 0 : debug_rt_mutex_unlock(lock);
1601 :
1602 0 : if (!rt_mutex_has_waiters(lock)) {
1603 0 : lock->owner = NULL;
1604 0 : return false; /* done */
1605 : }
1606 :
1607 : /*
1608 : * We've already deboosted, mark_wakeup_next_waiter() will
1609 : * retain preempt_disabled when we drop the wait_lock, to
1610 : * avoid inversion prior to the wakeup. preempt_disable()
1611 : * therein pairs with rt_mutex_postunlock().
1612 : */
1613 0 : mark_wakeup_next_waiter(wake_q, lock);
1614 :
1615 0 : return true; /* call postunlock() */
1616 : }
1617 :
1618 0 : void __sched rt_mutex_futex_unlock(struct rt_mutex *lock)
1619 : {
1620 0 : DEFINE_WAKE_Q(wake_q);
1621 0 : unsigned long flags;
1622 0 : bool postunlock;
1623 :
1624 0 : raw_spin_lock_irqsave(&lock->wait_lock, flags);
1625 0 : postunlock = __rt_mutex_futex_unlock(lock, &wake_q);
1626 0 : raw_spin_unlock_irqrestore(&lock->wait_lock, flags);
1627 :
1628 0 : if (postunlock)
1629 0 : rt_mutex_postunlock(&wake_q);
1630 0 : }
1631 :
1632 : /**
1633 : * rt_mutex_destroy - mark a mutex unusable
1634 : * @lock: the mutex to be destroyed
1635 : *
1636 : * This function marks the mutex uninitialized, and any subsequent
1637 : * use of the mutex is forbidden. The mutex must not be locked when
1638 : * this function is called.
1639 : */
1640 0 : void rt_mutex_destroy(struct rt_mutex *lock)
1641 : {
1642 0 : WARN_ON(rt_mutex_is_locked(lock));
1643 : #ifdef CONFIG_DEBUG_RT_MUTEXES
1644 0 : lock->magic = NULL;
1645 : #endif
1646 0 : }
1647 : EXPORT_SYMBOL_GPL(rt_mutex_destroy);
1648 :
1649 : /**
1650 : * __rt_mutex_init - initialize the rt_mutex
1651 : *
1652 : * @lock: The rt_mutex to be initialized
1653 : * @name: The lock name used for debugging
1654 : * @key: The lock class key used for debugging
1655 : *
1656 : * Initialize the rt_mutex to unlocked state.
1657 : *
1658 : * Initializing of a locked rt_mutex is not allowed
1659 : */
1660 0 : void __rt_mutex_init(struct rt_mutex *lock, const char *name,
1661 : struct lock_class_key *key)
1662 : {
1663 0 : lock->owner = NULL;
1664 0 : raw_spin_lock_init(&lock->wait_lock);
1665 0 : lock->waiters = RB_ROOT_CACHED;
1666 :
1667 0 : if (name && key)
1668 0 : debug_rt_mutex_init(lock, name, key);
1669 0 : }
1670 : EXPORT_SYMBOL_GPL(__rt_mutex_init);
1671 :
1672 : /**
1673 : * rt_mutex_init_proxy_locked - initialize and lock a rt_mutex on behalf of a
1674 : * proxy owner
1675 : *
1676 : * @lock: the rt_mutex to be locked
1677 : * @proxy_owner:the task to set as owner
1678 : *
1679 : * No locking. Caller has to do serializing itself
1680 : *
1681 : * Special API call for PI-futex support. This initializes the rtmutex and
1682 : * assigns it to @proxy_owner. Concurrent operations on the rtmutex are not
1683 : * possible at this point because the pi_state which contains the rtmutex
1684 : * is not yet visible to other tasks.
1685 : */
1686 0 : void rt_mutex_init_proxy_locked(struct rt_mutex *lock,
1687 : struct task_struct *proxy_owner)
1688 : {
1689 0 : __rt_mutex_init(lock, NULL, NULL);
1690 0 : debug_rt_mutex_proxy_lock(lock, proxy_owner);
1691 0 : rt_mutex_set_owner(lock, proxy_owner);
1692 0 : }
1693 :
1694 : /**
1695 : * rt_mutex_proxy_unlock - release a lock on behalf of owner
1696 : *
1697 : * @lock: the rt_mutex to be locked
1698 : *
1699 : * No locking. Caller has to do serializing itself
1700 : *
1701 : * Special API call for PI-futex support. This merrily cleans up the rtmutex
1702 : * (debugging) state. Concurrent operations on this rt_mutex are not
1703 : * possible because it belongs to the pi_state which is about to be freed
1704 : * and it is not longer visible to other tasks.
1705 : */
1706 0 : void rt_mutex_proxy_unlock(struct rt_mutex *lock)
1707 : {
1708 0 : debug_rt_mutex_proxy_unlock(lock);
1709 0 : rt_mutex_set_owner(lock, NULL);
1710 0 : }
1711 :
1712 : /**
1713 : * __rt_mutex_start_proxy_lock() - Start lock acquisition for another task
1714 : * @lock: the rt_mutex to take
1715 : * @waiter: the pre-initialized rt_mutex_waiter
1716 : * @task: the task to prepare
1717 : *
1718 : * Starts the rt_mutex acquire; it enqueues the @waiter and does deadlock
1719 : * detection. It does not wait, see rt_mutex_wait_proxy_lock() for that.
1720 : *
1721 : * NOTE: does _NOT_ remove the @waiter on failure; must either call
1722 : * rt_mutex_wait_proxy_lock() or rt_mutex_cleanup_proxy_lock() after this.
1723 : *
1724 : * Returns:
1725 : * 0 - task blocked on lock
1726 : * 1 - acquired the lock for task, caller should wake it up
1727 : * <0 - error
1728 : *
1729 : * Special API call for PI-futex support.
1730 : */
1731 0 : int __rt_mutex_start_proxy_lock(struct rt_mutex *lock,
1732 : struct rt_mutex_waiter *waiter,
1733 : struct task_struct *task)
1734 : {
1735 0 : int ret;
1736 :
1737 0 : lockdep_assert_held(&lock->wait_lock);
1738 :
1739 0 : if (try_to_take_rt_mutex(lock, task, NULL))
1740 : return 1;
1741 :
1742 : /* We enforce deadlock detection for futexes */
1743 0 : ret = task_blocks_on_rt_mutex(lock, waiter, task,
1744 : RT_MUTEX_FULL_CHAINWALK);
1745 :
1746 0 : if (ret && !rt_mutex_owner(lock)) {
1747 : /*
1748 : * Reset the return value. We might have
1749 : * returned with -EDEADLK and the owner
1750 : * released the lock while we were walking the
1751 : * pi chain. Let the waiter sort it out.
1752 : */
1753 0 : ret = 0;
1754 : }
1755 :
1756 0 : debug_rt_mutex_print_deadlock(waiter);
1757 :
1758 0 : return ret;
1759 : }
1760 :
1761 : /**
1762 : * rt_mutex_start_proxy_lock() - Start lock acquisition for another task
1763 : * @lock: the rt_mutex to take
1764 : * @waiter: the pre-initialized rt_mutex_waiter
1765 : * @task: the task to prepare
1766 : *
1767 : * Starts the rt_mutex acquire; it enqueues the @waiter and does deadlock
1768 : * detection. It does not wait, see rt_mutex_wait_proxy_lock() for that.
1769 : *
1770 : * NOTE: unlike __rt_mutex_start_proxy_lock this _DOES_ remove the @waiter
1771 : * on failure.
1772 : *
1773 : * Returns:
1774 : * 0 - task blocked on lock
1775 : * 1 - acquired the lock for task, caller should wake it up
1776 : * <0 - error
1777 : *
1778 : * Special API call for PI-futex support.
1779 : */
1780 0 : int rt_mutex_start_proxy_lock(struct rt_mutex *lock,
1781 : struct rt_mutex_waiter *waiter,
1782 : struct task_struct *task)
1783 : {
1784 0 : int ret;
1785 :
1786 0 : raw_spin_lock_irq(&lock->wait_lock);
1787 0 : ret = __rt_mutex_start_proxy_lock(lock, waiter, task);
1788 0 : if (unlikely(ret))
1789 0 : remove_waiter(lock, waiter);
1790 0 : raw_spin_unlock_irq(&lock->wait_lock);
1791 :
1792 0 : return ret;
1793 : }
1794 :
1795 : /**
1796 : * rt_mutex_next_owner - return the next owner of the lock
1797 : *
1798 : * @lock: the rt lock query
1799 : *
1800 : * Returns the next owner of the lock or NULL
1801 : *
1802 : * Caller has to serialize against other accessors to the lock
1803 : * itself.
1804 : *
1805 : * Special API call for PI-futex support
1806 : */
1807 0 : struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock)
1808 : {
1809 0 : if (!rt_mutex_has_waiters(lock))
1810 : return NULL;
1811 :
1812 0 : return rt_mutex_top_waiter(lock)->task;
1813 : }
1814 :
1815 : /**
1816 : * rt_mutex_wait_proxy_lock() - Wait for lock acquisition
1817 : * @lock: the rt_mutex we were woken on
1818 : * @to: the timeout, null if none. hrtimer should already have
1819 : * been started.
1820 : * @waiter: the pre-initialized rt_mutex_waiter
1821 : *
1822 : * Wait for the lock acquisition started on our behalf by
1823 : * rt_mutex_start_proxy_lock(). Upon failure, the caller must call
1824 : * rt_mutex_cleanup_proxy_lock().
1825 : *
1826 : * Returns:
1827 : * 0 - success
1828 : * <0 - error, one of -EINTR, -ETIMEDOUT
1829 : *
1830 : * Special API call for PI-futex support
1831 : */
1832 0 : int rt_mutex_wait_proxy_lock(struct rt_mutex *lock,
1833 : struct hrtimer_sleeper *to,
1834 : struct rt_mutex_waiter *waiter)
1835 : {
1836 0 : int ret;
1837 :
1838 0 : raw_spin_lock_irq(&lock->wait_lock);
1839 : /* sleep on the mutex */
1840 0 : set_current_state(TASK_INTERRUPTIBLE);
1841 0 : ret = __rt_mutex_slowlock(lock, TASK_INTERRUPTIBLE, to, waiter);
1842 : /*
1843 : * try_to_take_rt_mutex() sets the waiter bit unconditionally. We might
1844 : * have to fix that up.
1845 : */
1846 0 : fixup_rt_mutex_waiters(lock);
1847 0 : raw_spin_unlock_irq(&lock->wait_lock);
1848 :
1849 0 : return ret;
1850 : }
1851 :
1852 : /**
1853 : * rt_mutex_cleanup_proxy_lock() - Cleanup failed lock acquisition
1854 : * @lock: the rt_mutex we were woken on
1855 : * @waiter: the pre-initialized rt_mutex_waiter
1856 : *
1857 : * Attempt to clean up after a failed __rt_mutex_start_proxy_lock() or
1858 : * rt_mutex_wait_proxy_lock().
1859 : *
1860 : * Unless we acquired the lock; we're still enqueued on the wait-list and can
1861 : * in fact still be granted ownership until we're removed. Therefore we can
1862 : * find we are in fact the owner and must disregard the
1863 : * rt_mutex_wait_proxy_lock() failure.
1864 : *
1865 : * Returns:
1866 : * true - did the cleanup, we done.
1867 : * false - we acquired the lock after rt_mutex_wait_proxy_lock() returned,
1868 : * caller should disregards its return value.
1869 : *
1870 : * Special API call for PI-futex support
1871 : */
1872 0 : bool rt_mutex_cleanup_proxy_lock(struct rt_mutex *lock,
1873 : struct rt_mutex_waiter *waiter)
1874 : {
1875 0 : bool cleanup = false;
1876 :
1877 0 : raw_spin_lock_irq(&lock->wait_lock);
1878 : /*
1879 : * Do an unconditional try-lock, this deals with the lock stealing
1880 : * state where __rt_mutex_futex_unlock() -> mark_wakeup_next_waiter()
1881 : * sets a NULL owner.
1882 : *
1883 : * We're not interested in the return value, because the subsequent
1884 : * test on rt_mutex_owner() will infer that. If the trylock succeeded,
1885 : * we will own the lock and it will have removed the waiter. If we
1886 : * failed the trylock, we're still not owner and we need to remove
1887 : * ourselves.
1888 : */
1889 0 : try_to_take_rt_mutex(lock, current, waiter);
1890 : /*
1891 : * Unless we're the owner; we're still enqueued on the wait_list.
1892 : * So check if we became owner, if not, take us off the wait_list.
1893 : */
1894 0 : if (rt_mutex_owner(lock) != current) {
1895 0 : remove_waiter(lock, waiter);
1896 0 : cleanup = true;
1897 : }
1898 : /*
1899 : * try_to_take_rt_mutex() sets the waiter bit unconditionally. We might
1900 : * have to fix that up.
1901 : */
1902 0 : fixup_rt_mutex_waiters(lock);
1903 :
1904 0 : raw_spin_unlock_irq(&lock->wait_lock);
1905 :
1906 0 : return cleanup;
1907 : }
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