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Commit | Line | Data |
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23f78d4a IM |
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 | |
d07fe82c SR |
10 | * |
11 | * See Documentation/rt-mutex-design.txt for details. | |
23f78d4a IM |
12 | */ |
13 | #include <linux/spinlock.h> | |
9984de1a | 14 | #include <linux/export.h> |
23f78d4a | 15 | #include <linux/sched.h> |
8bd75c77 | 16 | #include <linux/sched/rt.h> |
fb00aca4 | 17 | #include <linux/sched/deadline.h> |
23f78d4a IM |
18 | #include <linux/timer.h> |
19 | ||
20 | #include "rtmutex_common.h" | |
21 | ||
23f78d4a IM |
22 | /* |
23 | * lock->owner state tracking: | |
24 | * | |
8161239a LJ |
25 | * lock->owner holds the task_struct pointer of the owner. Bit 0 |
26 | * is used to keep track of the "lock has waiters" state. | |
23f78d4a | 27 | * |
8161239a LJ |
28 | * owner bit0 |
29 | * NULL 0 lock is free (fast acquire possible) | |
30 | * NULL 1 lock is free and has waiters and the top waiter | |
31 | * is going to take the lock* | |
32 | * taskpointer 0 lock is held (fast release possible) | |
33 | * taskpointer 1 lock is held and has waiters** | |
23f78d4a IM |
34 | * |
35 | * The fast atomic compare exchange based acquire and release is only | |
8161239a LJ |
36 | * possible when bit 0 of lock->owner is 0. |
37 | * | |
38 | * (*) It also can be a transitional state when grabbing the lock | |
39 | * with ->wait_lock is held. To prevent any fast path cmpxchg to the lock, | |
40 | * we need to set the bit0 before looking at the lock, and the owner may be | |
41 | * NULL in this small time, hence this can be a transitional state. | |
23f78d4a | 42 | * |
8161239a LJ |
43 | * (**) There is a small time when bit 0 is set but there are no |
44 | * waiters. This can happen when grabbing the lock in the slow path. | |
45 | * To prevent a cmpxchg of the owner releasing the lock, we need to | |
46 | * set this bit before looking at the lock. | |
23f78d4a IM |
47 | */ |
48 | ||
bd197234 | 49 | static void |
8161239a | 50 | rt_mutex_set_owner(struct rt_mutex *lock, struct task_struct *owner) |
23f78d4a | 51 | { |
8161239a | 52 | unsigned long val = (unsigned long)owner; |
23f78d4a IM |
53 | |
54 | if (rt_mutex_has_waiters(lock)) | |
55 | val |= RT_MUTEX_HAS_WAITERS; | |
56 | ||
57 | lock->owner = (struct task_struct *)val; | |
58 | } | |
59 | ||
60 | static inline void clear_rt_mutex_waiters(struct rt_mutex *lock) | |
61 | { | |
62 | lock->owner = (struct task_struct *) | |
63 | ((unsigned long)lock->owner & ~RT_MUTEX_HAS_WAITERS); | |
64 | } | |
65 | ||
66 | static void fixup_rt_mutex_waiters(struct rt_mutex *lock) | |
67 | { | |
68 | if (!rt_mutex_has_waiters(lock)) | |
69 | clear_rt_mutex_waiters(lock); | |
70 | } | |
71 | ||
bd197234 TG |
72 | /* |
73 | * We can speed up the acquire/release, if the architecture | |
74 | * supports cmpxchg and if there's no debugging state to be set up | |
75 | */ | |
76 | #if defined(__HAVE_ARCH_CMPXCHG) && !defined(CONFIG_DEBUG_RT_MUTEXES) | |
77 | # define rt_mutex_cmpxchg(l,c,n) (cmpxchg(&l->owner, c, n) == c) | |
78 | static inline void mark_rt_mutex_waiters(struct rt_mutex *lock) | |
79 | { | |
80 | unsigned long owner, *p = (unsigned long *) &lock->owner; | |
81 | ||
82 | do { | |
83 | owner = *p; | |
84 | } while (cmpxchg(p, owner, owner | RT_MUTEX_HAS_WAITERS) != owner); | |
85 | } | |
27e35715 TG |
86 | |
87 | /* | |
88 | * Safe fastpath aware unlock: | |
89 | * 1) Clear the waiters bit | |
90 | * 2) Drop lock->wait_lock | |
91 | * 3) Try to unlock the lock with cmpxchg | |
92 | */ | |
93 | static inline bool unlock_rt_mutex_safe(struct rt_mutex *lock) | |
94 | __releases(lock->wait_lock) | |
95 | { | |
96 | struct task_struct *owner = rt_mutex_owner(lock); | |
97 | ||
98 | clear_rt_mutex_waiters(lock); | |
99 | raw_spin_unlock(&lock->wait_lock); | |
100 | /* | |
101 | * If a new waiter comes in between the unlock and the cmpxchg | |
102 | * we have two situations: | |
103 | * | |
104 | * unlock(wait_lock); | |
105 | * lock(wait_lock); | |
106 | * cmpxchg(p, owner, 0) == owner | |
107 | * mark_rt_mutex_waiters(lock); | |
108 | * acquire(lock); | |
109 | * or: | |
110 | * | |
111 | * unlock(wait_lock); | |
112 | * lock(wait_lock); | |
113 | * mark_rt_mutex_waiters(lock); | |
114 | * | |
115 | * cmpxchg(p, owner, 0) != owner | |
116 | * enqueue_waiter(); | |
117 | * unlock(wait_lock); | |
118 | * lock(wait_lock); | |
119 | * wake waiter(); | |
120 | * unlock(wait_lock); | |
121 | * lock(wait_lock); | |
122 | * acquire(lock); | |
123 | */ | |
124 | return rt_mutex_cmpxchg(lock, owner, NULL); | |
125 | } | |
126 | ||
bd197234 TG |
127 | #else |
128 | # define rt_mutex_cmpxchg(l,c,n) (0) | |
129 | static inline void mark_rt_mutex_waiters(struct rt_mutex *lock) | |
130 | { | |
131 | lock->owner = (struct task_struct *) | |
132 | ((unsigned long)lock->owner | RT_MUTEX_HAS_WAITERS); | |
133 | } | |
27e35715 TG |
134 | |
135 | /* | |
136 | * Simple slow path only version: lock->owner is protected by lock->wait_lock. | |
137 | */ | |
138 | static inline bool unlock_rt_mutex_safe(struct rt_mutex *lock) | |
139 | __releases(lock->wait_lock) | |
140 | { | |
141 | lock->owner = NULL; | |
142 | raw_spin_unlock(&lock->wait_lock); | |
143 | return true; | |
144 | } | |
bd197234 TG |
145 | #endif |
146 | ||
fb00aca4 PZ |
147 | static inline int |
148 | rt_mutex_waiter_less(struct rt_mutex_waiter *left, | |
149 | struct rt_mutex_waiter *right) | |
150 | { | |
2d3d891d | 151 | if (left->prio < right->prio) |
fb00aca4 PZ |
152 | return 1; |
153 | ||
154 | /* | |
2d3d891d DF |
155 | * If both waiters have dl_prio(), we check the deadlines of the |
156 | * associated tasks. | |
157 | * If left waiter has a dl_prio(), and we didn't return 1 above, | |
158 | * then right waiter has a dl_prio() too. | |
fb00aca4 | 159 | */ |
2d3d891d | 160 | if (dl_prio(left->prio)) |
fb00aca4 PZ |
161 | return (left->task->dl.deadline < right->task->dl.deadline); |
162 | ||
163 | return 0; | |
164 | } | |
165 | ||
166 | static void | |
167 | rt_mutex_enqueue(struct rt_mutex *lock, struct rt_mutex_waiter *waiter) | |
168 | { | |
169 | struct rb_node **link = &lock->waiters.rb_node; | |
170 | struct rb_node *parent = NULL; | |
171 | struct rt_mutex_waiter *entry; | |
172 | int leftmost = 1; | |
173 | ||
174 | while (*link) { | |
175 | parent = *link; | |
176 | entry = rb_entry(parent, struct rt_mutex_waiter, tree_entry); | |
177 | if (rt_mutex_waiter_less(waiter, entry)) { | |
178 | link = &parent->rb_left; | |
179 | } else { | |
180 | link = &parent->rb_right; | |
181 | leftmost = 0; | |
182 | } | |
183 | } | |
184 | ||
185 | if (leftmost) | |
186 | lock->waiters_leftmost = &waiter->tree_entry; | |
187 | ||
188 | rb_link_node(&waiter->tree_entry, parent, link); | |
189 | rb_insert_color(&waiter->tree_entry, &lock->waiters); | |
190 | } | |
191 | ||
192 | static void | |
193 | rt_mutex_dequeue(struct rt_mutex *lock, struct rt_mutex_waiter *waiter) | |
194 | { | |
195 | if (RB_EMPTY_NODE(&waiter->tree_entry)) | |
196 | return; | |
197 | ||
198 | if (lock->waiters_leftmost == &waiter->tree_entry) | |
199 | lock->waiters_leftmost = rb_next(&waiter->tree_entry); | |
200 | ||
201 | rb_erase(&waiter->tree_entry, &lock->waiters); | |
202 | RB_CLEAR_NODE(&waiter->tree_entry); | |
203 | } | |
204 | ||
205 | static void | |
206 | rt_mutex_enqueue_pi(struct task_struct *task, struct rt_mutex_waiter *waiter) | |
207 | { | |
208 | struct rb_node **link = &task->pi_waiters.rb_node; | |
209 | struct rb_node *parent = NULL; | |
210 | struct rt_mutex_waiter *entry; | |
211 | int leftmost = 1; | |
212 | ||
213 | while (*link) { | |
214 | parent = *link; | |
215 | entry = rb_entry(parent, struct rt_mutex_waiter, pi_tree_entry); | |
216 | if (rt_mutex_waiter_less(waiter, entry)) { | |
217 | link = &parent->rb_left; | |
218 | } else { | |
219 | link = &parent->rb_right; | |
220 | leftmost = 0; | |
221 | } | |
222 | } | |
223 | ||
224 | if (leftmost) | |
225 | task->pi_waiters_leftmost = &waiter->pi_tree_entry; | |
226 | ||
227 | rb_link_node(&waiter->pi_tree_entry, parent, link); | |
228 | rb_insert_color(&waiter->pi_tree_entry, &task->pi_waiters); | |
229 | } | |
230 | ||
231 | static void | |
232 | rt_mutex_dequeue_pi(struct task_struct *task, struct rt_mutex_waiter *waiter) | |
233 | { | |
234 | if (RB_EMPTY_NODE(&waiter->pi_tree_entry)) | |
235 | return; | |
236 | ||
237 | if (task->pi_waiters_leftmost == &waiter->pi_tree_entry) | |
238 | task->pi_waiters_leftmost = rb_next(&waiter->pi_tree_entry); | |
239 | ||
240 | rb_erase(&waiter->pi_tree_entry, &task->pi_waiters); | |
241 | RB_CLEAR_NODE(&waiter->pi_tree_entry); | |
242 | } | |
243 | ||
23f78d4a | 244 | /* |
fb00aca4 | 245 | * Calculate task priority from the waiter tree priority |
23f78d4a | 246 | * |
fb00aca4 | 247 | * Return task->normal_prio when the waiter tree is empty or when |
23f78d4a IM |
248 | * the waiter is not allowed to do priority boosting |
249 | */ | |
250 | int rt_mutex_getprio(struct task_struct *task) | |
251 | { | |
252 | if (likely(!task_has_pi_waiters(task))) | |
253 | return task->normal_prio; | |
254 | ||
2d3d891d | 255 | return min(task_top_pi_waiter(task)->prio, |
23f78d4a IM |
256 | task->normal_prio); |
257 | } | |
258 | ||
2d3d891d DF |
259 | struct task_struct *rt_mutex_get_top_task(struct task_struct *task) |
260 | { | |
261 | if (likely(!task_has_pi_waiters(task))) | |
262 | return NULL; | |
263 | ||
264 | return task_top_pi_waiter(task)->task; | |
265 | } | |
266 | ||
c365c292 TG |
267 | /* |
268 | * Called by sched_setscheduler() to check whether the priority change | |
269 | * is overruled by a possible priority boosting. | |
270 | */ | |
271 | int rt_mutex_check_prio(struct task_struct *task, int newprio) | |
272 | { | |
273 | if (!task_has_pi_waiters(task)) | |
274 | return 0; | |
275 | ||
276 | return task_top_pi_waiter(task)->task->prio <= newprio; | |
277 | } | |
278 | ||
23f78d4a IM |
279 | /* |
280 | * Adjust the priority of a task, after its pi_waiters got modified. | |
281 | * | |
282 | * This can be both boosting and unboosting. task->pi_lock must be held. | |
283 | */ | |
bd197234 | 284 | static void __rt_mutex_adjust_prio(struct task_struct *task) |
23f78d4a IM |
285 | { |
286 | int prio = rt_mutex_getprio(task); | |
287 | ||
2d3d891d | 288 | if (task->prio != prio || dl_prio(prio)) |
23f78d4a IM |
289 | rt_mutex_setprio(task, prio); |
290 | } | |
291 | ||
292 | /* | |
293 | * Adjust task priority (undo boosting). Called from the exit path of | |
294 | * rt_mutex_slowunlock() and rt_mutex_slowlock(). | |
295 | * | |
296 | * (Note: We do this outside of the protection of lock->wait_lock to | |
297 | * allow the lock to be taken while or before we readjust the priority | |
298 | * of task. We do not use the spin_xx_mutex() variants here as we are | |
299 | * outside of the debug path.) | |
300 | */ | |
301 | static void rt_mutex_adjust_prio(struct task_struct *task) | |
302 | { | |
303 | unsigned long flags; | |
304 | ||
1d615482 | 305 | raw_spin_lock_irqsave(&task->pi_lock, flags); |
23f78d4a | 306 | __rt_mutex_adjust_prio(task); |
1d615482 | 307 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
23f78d4a IM |
308 | } |
309 | ||
310 | /* | |
311 | * Max number of times we'll walk the boosting chain: | |
312 | */ | |
313 | int max_lock_depth = 1024; | |
314 | ||
82084984 TG |
315 | static inline struct rt_mutex *task_blocked_on_lock(struct task_struct *p) |
316 | { | |
317 | return p->pi_blocked_on ? p->pi_blocked_on->lock : NULL; | |
318 | } | |
319 | ||
23f78d4a IM |
320 | /* |
321 | * Adjust the priority chain. Also used for deadlock detection. | |
322 | * Decreases task's usage by one - may thus free the task. | |
0c106173 | 323 | * |
82084984 TG |
324 | * @task: the task owning the mutex (owner) for which a chain walk is |
325 | * probably needed | |
0c106173 | 326 | * @deadlock_detect: do we have to carry out deadlock detection? |
82084984 TG |
327 | * @orig_lock: the mutex (can be NULL if we are walking the chain to recheck |
328 | * things for a task that has just got its priority adjusted, and | |
329 | * is waiting on a mutex) | |
330 | * @next_lock: the mutex on which the owner of @orig_lock was blocked before | |
331 | * we dropped its pi_lock. Is never dereferenced, only used for | |
332 | * comparison to detect lock chain changes. | |
0c106173 | 333 | * @orig_waiter: rt_mutex_waiter struct for the task that has just donated |
82084984 TG |
334 | * its priority to the mutex owner (can be NULL in the case |
335 | * depicted above or if the top waiter is gone away and we are | |
336 | * actually deboosting the owner) | |
337 | * @top_task: the current top waiter | |
0c106173 | 338 | * |
23f78d4a | 339 | * Returns 0 or -EDEADLK. |
3eb65aea TG |
340 | * |
341 | * Chain walk basics and protection scope | |
342 | * | |
343 | * [R] refcount on task | |
344 | * [P] task->pi_lock held | |
345 | * [L] rtmutex->wait_lock held | |
346 | * | |
347 | * Step Description Protected by | |
348 | * function arguments: | |
349 | * @task [R] | |
350 | * @orig_lock if != NULL @top_task is blocked on it | |
351 | * @next_lock Unprotected. Cannot be | |
352 | * dereferenced. Only used for | |
353 | * comparison. | |
354 | * @orig_waiter if != NULL @top_task is blocked on it | |
355 | * @top_task current, or in case of proxy | |
356 | * locking protected by calling | |
357 | * code | |
358 | * again: | |
359 | * loop_sanity_check(); | |
360 | * retry: | |
361 | * [1] lock(task->pi_lock); [R] acquire [P] | |
362 | * [2] waiter = task->pi_blocked_on; [P] | |
363 | * [3] check_exit_conditions_1(); [P] | |
364 | * [4] lock = waiter->lock; [P] | |
365 | * [5] if (!try_lock(lock->wait_lock)) { [P] try to acquire [L] | |
366 | * unlock(task->pi_lock); release [P] | |
367 | * goto retry; | |
368 | * } | |
369 | * [6] check_exit_conditions_2(); [P] + [L] | |
370 | * [7] requeue_lock_waiter(lock, waiter); [P] + [L] | |
371 | * [8] unlock(task->pi_lock); release [P] | |
372 | * put_task_struct(task); release [R] | |
373 | * [9] check_exit_conditions_3(); [L] | |
374 | * [10] task = owner(lock); [L] | |
375 | * get_task_struct(task); [L] acquire [R] | |
376 | * lock(task->pi_lock); [L] acquire [P] | |
377 | * [11] requeue_pi_waiter(tsk, waiters(lock));[P] + [L] | |
378 | * [12] check_exit_conditions_4(); [P] + [L] | |
379 | * [13] unlock(task->pi_lock); release [P] | |
380 | * unlock(lock->wait_lock); release [L] | |
381 | * goto again; | |
23f78d4a | 382 | */ |
bd197234 TG |
383 | static int rt_mutex_adjust_prio_chain(struct task_struct *task, |
384 | int deadlock_detect, | |
385 | struct rt_mutex *orig_lock, | |
82084984 | 386 | struct rt_mutex *next_lock, |
bd197234 TG |
387 | struct rt_mutex_waiter *orig_waiter, |
388 | struct task_struct *top_task) | |
23f78d4a | 389 | { |
23f78d4a | 390 | struct rt_mutex_waiter *waiter, *top_waiter = orig_waiter; |
a57594a1 | 391 | struct rt_mutex_waiter *prerequeue_top_waiter; |
23f78d4a | 392 | int detect_deadlock, ret = 0, depth = 0; |
a57594a1 | 393 | struct rt_mutex *lock; |
23f78d4a IM |
394 | unsigned long flags; |
395 | ||
396 | detect_deadlock = debug_rt_mutex_detect_deadlock(orig_waiter, | |
397 | deadlock_detect); | |
398 | ||
399 | /* | |
400 | * The (de)boosting is a step by step approach with a lot of | |
401 | * pitfalls. We want this to be preemptible and we want hold a | |
402 | * maximum of two locks per step. So we have to check | |
403 | * carefully whether things change under us. | |
404 | */ | |
405 | again: | |
3eb65aea TG |
406 | /* |
407 | * We limit the lock chain length for each invocation. | |
408 | */ | |
23f78d4a IM |
409 | if (++depth > max_lock_depth) { |
410 | static int prev_max; | |
411 | ||
412 | /* | |
413 | * Print this only once. If the admin changes the limit, | |
414 | * print a new message when reaching the limit again. | |
415 | */ | |
416 | if (prev_max != max_lock_depth) { | |
417 | prev_max = max_lock_depth; | |
418 | printk(KERN_WARNING "Maximum lock depth %d reached " | |
419 | "task: %s (%d)\n", max_lock_depth, | |
ba25f9dc | 420 | top_task->comm, task_pid_nr(top_task)); |
23f78d4a IM |
421 | } |
422 | put_task_struct(task); | |
423 | ||
3d5c9340 | 424 | return -EDEADLK; |
23f78d4a | 425 | } |
3eb65aea TG |
426 | |
427 | /* | |
428 | * We are fully preemptible here and only hold the refcount on | |
429 | * @task. So everything can have changed under us since the | |
430 | * caller or our own code below (goto retry/again) dropped all | |
431 | * locks. | |
432 | */ | |
23f78d4a IM |
433 | retry: |
434 | /* | |
3eb65aea | 435 | * [1] Task cannot go away as we did a get_task() before ! |
23f78d4a | 436 | */ |
1d615482 | 437 | raw_spin_lock_irqsave(&task->pi_lock, flags); |
23f78d4a | 438 | |
3eb65aea TG |
439 | /* |
440 | * [2] Get the waiter on which @task is blocked on. | |
441 | */ | |
23f78d4a | 442 | waiter = task->pi_blocked_on; |
3eb65aea TG |
443 | |
444 | /* | |
445 | * [3] check_exit_conditions_1() protected by task->pi_lock. | |
446 | */ | |
447 | ||
23f78d4a IM |
448 | /* |
449 | * Check whether the end of the boosting chain has been | |
450 | * reached or the state of the chain has changed while we | |
451 | * dropped the locks. | |
452 | */ | |
8161239a | 453 | if (!waiter) |
23f78d4a IM |
454 | goto out_unlock_pi; |
455 | ||
1a539a87 TG |
456 | /* |
457 | * Check the orig_waiter state. After we dropped the locks, | |
8161239a | 458 | * the previous owner of the lock might have released the lock. |
1a539a87 | 459 | */ |
8161239a | 460 | if (orig_waiter && !rt_mutex_owner(orig_lock)) |
1a539a87 TG |
461 | goto out_unlock_pi; |
462 | ||
82084984 TG |
463 | /* |
464 | * We dropped all locks after taking a refcount on @task, so | |
465 | * the task might have moved on in the lock chain or even left | |
466 | * the chain completely and blocks now on an unrelated lock or | |
467 | * on @orig_lock. | |
468 | * | |
469 | * We stored the lock on which @task was blocked in @next_lock, | |
470 | * so we can detect the chain change. | |
471 | */ | |
472 | if (next_lock != waiter->lock) | |
473 | goto out_unlock_pi; | |
474 | ||
1a539a87 TG |
475 | /* |
476 | * Drop out, when the task has no waiters. Note, | |
477 | * top_waiter can be NULL, when we are in the deboosting | |
478 | * mode! | |
479 | */ | |
397335f0 TG |
480 | if (top_waiter) { |
481 | if (!task_has_pi_waiters(task)) | |
482 | goto out_unlock_pi; | |
483 | /* | |
484 | * If deadlock detection is off, we stop here if we | |
485 | * are not the top pi waiter of the task. | |
486 | */ | |
487 | if (!detect_deadlock && top_waiter != task_top_pi_waiter(task)) | |
488 | goto out_unlock_pi; | |
489 | } | |
23f78d4a IM |
490 | |
491 | /* | |
492 | * When deadlock detection is off then we check, if further | |
493 | * priority adjustment is necessary. | |
494 | */ | |
2d3d891d | 495 | if (!detect_deadlock && waiter->prio == task->prio) |
23f78d4a IM |
496 | goto out_unlock_pi; |
497 | ||
3eb65aea TG |
498 | /* |
499 | * [4] Get the next lock | |
500 | */ | |
23f78d4a | 501 | lock = waiter->lock; |
3eb65aea TG |
502 | /* |
503 | * [5] We need to trylock here as we are holding task->pi_lock, | |
504 | * which is the reverse lock order versus the other rtmutex | |
505 | * operations. | |
506 | */ | |
d209d74d | 507 | if (!raw_spin_trylock(&lock->wait_lock)) { |
1d615482 | 508 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
23f78d4a IM |
509 | cpu_relax(); |
510 | goto retry; | |
511 | } | |
512 | ||
397335f0 | 513 | /* |
3eb65aea TG |
514 | * [6] check_exit_conditions_2() protected by task->pi_lock and |
515 | * lock->wait_lock. | |
516 | * | |
397335f0 TG |
517 | * Deadlock detection. If the lock is the same as the original |
518 | * lock which caused us to walk the lock chain or if the | |
519 | * current lock is owned by the task which initiated the chain | |
520 | * walk, we detected a deadlock. | |
521 | */ | |
95e02ca9 | 522 | if (lock == orig_lock || rt_mutex_owner(lock) == top_task) { |
23f78d4a | 523 | debug_rt_mutex_deadlock(deadlock_detect, orig_waiter, lock); |
d209d74d | 524 | raw_spin_unlock(&lock->wait_lock); |
3d5c9340 | 525 | ret = -EDEADLK; |
23f78d4a IM |
526 | goto out_unlock_pi; |
527 | } | |
528 | ||
a57594a1 TG |
529 | /* |
530 | * Store the current top waiter before doing the requeue | |
531 | * operation on @lock. We need it for the boost/deboost | |
532 | * decision below. | |
533 | */ | |
534 | prerequeue_top_waiter = rt_mutex_top_waiter(lock); | |
23f78d4a | 535 | |
3eb65aea | 536 | /* [7] Requeue the waiter in the lock waiter list. */ |
fb00aca4 | 537 | rt_mutex_dequeue(lock, waiter); |
2d3d891d | 538 | waiter->prio = task->prio; |
fb00aca4 | 539 | rt_mutex_enqueue(lock, waiter); |
23f78d4a | 540 | |
3eb65aea | 541 | /* [8] Release the task */ |
1d615482 | 542 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
2ffa5a5c TG |
543 | put_task_struct(task); |
544 | ||
a57594a1 | 545 | /* |
3eb65aea TG |
546 | * [9] check_exit_conditions_3 protected by lock->wait_lock. |
547 | * | |
a57594a1 TG |
548 | * We must abort the chain walk if there is no lock owner even |
549 | * in the dead lock detection case, as we have nothing to | |
550 | * follow here. This is the end of the chain we are walking. | |
551 | */ | |
8161239a LJ |
552 | if (!rt_mutex_owner(lock)) { |
553 | /* | |
3eb65aea TG |
554 | * If the requeue [7] above changed the top waiter, |
555 | * then we need to wake the new top waiter up to try | |
556 | * to get the lock. | |
8161239a | 557 | */ |
a57594a1 | 558 | if (prerequeue_top_waiter != rt_mutex_top_waiter(lock)) |
8161239a LJ |
559 | wake_up_process(rt_mutex_top_waiter(lock)->task); |
560 | raw_spin_unlock(&lock->wait_lock); | |
2ffa5a5c | 561 | return 0; |
8161239a | 562 | } |
23f78d4a | 563 | |
3eb65aea | 564 | /* [10] Grab the next task, i.e. the owner of @lock */ |
23f78d4a | 565 | task = rt_mutex_owner(lock); |
db630637 | 566 | get_task_struct(task); |
1d615482 | 567 | raw_spin_lock_irqsave(&task->pi_lock, flags); |
23f78d4a | 568 | |
3eb65aea | 569 | /* [11] requeue the pi waiters if necessary */ |
23f78d4a | 570 | if (waiter == rt_mutex_top_waiter(lock)) { |
a57594a1 TG |
571 | /* |
572 | * The waiter became the new top (highest priority) | |
573 | * waiter on the lock. Replace the previous top waiter | |
574 | * in the owner tasks pi waiters list with this waiter | |
575 | * and adjust the priority of the owner. | |
576 | */ | |
577 | rt_mutex_dequeue_pi(task, prerequeue_top_waiter); | |
fb00aca4 | 578 | rt_mutex_enqueue_pi(task, waiter); |
23f78d4a IM |
579 | __rt_mutex_adjust_prio(task); |
580 | ||
a57594a1 TG |
581 | } else if (prerequeue_top_waiter == waiter) { |
582 | /* | |
583 | * The waiter was the top waiter on the lock, but is | |
584 | * no longer the top prority waiter. Replace waiter in | |
585 | * the owner tasks pi waiters list with the new top | |
586 | * (highest priority) waiter and adjust the priority | |
587 | * of the owner. | |
588 | * The new top waiter is stored in @waiter so that | |
589 | * @waiter == @top_waiter evaluates to true below and | |
590 | * we continue to deboost the rest of the chain. | |
591 | */ | |
fb00aca4 | 592 | rt_mutex_dequeue_pi(task, waiter); |
23f78d4a | 593 | waiter = rt_mutex_top_waiter(lock); |
fb00aca4 | 594 | rt_mutex_enqueue_pi(task, waiter); |
23f78d4a | 595 | __rt_mutex_adjust_prio(task); |
a57594a1 TG |
596 | } else { |
597 | /* | |
598 | * Nothing changed. No need to do any priority | |
599 | * adjustment. | |
600 | */ | |
23f78d4a IM |
601 | } |
602 | ||
82084984 | 603 | /* |
3eb65aea TG |
604 | * [12] check_exit_conditions_4() protected by task->pi_lock |
605 | * and lock->wait_lock. The actual decisions are made after we | |
606 | * dropped the locks. | |
607 | * | |
82084984 TG |
608 | * Check whether the task which owns the current lock is pi |
609 | * blocked itself. If yes we store a pointer to the lock for | |
610 | * the lock chain change detection above. After we dropped | |
611 | * task->pi_lock next_lock cannot be dereferenced anymore. | |
612 | */ | |
613 | next_lock = task_blocked_on_lock(task); | |
a57594a1 TG |
614 | /* |
615 | * Store the top waiter of @lock for the end of chain walk | |
616 | * decision below. | |
617 | */ | |
23f78d4a | 618 | top_waiter = rt_mutex_top_waiter(lock); |
3eb65aea TG |
619 | |
620 | /* [13] Drop the locks */ | |
621 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); | |
d209d74d | 622 | raw_spin_unlock(&lock->wait_lock); |
23f78d4a | 623 | |
82084984 | 624 | /* |
3eb65aea TG |
625 | * Make the actual exit decisions [12], based on the stored |
626 | * values. | |
627 | * | |
82084984 TG |
628 | * We reached the end of the lock chain. Stop right here. No |
629 | * point to go back just to figure that out. | |
630 | */ | |
631 | if (!next_lock) | |
632 | goto out_put_task; | |
633 | ||
a57594a1 TG |
634 | /* |
635 | * If the current waiter is not the top waiter on the lock, | |
636 | * then we can stop the chain walk here if we are not in full | |
637 | * deadlock detection mode. | |
638 | */ | |
23f78d4a IM |
639 | if (!detect_deadlock && waiter != top_waiter) |
640 | goto out_put_task; | |
641 | ||
642 | goto again; | |
643 | ||
644 | out_unlock_pi: | |
1d615482 | 645 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
23f78d4a IM |
646 | out_put_task: |
647 | put_task_struct(task); | |
36c8b586 | 648 | |
23f78d4a IM |
649 | return ret; |
650 | } | |
651 | ||
23f78d4a IM |
652 | /* |
653 | * Try to take an rt-mutex | |
654 | * | |
23f78d4a | 655 | * Must be called with lock->wait_lock held. |
8161239a | 656 | * |
358c331f TG |
657 | * @lock: The lock to be acquired. |
658 | * @task: The task which wants to acquire the lock | |
659 | * @waiter: The waiter that is queued to the lock's wait list if the | |
660 | * callsite called task_blocked_on_lock(), otherwise NULL | |
23f78d4a | 661 | */ |
8161239a | 662 | static int try_to_take_rt_mutex(struct rt_mutex *lock, struct task_struct *task, |
358c331f | 663 | struct rt_mutex_waiter *waiter) |
23f78d4a | 664 | { |
358c331f TG |
665 | unsigned long flags; |
666 | ||
23f78d4a | 667 | /* |
358c331f TG |
668 | * Before testing whether we can acquire @lock, we set the |
669 | * RT_MUTEX_HAS_WAITERS bit in @lock->owner. This forces all | |
670 | * other tasks which try to modify @lock into the slow path | |
671 | * and they serialize on @lock->wait_lock. | |
23f78d4a | 672 | * |
358c331f TG |
673 | * The RT_MUTEX_HAS_WAITERS bit can have a transitional state |
674 | * as explained at the top of this file if and only if: | |
23f78d4a | 675 | * |
358c331f TG |
676 | * - There is a lock owner. The caller must fixup the |
677 | * transient state if it does a trylock or leaves the lock | |
678 | * function due to a signal or timeout. | |
679 | * | |
680 | * - @task acquires the lock and there are no other | |
681 | * waiters. This is undone in rt_mutex_set_owner(@task) at | |
682 | * the end of this function. | |
23f78d4a IM |
683 | */ |
684 | mark_rt_mutex_waiters(lock); | |
685 | ||
358c331f TG |
686 | /* |
687 | * If @lock has an owner, give up. | |
688 | */ | |
8161239a | 689 | if (rt_mutex_owner(lock)) |
23f78d4a IM |
690 | return 0; |
691 | ||
8161239a | 692 | /* |
358c331f TG |
693 | * If @waiter != NULL, @task has already enqueued the waiter |
694 | * into @lock waiter list. If @waiter == NULL then this is a | |
695 | * trylock attempt. | |
8161239a | 696 | */ |
358c331f TG |
697 | if (waiter) { |
698 | /* | |
699 | * If waiter is not the highest priority waiter of | |
700 | * @lock, give up. | |
701 | */ | |
702 | if (waiter != rt_mutex_top_waiter(lock)) | |
703 | return 0; | |
8161239a | 704 | |
358c331f TG |
705 | /* |
706 | * We can acquire the lock. Remove the waiter from the | |
707 | * lock waiters list. | |
708 | */ | |
709 | rt_mutex_dequeue(lock, waiter); | |
8161239a | 710 | |
358c331f | 711 | } else { |
8161239a | 712 | /* |
358c331f TG |
713 | * If the lock has waiters already we check whether @task is |
714 | * eligible to take over the lock. | |
715 | * | |
716 | * If there are no other waiters, @task can acquire | |
717 | * the lock. @task->pi_blocked_on is NULL, so it does | |
718 | * not need to be dequeued. | |
8161239a LJ |
719 | */ |
720 | if (rt_mutex_has_waiters(lock)) { | |
358c331f TG |
721 | /* |
722 | * If @task->prio is greater than or equal to | |
723 | * the top waiter priority (kernel view), | |
724 | * @task lost. | |
725 | */ | |
726 | if (task->prio >= rt_mutex_top_waiter(lock)->prio) | |
727 | return 0; | |
728 | ||
729 | /* | |
730 | * The current top waiter stays enqueued. We | |
731 | * don't have to change anything in the lock | |
732 | * waiters order. | |
733 | */ | |
734 | } else { | |
735 | /* | |
736 | * No waiters. Take the lock without the | |
737 | * pi_lock dance.@task->pi_blocked_on is NULL | |
738 | * and we have no waiters to enqueue in @task | |
739 | * pi waiters list. | |
740 | */ | |
741 | goto takeit; | |
8161239a | 742 | } |
8161239a LJ |
743 | } |
744 | ||
358c331f TG |
745 | /* |
746 | * Clear @task->pi_blocked_on. Requires protection by | |
747 | * @task->pi_lock. Redundant operation for the @waiter == NULL | |
748 | * case, but conditionals are more expensive than a redundant | |
749 | * store. | |
750 | */ | |
751 | raw_spin_lock_irqsave(&task->pi_lock, flags); | |
752 | task->pi_blocked_on = NULL; | |
753 | /* | |
754 | * Finish the lock acquisition. @task is the new owner. If | |
755 | * other waiters exist we have to insert the highest priority | |
756 | * waiter into @task->pi_waiters list. | |
757 | */ | |
758 | if (rt_mutex_has_waiters(lock)) | |
759 | rt_mutex_enqueue_pi(task, rt_mutex_top_waiter(lock)); | |
760 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); | |
761 | ||
762 | takeit: | |
23f78d4a | 763 | /* We got the lock. */ |
9a11b49a | 764 | debug_rt_mutex_lock(lock); |
23f78d4a | 765 | |
358c331f TG |
766 | /* |
767 | * This either preserves the RT_MUTEX_HAS_WAITERS bit if there | |
768 | * are still waiters or clears it. | |
769 | */ | |
8161239a | 770 | rt_mutex_set_owner(lock, task); |
23f78d4a | 771 | |
8161239a | 772 | rt_mutex_deadlock_account_lock(lock, task); |
23f78d4a IM |
773 | |
774 | return 1; | |
775 | } | |
776 | ||
777 | /* | |
778 | * Task blocks on lock. | |
779 | * | |
780 | * Prepare waiter and propagate pi chain | |
781 | * | |
782 | * This must be called with lock->wait_lock held. | |
783 | */ | |
784 | static int task_blocks_on_rt_mutex(struct rt_mutex *lock, | |
785 | struct rt_mutex_waiter *waiter, | |
8dac456a | 786 | struct task_struct *task, |
9a11b49a | 787 | int detect_deadlock) |
23f78d4a | 788 | { |
36c8b586 | 789 | struct task_struct *owner = rt_mutex_owner(lock); |
23f78d4a | 790 | struct rt_mutex_waiter *top_waiter = waiter; |
82084984 | 791 | struct rt_mutex *next_lock; |
db630637 | 792 | int chain_walk = 0, res; |
82084984 | 793 | unsigned long flags; |
23f78d4a | 794 | |
397335f0 TG |
795 | /* |
796 | * Early deadlock detection. We really don't want the task to | |
797 | * enqueue on itself just to untangle the mess later. It's not | |
798 | * only an optimization. We drop the locks, so another waiter | |
799 | * can come in before the chain walk detects the deadlock. So | |
800 | * the other will detect the deadlock and return -EDEADLOCK, | |
801 | * which is wrong, as the other waiter is not in a deadlock | |
802 | * situation. | |
803 | */ | |
3d5c9340 | 804 | if (owner == task) |
397335f0 TG |
805 | return -EDEADLK; |
806 | ||
1d615482 | 807 | raw_spin_lock_irqsave(&task->pi_lock, flags); |
8dac456a DH |
808 | __rt_mutex_adjust_prio(task); |
809 | waiter->task = task; | |
23f78d4a | 810 | waiter->lock = lock; |
2d3d891d | 811 | waiter->prio = task->prio; |
23f78d4a IM |
812 | |
813 | /* Get the top priority waiter on the lock */ | |
814 | if (rt_mutex_has_waiters(lock)) | |
815 | top_waiter = rt_mutex_top_waiter(lock); | |
fb00aca4 | 816 | rt_mutex_enqueue(lock, waiter); |
23f78d4a | 817 | |
8dac456a | 818 | task->pi_blocked_on = waiter; |
23f78d4a | 819 | |
1d615482 | 820 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
23f78d4a | 821 | |
8161239a LJ |
822 | if (!owner) |
823 | return 0; | |
824 | ||
82084984 | 825 | raw_spin_lock_irqsave(&owner->pi_lock, flags); |
23f78d4a | 826 | if (waiter == rt_mutex_top_waiter(lock)) { |
fb00aca4 PZ |
827 | rt_mutex_dequeue_pi(owner, top_waiter); |
828 | rt_mutex_enqueue_pi(owner, waiter); | |
23f78d4a IM |
829 | |
830 | __rt_mutex_adjust_prio(owner); | |
db630637 SR |
831 | if (owner->pi_blocked_on) |
832 | chain_walk = 1; | |
82084984 | 833 | } else if (debug_rt_mutex_detect_deadlock(waiter, detect_deadlock)) { |
db630637 | 834 | chain_walk = 1; |
82084984 | 835 | } |
db630637 | 836 | |
82084984 TG |
837 | /* Store the lock on which owner is blocked or NULL */ |
838 | next_lock = task_blocked_on_lock(owner); | |
839 | ||
840 | raw_spin_unlock_irqrestore(&owner->pi_lock, flags); | |
841 | /* | |
842 | * Even if full deadlock detection is on, if the owner is not | |
843 | * blocked itself, we can avoid finding this out in the chain | |
844 | * walk. | |
845 | */ | |
846 | if (!chain_walk || !next_lock) | |
23f78d4a IM |
847 | return 0; |
848 | ||
db630637 SR |
849 | /* |
850 | * The owner can't disappear while holding a lock, | |
851 | * so the owner struct is protected by wait_lock. | |
852 | * Gets dropped in rt_mutex_adjust_prio_chain()! | |
853 | */ | |
854 | get_task_struct(owner); | |
855 | ||
d209d74d | 856 | raw_spin_unlock(&lock->wait_lock); |
23f78d4a | 857 | |
82084984 TG |
858 | res = rt_mutex_adjust_prio_chain(owner, detect_deadlock, lock, |
859 | next_lock, waiter, task); | |
23f78d4a | 860 | |
d209d74d | 861 | raw_spin_lock(&lock->wait_lock); |
23f78d4a IM |
862 | |
863 | return res; | |
864 | } | |
865 | ||
866 | /* | |
867 | * Wake up the next waiter on the lock. | |
868 | * | |
27e35715 TG |
869 | * Remove the top waiter from the current tasks pi waiter list and |
870 | * wake it up. | |
23f78d4a IM |
871 | * |
872 | * Called with lock->wait_lock held. | |
873 | */ | |
874 | static void wakeup_next_waiter(struct rt_mutex *lock) | |
875 | { | |
876 | struct rt_mutex_waiter *waiter; | |
23f78d4a IM |
877 | unsigned long flags; |
878 | ||
1d615482 | 879 | raw_spin_lock_irqsave(¤t->pi_lock, flags); |
23f78d4a IM |
880 | |
881 | waiter = rt_mutex_top_waiter(lock); | |
23f78d4a IM |
882 | |
883 | /* | |
884 | * Remove it from current->pi_waiters. We do not adjust a | |
885 | * possible priority boost right now. We execute wakeup in the | |
886 | * boosted mode and go back to normal after releasing | |
887 | * lock->wait_lock. | |
888 | */ | |
fb00aca4 | 889 | rt_mutex_dequeue_pi(current, waiter); |
23f78d4a | 890 | |
27e35715 TG |
891 | /* |
892 | * As we are waking up the top waiter, and the waiter stays | |
893 | * queued on the lock until it gets the lock, this lock | |
894 | * obviously has waiters. Just set the bit here and this has | |
895 | * the added benefit of forcing all new tasks into the | |
896 | * slow path making sure no task of lower priority than | |
897 | * the top waiter can steal this lock. | |
898 | */ | |
899 | lock->owner = (void *) RT_MUTEX_HAS_WAITERS; | |
23f78d4a | 900 | |
1d615482 | 901 | raw_spin_unlock_irqrestore(¤t->pi_lock, flags); |
23f78d4a | 902 | |
27e35715 TG |
903 | /* |
904 | * It's safe to dereference waiter as it cannot go away as | |
905 | * long as we hold lock->wait_lock. The waiter task needs to | |
906 | * acquire it in order to dequeue the waiter. | |
907 | */ | |
8161239a | 908 | wake_up_process(waiter->task); |
23f78d4a IM |
909 | } |
910 | ||
911 | /* | |
8161239a | 912 | * Remove a waiter from a lock and give up |
23f78d4a | 913 | * |
8161239a LJ |
914 | * Must be called with lock->wait_lock held and |
915 | * have just failed to try_to_take_rt_mutex(). | |
23f78d4a | 916 | */ |
bd197234 TG |
917 | static void remove_waiter(struct rt_mutex *lock, |
918 | struct rt_mutex_waiter *waiter) | |
23f78d4a | 919 | { |
1ca7b860 | 920 | bool is_top_waiter = (waiter == rt_mutex_top_waiter(lock)); |
36c8b586 | 921 | struct task_struct *owner = rt_mutex_owner(lock); |
1ca7b860 | 922 | struct rt_mutex *next_lock; |
23f78d4a IM |
923 | unsigned long flags; |
924 | ||
1d615482 | 925 | raw_spin_lock_irqsave(¤t->pi_lock, flags); |
fb00aca4 | 926 | rt_mutex_dequeue(lock, waiter); |
23f78d4a | 927 | current->pi_blocked_on = NULL; |
1d615482 | 928 | raw_spin_unlock_irqrestore(¤t->pi_lock, flags); |
23f78d4a | 929 | |
1ca7b860 TG |
930 | /* |
931 | * Only update priority if the waiter was the highest priority | |
932 | * waiter of the lock and there is an owner to update. | |
933 | */ | |
934 | if (!owner || !is_top_waiter) | |
8161239a LJ |
935 | return; |
936 | ||
1ca7b860 | 937 | raw_spin_lock_irqsave(&owner->pi_lock, flags); |
23f78d4a | 938 | |
1ca7b860 | 939 | rt_mutex_dequeue_pi(owner, waiter); |
23f78d4a | 940 | |
1ca7b860 TG |
941 | if (rt_mutex_has_waiters(lock)) |
942 | rt_mutex_enqueue_pi(owner, rt_mutex_top_waiter(lock)); | |
23f78d4a | 943 | |
1ca7b860 | 944 | __rt_mutex_adjust_prio(owner); |
23f78d4a | 945 | |
1ca7b860 TG |
946 | /* Store the lock on which owner is blocked or NULL */ |
947 | next_lock = task_blocked_on_lock(owner); | |
db630637 | 948 | |
1ca7b860 | 949 | raw_spin_unlock_irqrestore(&owner->pi_lock, flags); |
23f78d4a | 950 | |
1ca7b860 TG |
951 | /* |
952 | * Don't walk the chain, if the owner task is not blocked | |
953 | * itself. | |
954 | */ | |
82084984 | 955 | if (!next_lock) |
23f78d4a IM |
956 | return; |
957 | ||
db630637 SR |
958 | /* gets dropped in rt_mutex_adjust_prio_chain()! */ |
959 | get_task_struct(owner); | |
960 | ||
d209d74d | 961 | raw_spin_unlock(&lock->wait_lock); |
23f78d4a | 962 | |
82084984 | 963 | rt_mutex_adjust_prio_chain(owner, 0, lock, next_lock, NULL, current); |
23f78d4a | 964 | |
d209d74d | 965 | raw_spin_lock(&lock->wait_lock); |
23f78d4a IM |
966 | } |
967 | ||
95e02ca9 TG |
968 | /* |
969 | * Recheck the pi chain, in case we got a priority setting | |
970 | * | |
971 | * Called from sched_setscheduler | |
972 | */ | |
973 | void rt_mutex_adjust_pi(struct task_struct *task) | |
974 | { | |
975 | struct rt_mutex_waiter *waiter; | |
82084984 | 976 | struct rt_mutex *next_lock; |
95e02ca9 TG |
977 | unsigned long flags; |
978 | ||
1d615482 | 979 | raw_spin_lock_irqsave(&task->pi_lock, flags); |
95e02ca9 TG |
980 | |
981 | waiter = task->pi_blocked_on; | |
2d3d891d DF |
982 | if (!waiter || (waiter->prio == task->prio && |
983 | !dl_prio(task->prio))) { | |
1d615482 | 984 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
95e02ca9 TG |
985 | return; |
986 | } | |
82084984 | 987 | next_lock = waiter->lock; |
1d615482 | 988 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
95e02ca9 | 989 | |
db630637 SR |
990 | /* gets dropped in rt_mutex_adjust_prio_chain()! */ |
991 | get_task_struct(task); | |
82084984 TG |
992 | |
993 | rt_mutex_adjust_prio_chain(task, 0, NULL, next_lock, NULL, task); | |
95e02ca9 TG |
994 | } |
995 | ||
8dac456a DH |
996 | /** |
997 | * __rt_mutex_slowlock() - Perform the wait-wake-try-to-take loop | |
998 | * @lock: the rt_mutex to take | |
999 | * @state: the state the task should block in (TASK_INTERRUPTIBLE | |
1000 | * or TASK_UNINTERRUPTIBLE) | |
1001 | * @timeout: the pre-initialized and started timer, or NULL for none | |
1002 | * @waiter: the pre-initialized rt_mutex_waiter | |
8dac456a DH |
1003 | * |
1004 | * lock->wait_lock must be held by the caller. | |
23f78d4a IM |
1005 | */ |
1006 | static int __sched | |
8dac456a DH |
1007 | __rt_mutex_slowlock(struct rt_mutex *lock, int state, |
1008 | struct hrtimer_sleeper *timeout, | |
8161239a | 1009 | struct rt_mutex_waiter *waiter) |
23f78d4a | 1010 | { |
23f78d4a IM |
1011 | int ret = 0; |
1012 | ||
23f78d4a IM |
1013 | for (;;) { |
1014 | /* Try to acquire the lock: */ | |
8161239a | 1015 | if (try_to_take_rt_mutex(lock, current, waiter)) |
23f78d4a IM |
1016 | break; |
1017 | ||
1018 | /* | |
1019 | * TASK_INTERRUPTIBLE checks for signals and | |
1020 | * timeout. Ignored otherwise. | |
1021 | */ | |
1022 | if (unlikely(state == TASK_INTERRUPTIBLE)) { | |
1023 | /* Signal pending? */ | |
1024 | if (signal_pending(current)) | |
1025 | ret = -EINTR; | |
1026 | if (timeout && !timeout->task) | |
1027 | ret = -ETIMEDOUT; | |
1028 | if (ret) | |
1029 | break; | |
1030 | } | |
1031 | ||
d209d74d | 1032 | raw_spin_unlock(&lock->wait_lock); |
23f78d4a | 1033 | |
8dac456a | 1034 | debug_rt_mutex_print_deadlock(waiter); |
23f78d4a | 1035 | |
8161239a | 1036 | schedule_rt_mutex(lock); |
23f78d4a | 1037 | |
d209d74d | 1038 | raw_spin_lock(&lock->wait_lock); |
23f78d4a IM |
1039 | set_current_state(state); |
1040 | } | |
1041 | ||
8dac456a DH |
1042 | return ret; |
1043 | } | |
1044 | ||
3d5c9340 TG |
1045 | static void rt_mutex_handle_deadlock(int res, int detect_deadlock, |
1046 | struct rt_mutex_waiter *w) | |
1047 | { | |
1048 | /* | |
1049 | * If the result is not -EDEADLOCK or the caller requested | |
1050 | * deadlock detection, nothing to do here. | |
1051 | */ | |
1052 | if (res != -EDEADLOCK || detect_deadlock) | |
1053 | return; | |
1054 | ||
1055 | /* | |
1056 | * Yell lowdly and stop the task right here. | |
1057 | */ | |
1058 | rt_mutex_print_deadlock(w); | |
1059 | while (1) { | |
1060 | set_current_state(TASK_INTERRUPTIBLE); | |
1061 | schedule(); | |
1062 | } | |
1063 | } | |
1064 | ||
8dac456a DH |
1065 | /* |
1066 | * Slow path lock function: | |
1067 | */ | |
1068 | static int __sched | |
1069 | rt_mutex_slowlock(struct rt_mutex *lock, int state, | |
1070 | struct hrtimer_sleeper *timeout, | |
1071 | int detect_deadlock) | |
1072 | { | |
1073 | struct rt_mutex_waiter waiter; | |
1074 | int ret = 0; | |
1075 | ||
1076 | debug_rt_mutex_init_waiter(&waiter); | |
fb00aca4 PZ |
1077 | RB_CLEAR_NODE(&waiter.pi_tree_entry); |
1078 | RB_CLEAR_NODE(&waiter.tree_entry); | |
8dac456a | 1079 | |
d209d74d | 1080 | raw_spin_lock(&lock->wait_lock); |
8dac456a DH |
1081 | |
1082 | /* Try to acquire the lock again: */ | |
8161239a | 1083 | if (try_to_take_rt_mutex(lock, current, NULL)) { |
d209d74d | 1084 | raw_spin_unlock(&lock->wait_lock); |
8dac456a DH |
1085 | return 0; |
1086 | } | |
1087 | ||
1088 | set_current_state(state); | |
1089 | ||
1090 | /* Setup the timer, when timeout != NULL */ | |
1091 | if (unlikely(timeout)) { | |
1092 | hrtimer_start_expires(&timeout->timer, HRTIMER_MODE_ABS); | |
1093 | if (!hrtimer_active(&timeout->timer)) | |
1094 | timeout->task = NULL; | |
1095 | } | |
1096 | ||
8161239a LJ |
1097 | ret = task_blocks_on_rt_mutex(lock, &waiter, current, detect_deadlock); |
1098 | ||
1099 | if (likely(!ret)) | |
1100 | ret = __rt_mutex_slowlock(lock, state, timeout, &waiter); | |
8dac456a | 1101 | |
23f78d4a IM |
1102 | set_current_state(TASK_RUNNING); |
1103 | ||
3d5c9340 | 1104 | if (unlikely(ret)) { |
9a11b49a | 1105 | remove_waiter(lock, &waiter); |
3d5c9340 TG |
1106 | rt_mutex_handle_deadlock(ret, detect_deadlock, &waiter); |
1107 | } | |
23f78d4a IM |
1108 | |
1109 | /* | |
1110 | * try_to_take_rt_mutex() sets the waiter bit | |
1111 | * unconditionally. We might have to fix that up. | |
1112 | */ | |
1113 | fixup_rt_mutex_waiters(lock); | |
1114 | ||
d209d74d | 1115 | raw_spin_unlock(&lock->wait_lock); |
23f78d4a IM |
1116 | |
1117 | /* Remove pending timer: */ | |
1118 | if (unlikely(timeout)) | |
1119 | hrtimer_cancel(&timeout->timer); | |
1120 | ||
23f78d4a IM |
1121 | debug_rt_mutex_free_waiter(&waiter); |
1122 | ||
1123 | return ret; | |
1124 | } | |
1125 | ||
1126 | /* | |
1127 | * Slow path try-lock function: | |
1128 | */ | |
88f2b4c1 | 1129 | static inline int rt_mutex_slowtrylock(struct rt_mutex *lock) |
23f78d4a | 1130 | { |
88f2b4c1 TG |
1131 | int ret; |
1132 | ||
1133 | /* | |
1134 | * If the lock already has an owner we fail to get the lock. | |
1135 | * This can be done without taking the @lock->wait_lock as | |
1136 | * it is only being read, and this is a trylock anyway. | |
1137 | */ | |
1138 | if (rt_mutex_owner(lock)) | |
1139 | return 0; | |
23f78d4a | 1140 | |
88f2b4c1 TG |
1141 | /* |
1142 | * The mutex has currently no owner. Lock the wait lock and | |
1143 | * try to acquire the lock. | |
1144 | */ | |
d209d74d | 1145 | raw_spin_lock(&lock->wait_lock); |
23f78d4a | 1146 | |
88f2b4c1 | 1147 | ret = try_to_take_rt_mutex(lock, current, NULL); |
23f78d4a | 1148 | |
88f2b4c1 TG |
1149 | /* |
1150 | * try_to_take_rt_mutex() sets the lock waiters bit | |
1151 | * unconditionally. Clean this up. | |
1152 | */ | |
1153 | fixup_rt_mutex_waiters(lock); | |
23f78d4a | 1154 | |
d209d74d | 1155 | raw_spin_unlock(&lock->wait_lock); |
23f78d4a IM |
1156 | |
1157 | return ret; | |
1158 | } | |
1159 | ||
1160 | /* | |
1161 | * Slow path to release a rt-mutex: | |
1162 | */ | |
1163 | static void __sched | |
1164 | rt_mutex_slowunlock(struct rt_mutex *lock) | |
1165 | { | |
d209d74d | 1166 | raw_spin_lock(&lock->wait_lock); |
23f78d4a IM |
1167 | |
1168 | debug_rt_mutex_unlock(lock); | |
1169 | ||
1170 | rt_mutex_deadlock_account_unlock(current); | |
1171 | ||
27e35715 TG |
1172 | /* |
1173 | * We must be careful here if the fast path is enabled. If we | |
1174 | * have no waiters queued we cannot set owner to NULL here | |
1175 | * because of: | |
1176 | * | |
1177 | * foo->lock->owner = NULL; | |
1178 | * rtmutex_lock(foo->lock); <- fast path | |
1179 | * free = atomic_dec_and_test(foo->refcnt); | |
1180 | * rtmutex_unlock(foo->lock); <- fast path | |
1181 | * if (free) | |
1182 | * kfree(foo); | |
1183 | * raw_spin_unlock(foo->lock->wait_lock); | |
1184 | * | |
1185 | * So for the fastpath enabled kernel: | |
1186 | * | |
1187 | * Nothing can set the waiters bit as long as we hold | |
1188 | * lock->wait_lock. So we do the following sequence: | |
1189 | * | |
1190 | * owner = rt_mutex_owner(lock); | |
1191 | * clear_rt_mutex_waiters(lock); | |
1192 | * raw_spin_unlock(&lock->wait_lock); | |
1193 | * if (cmpxchg(&lock->owner, owner, 0) == owner) | |
1194 | * return; | |
1195 | * goto retry; | |
1196 | * | |
1197 | * The fastpath disabled variant is simple as all access to | |
1198 | * lock->owner is serialized by lock->wait_lock: | |
1199 | * | |
1200 | * lock->owner = NULL; | |
1201 | * raw_spin_unlock(&lock->wait_lock); | |
1202 | */ | |
1203 | while (!rt_mutex_has_waiters(lock)) { | |
1204 | /* Drops lock->wait_lock ! */ | |
1205 | if (unlock_rt_mutex_safe(lock) == true) | |
1206 | return; | |
1207 | /* Relock the rtmutex and try again */ | |
1208 | raw_spin_lock(&lock->wait_lock); | |
23f78d4a IM |
1209 | } |
1210 | ||
27e35715 TG |
1211 | /* |
1212 | * The wakeup next waiter path does not suffer from the above | |
1213 | * race. See the comments there. | |
1214 | */ | |
23f78d4a IM |
1215 | wakeup_next_waiter(lock); |
1216 | ||
d209d74d | 1217 | raw_spin_unlock(&lock->wait_lock); |
23f78d4a IM |
1218 | |
1219 | /* Undo pi boosting if necessary: */ | |
1220 | rt_mutex_adjust_prio(current); | |
1221 | } | |
1222 | ||
1223 | /* | |
1224 | * debug aware fast / slowpath lock,trylock,unlock | |
1225 | * | |
1226 | * The atomic acquire/release ops are compiled away, when either the | |
1227 | * architecture does not support cmpxchg or when debugging is enabled. | |
1228 | */ | |
1229 | static inline int | |
1230 | rt_mutex_fastlock(struct rt_mutex *lock, int state, | |
23f78d4a IM |
1231 | int (*slowfn)(struct rt_mutex *lock, int state, |
1232 | struct hrtimer_sleeper *timeout, | |
9a11b49a | 1233 | int detect_deadlock)) |
23f78d4a | 1234 | { |
c051b21f | 1235 | if (likely(rt_mutex_cmpxchg(lock, NULL, current))) { |
23f78d4a IM |
1236 | rt_mutex_deadlock_account_lock(lock, current); |
1237 | return 0; | |
1238 | } else | |
c051b21f | 1239 | return slowfn(lock, state, NULL, 0); |
23f78d4a IM |
1240 | } |
1241 | ||
1242 | static inline int | |
1243 | rt_mutex_timed_fastlock(struct rt_mutex *lock, int state, | |
1244 | struct hrtimer_sleeper *timeout, int detect_deadlock, | |
1245 | int (*slowfn)(struct rt_mutex *lock, int state, | |
1246 | struct hrtimer_sleeper *timeout, | |
9a11b49a | 1247 | int detect_deadlock)) |
23f78d4a IM |
1248 | { |
1249 | if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) { | |
1250 | rt_mutex_deadlock_account_lock(lock, current); | |
1251 | return 0; | |
1252 | } else | |
9a11b49a | 1253 | return slowfn(lock, state, timeout, detect_deadlock); |
23f78d4a IM |
1254 | } |
1255 | ||
1256 | static inline int | |
1257 | rt_mutex_fasttrylock(struct rt_mutex *lock, | |
9a11b49a | 1258 | int (*slowfn)(struct rt_mutex *lock)) |
23f78d4a IM |
1259 | { |
1260 | if (likely(rt_mutex_cmpxchg(lock, NULL, current))) { | |
1261 | rt_mutex_deadlock_account_lock(lock, current); | |
1262 | return 1; | |
1263 | } | |
9a11b49a | 1264 | return slowfn(lock); |
23f78d4a IM |
1265 | } |
1266 | ||
1267 | static inline void | |
1268 | rt_mutex_fastunlock(struct rt_mutex *lock, | |
1269 | void (*slowfn)(struct rt_mutex *lock)) | |
1270 | { | |
1271 | if (likely(rt_mutex_cmpxchg(lock, current, NULL))) | |
1272 | rt_mutex_deadlock_account_unlock(current); | |
1273 | else | |
1274 | slowfn(lock); | |
1275 | } | |
1276 | ||
1277 | /** | |
1278 | * rt_mutex_lock - lock a rt_mutex | |
1279 | * | |
1280 | * @lock: the rt_mutex to be locked | |
1281 | */ | |
1282 | void __sched rt_mutex_lock(struct rt_mutex *lock) | |
1283 | { | |
1284 | might_sleep(); | |
1285 | ||
c051b21f | 1286 | rt_mutex_fastlock(lock, TASK_UNINTERRUPTIBLE, rt_mutex_slowlock); |
23f78d4a IM |
1287 | } |
1288 | EXPORT_SYMBOL_GPL(rt_mutex_lock); | |
1289 | ||
1290 | /** | |
1291 | * rt_mutex_lock_interruptible - lock a rt_mutex interruptible | |
1292 | * | |
c051b21f | 1293 | * @lock: the rt_mutex to be locked |
23f78d4a IM |
1294 | * |
1295 | * Returns: | |
c051b21f TG |
1296 | * 0 on success |
1297 | * -EINTR when interrupted by a signal | |
23f78d4a | 1298 | */ |
c051b21f | 1299 | int __sched rt_mutex_lock_interruptible(struct rt_mutex *lock) |
23f78d4a IM |
1300 | { |
1301 | might_sleep(); | |
1302 | ||
c051b21f | 1303 | return rt_mutex_fastlock(lock, TASK_INTERRUPTIBLE, rt_mutex_slowlock); |
23f78d4a IM |
1304 | } |
1305 | EXPORT_SYMBOL_GPL(rt_mutex_lock_interruptible); | |
1306 | ||
c051b21f TG |
1307 | /* |
1308 | * Futex variant with full deadlock detection. | |
1309 | */ | |
1310 | int rt_mutex_timed_futex_lock(struct rt_mutex *lock, | |
1311 | struct hrtimer_sleeper *timeout) | |
1312 | { | |
1313 | might_sleep(); | |
1314 | ||
1315 | return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout, 1, | |
1316 | rt_mutex_slowlock); | |
1317 | } | |
1318 | ||
23f78d4a | 1319 | /** |
23b94b96 LH |
1320 | * rt_mutex_timed_lock - lock a rt_mutex interruptible |
1321 | * the timeout structure is provided | |
1322 | * by the caller | |
23f78d4a | 1323 | * |
c051b21f | 1324 | * @lock: the rt_mutex to be locked |
23f78d4a | 1325 | * @timeout: timeout structure or NULL (no timeout) |
23f78d4a IM |
1326 | * |
1327 | * Returns: | |
c051b21f TG |
1328 | * 0 on success |
1329 | * -EINTR when interrupted by a signal | |
3ac49a1c | 1330 | * -ETIMEDOUT when the timeout expired |
23f78d4a IM |
1331 | */ |
1332 | int | |
c051b21f | 1333 | rt_mutex_timed_lock(struct rt_mutex *lock, struct hrtimer_sleeper *timeout) |
23f78d4a IM |
1334 | { |
1335 | might_sleep(); | |
1336 | ||
c051b21f TG |
1337 | return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout, 0, |
1338 | rt_mutex_slowlock); | |
23f78d4a IM |
1339 | } |
1340 | EXPORT_SYMBOL_GPL(rt_mutex_timed_lock); | |
1341 | ||
1342 | /** | |
1343 | * rt_mutex_trylock - try to lock a rt_mutex | |
1344 | * | |
1345 | * @lock: the rt_mutex to be locked | |
1346 | * | |
1347 | * Returns 1 on success and 0 on contention | |
1348 | */ | |
1349 | int __sched rt_mutex_trylock(struct rt_mutex *lock) | |
1350 | { | |
1351 | return rt_mutex_fasttrylock(lock, rt_mutex_slowtrylock); | |
1352 | } | |
1353 | EXPORT_SYMBOL_GPL(rt_mutex_trylock); | |
1354 | ||
1355 | /** | |
1356 | * rt_mutex_unlock - unlock a rt_mutex | |
1357 | * | |
1358 | * @lock: the rt_mutex to be unlocked | |
1359 | */ | |
1360 | void __sched rt_mutex_unlock(struct rt_mutex *lock) | |
1361 | { | |
1362 | rt_mutex_fastunlock(lock, rt_mutex_slowunlock); | |
1363 | } | |
1364 | EXPORT_SYMBOL_GPL(rt_mutex_unlock); | |
1365 | ||
23b94b96 | 1366 | /** |
23f78d4a IM |
1367 | * rt_mutex_destroy - mark a mutex unusable |
1368 | * @lock: the mutex to be destroyed | |
1369 | * | |
1370 | * This function marks the mutex uninitialized, and any subsequent | |
1371 | * use of the mutex is forbidden. The mutex must not be locked when | |
1372 | * this function is called. | |
1373 | */ | |
1374 | void rt_mutex_destroy(struct rt_mutex *lock) | |
1375 | { | |
1376 | WARN_ON(rt_mutex_is_locked(lock)); | |
1377 | #ifdef CONFIG_DEBUG_RT_MUTEXES | |
1378 | lock->magic = NULL; | |
1379 | #endif | |
1380 | } | |
1381 | ||
1382 | EXPORT_SYMBOL_GPL(rt_mutex_destroy); | |
1383 | ||
1384 | /** | |
1385 | * __rt_mutex_init - initialize the rt lock | |
1386 | * | |
1387 | * @lock: the rt lock to be initialized | |
1388 | * | |
1389 | * Initialize the rt lock to unlocked state. | |
1390 | * | |
1391 | * Initializing of a locked rt lock is not allowed | |
1392 | */ | |
1393 | void __rt_mutex_init(struct rt_mutex *lock, const char *name) | |
1394 | { | |
1395 | lock->owner = NULL; | |
d209d74d | 1396 | raw_spin_lock_init(&lock->wait_lock); |
fb00aca4 PZ |
1397 | lock->waiters = RB_ROOT; |
1398 | lock->waiters_leftmost = NULL; | |
23f78d4a IM |
1399 | |
1400 | debug_rt_mutex_init(lock, name); | |
1401 | } | |
1402 | EXPORT_SYMBOL_GPL(__rt_mutex_init); | |
0cdbee99 IM |
1403 | |
1404 | /** | |
1405 | * rt_mutex_init_proxy_locked - initialize and lock a rt_mutex on behalf of a | |
1406 | * proxy owner | |
1407 | * | |
1408 | * @lock: the rt_mutex to be locked | |
1409 | * @proxy_owner:the task to set as owner | |
1410 | * | |
1411 | * No locking. Caller has to do serializing itself | |
1412 | * Special API call for PI-futex support | |
1413 | */ | |
1414 | void rt_mutex_init_proxy_locked(struct rt_mutex *lock, | |
1415 | struct task_struct *proxy_owner) | |
1416 | { | |
1417 | __rt_mutex_init(lock, NULL); | |
9a11b49a | 1418 | debug_rt_mutex_proxy_lock(lock, proxy_owner); |
8161239a | 1419 | rt_mutex_set_owner(lock, proxy_owner); |
0cdbee99 IM |
1420 | rt_mutex_deadlock_account_lock(lock, proxy_owner); |
1421 | } | |
1422 | ||
1423 | /** | |
1424 | * rt_mutex_proxy_unlock - release a lock on behalf of owner | |
1425 | * | |
1426 | * @lock: the rt_mutex to be locked | |
1427 | * | |
1428 | * No locking. Caller has to do serializing itself | |
1429 | * Special API call for PI-futex support | |
1430 | */ | |
1431 | void rt_mutex_proxy_unlock(struct rt_mutex *lock, | |
1432 | struct task_struct *proxy_owner) | |
1433 | { | |
1434 | debug_rt_mutex_proxy_unlock(lock); | |
8161239a | 1435 | rt_mutex_set_owner(lock, NULL); |
0cdbee99 IM |
1436 | rt_mutex_deadlock_account_unlock(proxy_owner); |
1437 | } | |
1438 | ||
8dac456a DH |
1439 | /** |
1440 | * rt_mutex_start_proxy_lock() - Start lock acquisition for another task | |
1441 | * @lock: the rt_mutex to take | |
1442 | * @waiter: the pre-initialized rt_mutex_waiter | |
1443 | * @task: the task to prepare | |
8dac456a DH |
1444 | * |
1445 | * Returns: | |
1446 | * 0 - task blocked on lock | |
1447 | * 1 - acquired the lock for task, caller should wake it up | |
1448 | * <0 - error | |
1449 | * | |
1450 | * Special API call for FUTEX_REQUEUE_PI support. | |
1451 | */ | |
1452 | int rt_mutex_start_proxy_lock(struct rt_mutex *lock, | |
1453 | struct rt_mutex_waiter *waiter, | |
c051b21f | 1454 | struct task_struct *task) |
8dac456a DH |
1455 | { |
1456 | int ret; | |
1457 | ||
d209d74d | 1458 | raw_spin_lock(&lock->wait_lock); |
8dac456a | 1459 | |
8161239a | 1460 | if (try_to_take_rt_mutex(lock, task, NULL)) { |
d209d74d | 1461 | raw_spin_unlock(&lock->wait_lock); |
8dac456a DH |
1462 | return 1; |
1463 | } | |
1464 | ||
3d5c9340 TG |
1465 | /* We enforce deadlock detection for futexes */ |
1466 | ret = task_blocks_on_rt_mutex(lock, waiter, task, 1); | |
8dac456a | 1467 | |
8161239a | 1468 | if (ret && !rt_mutex_owner(lock)) { |
8dac456a DH |
1469 | /* |
1470 | * Reset the return value. We might have | |
1471 | * returned with -EDEADLK and the owner | |
1472 | * released the lock while we were walking the | |
1473 | * pi chain. Let the waiter sort it out. | |
1474 | */ | |
1475 | ret = 0; | |
1476 | } | |
8161239a LJ |
1477 | |
1478 | if (unlikely(ret)) | |
1479 | remove_waiter(lock, waiter); | |
1480 | ||
d209d74d | 1481 | raw_spin_unlock(&lock->wait_lock); |
8dac456a DH |
1482 | |
1483 | debug_rt_mutex_print_deadlock(waiter); | |
1484 | ||
1485 | return ret; | |
1486 | } | |
1487 | ||
0cdbee99 IM |
1488 | /** |
1489 | * rt_mutex_next_owner - return the next owner of the lock | |
1490 | * | |
1491 | * @lock: the rt lock query | |
1492 | * | |
1493 | * Returns the next owner of the lock or NULL | |
1494 | * | |
1495 | * Caller has to serialize against other accessors to the lock | |
1496 | * itself. | |
1497 | * | |
1498 | * Special API call for PI-futex support | |
1499 | */ | |
1500 | struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock) | |
1501 | { | |
1502 | if (!rt_mutex_has_waiters(lock)) | |
1503 | return NULL; | |
1504 | ||
1505 | return rt_mutex_top_waiter(lock)->task; | |
1506 | } | |
8dac456a DH |
1507 | |
1508 | /** | |
1509 | * rt_mutex_finish_proxy_lock() - Complete lock acquisition | |
1510 | * @lock: the rt_mutex we were woken on | |
1511 | * @to: the timeout, null if none. hrtimer should already have | |
c051b21f | 1512 | * been started. |
8dac456a | 1513 | * @waiter: the pre-initialized rt_mutex_waiter |
8dac456a DH |
1514 | * |
1515 | * Complete the lock acquisition started our behalf by another thread. | |
1516 | * | |
1517 | * Returns: | |
1518 | * 0 - success | |
c051b21f | 1519 | * <0 - error, one of -EINTR, -ETIMEDOUT |
8dac456a DH |
1520 | * |
1521 | * Special API call for PI-futex requeue support | |
1522 | */ | |
1523 | int rt_mutex_finish_proxy_lock(struct rt_mutex *lock, | |
1524 | struct hrtimer_sleeper *to, | |
c051b21f | 1525 | struct rt_mutex_waiter *waiter) |
8dac456a DH |
1526 | { |
1527 | int ret; | |
1528 | ||
d209d74d | 1529 | raw_spin_lock(&lock->wait_lock); |
8dac456a DH |
1530 | |
1531 | set_current_state(TASK_INTERRUPTIBLE); | |
1532 | ||
8161239a | 1533 | ret = __rt_mutex_slowlock(lock, TASK_INTERRUPTIBLE, to, waiter); |
8dac456a DH |
1534 | |
1535 | set_current_state(TASK_RUNNING); | |
1536 | ||
8161239a | 1537 | if (unlikely(ret)) |
8dac456a DH |
1538 | remove_waiter(lock, waiter); |
1539 | ||
1540 | /* | |
1541 | * try_to_take_rt_mutex() sets the waiter bit unconditionally. We might | |
1542 | * have to fix that up. | |
1543 | */ | |
1544 | fixup_rt_mutex_waiters(lock); | |
1545 | ||
d209d74d | 1546 | raw_spin_unlock(&lock->wait_lock); |
8dac456a | 1547 | |
8dac456a DH |
1548 | return ret; |
1549 | } |