Commit | Line | Data |
---|---|---|
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> |
23f78d4a IM |
17 | #include <linux/timer.h> |
18 | ||
19 | #include "rtmutex_common.h" | |
20 | ||
23f78d4a IM |
21 | /* |
22 | * lock->owner state tracking: | |
23 | * | |
8161239a LJ |
24 | * lock->owner holds the task_struct pointer of the owner. Bit 0 |
25 | * is used to keep track of the "lock has waiters" state. | |
23f78d4a | 26 | * |
8161239a LJ |
27 | * owner bit0 |
28 | * NULL 0 lock is free (fast acquire possible) | |
29 | * NULL 1 lock is free and has waiters and the top waiter | |
30 | * is going to take the lock* | |
31 | * taskpointer 0 lock is held (fast release possible) | |
32 | * taskpointer 1 lock is held and has waiters** | |
23f78d4a IM |
33 | * |
34 | * The fast atomic compare exchange based acquire and release is only | |
8161239a LJ |
35 | * possible when bit 0 of lock->owner is 0. |
36 | * | |
37 | * (*) It also can be a transitional state when grabbing the lock | |
38 | * with ->wait_lock is held. To prevent any fast path cmpxchg to the lock, | |
39 | * we need to set the bit0 before looking at the lock, and the owner may be | |
40 | * NULL in this small time, hence this can be a transitional state. | |
23f78d4a | 41 | * |
8161239a LJ |
42 | * (**) There is a small time when bit 0 is set but there are no |
43 | * waiters. This can happen when grabbing the lock in the slow path. | |
44 | * To prevent a cmpxchg of the owner releasing the lock, we need to | |
45 | * set this bit before looking at the lock. | |
23f78d4a IM |
46 | */ |
47 | ||
bd197234 | 48 | static void |
8161239a | 49 | rt_mutex_set_owner(struct rt_mutex *lock, struct task_struct *owner) |
23f78d4a | 50 | { |
8161239a | 51 | unsigned long val = (unsigned long)owner; |
23f78d4a IM |
52 | |
53 | if (rt_mutex_has_waiters(lock)) | |
54 | val |= RT_MUTEX_HAS_WAITERS; | |
55 | ||
56 | lock->owner = (struct task_struct *)val; | |
57 | } | |
58 | ||
59 | static inline void clear_rt_mutex_waiters(struct rt_mutex *lock) | |
60 | { | |
61 | lock->owner = (struct task_struct *) | |
62 | ((unsigned long)lock->owner & ~RT_MUTEX_HAS_WAITERS); | |
63 | } | |
64 | ||
65 | static void fixup_rt_mutex_waiters(struct rt_mutex *lock) | |
66 | { | |
67 | if (!rt_mutex_has_waiters(lock)) | |
68 | clear_rt_mutex_waiters(lock); | |
69 | } | |
70 | ||
bd197234 TG |
71 | /* |
72 | * We can speed up the acquire/release, if the architecture | |
73 | * supports cmpxchg and if there's no debugging state to be set up | |
74 | */ | |
75 | #if defined(__HAVE_ARCH_CMPXCHG) && !defined(CONFIG_DEBUG_RT_MUTEXES) | |
76 | # define rt_mutex_cmpxchg(l,c,n) (cmpxchg(&l->owner, c, n) == c) | |
77 | static inline void mark_rt_mutex_waiters(struct rt_mutex *lock) | |
78 | { | |
79 | unsigned long owner, *p = (unsigned long *) &lock->owner; | |
80 | ||
81 | do { | |
82 | owner = *p; | |
83 | } while (cmpxchg(p, owner, owner | RT_MUTEX_HAS_WAITERS) != owner); | |
84 | } | |
2371e977 TG |
85 | |
86 | /* | |
87 | * Safe fastpath aware unlock: | |
88 | * 1) Clear the waiters bit | |
89 | * 2) Drop lock->wait_lock | |
90 | * 3) Try to unlock the lock with cmpxchg | |
91 | */ | |
92 | static inline bool unlock_rt_mutex_safe(struct rt_mutex *lock) | |
93 | __releases(lock->wait_lock) | |
94 | { | |
95 | struct task_struct *owner = rt_mutex_owner(lock); | |
96 | ||
97 | clear_rt_mutex_waiters(lock); | |
98 | raw_spin_unlock(&lock->wait_lock); | |
99 | /* | |
100 | * If a new waiter comes in between the unlock and the cmpxchg | |
101 | * we have two situations: | |
102 | * | |
103 | * unlock(wait_lock); | |
104 | * lock(wait_lock); | |
105 | * cmpxchg(p, owner, 0) == owner | |
106 | * mark_rt_mutex_waiters(lock); | |
107 | * acquire(lock); | |
108 | * or: | |
109 | * | |
110 | * unlock(wait_lock); | |
111 | * lock(wait_lock); | |
112 | * mark_rt_mutex_waiters(lock); | |
113 | * | |
114 | * cmpxchg(p, owner, 0) != owner | |
115 | * enqueue_waiter(); | |
116 | * unlock(wait_lock); | |
117 | * lock(wait_lock); | |
118 | * wake waiter(); | |
119 | * unlock(wait_lock); | |
120 | * lock(wait_lock); | |
121 | * acquire(lock); | |
122 | */ | |
123 | return rt_mutex_cmpxchg(lock, owner, NULL); | |
124 | } | |
125 | ||
bd197234 TG |
126 | #else |
127 | # define rt_mutex_cmpxchg(l,c,n) (0) | |
128 | static inline void mark_rt_mutex_waiters(struct rt_mutex *lock) | |
129 | { | |
130 | lock->owner = (struct task_struct *) | |
131 | ((unsigned long)lock->owner | RT_MUTEX_HAS_WAITERS); | |
132 | } | |
2371e977 TG |
133 | |
134 | /* | |
135 | * Simple slow path only version: lock->owner is protected by lock->wait_lock. | |
136 | */ | |
137 | static inline bool unlock_rt_mutex_safe(struct rt_mutex *lock) | |
138 | __releases(lock->wait_lock) | |
139 | { | |
140 | lock->owner = NULL; | |
141 | raw_spin_unlock(&lock->wait_lock); | |
142 | return true; | |
143 | } | |
bd197234 TG |
144 | #endif |
145 | ||
23f78d4a IM |
146 | /* |
147 | * Calculate task priority from the waiter list priority | |
148 | * | |
149 | * Return task->normal_prio when the waiter list is empty or when | |
150 | * the waiter is not allowed to do priority boosting | |
151 | */ | |
152 | int rt_mutex_getprio(struct task_struct *task) | |
153 | { | |
154 | if (likely(!task_has_pi_waiters(task))) | |
155 | return task->normal_prio; | |
156 | ||
157 | return min(task_top_pi_waiter(task)->pi_list_entry.prio, | |
158 | task->normal_prio); | |
159 | } | |
160 | ||
161 | /* | |
162 | * Adjust the priority of a task, after its pi_waiters got modified. | |
163 | * | |
164 | * This can be both boosting and unboosting. task->pi_lock must be held. | |
165 | */ | |
bd197234 | 166 | static void __rt_mutex_adjust_prio(struct task_struct *task) |
23f78d4a IM |
167 | { |
168 | int prio = rt_mutex_getprio(task); | |
169 | ||
170 | if (task->prio != prio) | |
171 | rt_mutex_setprio(task, prio); | |
172 | } | |
173 | ||
174 | /* | |
175 | * Adjust task priority (undo boosting). Called from the exit path of | |
176 | * rt_mutex_slowunlock() and rt_mutex_slowlock(). | |
177 | * | |
178 | * (Note: We do this outside of the protection of lock->wait_lock to | |
179 | * allow the lock to be taken while or before we readjust the priority | |
180 | * of task. We do not use the spin_xx_mutex() variants here as we are | |
181 | * outside of the debug path.) | |
182 | */ | |
183 | static void rt_mutex_adjust_prio(struct task_struct *task) | |
184 | { | |
185 | unsigned long flags; | |
186 | ||
1d615482 | 187 | raw_spin_lock_irqsave(&task->pi_lock, flags); |
23f78d4a | 188 | __rt_mutex_adjust_prio(task); |
1d615482 | 189 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
23f78d4a IM |
190 | } |
191 | ||
192 | /* | |
193 | * Max number of times we'll walk the boosting chain: | |
194 | */ | |
195 | int max_lock_depth = 1024; | |
196 | ||
98be12bc TG |
197 | static inline struct rt_mutex *task_blocked_on_lock(struct task_struct *p) |
198 | { | |
199 | return p->pi_blocked_on ? p->pi_blocked_on->lock : NULL; | |
200 | } | |
201 | ||
23f78d4a IM |
202 | /* |
203 | * Adjust the priority chain. Also used for deadlock detection. | |
204 | * Decreases task's usage by one - may thus free the task. | |
205 | * Returns 0 or -EDEADLK. | |
206 | */ | |
bd197234 TG |
207 | static int rt_mutex_adjust_prio_chain(struct task_struct *task, |
208 | int deadlock_detect, | |
209 | struct rt_mutex *orig_lock, | |
98be12bc | 210 | struct rt_mutex *next_lock, |
bd197234 TG |
211 | struct rt_mutex_waiter *orig_waiter, |
212 | struct task_struct *top_task) | |
23f78d4a IM |
213 | { |
214 | struct rt_mutex *lock; | |
215 | struct rt_mutex_waiter *waiter, *top_waiter = orig_waiter; | |
216 | int detect_deadlock, ret = 0, depth = 0; | |
217 | unsigned long flags; | |
218 | ||
219 | detect_deadlock = debug_rt_mutex_detect_deadlock(orig_waiter, | |
220 | deadlock_detect); | |
221 | ||
222 | /* | |
223 | * The (de)boosting is a step by step approach with a lot of | |
224 | * pitfalls. We want this to be preemptible and we want hold a | |
225 | * maximum of two locks per step. So we have to check | |
226 | * carefully whether things change under us. | |
227 | */ | |
228 | again: | |
229 | if (++depth > max_lock_depth) { | |
230 | static int prev_max; | |
231 | ||
232 | /* | |
233 | * Print this only once. If the admin changes the limit, | |
234 | * print a new message when reaching the limit again. | |
235 | */ | |
236 | if (prev_max != max_lock_depth) { | |
237 | prev_max = max_lock_depth; | |
238 | printk(KERN_WARNING "Maximum lock depth %d reached " | |
239 | "task: %s (%d)\n", max_lock_depth, | |
ba25f9dc | 240 | top_task->comm, task_pid_nr(top_task)); |
23f78d4a IM |
241 | } |
242 | put_task_struct(task); | |
243 | ||
1201613a | 244 | return -EDEADLK; |
23f78d4a IM |
245 | } |
246 | retry: | |
247 | /* | |
248 | * Task can not go away as we did a get_task() before ! | |
249 | */ | |
1d615482 | 250 | raw_spin_lock_irqsave(&task->pi_lock, flags); |
23f78d4a IM |
251 | |
252 | waiter = task->pi_blocked_on; | |
253 | /* | |
254 | * Check whether the end of the boosting chain has been | |
255 | * reached or the state of the chain has changed while we | |
256 | * dropped the locks. | |
257 | */ | |
8161239a | 258 | if (!waiter) |
23f78d4a IM |
259 | goto out_unlock_pi; |
260 | ||
1a539a87 TG |
261 | /* |
262 | * Check the orig_waiter state. After we dropped the locks, | |
8161239a | 263 | * the previous owner of the lock might have released the lock. |
1a539a87 | 264 | */ |
8161239a | 265 | if (orig_waiter && !rt_mutex_owner(orig_lock)) |
1a539a87 TG |
266 | goto out_unlock_pi; |
267 | ||
98be12bc TG |
268 | /* |
269 | * We dropped all locks after taking a refcount on @task, so | |
270 | * the task might have moved on in the lock chain or even left | |
271 | * the chain completely and blocks now on an unrelated lock or | |
272 | * on @orig_lock. | |
273 | * | |
274 | * We stored the lock on which @task was blocked in @next_lock, | |
275 | * so we can detect the chain change. | |
276 | */ | |
277 | if (next_lock != waiter->lock) | |
278 | goto out_unlock_pi; | |
279 | ||
1a539a87 TG |
280 | /* |
281 | * Drop out, when the task has no waiters. Note, | |
282 | * top_waiter can be NULL, when we are in the deboosting | |
283 | * mode! | |
284 | */ | |
d88b1b40 TG |
285 | if (top_waiter) { |
286 | if (!task_has_pi_waiters(task)) | |
287 | goto out_unlock_pi; | |
288 | /* | |
289 | * If deadlock detection is off, we stop here if we | |
290 | * are not the top pi waiter of the task. | |
291 | */ | |
292 | if (!detect_deadlock && top_waiter != task_top_pi_waiter(task)) | |
293 | goto out_unlock_pi; | |
294 | } | |
23f78d4a IM |
295 | |
296 | /* | |
297 | * When deadlock detection is off then we check, if further | |
298 | * priority adjustment is necessary. | |
299 | */ | |
300 | if (!detect_deadlock && waiter->list_entry.prio == task->prio) | |
301 | goto out_unlock_pi; | |
302 | ||
303 | lock = waiter->lock; | |
d209d74d | 304 | if (!raw_spin_trylock(&lock->wait_lock)) { |
1d615482 | 305 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
23f78d4a IM |
306 | cpu_relax(); |
307 | goto retry; | |
308 | } | |
309 | ||
d88b1b40 TG |
310 | /* |
311 | * Deadlock detection. If the lock is the same as the original | |
312 | * lock which caused us to walk the lock chain or if the | |
313 | * current lock is owned by the task which initiated the chain | |
314 | * walk, we detected a deadlock. | |
315 | */ | |
95e02ca9 | 316 | if (lock == orig_lock || rt_mutex_owner(lock) == top_task) { |
23f78d4a | 317 | debug_rt_mutex_deadlock(deadlock_detect, orig_waiter, lock); |
d209d74d | 318 | raw_spin_unlock(&lock->wait_lock); |
1201613a | 319 | ret = -EDEADLK; |
23f78d4a IM |
320 | goto out_unlock_pi; |
321 | } | |
322 | ||
323 | top_waiter = rt_mutex_top_waiter(lock); | |
324 | ||
325 | /* Requeue the waiter */ | |
326 | plist_del(&waiter->list_entry, &lock->wait_list); | |
327 | waiter->list_entry.prio = task->prio; | |
328 | plist_add(&waiter->list_entry, &lock->wait_list); | |
329 | ||
330 | /* Release the task */ | |
1d615482 | 331 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
8161239a LJ |
332 | if (!rt_mutex_owner(lock)) { |
333 | /* | |
334 | * If the requeue above changed the top waiter, then we need | |
335 | * to wake the new top waiter up to try to get the lock. | |
336 | */ | |
337 | ||
338 | if (top_waiter != rt_mutex_top_waiter(lock)) | |
339 | wake_up_process(rt_mutex_top_waiter(lock)->task); | |
340 | raw_spin_unlock(&lock->wait_lock); | |
341 | goto out_put_task; | |
342 | } | |
23f78d4a IM |
343 | put_task_struct(task); |
344 | ||
345 | /* Grab the next task */ | |
346 | task = rt_mutex_owner(lock); | |
db630637 | 347 | get_task_struct(task); |
1d615482 | 348 | raw_spin_lock_irqsave(&task->pi_lock, flags); |
23f78d4a IM |
349 | |
350 | if (waiter == rt_mutex_top_waiter(lock)) { | |
351 | /* Boost the owner */ | |
352 | plist_del(&top_waiter->pi_list_entry, &task->pi_waiters); | |
353 | waiter->pi_list_entry.prio = waiter->list_entry.prio; | |
354 | plist_add(&waiter->pi_list_entry, &task->pi_waiters); | |
355 | __rt_mutex_adjust_prio(task); | |
356 | ||
357 | } else if (top_waiter == waiter) { | |
358 | /* Deboost the owner */ | |
359 | plist_del(&waiter->pi_list_entry, &task->pi_waiters); | |
360 | waiter = rt_mutex_top_waiter(lock); | |
361 | waiter->pi_list_entry.prio = waiter->list_entry.prio; | |
362 | plist_add(&waiter->pi_list_entry, &task->pi_waiters); | |
363 | __rt_mutex_adjust_prio(task); | |
364 | } | |
365 | ||
98be12bc TG |
366 | /* |
367 | * Check whether the task which owns the current lock is pi | |
368 | * blocked itself. If yes we store a pointer to the lock for | |
369 | * the lock chain change detection above. After we dropped | |
370 | * task->pi_lock next_lock cannot be dereferenced anymore. | |
371 | */ | |
372 | next_lock = task_blocked_on_lock(task); | |
373 | ||
1d615482 | 374 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
23f78d4a IM |
375 | |
376 | top_waiter = rt_mutex_top_waiter(lock); | |
d209d74d | 377 | raw_spin_unlock(&lock->wait_lock); |
23f78d4a | 378 | |
98be12bc TG |
379 | /* |
380 | * We reached the end of the lock chain. Stop right here. No | |
381 | * point to go back just to figure that out. | |
382 | */ | |
383 | if (!next_lock) | |
384 | goto out_put_task; | |
385 | ||
23f78d4a IM |
386 | if (!detect_deadlock && waiter != top_waiter) |
387 | goto out_put_task; | |
388 | ||
389 | goto again; | |
390 | ||
391 | out_unlock_pi: | |
1d615482 | 392 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
23f78d4a IM |
393 | out_put_task: |
394 | put_task_struct(task); | |
36c8b586 | 395 | |
23f78d4a IM |
396 | return ret; |
397 | } | |
398 | ||
23f78d4a IM |
399 | /* |
400 | * Try to take an rt-mutex | |
401 | * | |
23f78d4a | 402 | * Must be called with lock->wait_lock held. |
8161239a LJ |
403 | * |
404 | * @lock: the lock to be acquired. | |
405 | * @task: the task which wants to acquire the lock | |
406 | * @waiter: the waiter that is queued to the lock's wait list. (could be NULL) | |
23f78d4a | 407 | */ |
8161239a LJ |
408 | static int try_to_take_rt_mutex(struct rt_mutex *lock, struct task_struct *task, |
409 | struct rt_mutex_waiter *waiter) | |
23f78d4a IM |
410 | { |
411 | /* | |
412 | * We have to be careful here if the atomic speedups are | |
413 | * enabled, such that, when | |
414 | * - no other waiter is on the lock | |
415 | * - the lock has been released since we did the cmpxchg | |
416 | * the lock can be released or taken while we are doing the | |
417 | * checks and marking the lock with RT_MUTEX_HAS_WAITERS. | |
418 | * | |
419 | * The atomic acquire/release aware variant of | |
420 | * mark_rt_mutex_waiters uses a cmpxchg loop. After setting | |
421 | * the WAITERS bit, the atomic release / acquire can not | |
422 | * happen anymore and lock->wait_lock protects us from the | |
423 | * non-atomic case. | |
424 | * | |
425 | * Note, that this might set lock->owner = | |
426 | * RT_MUTEX_HAS_WAITERS in the case the lock is not contended | |
427 | * any more. This is fixed up when we take the ownership. | |
428 | * This is the transitional state explained at the top of this file. | |
429 | */ | |
430 | mark_rt_mutex_waiters(lock); | |
431 | ||
8161239a | 432 | if (rt_mutex_owner(lock)) |
23f78d4a IM |
433 | return 0; |
434 | ||
8161239a LJ |
435 | /* |
436 | * It will get the lock because of one of these conditions: | |
437 | * 1) there is no waiter | |
438 | * 2) higher priority than waiters | |
439 | * 3) it is top waiter | |
440 | */ | |
441 | if (rt_mutex_has_waiters(lock)) { | |
442 | if (task->prio >= rt_mutex_top_waiter(lock)->list_entry.prio) { | |
443 | if (!waiter || waiter != rt_mutex_top_waiter(lock)) | |
444 | return 0; | |
445 | } | |
446 | } | |
447 | ||
448 | if (waiter || rt_mutex_has_waiters(lock)) { | |
449 | unsigned long flags; | |
450 | struct rt_mutex_waiter *top; | |
451 | ||
452 | raw_spin_lock_irqsave(&task->pi_lock, flags); | |
453 | ||
454 | /* remove the queued waiter. */ | |
455 | if (waiter) { | |
456 | plist_del(&waiter->list_entry, &lock->wait_list); | |
457 | task->pi_blocked_on = NULL; | |
458 | } | |
459 | ||
460 | /* | |
461 | * We have to enqueue the top waiter(if it exists) into | |
462 | * task->pi_waiters list. | |
463 | */ | |
464 | if (rt_mutex_has_waiters(lock)) { | |
465 | top = rt_mutex_top_waiter(lock); | |
466 | top->pi_list_entry.prio = top->list_entry.prio; | |
467 | plist_add(&top->pi_list_entry, &task->pi_waiters); | |
468 | } | |
469 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); | |
470 | } | |
471 | ||
23f78d4a | 472 | /* We got the lock. */ |
9a11b49a | 473 | debug_rt_mutex_lock(lock); |
23f78d4a | 474 | |
8161239a | 475 | rt_mutex_set_owner(lock, task); |
23f78d4a | 476 | |
8161239a | 477 | rt_mutex_deadlock_account_lock(lock, task); |
23f78d4a IM |
478 | |
479 | return 1; | |
480 | } | |
481 | ||
482 | /* | |
483 | * Task blocks on lock. | |
484 | * | |
485 | * Prepare waiter and propagate pi chain | |
486 | * | |
487 | * This must be called with lock->wait_lock held. | |
488 | */ | |
489 | static int task_blocks_on_rt_mutex(struct rt_mutex *lock, | |
490 | struct rt_mutex_waiter *waiter, | |
8dac456a | 491 | struct task_struct *task, |
9a11b49a | 492 | int detect_deadlock) |
23f78d4a | 493 | { |
36c8b586 | 494 | struct task_struct *owner = rt_mutex_owner(lock); |
23f78d4a | 495 | struct rt_mutex_waiter *top_waiter = waiter; |
98be12bc | 496 | struct rt_mutex *next_lock; |
db630637 | 497 | int chain_walk = 0, res; |
98be12bc | 498 | unsigned long flags; |
23f78d4a | 499 | |
d88b1b40 TG |
500 | /* |
501 | * Early deadlock detection. We really don't want the task to | |
502 | * enqueue on itself just to untangle the mess later. It's not | |
503 | * only an optimization. We drop the locks, so another waiter | |
504 | * can come in before the chain walk detects the deadlock. So | |
505 | * the other will detect the deadlock and return -EDEADLOCK, | |
506 | * which is wrong, as the other waiter is not in a deadlock | |
507 | * situation. | |
508 | */ | |
1201613a | 509 | if (owner == task) |
d88b1b40 TG |
510 | return -EDEADLK; |
511 | ||
1d615482 | 512 | raw_spin_lock_irqsave(&task->pi_lock, flags); |
8dac456a DH |
513 | __rt_mutex_adjust_prio(task); |
514 | waiter->task = task; | |
23f78d4a | 515 | waiter->lock = lock; |
8dac456a DH |
516 | plist_node_init(&waiter->list_entry, task->prio); |
517 | plist_node_init(&waiter->pi_list_entry, task->prio); | |
23f78d4a IM |
518 | |
519 | /* Get the top priority waiter on the lock */ | |
520 | if (rt_mutex_has_waiters(lock)) | |
521 | top_waiter = rt_mutex_top_waiter(lock); | |
522 | plist_add(&waiter->list_entry, &lock->wait_list); | |
523 | ||
8dac456a | 524 | task->pi_blocked_on = waiter; |
23f78d4a | 525 | |
1d615482 | 526 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
23f78d4a | 527 | |
8161239a LJ |
528 | if (!owner) |
529 | return 0; | |
530 | ||
98be12bc | 531 | raw_spin_lock_irqsave(&owner->pi_lock, flags); |
23f78d4a | 532 | if (waiter == rt_mutex_top_waiter(lock)) { |
23f78d4a IM |
533 | plist_del(&top_waiter->pi_list_entry, &owner->pi_waiters); |
534 | plist_add(&waiter->pi_list_entry, &owner->pi_waiters); | |
535 | ||
536 | __rt_mutex_adjust_prio(owner); | |
db630637 SR |
537 | if (owner->pi_blocked_on) |
538 | chain_walk = 1; | |
98be12bc | 539 | } else if (debug_rt_mutex_detect_deadlock(waiter, detect_deadlock)) { |
db630637 | 540 | chain_walk = 1; |
98be12bc | 541 | } |
db630637 | 542 | |
98be12bc TG |
543 | /* Store the lock on which owner is blocked or NULL */ |
544 | next_lock = task_blocked_on_lock(owner); | |
545 | ||
546 | raw_spin_unlock_irqrestore(&owner->pi_lock, flags); | |
547 | /* | |
548 | * Even if full deadlock detection is on, if the owner is not | |
549 | * blocked itself, we can avoid finding this out in the chain | |
550 | * walk. | |
551 | */ | |
552 | if (!chain_walk || !next_lock) | |
23f78d4a IM |
553 | return 0; |
554 | ||
db630637 SR |
555 | /* |
556 | * The owner can't disappear while holding a lock, | |
557 | * so the owner struct is protected by wait_lock. | |
558 | * Gets dropped in rt_mutex_adjust_prio_chain()! | |
559 | */ | |
560 | get_task_struct(owner); | |
561 | ||
d209d74d | 562 | raw_spin_unlock(&lock->wait_lock); |
23f78d4a | 563 | |
98be12bc TG |
564 | res = rt_mutex_adjust_prio_chain(owner, detect_deadlock, lock, |
565 | next_lock, waiter, task); | |
23f78d4a | 566 | |
d209d74d | 567 | raw_spin_lock(&lock->wait_lock); |
23f78d4a IM |
568 | |
569 | return res; | |
570 | } | |
571 | ||
572 | /* | |
573 | * Wake up the next waiter on the lock. | |
574 | * | |
2371e977 TG |
575 | * Remove the top waiter from the current tasks pi waiter list and |
576 | * wake it up. | |
23f78d4a IM |
577 | * |
578 | * Called with lock->wait_lock held. | |
579 | */ | |
580 | static void wakeup_next_waiter(struct rt_mutex *lock) | |
581 | { | |
582 | struct rt_mutex_waiter *waiter; | |
23f78d4a IM |
583 | unsigned long flags; |
584 | ||
1d615482 | 585 | raw_spin_lock_irqsave(¤t->pi_lock, flags); |
23f78d4a IM |
586 | |
587 | waiter = rt_mutex_top_waiter(lock); | |
23f78d4a IM |
588 | |
589 | /* | |
590 | * Remove it from current->pi_waiters. We do not adjust a | |
591 | * possible priority boost right now. We execute wakeup in the | |
592 | * boosted mode and go back to normal after releasing | |
593 | * lock->wait_lock. | |
594 | */ | |
595 | plist_del(&waiter->pi_list_entry, ¤t->pi_waiters); | |
23f78d4a | 596 | |
2371e977 TG |
597 | /* |
598 | * As we are waking up the top waiter, and the waiter stays | |
599 | * queued on the lock until it gets the lock, this lock | |
600 | * obviously has waiters. Just set the bit here and this has | |
601 | * the added benefit of forcing all new tasks into the | |
602 | * slow path making sure no task of lower priority than | |
603 | * the top waiter can steal this lock. | |
604 | */ | |
605 | lock->owner = (void *) RT_MUTEX_HAS_WAITERS; | |
23f78d4a | 606 | |
1d615482 | 607 | raw_spin_unlock_irqrestore(¤t->pi_lock, flags); |
23f78d4a | 608 | |
2371e977 TG |
609 | /* |
610 | * It's safe to dereference waiter as it cannot go away as | |
611 | * long as we hold lock->wait_lock. The waiter task needs to | |
612 | * acquire it in order to dequeue the waiter. | |
613 | */ | |
8161239a | 614 | wake_up_process(waiter->task); |
23f78d4a IM |
615 | } |
616 | ||
617 | /* | |
8161239a | 618 | * Remove a waiter from a lock and give up |
23f78d4a | 619 | * |
8161239a LJ |
620 | * Must be called with lock->wait_lock held and |
621 | * have just failed to try_to_take_rt_mutex(). | |
23f78d4a | 622 | */ |
bd197234 TG |
623 | static void remove_waiter(struct rt_mutex *lock, |
624 | struct rt_mutex_waiter *waiter) | |
23f78d4a IM |
625 | { |
626 | int first = (waiter == rt_mutex_top_waiter(lock)); | |
36c8b586 | 627 | struct task_struct *owner = rt_mutex_owner(lock); |
98be12bc | 628 | struct rt_mutex *next_lock = NULL; |
23f78d4a IM |
629 | unsigned long flags; |
630 | ||
1d615482 | 631 | raw_spin_lock_irqsave(¤t->pi_lock, flags); |
23f78d4a | 632 | plist_del(&waiter->list_entry, &lock->wait_list); |
23f78d4a | 633 | current->pi_blocked_on = NULL; |
1d615482 | 634 | raw_spin_unlock_irqrestore(¤t->pi_lock, flags); |
23f78d4a | 635 | |
8161239a LJ |
636 | if (!owner) |
637 | return; | |
638 | ||
639 | if (first) { | |
23f78d4a | 640 | |
1d615482 | 641 | raw_spin_lock_irqsave(&owner->pi_lock, flags); |
23f78d4a IM |
642 | |
643 | plist_del(&waiter->pi_list_entry, &owner->pi_waiters); | |
644 | ||
645 | if (rt_mutex_has_waiters(lock)) { | |
646 | struct rt_mutex_waiter *next; | |
647 | ||
648 | next = rt_mutex_top_waiter(lock); | |
649 | plist_add(&next->pi_list_entry, &owner->pi_waiters); | |
650 | } | |
651 | __rt_mutex_adjust_prio(owner); | |
652 | ||
98be12bc TG |
653 | /* Store the lock on which owner is blocked or NULL */ |
654 | next_lock = task_blocked_on_lock(owner); | |
db630637 | 655 | |
1d615482 | 656 | raw_spin_unlock_irqrestore(&owner->pi_lock, flags); |
23f78d4a IM |
657 | } |
658 | ||
659 | WARN_ON(!plist_node_empty(&waiter->pi_list_entry)); | |
660 | ||
98be12bc | 661 | if (!next_lock) |
23f78d4a IM |
662 | return; |
663 | ||
db630637 SR |
664 | /* gets dropped in rt_mutex_adjust_prio_chain()! */ |
665 | get_task_struct(owner); | |
666 | ||
d209d74d | 667 | raw_spin_unlock(&lock->wait_lock); |
23f78d4a | 668 | |
98be12bc | 669 | rt_mutex_adjust_prio_chain(owner, 0, lock, next_lock, NULL, current); |
23f78d4a | 670 | |
d209d74d | 671 | raw_spin_lock(&lock->wait_lock); |
23f78d4a IM |
672 | } |
673 | ||
95e02ca9 TG |
674 | /* |
675 | * Recheck the pi chain, in case we got a priority setting | |
676 | * | |
677 | * Called from sched_setscheduler | |
678 | */ | |
679 | void rt_mutex_adjust_pi(struct task_struct *task) | |
680 | { | |
681 | struct rt_mutex_waiter *waiter; | |
98be12bc | 682 | struct rt_mutex *next_lock; |
95e02ca9 TG |
683 | unsigned long flags; |
684 | ||
1d615482 | 685 | raw_spin_lock_irqsave(&task->pi_lock, flags); |
95e02ca9 TG |
686 | |
687 | waiter = task->pi_blocked_on; | |
688 | if (!waiter || waiter->list_entry.prio == task->prio) { | |
1d615482 | 689 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
95e02ca9 TG |
690 | return; |
691 | } | |
98be12bc | 692 | next_lock = waiter->lock; |
1d615482 | 693 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
95e02ca9 | 694 | |
db630637 SR |
695 | /* gets dropped in rt_mutex_adjust_prio_chain()! */ |
696 | get_task_struct(task); | |
98be12bc TG |
697 | |
698 | rt_mutex_adjust_prio_chain(task, 0, NULL, next_lock, NULL, task); | |
95e02ca9 TG |
699 | } |
700 | ||
8dac456a DH |
701 | /** |
702 | * __rt_mutex_slowlock() - Perform the wait-wake-try-to-take loop | |
703 | * @lock: the rt_mutex to take | |
704 | * @state: the state the task should block in (TASK_INTERRUPTIBLE | |
705 | * or TASK_UNINTERRUPTIBLE) | |
706 | * @timeout: the pre-initialized and started timer, or NULL for none | |
707 | * @waiter: the pre-initialized rt_mutex_waiter | |
8dac456a DH |
708 | * |
709 | * lock->wait_lock must be held by the caller. | |
23f78d4a IM |
710 | */ |
711 | static int __sched | |
8dac456a DH |
712 | __rt_mutex_slowlock(struct rt_mutex *lock, int state, |
713 | struct hrtimer_sleeper *timeout, | |
8161239a | 714 | struct rt_mutex_waiter *waiter) |
23f78d4a | 715 | { |
23f78d4a IM |
716 | int ret = 0; |
717 | ||
23f78d4a IM |
718 | for (;;) { |
719 | /* Try to acquire the lock: */ | |
8161239a | 720 | if (try_to_take_rt_mutex(lock, current, waiter)) |
23f78d4a IM |
721 | break; |
722 | ||
723 | /* | |
724 | * TASK_INTERRUPTIBLE checks for signals and | |
725 | * timeout. Ignored otherwise. | |
726 | */ | |
727 | if (unlikely(state == TASK_INTERRUPTIBLE)) { | |
728 | /* Signal pending? */ | |
729 | if (signal_pending(current)) | |
730 | ret = -EINTR; | |
731 | if (timeout && !timeout->task) | |
732 | ret = -ETIMEDOUT; | |
733 | if (ret) | |
734 | break; | |
735 | } | |
736 | ||
d209d74d | 737 | raw_spin_unlock(&lock->wait_lock); |
23f78d4a | 738 | |
8dac456a | 739 | debug_rt_mutex_print_deadlock(waiter); |
23f78d4a | 740 | |
8161239a | 741 | schedule_rt_mutex(lock); |
23f78d4a | 742 | |
d209d74d | 743 | raw_spin_lock(&lock->wait_lock); |
23f78d4a IM |
744 | set_current_state(state); |
745 | } | |
746 | ||
8dac456a DH |
747 | return ret; |
748 | } | |
749 | ||
1201613a TG |
750 | static void rt_mutex_handle_deadlock(int res, int detect_deadlock, |
751 | struct rt_mutex_waiter *w) | |
752 | { | |
753 | /* | |
754 | * If the result is not -EDEADLOCK or the caller requested | |
755 | * deadlock detection, nothing to do here. | |
756 | */ | |
757 | if (res != -EDEADLOCK || detect_deadlock) | |
758 | return; | |
759 | ||
760 | /* | |
761 | * Yell lowdly and stop the task right here. | |
762 | */ | |
763 | rt_mutex_print_deadlock(w); | |
764 | while (1) { | |
765 | set_current_state(TASK_INTERRUPTIBLE); | |
766 | schedule(); | |
767 | } | |
768 | } | |
769 | ||
8dac456a DH |
770 | /* |
771 | * Slow path lock function: | |
772 | */ | |
773 | static int __sched | |
774 | rt_mutex_slowlock(struct rt_mutex *lock, int state, | |
775 | struct hrtimer_sleeper *timeout, | |
776 | int detect_deadlock) | |
777 | { | |
778 | struct rt_mutex_waiter waiter; | |
779 | int ret = 0; | |
780 | ||
781 | debug_rt_mutex_init_waiter(&waiter); | |
8dac456a | 782 | |
d209d74d | 783 | raw_spin_lock(&lock->wait_lock); |
8dac456a DH |
784 | |
785 | /* Try to acquire the lock again: */ | |
8161239a | 786 | if (try_to_take_rt_mutex(lock, current, NULL)) { |
d209d74d | 787 | raw_spin_unlock(&lock->wait_lock); |
8dac456a DH |
788 | return 0; |
789 | } | |
790 | ||
791 | set_current_state(state); | |
792 | ||
793 | /* Setup the timer, when timeout != NULL */ | |
794 | if (unlikely(timeout)) { | |
795 | hrtimer_start_expires(&timeout->timer, HRTIMER_MODE_ABS); | |
796 | if (!hrtimer_active(&timeout->timer)) | |
797 | timeout->task = NULL; | |
798 | } | |
799 | ||
8161239a LJ |
800 | ret = task_blocks_on_rt_mutex(lock, &waiter, current, detect_deadlock); |
801 | ||
802 | if (likely(!ret)) | |
803 | ret = __rt_mutex_slowlock(lock, state, timeout, &waiter); | |
8dac456a | 804 | |
23f78d4a IM |
805 | set_current_state(TASK_RUNNING); |
806 | ||
1201613a | 807 | if (unlikely(ret)) { |
9a11b49a | 808 | remove_waiter(lock, &waiter); |
1201613a TG |
809 | rt_mutex_handle_deadlock(ret, detect_deadlock, &waiter); |
810 | } | |
23f78d4a IM |
811 | |
812 | /* | |
813 | * try_to_take_rt_mutex() sets the waiter bit | |
814 | * unconditionally. We might have to fix that up. | |
815 | */ | |
816 | fixup_rt_mutex_waiters(lock); | |
817 | ||
d209d74d | 818 | raw_spin_unlock(&lock->wait_lock); |
23f78d4a IM |
819 | |
820 | /* Remove pending timer: */ | |
821 | if (unlikely(timeout)) | |
822 | hrtimer_cancel(&timeout->timer); | |
823 | ||
23f78d4a IM |
824 | debug_rt_mutex_free_waiter(&waiter); |
825 | ||
826 | return ret; | |
827 | } | |
828 | ||
829 | /* | |
830 | * Slow path try-lock function: | |
831 | */ | |
832 | static inline int | |
9a11b49a | 833 | rt_mutex_slowtrylock(struct rt_mutex *lock) |
23f78d4a IM |
834 | { |
835 | int ret = 0; | |
836 | ||
d209d74d | 837 | raw_spin_lock(&lock->wait_lock); |
23f78d4a IM |
838 | |
839 | if (likely(rt_mutex_owner(lock) != current)) { | |
840 | ||
8161239a | 841 | ret = try_to_take_rt_mutex(lock, current, NULL); |
23f78d4a IM |
842 | /* |
843 | * try_to_take_rt_mutex() sets the lock waiters | |
844 | * bit unconditionally. Clean this up. | |
845 | */ | |
846 | fixup_rt_mutex_waiters(lock); | |
847 | } | |
848 | ||
d209d74d | 849 | raw_spin_unlock(&lock->wait_lock); |
23f78d4a IM |
850 | |
851 | return ret; | |
852 | } | |
853 | ||
854 | /* | |
855 | * Slow path to release a rt-mutex: | |
856 | */ | |
857 | static void __sched | |
858 | rt_mutex_slowunlock(struct rt_mutex *lock) | |
859 | { | |
d209d74d | 860 | raw_spin_lock(&lock->wait_lock); |
23f78d4a IM |
861 | |
862 | debug_rt_mutex_unlock(lock); | |
863 | ||
864 | rt_mutex_deadlock_account_unlock(current); | |
865 | ||
2371e977 TG |
866 | /* |
867 | * We must be careful here if the fast path is enabled. If we | |
868 | * have no waiters queued we cannot set owner to NULL here | |
869 | * because of: | |
870 | * | |
871 | * foo->lock->owner = NULL; | |
872 | * rtmutex_lock(foo->lock); <- fast path | |
873 | * free = atomic_dec_and_test(foo->refcnt); | |
874 | * rtmutex_unlock(foo->lock); <- fast path | |
875 | * if (free) | |
876 | * kfree(foo); | |
877 | * raw_spin_unlock(foo->lock->wait_lock); | |
878 | * | |
879 | * So for the fastpath enabled kernel: | |
880 | * | |
881 | * Nothing can set the waiters bit as long as we hold | |
882 | * lock->wait_lock. So we do the following sequence: | |
883 | * | |
884 | * owner = rt_mutex_owner(lock); | |
885 | * clear_rt_mutex_waiters(lock); | |
886 | * raw_spin_unlock(&lock->wait_lock); | |
887 | * if (cmpxchg(&lock->owner, owner, 0) == owner) | |
888 | * return; | |
889 | * goto retry; | |
890 | * | |
891 | * The fastpath disabled variant is simple as all access to | |
892 | * lock->owner is serialized by lock->wait_lock: | |
893 | * | |
894 | * lock->owner = NULL; | |
895 | * raw_spin_unlock(&lock->wait_lock); | |
896 | */ | |
897 | while (!rt_mutex_has_waiters(lock)) { | |
898 | /* Drops lock->wait_lock ! */ | |
899 | if (unlock_rt_mutex_safe(lock) == true) | |
900 | return; | |
901 | /* Relock the rtmutex and try again */ | |
902 | raw_spin_lock(&lock->wait_lock); | |
23f78d4a IM |
903 | } |
904 | ||
2371e977 TG |
905 | /* |
906 | * The wakeup next waiter path does not suffer from the above | |
907 | * race. See the comments there. | |
908 | */ | |
23f78d4a IM |
909 | wakeup_next_waiter(lock); |
910 | ||
d209d74d | 911 | raw_spin_unlock(&lock->wait_lock); |
23f78d4a IM |
912 | |
913 | /* Undo pi boosting if necessary: */ | |
914 | rt_mutex_adjust_prio(current); | |
915 | } | |
916 | ||
917 | /* | |
918 | * debug aware fast / slowpath lock,trylock,unlock | |
919 | * | |
920 | * The atomic acquire/release ops are compiled away, when either the | |
921 | * architecture does not support cmpxchg or when debugging is enabled. | |
922 | */ | |
923 | static inline int | |
924 | rt_mutex_fastlock(struct rt_mutex *lock, int state, | |
925 | int detect_deadlock, | |
926 | int (*slowfn)(struct rt_mutex *lock, int state, | |
927 | struct hrtimer_sleeper *timeout, | |
9a11b49a | 928 | int detect_deadlock)) |
23f78d4a IM |
929 | { |
930 | if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) { | |
931 | rt_mutex_deadlock_account_lock(lock, current); | |
932 | return 0; | |
933 | } else | |
9a11b49a | 934 | return slowfn(lock, state, NULL, detect_deadlock); |
23f78d4a IM |
935 | } |
936 | ||
937 | static inline int | |
938 | rt_mutex_timed_fastlock(struct rt_mutex *lock, int state, | |
939 | struct hrtimer_sleeper *timeout, int detect_deadlock, | |
940 | int (*slowfn)(struct rt_mutex *lock, int state, | |
941 | struct hrtimer_sleeper *timeout, | |
9a11b49a | 942 | int detect_deadlock)) |
23f78d4a IM |
943 | { |
944 | if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) { | |
945 | rt_mutex_deadlock_account_lock(lock, current); | |
946 | return 0; | |
947 | } else | |
9a11b49a | 948 | return slowfn(lock, state, timeout, detect_deadlock); |
23f78d4a IM |
949 | } |
950 | ||
951 | static inline int | |
952 | rt_mutex_fasttrylock(struct rt_mutex *lock, | |
9a11b49a | 953 | int (*slowfn)(struct rt_mutex *lock)) |
23f78d4a IM |
954 | { |
955 | if (likely(rt_mutex_cmpxchg(lock, NULL, current))) { | |
956 | rt_mutex_deadlock_account_lock(lock, current); | |
957 | return 1; | |
958 | } | |
9a11b49a | 959 | return slowfn(lock); |
23f78d4a IM |
960 | } |
961 | ||
962 | static inline void | |
963 | rt_mutex_fastunlock(struct rt_mutex *lock, | |
964 | void (*slowfn)(struct rt_mutex *lock)) | |
965 | { | |
966 | if (likely(rt_mutex_cmpxchg(lock, current, NULL))) | |
967 | rt_mutex_deadlock_account_unlock(current); | |
968 | else | |
969 | slowfn(lock); | |
970 | } | |
971 | ||
972 | /** | |
973 | * rt_mutex_lock - lock a rt_mutex | |
974 | * | |
975 | * @lock: the rt_mutex to be locked | |
976 | */ | |
977 | void __sched rt_mutex_lock(struct rt_mutex *lock) | |
978 | { | |
979 | might_sleep(); | |
980 | ||
981 | rt_mutex_fastlock(lock, TASK_UNINTERRUPTIBLE, 0, rt_mutex_slowlock); | |
982 | } | |
983 | EXPORT_SYMBOL_GPL(rt_mutex_lock); | |
984 | ||
985 | /** | |
986 | * rt_mutex_lock_interruptible - lock a rt_mutex interruptible | |
987 | * | |
988 | * @lock: the rt_mutex to be locked | |
989 | * @detect_deadlock: deadlock detection on/off | |
990 | * | |
991 | * Returns: | |
992 | * 0 on success | |
993 | * -EINTR when interrupted by a signal | |
994 | * -EDEADLK when the lock would deadlock (when deadlock detection is on) | |
995 | */ | |
996 | int __sched rt_mutex_lock_interruptible(struct rt_mutex *lock, | |
997 | int detect_deadlock) | |
998 | { | |
999 | might_sleep(); | |
1000 | ||
1001 | return rt_mutex_fastlock(lock, TASK_INTERRUPTIBLE, | |
1002 | detect_deadlock, rt_mutex_slowlock); | |
1003 | } | |
1004 | EXPORT_SYMBOL_GPL(rt_mutex_lock_interruptible); | |
1005 | ||
1006 | /** | |
23b94b96 LH |
1007 | * rt_mutex_timed_lock - lock a rt_mutex interruptible |
1008 | * the timeout structure is provided | |
1009 | * by the caller | |
23f78d4a IM |
1010 | * |
1011 | * @lock: the rt_mutex to be locked | |
1012 | * @timeout: timeout structure or NULL (no timeout) | |
1013 | * @detect_deadlock: deadlock detection on/off | |
1014 | * | |
1015 | * Returns: | |
1016 | * 0 on success | |
1017 | * -EINTR when interrupted by a signal | |
3ac49a1c | 1018 | * -ETIMEDOUT when the timeout expired |
23f78d4a IM |
1019 | * -EDEADLK when the lock would deadlock (when deadlock detection is on) |
1020 | */ | |
1021 | int | |
1022 | rt_mutex_timed_lock(struct rt_mutex *lock, struct hrtimer_sleeper *timeout, | |
1023 | int detect_deadlock) | |
1024 | { | |
1025 | might_sleep(); | |
1026 | ||
1027 | return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout, | |
1028 | detect_deadlock, rt_mutex_slowlock); | |
1029 | } | |
1030 | EXPORT_SYMBOL_GPL(rt_mutex_timed_lock); | |
1031 | ||
1032 | /** | |
1033 | * rt_mutex_trylock - try to lock a rt_mutex | |
1034 | * | |
1035 | * @lock: the rt_mutex to be locked | |
1036 | * | |
1037 | * Returns 1 on success and 0 on contention | |
1038 | */ | |
1039 | int __sched rt_mutex_trylock(struct rt_mutex *lock) | |
1040 | { | |
1041 | return rt_mutex_fasttrylock(lock, rt_mutex_slowtrylock); | |
1042 | } | |
1043 | EXPORT_SYMBOL_GPL(rt_mutex_trylock); | |
1044 | ||
1045 | /** | |
1046 | * rt_mutex_unlock - unlock a rt_mutex | |
1047 | * | |
1048 | * @lock: the rt_mutex to be unlocked | |
1049 | */ | |
1050 | void __sched rt_mutex_unlock(struct rt_mutex *lock) | |
1051 | { | |
1052 | rt_mutex_fastunlock(lock, rt_mutex_slowunlock); | |
1053 | } | |
1054 | EXPORT_SYMBOL_GPL(rt_mutex_unlock); | |
1055 | ||
23b94b96 | 1056 | /** |
23f78d4a IM |
1057 | * rt_mutex_destroy - mark a mutex unusable |
1058 | * @lock: the mutex to be destroyed | |
1059 | * | |
1060 | * This function marks the mutex uninitialized, and any subsequent | |
1061 | * use of the mutex is forbidden. The mutex must not be locked when | |
1062 | * this function is called. | |
1063 | */ | |
1064 | void rt_mutex_destroy(struct rt_mutex *lock) | |
1065 | { | |
1066 | WARN_ON(rt_mutex_is_locked(lock)); | |
1067 | #ifdef CONFIG_DEBUG_RT_MUTEXES | |
1068 | lock->magic = NULL; | |
1069 | #endif | |
1070 | } | |
1071 | ||
1072 | EXPORT_SYMBOL_GPL(rt_mutex_destroy); | |
1073 | ||
1074 | /** | |
1075 | * __rt_mutex_init - initialize the rt lock | |
1076 | * | |
1077 | * @lock: the rt lock to be initialized | |
1078 | * | |
1079 | * Initialize the rt lock to unlocked state. | |
1080 | * | |
1081 | * Initializing of a locked rt lock is not allowed | |
1082 | */ | |
1083 | void __rt_mutex_init(struct rt_mutex *lock, const char *name) | |
1084 | { | |
1085 | lock->owner = NULL; | |
d209d74d | 1086 | raw_spin_lock_init(&lock->wait_lock); |
732375c6 | 1087 | plist_head_init(&lock->wait_list); |
23f78d4a IM |
1088 | |
1089 | debug_rt_mutex_init(lock, name); | |
1090 | } | |
1091 | EXPORT_SYMBOL_GPL(__rt_mutex_init); | |
0cdbee99 IM |
1092 | |
1093 | /** | |
1094 | * rt_mutex_init_proxy_locked - initialize and lock a rt_mutex on behalf of a | |
1095 | * proxy owner | |
1096 | * | |
1097 | * @lock: the rt_mutex to be locked | |
1098 | * @proxy_owner:the task to set as owner | |
1099 | * | |
1100 | * No locking. Caller has to do serializing itself | |
1101 | * Special API call for PI-futex support | |
1102 | */ | |
1103 | void rt_mutex_init_proxy_locked(struct rt_mutex *lock, | |
1104 | struct task_struct *proxy_owner) | |
1105 | { | |
1106 | __rt_mutex_init(lock, NULL); | |
9a11b49a | 1107 | debug_rt_mutex_proxy_lock(lock, proxy_owner); |
8161239a | 1108 | rt_mutex_set_owner(lock, proxy_owner); |
0cdbee99 IM |
1109 | rt_mutex_deadlock_account_lock(lock, proxy_owner); |
1110 | } | |
1111 | ||
1112 | /** | |
1113 | * rt_mutex_proxy_unlock - release a lock on behalf of owner | |
1114 | * | |
1115 | * @lock: the rt_mutex to be locked | |
1116 | * | |
1117 | * No locking. Caller has to do serializing itself | |
1118 | * Special API call for PI-futex support | |
1119 | */ | |
1120 | void rt_mutex_proxy_unlock(struct rt_mutex *lock, | |
1121 | struct task_struct *proxy_owner) | |
1122 | { | |
1123 | debug_rt_mutex_proxy_unlock(lock); | |
8161239a | 1124 | rt_mutex_set_owner(lock, NULL); |
0cdbee99 IM |
1125 | rt_mutex_deadlock_account_unlock(proxy_owner); |
1126 | } | |
1127 | ||
8dac456a DH |
1128 | /** |
1129 | * rt_mutex_start_proxy_lock() - Start lock acquisition for another task | |
1130 | * @lock: the rt_mutex to take | |
1131 | * @waiter: the pre-initialized rt_mutex_waiter | |
1132 | * @task: the task to prepare | |
1133 | * @detect_deadlock: perform deadlock detection (1) or not (0) | |
1134 | * | |
1135 | * Returns: | |
1136 | * 0 - task blocked on lock | |
1137 | * 1 - acquired the lock for task, caller should wake it up | |
1138 | * <0 - error | |
1139 | * | |
1140 | * Special API call for FUTEX_REQUEUE_PI support. | |
1141 | */ | |
1142 | int rt_mutex_start_proxy_lock(struct rt_mutex *lock, | |
1143 | struct rt_mutex_waiter *waiter, | |
1144 | struct task_struct *task, int detect_deadlock) | |
1145 | { | |
1146 | int ret; | |
1147 | ||
d209d74d | 1148 | raw_spin_lock(&lock->wait_lock); |
8dac456a | 1149 | |
8161239a | 1150 | if (try_to_take_rt_mutex(lock, task, NULL)) { |
d209d74d | 1151 | raw_spin_unlock(&lock->wait_lock); |
8dac456a DH |
1152 | return 1; |
1153 | } | |
1154 | ||
1201613a TG |
1155 | /* We enforce deadlock detection for futexes */ |
1156 | ret = task_blocks_on_rt_mutex(lock, waiter, task, 1); | |
8dac456a | 1157 | |
8161239a | 1158 | if (ret && !rt_mutex_owner(lock)) { |
8dac456a DH |
1159 | /* |
1160 | * Reset the return value. We might have | |
1161 | * returned with -EDEADLK and the owner | |
1162 | * released the lock while we were walking the | |
1163 | * pi chain. Let the waiter sort it out. | |
1164 | */ | |
1165 | ret = 0; | |
1166 | } | |
8161239a LJ |
1167 | |
1168 | if (unlikely(ret)) | |
1169 | remove_waiter(lock, waiter); | |
1170 | ||
d209d74d | 1171 | raw_spin_unlock(&lock->wait_lock); |
8dac456a DH |
1172 | |
1173 | debug_rt_mutex_print_deadlock(waiter); | |
1174 | ||
1175 | return ret; | |
1176 | } | |
1177 | ||
0cdbee99 IM |
1178 | /** |
1179 | * rt_mutex_next_owner - return the next owner of the lock | |
1180 | * | |
1181 | * @lock: the rt lock query | |
1182 | * | |
1183 | * Returns the next owner of the lock or NULL | |
1184 | * | |
1185 | * Caller has to serialize against other accessors to the lock | |
1186 | * itself. | |
1187 | * | |
1188 | * Special API call for PI-futex support | |
1189 | */ | |
1190 | struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock) | |
1191 | { | |
1192 | if (!rt_mutex_has_waiters(lock)) | |
1193 | return NULL; | |
1194 | ||
1195 | return rt_mutex_top_waiter(lock)->task; | |
1196 | } | |
8dac456a DH |
1197 | |
1198 | /** | |
1199 | * rt_mutex_finish_proxy_lock() - Complete lock acquisition | |
1200 | * @lock: the rt_mutex we were woken on | |
1201 | * @to: the timeout, null if none. hrtimer should already have | |
1202 | * been started. | |
1203 | * @waiter: the pre-initialized rt_mutex_waiter | |
1204 | * @detect_deadlock: perform deadlock detection (1) or not (0) | |
1205 | * | |
1206 | * Complete the lock acquisition started our behalf by another thread. | |
1207 | * | |
1208 | * Returns: | |
1209 | * 0 - success | |
1210 | * <0 - error, one of -EINTR, -ETIMEDOUT, or -EDEADLK | |
1211 | * | |
1212 | * Special API call for PI-futex requeue support | |
1213 | */ | |
1214 | int rt_mutex_finish_proxy_lock(struct rt_mutex *lock, | |
1215 | struct hrtimer_sleeper *to, | |
1216 | struct rt_mutex_waiter *waiter, | |
1217 | int detect_deadlock) | |
1218 | { | |
1219 | int ret; | |
1220 | ||
d209d74d | 1221 | raw_spin_lock(&lock->wait_lock); |
8dac456a DH |
1222 | |
1223 | set_current_state(TASK_INTERRUPTIBLE); | |
1224 | ||
8161239a | 1225 | ret = __rt_mutex_slowlock(lock, TASK_INTERRUPTIBLE, to, waiter); |
8dac456a DH |
1226 | |
1227 | set_current_state(TASK_RUNNING); | |
1228 | ||
8161239a | 1229 | if (unlikely(ret)) |
8dac456a DH |
1230 | remove_waiter(lock, waiter); |
1231 | ||
1232 | /* | |
1233 | * try_to_take_rt_mutex() sets the waiter bit unconditionally. We might | |
1234 | * have to fix that up. | |
1235 | */ | |
1236 | fixup_rt_mutex_waiters(lock); | |
1237 | ||
d209d74d | 1238 | raw_spin_unlock(&lock->wait_lock); |
8dac456a | 1239 | |
8dac456a DH |
1240 | return ret; |
1241 | } |