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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 | |
10 | */ | |
11 | #include <linux/spinlock.h> | |
12 | #include <linux/module.h> | |
13 | #include <linux/sched.h> | |
14 | #include <linux/timer.h> | |
15 | ||
16 | #include "rtmutex_common.h" | |
17 | ||
18 | #ifdef CONFIG_DEBUG_RT_MUTEXES | |
19 | # include "rtmutex-debug.h" | |
20 | #else | |
21 | # include "rtmutex.h" | |
22 | #endif | |
23 | ||
24 | /* | |
25 | * lock->owner state tracking: | |
26 | * | |
27 | * lock->owner holds the task_struct pointer of the owner. Bit 0 and 1 | |
28 | * are used to keep track of the "owner is pending" and "lock has | |
29 | * waiters" state. | |
30 | * | |
31 | * owner bit1 bit0 | |
32 | * NULL 0 0 lock is free (fast acquire possible) | |
33 | * NULL 0 1 invalid state | |
34 | * NULL 1 0 Transitional State* | |
35 | * NULL 1 1 invalid state | |
36 | * taskpointer 0 0 lock is held (fast release possible) | |
37 | * taskpointer 0 1 task is pending owner | |
38 | * taskpointer 1 0 lock is held and has waiters | |
39 | * taskpointer 1 1 task is pending owner and lock has more waiters | |
40 | * | |
41 | * Pending ownership is assigned to the top (highest priority) | |
42 | * waiter of the lock, when the lock is released. The thread is woken | |
43 | * up and can now take the lock. Until the lock is taken (bit 0 | |
44 | * cleared) a competing higher priority thread can steal the lock | |
45 | * which puts the woken up thread back on the waiters list. | |
46 | * | |
47 | * The fast atomic compare exchange based acquire and release is only | |
48 | * possible when bit 0 and 1 of lock->owner are 0. | |
49 | * | |
50 | * (*) There's a small time where the owner can be NULL and the | |
51 | * "lock has waiters" bit is set. This can happen when grabbing the lock. | |
52 | * To prevent a cmpxchg of the owner releasing the lock, we need to set this | |
53 | * bit before looking at the lock, hence the reason this is a transitional | |
54 | * state. | |
55 | */ | |
56 | ||
57 | static void | |
58 | rt_mutex_set_owner(struct rt_mutex *lock, struct task_struct *owner, | |
59 | unsigned long mask) | |
60 | { | |
61 | unsigned long val = (unsigned long)owner | mask; | |
62 | ||
63 | if (rt_mutex_has_waiters(lock)) | |
64 | val |= RT_MUTEX_HAS_WAITERS; | |
65 | ||
66 | lock->owner = (struct task_struct *)val; | |
67 | } | |
68 | ||
69 | static inline void clear_rt_mutex_waiters(struct rt_mutex *lock) | |
70 | { | |
71 | lock->owner = (struct task_struct *) | |
72 | ((unsigned long)lock->owner & ~RT_MUTEX_HAS_WAITERS); | |
73 | } | |
74 | ||
75 | static void fixup_rt_mutex_waiters(struct rt_mutex *lock) | |
76 | { | |
77 | if (!rt_mutex_has_waiters(lock)) | |
78 | clear_rt_mutex_waiters(lock); | |
79 | } | |
80 | ||
81 | /* | |
82 | * We can speed up the acquire/release, if the architecture | |
83 | * supports cmpxchg and if there's no debugging state to be set up | |
84 | */ | |
85 | #if defined(__HAVE_ARCH_CMPXCHG) && !defined(CONFIG_DEBUG_RT_MUTEXES) | |
86 | # define rt_mutex_cmpxchg(l,c,n) (cmpxchg(&l->owner, c, n) == c) | |
87 | static inline void mark_rt_mutex_waiters(struct rt_mutex *lock) | |
88 | { | |
89 | unsigned long owner, *p = (unsigned long *) &lock->owner; | |
90 | ||
91 | do { | |
92 | owner = *p; | |
93 | } while (cmpxchg(p, owner, owner | RT_MUTEX_HAS_WAITERS) != owner); | |
94 | } | |
95 | #else | |
96 | # define rt_mutex_cmpxchg(l,c,n) (0) | |
97 | static inline void mark_rt_mutex_waiters(struct rt_mutex *lock) | |
98 | { | |
99 | lock->owner = (struct task_struct *) | |
100 | ((unsigned long)lock->owner | RT_MUTEX_HAS_WAITERS); | |
101 | } | |
102 | #endif | |
103 | ||
104 | /* | |
105 | * Calculate task priority from the waiter list priority | |
106 | * | |
107 | * Return task->normal_prio when the waiter list is empty or when | |
108 | * the waiter is not allowed to do priority boosting | |
109 | */ | |
110 | int rt_mutex_getprio(struct task_struct *task) | |
111 | { | |
112 | if (likely(!task_has_pi_waiters(task))) | |
113 | return task->normal_prio; | |
114 | ||
115 | return min(task_top_pi_waiter(task)->pi_list_entry.prio, | |
116 | task->normal_prio); | |
117 | } | |
118 | ||
119 | /* | |
120 | * Adjust the priority of a task, after its pi_waiters got modified. | |
121 | * | |
122 | * This can be both boosting and unboosting. task->pi_lock must be held. | |
123 | */ | |
124 | static void __rt_mutex_adjust_prio(struct task_struct *task) | |
125 | { | |
126 | int prio = rt_mutex_getprio(task); | |
127 | ||
128 | if (task->prio != prio) | |
129 | rt_mutex_setprio(task, prio); | |
130 | } | |
131 | ||
132 | /* | |
133 | * Adjust task priority (undo boosting). Called from the exit path of | |
134 | * rt_mutex_slowunlock() and rt_mutex_slowlock(). | |
135 | * | |
136 | * (Note: We do this outside of the protection of lock->wait_lock to | |
137 | * allow the lock to be taken while or before we readjust the priority | |
138 | * of task. We do not use the spin_xx_mutex() variants here as we are | |
139 | * outside of the debug path.) | |
140 | */ | |
141 | static void rt_mutex_adjust_prio(struct task_struct *task) | |
142 | { | |
143 | unsigned long flags; | |
144 | ||
145 | spin_lock_irqsave(&task->pi_lock, flags); | |
146 | __rt_mutex_adjust_prio(task); | |
147 | spin_unlock_irqrestore(&task->pi_lock, flags); | |
148 | } | |
149 | ||
150 | /* | |
151 | * Max number of times we'll walk the boosting chain: | |
152 | */ | |
153 | int max_lock_depth = 1024; | |
154 | ||
155 | /* | |
156 | * Adjust the priority chain. Also used for deadlock detection. | |
157 | * Decreases task's usage by one - may thus free the task. | |
158 | * Returns 0 or -EDEADLK. | |
159 | */ | |
160 | static int rt_mutex_adjust_prio_chain(task_t *task, | |
161 | int deadlock_detect, | |
162 | struct rt_mutex *orig_lock, | |
95e02ca9 TG |
163 | struct rt_mutex_waiter *orig_waiter, |
164 | struct task_struct *top_task | |
23f78d4a IM |
165 | __IP_DECL__) |
166 | { | |
167 | struct rt_mutex *lock; | |
168 | struct rt_mutex_waiter *waiter, *top_waiter = orig_waiter; | |
169 | int detect_deadlock, ret = 0, depth = 0; | |
170 | unsigned long flags; | |
171 | ||
172 | detect_deadlock = debug_rt_mutex_detect_deadlock(orig_waiter, | |
173 | deadlock_detect); | |
174 | ||
175 | /* | |
176 | * The (de)boosting is a step by step approach with a lot of | |
177 | * pitfalls. We want this to be preemptible and we want hold a | |
178 | * maximum of two locks per step. So we have to check | |
179 | * carefully whether things change under us. | |
180 | */ | |
181 | again: | |
182 | if (++depth > max_lock_depth) { | |
183 | static int prev_max; | |
184 | ||
185 | /* | |
186 | * Print this only once. If the admin changes the limit, | |
187 | * print a new message when reaching the limit again. | |
188 | */ | |
189 | if (prev_max != max_lock_depth) { | |
190 | prev_max = max_lock_depth; | |
191 | printk(KERN_WARNING "Maximum lock depth %d reached " | |
192 | "task: %s (%d)\n", max_lock_depth, | |
95e02ca9 | 193 | top_task->comm, top_task->pid); |
23f78d4a IM |
194 | } |
195 | put_task_struct(task); | |
196 | ||
197 | return deadlock_detect ? -EDEADLK : 0; | |
198 | } | |
199 | retry: | |
200 | /* | |
201 | * Task can not go away as we did a get_task() before ! | |
202 | */ | |
203 | spin_lock_irqsave(&task->pi_lock, flags); | |
204 | ||
205 | waiter = task->pi_blocked_on; | |
206 | /* | |
207 | * Check whether the end of the boosting chain has been | |
208 | * reached or the state of the chain has changed while we | |
209 | * dropped the locks. | |
210 | */ | |
211 | if (!waiter || !waiter->task) | |
212 | goto out_unlock_pi; | |
213 | ||
214 | if (top_waiter && (!task_has_pi_waiters(task) || | |
215 | top_waiter != task_top_pi_waiter(task))) | |
216 | goto out_unlock_pi; | |
217 | ||
218 | /* | |
219 | * When deadlock detection is off then we check, if further | |
220 | * priority adjustment is necessary. | |
221 | */ | |
222 | if (!detect_deadlock && waiter->list_entry.prio == task->prio) | |
223 | goto out_unlock_pi; | |
224 | ||
225 | lock = waiter->lock; | |
226 | if (!spin_trylock(&lock->wait_lock)) { | |
227 | spin_unlock_irqrestore(&task->pi_lock, flags); | |
228 | cpu_relax(); | |
229 | goto retry; | |
230 | } | |
231 | ||
232 | /* Deadlock detection */ | |
95e02ca9 | 233 | if (lock == orig_lock || rt_mutex_owner(lock) == top_task) { |
23f78d4a IM |
234 | debug_rt_mutex_deadlock(deadlock_detect, orig_waiter, lock); |
235 | spin_unlock(&lock->wait_lock); | |
236 | ret = deadlock_detect ? -EDEADLK : 0; | |
237 | goto out_unlock_pi; | |
238 | } | |
239 | ||
240 | top_waiter = rt_mutex_top_waiter(lock); | |
241 | ||
242 | /* Requeue the waiter */ | |
243 | plist_del(&waiter->list_entry, &lock->wait_list); | |
244 | waiter->list_entry.prio = task->prio; | |
245 | plist_add(&waiter->list_entry, &lock->wait_list); | |
246 | ||
247 | /* Release the task */ | |
248 | spin_unlock_irqrestore(&task->pi_lock, flags); | |
249 | put_task_struct(task); | |
250 | ||
251 | /* Grab the next task */ | |
252 | task = rt_mutex_owner(lock); | |
253 | spin_lock_irqsave(&task->pi_lock, flags); | |
254 | ||
255 | if (waiter == rt_mutex_top_waiter(lock)) { | |
256 | /* Boost the owner */ | |
257 | plist_del(&top_waiter->pi_list_entry, &task->pi_waiters); | |
258 | waiter->pi_list_entry.prio = waiter->list_entry.prio; | |
259 | plist_add(&waiter->pi_list_entry, &task->pi_waiters); | |
260 | __rt_mutex_adjust_prio(task); | |
261 | ||
262 | } else if (top_waiter == waiter) { | |
263 | /* Deboost the owner */ | |
264 | plist_del(&waiter->pi_list_entry, &task->pi_waiters); | |
265 | waiter = rt_mutex_top_waiter(lock); | |
266 | waiter->pi_list_entry.prio = waiter->list_entry.prio; | |
267 | plist_add(&waiter->pi_list_entry, &task->pi_waiters); | |
268 | __rt_mutex_adjust_prio(task); | |
269 | } | |
270 | ||
271 | get_task_struct(task); | |
272 | spin_unlock_irqrestore(&task->pi_lock, flags); | |
273 | ||
274 | top_waiter = rt_mutex_top_waiter(lock); | |
275 | spin_unlock(&lock->wait_lock); | |
276 | ||
277 | if (!detect_deadlock && waiter != top_waiter) | |
278 | goto out_put_task; | |
279 | ||
280 | goto again; | |
281 | ||
282 | out_unlock_pi: | |
283 | spin_unlock_irqrestore(&task->pi_lock, flags); | |
284 | out_put_task: | |
285 | put_task_struct(task); | |
286 | return ret; | |
287 | } | |
288 | ||
289 | /* | |
290 | * Optimization: check if we can steal the lock from the | |
291 | * assigned pending owner [which might not have taken the | |
292 | * lock yet]: | |
293 | */ | |
294 | static inline int try_to_steal_lock(struct rt_mutex *lock) | |
295 | { | |
296 | struct task_struct *pendowner = rt_mutex_owner(lock); | |
297 | struct rt_mutex_waiter *next; | |
298 | unsigned long flags; | |
299 | ||
300 | if (!rt_mutex_owner_pending(lock)) | |
301 | return 0; | |
302 | ||
303 | if (pendowner == current) | |
304 | return 1; | |
305 | ||
306 | spin_lock_irqsave(&pendowner->pi_lock, flags); | |
307 | if (current->prio >= pendowner->prio) { | |
308 | spin_unlock_irqrestore(&pendowner->pi_lock, flags); | |
309 | return 0; | |
310 | } | |
311 | ||
312 | /* | |
313 | * Check if a waiter is enqueued on the pending owners | |
314 | * pi_waiters list. Remove it and readjust pending owners | |
315 | * priority. | |
316 | */ | |
317 | if (likely(!rt_mutex_has_waiters(lock))) { | |
318 | spin_unlock_irqrestore(&pendowner->pi_lock, flags); | |
319 | return 1; | |
320 | } | |
321 | ||
322 | /* No chain handling, pending owner is not blocked on anything: */ | |
323 | next = rt_mutex_top_waiter(lock); | |
324 | plist_del(&next->pi_list_entry, &pendowner->pi_waiters); | |
325 | __rt_mutex_adjust_prio(pendowner); | |
326 | spin_unlock_irqrestore(&pendowner->pi_lock, flags); | |
327 | ||
328 | /* | |
329 | * We are going to steal the lock and a waiter was | |
330 | * enqueued on the pending owners pi_waiters queue. So | |
331 | * we have to enqueue this waiter into | |
332 | * current->pi_waiters list. This covers the case, | |
333 | * where current is boosted because it holds another | |
334 | * lock and gets unboosted because the booster is | |
335 | * interrupted, so we would delay a waiter with higher | |
336 | * priority as current->normal_prio. | |
337 | * | |
338 | * Note: in the rare case of a SCHED_OTHER task changing | |
339 | * its priority and thus stealing the lock, next->task | |
340 | * might be current: | |
341 | */ | |
342 | if (likely(next->task != current)) { | |
343 | spin_lock_irqsave(¤t->pi_lock, flags); | |
344 | plist_add(&next->pi_list_entry, ¤t->pi_waiters); | |
345 | __rt_mutex_adjust_prio(current); | |
346 | spin_unlock_irqrestore(¤t->pi_lock, flags); | |
347 | } | |
348 | return 1; | |
349 | } | |
350 | ||
351 | /* | |
352 | * Try to take an rt-mutex | |
353 | * | |
354 | * This fails | |
355 | * - when the lock has a real owner | |
356 | * - when a different pending owner exists and has higher priority than current | |
357 | * | |
358 | * Must be called with lock->wait_lock held. | |
359 | */ | |
360 | static int try_to_take_rt_mutex(struct rt_mutex *lock __IP_DECL__) | |
361 | { | |
362 | /* | |
363 | * We have to be careful here if the atomic speedups are | |
364 | * enabled, such that, when | |
365 | * - no other waiter is on the lock | |
366 | * - the lock has been released since we did the cmpxchg | |
367 | * the lock can be released or taken while we are doing the | |
368 | * checks and marking the lock with RT_MUTEX_HAS_WAITERS. | |
369 | * | |
370 | * The atomic acquire/release aware variant of | |
371 | * mark_rt_mutex_waiters uses a cmpxchg loop. After setting | |
372 | * the WAITERS bit, the atomic release / acquire can not | |
373 | * happen anymore and lock->wait_lock protects us from the | |
374 | * non-atomic case. | |
375 | * | |
376 | * Note, that this might set lock->owner = | |
377 | * RT_MUTEX_HAS_WAITERS in the case the lock is not contended | |
378 | * any more. This is fixed up when we take the ownership. | |
379 | * This is the transitional state explained at the top of this file. | |
380 | */ | |
381 | mark_rt_mutex_waiters(lock); | |
382 | ||
383 | if (rt_mutex_owner(lock) && !try_to_steal_lock(lock)) | |
384 | return 0; | |
385 | ||
386 | /* We got the lock. */ | |
387 | debug_rt_mutex_lock(lock __IP__); | |
388 | ||
389 | rt_mutex_set_owner(lock, current, 0); | |
390 | ||
391 | rt_mutex_deadlock_account_lock(lock, current); | |
392 | ||
393 | return 1; | |
394 | } | |
395 | ||
396 | /* | |
397 | * Task blocks on lock. | |
398 | * | |
399 | * Prepare waiter and propagate pi chain | |
400 | * | |
401 | * This must be called with lock->wait_lock held. | |
402 | */ | |
403 | static int task_blocks_on_rt_mutex(struct rt_mutex *lock, | |
404 | struct rt_mutex_waiter *waiter, | |
405 | int detect_deadlock | |
406 | __IP_DECL__) | |
407 | { | |
408 | struct rt_mutex_waiter *top_waiter = waiter; | |
409 | task_t *owner = rt_mutex_owner(lock); | |
410 | int boost = 0, res; | |
411 | unsigned long flags; | |
412 | ||
413 | spin_lock_irqsave(¤t->pi_lock, flags); | |
414 | __rt_mutex_adjust_prio(current); | |
415 | waiter->task = current; | |
416 | waiter->lock = lock; | |
417 | plist_node_init(&waiter->list_entry, current->prio); | |
418 | plist_node_init(&waiter->pi_list_entry, current->prio); | |
419 | ||
420 | /* Get the top priority waiter on the lock */ | |
421 | if (rt_mutex_has_waiters(lock)) | |
422 | top_waiter = rt_mutex_top_waiter(lock); | |
423 | plist_add(&waiter->list_entry, &lock->wait_list); | |
424 | ||
425 | current->pi_blocked_on = waiter; | |
426 | ||
427 | spin_unlock_irqrestore(¤t->pi_lock, flags); | |
428 | ||
429 | if (waiter == rt_mutex_top_waiter(lock)) { | |
430 | spin_lock_irqsave(&owner->pi_lock, flags); | |
431 | plist_del(&top_waiter->pi_list_entry, &owner->pi_waiters); | |
432 | plist_add(&waiter->pi_list_entry, &owner->pi_waiters); | |
433 | ||
434 | __rt_mutex_adjust_prio(owner); | |
435 | if (owner->pi_blocked_on) { | |
436 | boost = 1; | |
95e02ca9 | 437 | /* gets dropped in rt_mutex_adjust_prio_chain()! */ |
23f78d4a IM |
438 | get_task_struct(owner); |
439 | } | |
440 | spin_unlock_irqrestore(&owner->pi_lock, flags); | |
441 | } | |
442 | else if (debug_rt_mutex_detect_deadlock(waiter, detect_deadlock)) { | |
443 | spin_lock_irqsave(&owner->pi_lock, flags); | |
444 | if (owner->pi_blocked_on) { | |
445 | boost = 1; | |
95e02ca9 | 446 | /* gets dropped in rt_mutex_adjust_prio_chain()! */ |
23f78d4a IM |
447 | get_task_struct(owner); |
448 | } | |
449 | spin_unlock_irqrestore(&owner->pi_lock, flags); | |
450 | } | |
451 | if (!boost) | |
452 | return 0; | |
453 | ||
454 | spin_unlock(&lock->wait_lock); | |
455 | ||
95e02ca9 TG |
456 | res = rt_mutex_adjust_prio_chain(owner, detect_deadlock, lock, waiter, |
457 | current __IP__); | |
23f78d4a IM |
458 | |
459 | spin_lock(&lock->wait_lock); | |
460 | ||
461 | return res; | |
462 | } | |
463 | ||
464 | /* | |
465 | * Wake up the next waiter on the lock. | |
466 | * | |
467 | * Remove the top waiter from the current tasks waiter list and from | |
468 | * the lock waiter list. Set it as pending owner. Then wake it up. | |
469 | * | |
470 | * Called with lock->wait_lock held. | |
471 | */ | |
472 | static void wakeup_next_waiter(struct rt_mutex *lock) | |
473 | { | |
474 | struct rt_mutex_waiter *waiter; | |
475 | struct task_struct *pendowner; | |
476 | unsigned long flags; | |
477 | ||
478 | spin_lock_irqsave(¤t->pi_lock, flags); | |
479 | ||
480 | waiter = rt_mutex_top_waiter(lock); | |
481 | plist_del(&waiter->list_entry, &lock->wait_list); | |
482 | ||
483 | /* | |
484 | * Remove it from current->pi_waiters. We do not adjust a | |
485 | * possible priority boost right now. We execute wakeup in the | |
486 | * boosted mode and go back to normal after releasing | |
487 | * lock->wait_lock. | |
488 | */ | |
489 | plist_del(&waiter->pi_list_entry, ¤t->pi_waiters); | |
490 | pendowner = waiter->task; | |
491 | waiter->task = NULL; | |
492 | ||
493 | rt_mutex_set_owner(lock, pendowner, RT_MUTEX_OWNER_PENDING); | |
494 | ||
495 | spin_unlock_irqrestore(¤t->pi_lock, flags); | |
496 | ||
497 | /* | |
498 | * Clear the pi_blocked_on variable and enqueue a possible | |
499 | * waiter into the pi_waiters list of the pending owner. This | |
500 | * prevents that in case the pending owner gets unboosted a | |
501 | * waiter with higher priority than pending-owner->normal_prio | |
502 | * is blocked on the unboosted (pending) owner. | |
503 | */ | |
504 | spin_lock_irqsave(&pendowner->pi_lock, flags); | |
505 | ||
506 | WARN_ON(!pendowner->pi_blocked_on); | |
507 | WARN_ON(pendowner->pi_blocked_on != waiter); | |
508 | WARN_ON(pendowner->pi_blocked_on->lock != lock); | |
509 | ||
510 | pendowner->pi_blocked_on = NULL; | |
511 | ||
512 | if (rt_mutex_has_waiters(lock)) { | |
513 | struct rt_mutex_waiter *next; | |
514 | ||
515 | next = rt_mutex_top_waiter(lock); | |
516 | plist_add(&next->pi_list_entry, &pendowner->pi_waiters); | |
517 | } | |
518 | spin_unlock_irqrestore(&pendowner->pi_lock, flags); | |
519 | ||
520 | wake_up_process(pendowner); | |
521 | } | |
522 | ||
523 | /* | |
524 | * Remove a waiter from a lock | |
525 | * | |
526 | * Must be called with lock->wait_lock held | |
527 | */ | |
528 | static void remove_waiter(struct rt_mutex *lock, | |
529 | struct rt_mutex_waiter *waiter __IP_DECL__) | |
530 | { | |
531 | int first = (waiter == rt_mutex_top_waiter(lock)); | |
532 | int boost = 0; | |
533 | task_t *owner = rt_mutex_owner(lock); | |
534 | unsigned long flags; | |
535 | ||
536 | spin_lock_irqsave(¤t->pi_lock, flags); | |
537 | plist_del(&waiter->list_entry, &lock->wait_list); | |
538 | waiter->task = NULL; | |
539 | current->pi_blocked_on = NULL; | |
540 | spin_unlock_irqrestore(¤t->pi_lock, flags); | |
541 | ||
542 | if (first && owner != current) { | |
543 | ||
544 | spin_lock_irqsave(&owner->pi_lock, flags); | |
545 | ||
546 | plist_del(&waiter->pi_list_entry, &owner->pi_waiters); | |
547 | ||
548 | if (rt_mutex_has_waiters(lock)) { | |
549 | struct rt_mutex_waiter *next; | |
550 | ||
551 | next = rt_mutex_top_waiter(lock); | |
552 | plist_add(&next->pi_list_entry, &owner->pi_waiters); | |
553 | } | |
554 | __rt_mutex_adjust_prio(owner); | |
555 | ||
556 | if (owner->pi_blocked_on) { | |
557 | boost = 1; | |
95e02ca9 | 558 | /* gets dropped in rt_mutex_adjust_prio_chain()! */ |
23f78d4a IM |
559 | get_task_struct(owner); |
560 | } | |
561 | spin_unlock_irqrestore(&owner->pi_lock, flags); | |
562 | } | |
563 | ||
564 | WARN_ON(!plist_node_empty(&waiter->pi_list_entry)); | |
565 | ||
566 | if (!boost) | |
567 | return; | |
568 | ||
569 | spin_unlock(&lock->wait_lock); | |
570 | ||
95e02ca9 | 571 | rt_mutex_adjust_prio_chain(owner, 0, lock, NULL, current __IP__); |
23f78d4a IM |
572 | |
573 | spin_lock(&lock->wait_lock); | |
574 | } | |
575 | ||
95e02ca9 TG |
576 | /* |
577 | * Recheck the pi chain, in case we got a priority setting | |
578 | * | |
579 | * Called from sched_setscheduler | |
580 | */ | |
581 | void rt_mutex_adjust_pi(struct task_struct *task) | |
582 | { | |
583 | struct rt_mutex_waiter *waiter; | |
584 | unsigned long flags; | |
585 | ||
586 | spin_lock_irqsave(&task->pi_lock, flags); | |
587 | ||
588 | waiter = task->pi_blocked_on; | |
589 | if (!waiter || waiter->list_entry.prio == task->prio) { | |
590 | spin_unlock_irqrestore(&task->pi_lock, flags); | |
591 | return; | |
592 | } | |
593 | ||
594 | /* gets dropped in rt_mutex_adjust_prio_chain()! */ | |
595 | get_task_struct(task); | |
596 | spin_unlock_irqrestore(&task->pi_lock, flags); | |
597 | ||
598 | rt_mutex_adjust_prio_chain(task, 0, NULL, NULL, task __RET_IP__); | |
599 | } | |
600 | ||
23f78d4a IM |
601 | /* |
602 | * Slow path lock function: | |
603 | */ | |
604 | static int __sched | |
605 | rt_mutex_slowlock(struct rt_mutex *lock, int state, | |
606 | struct hrtimer_sleeper *timeout, | |
607 | int detect_deadlock __IP_DECL__) | |
608 | { | |
609 | struct rt_mutex_waiter waiter; | |
610 | int ret = 0; | |
611 | ||
612 | debug_rt_mutex_init_waiter(&waiter); | |
613 | waiter.task = NULL; | |
614 | ||
615 | spin_lock(&lock->wait_lock); | |
616 | ||
617 | /* Try to acquire the lock again: */ | |
618 | if (try_to_take_rt_mutex(lock __IP__)) { | |
619 | spin_unlock(&lock->wait_lock); | |
620 | return 0; | |
621 | } | |
622 | ||
623 | set_current_state(state); | |
624 | ||
625 | /* Setup the timer, when timeout != NULL */ | |
626 | if (unlikely(timeout)) | |
627 | hrtimer_start(&timeout->timer, timeout->timer.expires, | |
628 | HRTIMER_ABS); | |
629 | ||
630 | for (;;) { | |
631 | /* Try to acquire the lock: */ | |
632 | if (try_to_take_rt_mutex(lock __IP__)) | |
633 | break; | |
634 | ||
635 | /* | |
636 | * TASK_INTERRUPTIBLE checks for signals and | |
637 | * timeout. Ignored otherwise. | |
638 | */ | |
639 | if (unlikely(state == TASK_INTERRUPTIBLE)) { | |
640 | /* Signal pending? */ | |
641 | if (signal_pending(current)) | |
642 | ret = -EINTR; | |
643 | if (timeout && !timeout->task) | |
644 | ret = -ETIMEDOUT; | |
645 | if (ret) | |
646 | break; | |
647 | } | |
648 | ||
649 | /* | |
650 | * waiter.task is NULL the first time we come here and | |
651 | * when we have been woken up by the previous owner | |
652 | * but the lock got stolen by a higher prio task. | |
653 | */ | |
654 | if (!waiter.task) { | |
655 | ret = task_blocks_on_rt_mutex(lock, &waiter, | |
656 | detect_deadlock __IP__); | |
657 | /* | |
658 | * If we got woken up by the owner then start loop | |
659 | * all over without going into schedule to try | |
660 | * to get the lock now: | |
661 | */ | |
662 | if (unlikely(!waiter.task)) | |
663 | continue; | |
664 | ||
665 | if (unlikely(ret)) | |
666 | break; | |
667 | } | |
95e02ca9 | 668 | |
23f78d4a IM |
669 | spin_unlock(&lock->wait_lock); |
670 | ||
671 | debug_rt_mutex_print_deadlock(&waiter); | |
672 | ||
61a87122 TG |
673 | if (waiter.task) |
674 | schedule_rt_mutex(lock); | |
23f78d4a IM |
675 | |
676 | spin_lock(&lock->wait_lock); | |
677 | set_current_state(state); | |
678 | } | |
679 | ||
680 | set_current_state(TASK_RUNNING); | |
681 | ||
682 | if (unlikely(waiter.task)) | |
683 | remove_waiter(lock, &waiter __IP__); | |
684 | ||
685 | /* | |
686 | * try_to_take_rt_mutex() sets the waiter bit | |
687 | * unconditionally. We might have to fix that up. | |
688 | */ | |
689 | fixup_rt_mutex_waiters(lock); | |
690 | ||
691 | spin_unlock(&lock->wait_lock); | |
692 | ||
693 | /* Remove pending timer: */ | |
694 | if (unlikely(timeout)) | |
695 | hrtimer_cancel(&timeout->timer); | |
696 | ||
697 | /* | |
698 | * Readjust priority, when we did not get the lock. We might | |
699 | * have been the pending owner and boosted. Since we did not | |
700 | * take the lock, the PI boost has to go. | |
701 | */ | |
702 | if (unlikely(ret)) | |
703 | rt_mutex_adjust_prio(current); | |
704 | ||
705 | debug_rt_mutex_free_waiter(&waiter); | |
706 | ||
707 | return ret; | |
708 | } | |
709 | ||
710 | /* | |
711 | * Slow path try-lock function: | |
712 | */ | |
713 | static inline int | |
714 | rt_mutex_slowtrylock(struct rt_mutex *lock __IP_DECL__) | |
715 | { | |
716 | int ret = 0; | |
717 | ||
718 | spin_lock(&lock->wait_lock); | |
719 | ||
720 | if (likely(rt_mutex_owner(lock) != current)) { | |
721 | ||
722 | ret = try_to_take_rt_mutex(lock __IP__); | |
723 | /* | |
724 | * try_to_take_rt_mutex() sets the lock waiters | |
725 | * bit unconditionally. Clean this up. | |
726 | */ | |
727 | fixup_rt_mutex_waiters(lock); | |
728 | } | |
729 | ||
730 | spin_unlock(&lock->wait_lock); | |
731 | ||
732 | return ret; | |
733 | } | |
734 | ||
735 | /* | |
736 | * Slow path to release a rt-mutex: | |
737 | */ | |
738 | static void __sched | |
739 | rt_mutex_slowunlock(struct rt_mutex *lock) | |
740 | { | |
741 | spin_lock(&lock->wait_lock); | |
742 | ||
743 | debug_rt_mutex_unlock(lock); | |
744 | ||
745 | rt_mutex_deadlock_account_unlock(current); | |
746 | ||
747 | if (!rt_mutex_has_waiters(lock)) { | |
748 | lock->owner = NULL; | |
749 | spin_unlock(&lock->wait_lock); | |
750 | return; | |
751 | } | |
752 | ||
753 | wakeup_next_waiter(lock); | |
754 | ||
755 | spin_unlock(&lock->wait_lock); | |
756 | ||
757 | /* Undo pi boosting if necessary: */ | |
758 | rt_mutex_adjust_prio(current); | |
759 | } | |
760 | ||
761 | /* | |
762 | * debug aware fast / slowpath lock,trylock,unlock | |
763 | * | |
764 | * The atomic acquire/release ops are compiled away, when either the | |
765 | * architecture does not support cmpxchg or when debugging is enabled. | |
766 | */ | |
767 | static inline int | |
768 | rt_mutex_fastlock(struct rt_mutex *lock, int state, | |
769 | int detect_deadlock, | |
770 | int (*slowfn)(struct rt_mutex *lock, int state, | |
771 | struct hrtimer_sleeper *timeout, | |
772 | int detect_deadlock __IP_DECL__)) | |
773 | { | |
774 | if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) { | |
775 | rt_mutex_deadlock_account_lock(lock, current); | |
776 | return 0; | |
777 | } else | |
778 | return slowfn(lock, state, NULL, detect_deadlock __RET_IP__); | |
779 | } | |
780 | ||
781 | static inline int | |
782 | rt_mutex_timed_fastlock(struct rt_mutex *lock, int state, | |
783 | struct hrtimer_sleeper *timeout, int detect_deadlock, | |
784 | int (*slowfn)(struct rt_mutex *lock, int state, | |
785 | struct hrtimer_sleeper *timeout, | |
786 | int detect_deadlock __IP_DECL__)) | |
787 | { | |
788 | if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) { | |
789 | rt_mutex_deadlock_account_lock(lock, current); | |
790 | return 0; | |
791 | } else | |
792 | return slowfn(lock, state, timeout, detect_deadlock __RET_IP__); | |
793 | } | |
794 | ||
795 | static inline int | |
796 | rt_mutex_fasttrylock(struct rt_mutex *lock, | |
797 | int (*slowfn)(struct rt_mutex *lock __IP_DECL__)) | |
798 | { | |
799 | if (likely(rt_mutex_cmpxchg(lock, NULL, current))) { | |
800 | rt_mutex_deadlock_account_lock(lock, current); | |
801 | return 1; | |
802 | } | |
803 | return slowfn(lock __RET_IP__); | |
804 | } | |
805 | ||
806 | static inline void | |
807 | rt_mutex_fastunlock(struct rt_mutex *lock, | |
808 | void (*slowfn)(struct rt_mutex *lock)) | |
809 | { | |
810 | if (likely(rt_mutex_cmpxchg(lock, current, NULL))) | |
811 | rt_mutex_deadlock_account_unlock(current); | |
812 | else | |
813 | slowfn(lock); | |
814 | } | |
815 | ||
816 | /** | |
817 | * rt_mutex_lock - lock a rt_mutex | |
818 | * | |
819 | * @lock: the rt_mutex to be locked | |
820 | */ | |
821 | void __sched rt_mutex_lock(struct rt_mutex *lock) | |
822 | { | |
823 | might_sleep(); | |
824 | ||
825 | rt_mutex_fastlock(lock, TASK_UNINTERRUPTIBLE, 0, rt_mutex_slowlock); | |
826 | } | |
827 | EXPORT_SYMBOL_GPL(rt_mutex_lock); | |
828 | ||
829 | /** | |
830 | * rt_mutex_lock_interruptible - lock a rt_mutex interruptible | |
831 | * | |
832 | * @lock: the rt_mutex to be locked | |
833 | * @detect_deadlock: deadlock detection on/off | |
834 | * | |
835 | * Returns: | |
836 | * 0 on success | |
837 | * -EINTR when interrupted by a signal | |
838 | * -EDEADLK when the lock would deadlock (when deadlock detection is on) | |
839 | */ | |
840 | int __sched rt_mutex_lock_interruptible(struct rt_mutex *lock, | |
841 | int detect_deadlock) | |
842 | { | |
843 | might_sleep(); | |
844 | ||
845 | return rt_mutex_fastlock(lock, TASK_INTERRUPTIBLE, | |
846 | detect_deadlock, rt_mutex_slowlock); | |
847 | } | |
848 | EXPORT_SYMBOL_GPL(rt_mutex_lock_interruptible); | |
849 | ||
850 | /** | |
851 | * rt_mutex_lock_interruptible_ktime - lock a rt_mutex interruptible | |
852 | * the timeout structure is provided | |
853 | * by the caller | |
854 | * | |
855 | * @lock: the rt_mutex to be locked | |
856 | * @timeout: timeout structure or NULL (no timeout) | |
857 | * @detect_deadlock: deadlock detection on/off | |
858 | * | |
859 | * Returns: | |
860 | * 0 on success | |
861 | * -EINTR when interrupted by a signal | |
862 | * -ETIMEOUT when the timeout expired | |
863 | * -EDEADLK when the lock would deadlock (when deadlock detection is on) | |
864 | */ | |
865 | int | |
866 | rt_mutex_timed_lock(struct rt_mutex *lock, struct hrtimer_sleeper *timeout, | |
867 | int detect_deadlock) | |
868 | { | |
869 | might_sleep(); | |
870 | ||
871 | return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout, | |
872 | detect_deadlock, rt_mutex_slowlock); | |
873 | } | |
874 | EXPORT_SYMBOL_GPL(rt_mutex_timed_lock); | |
875 | ||
876 | /** | |
877 | * rt_mutex_trylock - try to lock a rt_mutex | |
878 | * | |
879 | * @lock: the rt_mutex to be locked | |
880 | * | |
881 | * Returns 1 on success and 0 on contention | |
882 | */ | |
883 | int __sched rt_mutex_trylock(struct rt_mutex *lock) | |
884 | { | |
885 | return rt_mutex_fasttrylock(lock, rt_mutex_slowtrylock); | |
886 | } | |
887 | EXPORT_SYMBOL_GPL(rt_mutex_trylock); | |
888 | ||
889 | /** | |
890 | * rt_mutex_unlock - unlock a rt_mutex | |
891 | * | |
892 | * @lock: the rt_mutex to be unlocked | |
893 | */ | |
894 | void __sched rt_mutex_unlock(struct rt_mutex *lock) | |
895 | { | |
896 | rt_mutex_fastunlock(lock, rt_mutex_slowunlock); | |
897 | } | |
898 | EXPORT_SYMBOL_GPL(rt_mutex_unlock); | |
899 | ||
900 | /*** | |
901 | * rt_mutex_destroy - mark a mutex unusable | |
902 | * @lock: the mutex to be destroyed | |
903 | * | |
904 | * This function marks the mutex uninitialized, and any subsequent | |
905 | * use of the mutex is forbidden. The mutex must not be locked when | |
906 | * this function is called. | |
907 | */ | |
908 | void rt_mutex_destroy(struct rt_mutex *lock) | |
909 | { | |
910 | WARN_ON(rt_mutex_is_locked(lock)); | |
911 | #ifdef CONFIG_DEBUG_RT_MUTEXES | |
912 | lock->magic = NULL; | |
913 | #endif | |
914 | } | |
915 | ||
916 | EXPORT_SYMBOL_GPL(rt_mutex_destroy); | |
917 | ||
918 | /** | |
919 | * __rt_mutex_init - initialize the rt lock | |
920 | * | |
921 | * @lock: the rt lock to be initialized | |
922 | * | |
923 | * Initialize the rt lock to unlocked state. | |
924 | * | |
925 | * Initializing of a locked rt lock is not allowed | |
926 | */ | |
927 | void __rt_mutex_init(struct rt_mutex *lock, const char *name) | |
928 | { | |
929 | lock->owner = NULL; | |
930 | spin_lock_init(&lock->wait_lock); | |
931 | plist_head_init(&lock->wait_list, &lock->wait_lock); | |
932 | ||
933 | debug_rt_mutex_init(lock, name); | |
934 | } | |
935 | EXPORT_SYMBOL_GPL(__rt_mutex_init); | |
0cdbee99 IM |
936 | |
937 | /** | |
938 | * rt_mutex_init_proxy_locked - initialize and lock a rt_mutex on behalf of a | |
939 | * proxy owner | |
940 | * | |
941 | * @lock: the rt_mutex to be locked | |
942 | * @proxy_owner:the task to set as owner | |
943 | * | |
944 | * No locking. Caller has to do serializing itself | |
945 | * Special API call for PI-futex support | |
946 | */ | |
947 | void rt_mutex_init_proxy_locked(struct rt_mutex *lock, | |
948 | struct task_struct *proxy_owner) | |
949 | { | |
950 | __rt_mutex_init(lock, NULL); | |
951 | debug_rt_mutex_proxy_lock(lock, proxy_owner __RET_IP__); | |
952 | rt_mutex_set_owner(lock, proxy_owner, 0); | |
953 | rt_mutex_deadlock_account_lock(lock, proxy_owner); | |
954 | } | |
955 | ||
956 | /** | |
957 | * rt_mutex_proxy_unlock - release a lock on behalf of owner | |
958 | * | |
959 | * @lock: the rt_mutex to be locked | |
960 | * | |
961 | * No locking. Caller has to do serializing itself | |
962 | * Special API call for PI-futex support | |
963 | */ | |
964 | void rt_mutex_proxy_unlock(struct rt_mutex *lock, | |
965 | struct task_struct *proxy_owner) | |
966 | { | |
967 | debug_rt_mutex_proxy_unlock(lock); | |
968 | rt_mutex_set_owner(lock, NULL, 0); | |
969 | rt_mutex_deadlock_account_unlock(proxy_owner); | |
970 | } | |
971 | ||
972 | /** | |
973 | * rt_mutex_next_owner - return the next owner of the lock | |
974 | * | |
975 | * @lock: the rt lock query | |
976 | * | |
977 | * Returns the next owner of the lock or NULL | |
978 | * | |
979 | * Caller has to serialize against other accessors to the lock | |
980 | * itself. | |
981 | * | |
982 | * Special API call for PI-futex support | |
983 | */ | |
984 | struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock) | |
985 | { | |
986 | if (!rt_mutex_has_waiters(lock)) | |
987 | return NULL; | |
988 | ||
989 | return rt_mutex_top_waiter(lock)->task; | |
990 | } |