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> | |
14 | #include <linux/module.h> | |
15 | #include <linux/sched.h> | |
16 | #include <linux/timer.h> | |
17 | ||
18 | #include "rtmutex_common.h" | |
19 | ||
20 | #ifdef CONFIG_DEBUG_RT_MUTEXES | |
21 | # include "rtmutex-debug.h" | |
22 | #else | |
23 | # include "rtmutex.h" | |
24 | #endif | |
25 | ||
26 | /* | |
27 | * lock->owner state tracking: | |
28 | * | |
29 | * lock->owner holds the task_struct pointer of the owner. Bit 0 and 1 | |
30 | * are used to keep track of the "owner is pending" and "lock has | |
31 | * waiters" state. | |
32 | * | |
33 | * owner bit1 bit0 | |
34 | * NULL 0 0 lock is free (fast acquire possible) | |
35 | * NULL 0 1 invalid state | |
36 | * NULL 1 0 Transitional State* | |
37 | * NULL 1 1 invalid state | |
38 | * taskpointer 0 0 lock is held (fast release possible) | |
39 | * taskpointer 0 1 task is pending owner | |
40 | * taskpointer 1 0 lock is held and has waiters | |
41 | * taskpointer 1 1 task is pending owner and lock has more waiters | |
42 | * | |
43 | * Pending ownership is assigned to the top (highest priority) | |
44 | * waiter of the lock, when the lock is released. The thread is woken | |
45 | * up and can now take the lock. Until the lock is taken (bit 0 | |
46 | * cleared) a competing higher priority thread can steal the lock | |
47 | * which puts the woken up thread back on the waiters list. | |
48 | * | |
49 | * The fast atomic compare exchange based acquire and release is only | |
50 | * possible when bit 0 and 1 of lock->owner are 0. | |
51 | * | |
52 | * (*) There's a small time where the owner can be NULL and the | |
53 | * "lock has waiters" bit is set. This can happen when grabbing the lock. | |
54 | * To prevent a cmpxchg of the owner releasing the lock, we need to set this | |
55 | * bit before looking at the lock, hence the reason this is a transitional | |
56 | * state. | |
57 | */ | |
58 | ||
d0aa7a70 | 59 | void |
23f78d4a IM |
60 | rt_mutex_set_owner(struct rt_mutex *lock, struct task_struct *owner, |
61 | unsigned long mask) | |
62 | { | |
63 | unsigned long val = (unsigned long)owner | mask; | |
64 | ||
65 | if (rt_mutex_has_waiters(lock)) | |
66 | val |= RT_MUTEX_HAS_WAITERS; | |
67 | ||
68 | lock->owner = (struct task_struct *)val; | |
69 | } | |
70 | ||
71 | static inline void clear_rt_mutex_waiters(struct rt_mutex *lock) | |
72 | { | |
73 | lock->owner = (struct task_struct *) | |
74 | ((unsigned long)lock->owner & ~RT_MUTEX_HAS_WAITERS); | |
75 | } | |
76 | ||
77 | static void fixup_rt_mutex_waiters(struct rt_mutex *lock) | |
78 | { | |
79 | if (!rt_mutex_has_waiters(lock)) | |
80 | clear_rt_mutex_waiters(lock); | |
81 | } | |
82 | ||
23f78d4a IM |
83 | /* |
84 | * Calculate task priority from the waiter list priority | |
85 | * | |
86 | * Return task->normal_prio when the waiter list is empty or when | |
87 | * the waiter is not allowed to do priority boosting | |
88 | */ | |
89 | int rt_mutex_getprio(struct task_struct *task) | |
90 | { | |
91 | if (likely(!task_has_pi_waiters(task))) | |
92 | return task->normal_prio; | |
93 | ||
94 | return min(task_top_pi_waiter(task)->pi_list_entry.prio, | |
95 | task->normal_prio); | |
96 | } | |
97 | ||
98 | /* | |
99 | * Adjust the priority of a task, after its pi_waiters got modified. | |
100 | * | |
101 | * This can be both boosting and unboosting. task->pi_lock must be held. | |
102 | */ | |
d0aa7a70 | 103 | void __rt_mutex_adjust_prio(struct task_struct *task) |
23f78d4a IM |
104 | { |
105 | int prio = rt_mutex_getprio(task); | |
106 | ||
107 | if (task->prio != prio) | |
108 | rt_mutex_setprio(task, prio); | |
109 | } | |
110 | ||
111 | /* | |
112 | * Adjust task priority (undo boosting). Called from the exit path of | |
113 | * rt_mutex_slowunlock() and rt_mutex_slowlock(). | |
114 | * | |
115 | * (Note: We do this outside of the protection of lock->wait_lock to | |
116 | * allow the lock to be taken while or before we readjust the priority | |
117 | * of task. We do not use the spin_xx_mutex() variants here as we are | |
118 | * outside of the debug path.) | |
119 | */ | |
120 | static void rt_mutex_adjust_prio(struct task_struct *task) | |
121 | { | |
122 | unsigned long flags; | |
123 | ||
124 | spin_lock_irqsave(&task->pi_lock, flags); | |
125 | __rt_mutex_adjust_prio(task); | |
126 | spin_unlock_irqrestore(&task->pi_lock, flags); | |
127 | } | |
128 | ||
129 | /* | |
130 | * Max number of times we'll walk the boosting chain: | |
131 | */ | |
132 | int max_lock_depth = 1024; | |
133 | ||
134 | /* | |
135 | * Adjust the priority chain. Also used for deadlock detection. | |
136 | * Decreases task's usage by one - may thus free the task. | |
137 | * Returns 0 or -EDEADLK. | |
138 | */ | |
d0aa7a70 PP |
139 | int rt_mutex_adjust_prio_chain(struct task_struct *task, |
140 | int deadlock_detect, | |
141 | struct rt_mutex *orig_lock, | |
142 | struct rt_mutex_waiter *orig_waiter, | |
143 | struct task_struct *top_task) | |
23f78d4a IM |
144 | { |
145 | struct rt_mutex *lock; | |
146 | struct rt_mutex_waiter *waiter, *top_waiter = orig_waiter; | |
147 | int detect_deadlock, ret = 0, depth = 0; | |
148 | unsigned long flags; | |
149 | ||
150 | detect_deadlock = debug_rt_mutex_detect_deadlock(orig_waiter, | |
151 | deadlock_detect); | |
152 | ||
153 | /* | |
154 | * The (de)boosting is a step by step approach with a lot of | |
155 | * pitfalls. We want this to be preemptible and we want hold a | |
156 | * maximum of two locks per step. So we have to check | |
157 | * carefully whether things change under us. | |
158 | */ | |
159 | again: | |
160 | if (++depth > max_lock_depth) { | |
161 | static int prev_max; | |
162 | ||
163 | /* | |
164 | * Print this only once. If the admin changes the limit, | |
165 | * print a new message when reaching the limit again. | |
166 | */ | |
167 | if (prev_max != max_lock_depth) { | |
168 | prev_max = max_lock_depth; | |
169 | printk(KERN_WARNING "Maximum lock depth %d reached " | |
170 | "task: %s (%d)\n", max_lock_depth, | |
95e02ca9 | 171 | top_task->comm, top_task->pid); |
23f78d4a IM |
172 | } |
173 | put_task_struct(task); | |
174 | ||
175 | return deadlock_detect ? -EDEADLK : 0; | |
176 | } | |
177 | retry: | |
178 | /* | |
179 | * Task can not go away as we did a get_task() before ! | |
180 | */ | |
181 | spin_lock_irqsave(&task->pi_lock, flags); | |
182 | ||
183 | waiter = task->pi_blocked_on; | |
184 | /* | |
185 | * Check whether the end of the boosting chain has been | |
186 | * reached or the state of the chain has changed while we | |
187 | * dropped the locks. | |
188 | */ | |
189 | if (!waiter || !waiter->task) | |
190 | goto out_unlock_pi; | |
191 | ||
1a539a87 TG |
192 | /* |
193 | * Check the orig_waiter state. After we dropped the locks, | |
194 | * the previous owner of the lock might have released the lock | |
195 | * and made us the pending owner: | |
196 | */ | |
197 | if (orig_waiter && !orig_waiter->task) | |
198 | goto out_unlock_pi; | |
199 | ||
200 | /* | |
201 | * Drop out, when the task has no waiters. Note, | |
202 | * top_waiter can be NULL, when we are in the deboosting | |
203 | * mode! | |
204 | */ | |
23f78d4a IM |
205 | if (top_waiter && (!task_has_pi_waiters(task) || |
206 | top_waiter != task_top_pi_waiter(task))) | |
207 | goto out_unlock_pi; | |
208 | ||
209 | /* | |
210 | * When deadlock detection is off then we check, if further | |
211 | * priority adjustment is necessary. | |
212 | */ | |
213 | if (!detect_deadlock && waiter->list_entry.prio == task->prio) | |
214 | goto out_unlock_pi; | |
215 | ||
216 | lock = waiter->lock; | |
217 | if (!spin_trylock(&lock->wait_lock)) { | |
218 | spin_unlock_irqrestore(&task->pi_lock, flags); | |
219 | cpu_relax(); | |
220 | goto retry; | |
221 | } | |
222 | ||
223 | /* Deadlock detection */ | |
95e02ca9 | 224 | if (lock == orig_lock || rt_mutex_owner(lock) == top_task) { |
23f78d4a IM |
225 | debug_rt_mutex_deadlock(deadlock_detect, orig_waiter, lock); |
226 | spin_unlock(&lock->wait_lock); | |
227 | ret = deadlock_detect ? -EDEADLK : 0; | |
228 | goto out_unlock_pi; | |
229 | } | |
230 | ||
231 | top_waiter = rt_mutex_top_waiter(lock); | |
232 | ||
233 | /* Requeue the waiter */ | |
234 | plist_del(&waiter->list_entry, &lock->wait_list); | |
235 | waiter->list_entry.prio = task->prio; | |
236 | plist_add(&waiter->list_entry, &lock->wait_list); | |
237 | ||
238 | /* Release the task */ | |
239 | spin_unlock_irqrestore(&task->pi_lock, flags); | |
240 | put_task_struct(task); | |
241 | ||
242 | /* Grab the next task */ | |
243 | task = rt_mutex_owner(lock); | |
db630637 | 244 | get_task_struct(task); |
23f78d4a IM |
245 | spin_lock_irqsave(&task->pi_lock, flags); |
246 | ||
247 | if (waiter == rt_mutex_top_waiter(lock)) { | |
248 | /* Boost the owner */ | |
249 | plist_del(&top_waiter->pi_list_entry, &task->pi_waiters); | |
250 | waiter->pi_list_entry.prio = waiter->list_entry.prio; | |
251 | plist_add(&waiter->pi_list_entry, &task->pi_waiters); | |
252 | __rt_mutex_adjust_prio(task); | |
253 | ||
254 | } else if (top_waiter == waiter) { | |
255 | /* Deboost the owner */ | |
256 | plist_del(&waiter->pi_list_entry, &task->pi_waiters); | |
257 | waiter = rt_mutex_top_waiter(lock); | |
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 | ||
23f78d4a IM |
263 | spin_unlock_irqrestore(&task->pi_lock, flags); |
264 | ||
265 | top_waiter = rt_mutex_top_waiter(lock); | |
266 | spin_unlock(&lock->wait_lock); | |
267 | ||
268 | if (!detect_deadlock && waiter != top_waiter) | |
269 | goto out_put_task; | |
270 | ||
271 | goto again; | |
272 | ||
273 | out_unlock_pi: | |
274 | spin_unlock_irqrestore(&task->pi_lock, flags); | |
275 | out_put_task: | |
276 | put_task_struct(task); | |
36c8b586 | 277 | |
23f78d4a IM |
278 | return ret; |
279 | } | |
280 | ||
281 | /* | |
282 | * Optimization: check if we can steal the lock from the | |
283 | * assigned pending owner [which might not have taken the | |
284 | * lock yet]: | |
285 | */ | |
286 | static inline int try_to_steal_lock(struct rt_mutex *lock) | |
287 | { | |
288 | struct task_struct *pendowner = rt_mutex_owner(lock); | |
289 | struct rt_mutex_waiter *next; | |
290 | unsigned long flags; | |
291 | ||
292 | if (!rt_mutex_owner_pending(lock)) | |
293 | return 0; | |
294 | ||
295 | if (pendowner == current) | |
296 | return 1; | |
297 | ||
298 | spin_lock_irqsave(&pendowner->pi_lock, flags); | |
299 | if (current->prio >= pendowner->prio) { | |
300 | spin_unlock_irqrestore(&pendowner->pi_lock, flags); | |
301 | return 0; | |
302 | } | |
303 | ||
304 | /* | |
305 | * Check if a waiter is enqueued on the pending owners | |
306 | * pi_waiters list. Remove it and readjust pending owners | |
307 | * priority. | |
308 | */ | |
309 | if (likely(!rt_mutex_has_waiters(lock))) { | |
310 | spin_unlock_irqrestore(&pendowner->pi_lock, flags); | |
311 | return 1; | |
312 | } | |
313 | ||
314 | /* No chain handling, pending owner is not blocked on anything: */ | |
315 | next = rt_mutex_top_waiter(lock); | |
316 | plist_del(&next->pi_list_entry, &pendowner->pi_waiters); | |
317 | __rt_mutex_adjust_prio(pendowner); | |
318 | spin_unlock_irqrestore(&pendowner->pi_lock, flags); | |
319 | ||
320 | /* | |
321 | * We are going to steal the lock and a waiter was | |
322 | * enqueued on the pending owners pi_waiters queue. So | |
323 | * we have to enqueue this waiter into | |
324 | * current->pi_waiters list. This covers the case, | |
325 | * where current is boosted because it holds another | |
326 | * lock and gets unboosted because the booster is | |
327 | * interrupted, so we would delay a waiter with higher | |
328 | * priority as current->normal_prio. | |
329 | * | |
330 | * Note: in the rare case of a SCHED_OTHER task changing | |
331 | * its priority and thus stealing the lock, next->task | |
332 | * might be current: | |
333 | */ | |
334 | if (likely(next->task != current)) { | |
335 | spin_lock_irqsave(¤t->pi_lock, flags); | |
336 | plist_add(&next->pi_list_entry, ¤t->pi_waiters); | |
337 | __rt_mutex_adjust_prio(current); | |
338 | spin_unlock_irqrestore(¤t->pi_lock, flags); | |
339 | } | |
340 | return 1; | |
341 | } | |
342 | ||
343 | /* | |
344 | * Try to take an rt-mutex | |
345 | * | |
346 | * This fails | |
347 | * - when the lock has a real owner | |
348 | * - when a different pending owner exists and has higher priority than current | |
349 | * | |
350 | * Must be called with lock->wait_lock held. | |
351 | */ | |
9a11b49a | 352 | static int try_to_take_rt_mutex(struct rt_mutex *lock) |
23f78d4a IM |
353 | { |
354 | /* | |
355 | * We have to be careful here if the atomic speedups are | |
356 | * enabled, such that, when | |
357 | * - no other waiter is on the lock | |
358 | * - the lock has been released since we did the cmpxchg | |
359 | * the lock can be released or taken while we are doing the | |
360 | * checks and marking the lock with RT_MUTEX_HAS_WAITERS. | |
361 | * | |
362 | * The atomic acquire/release aware variant of | |
363 | * mark_rt_mutex_waiters uses a cmpxchg loop. After setting | |
364 | * the WAITERS bit, the atomic release / acquire can not | |
365 | * happen anymore and lock->wait_lock protects us from the | |
366 | * non-atomic case. | |
367 | * | |
368 | * Note, that this might set lock->owner = | |
369 | * RT_MUTEX_HAS_WAITERS in the case the lock is not contended | |
370 | * any more. This is fixed up when we take the ownership. | |
371 | * This is the transitional state explained at the top of this file. | |
372 | */ | |
373 | mark_rt_mutex_waiters(lock); | |
374 | ||
375 | if (rt_mutex_owner(lock) && !try_to_steal_lock(lock)) | |
376 | return 0; | |
377 | ||
378 | /* We got the lock. */ | |
9a11b49a | 379 | debug_rt_mutex_lock(lock); |
23f78d4a IM |
380 | |
381 | rt_mutex_set_owner(lock, current, 0); | |
382 | ||
383 | rt_mutex_deadlock_account_lock(lock, current); | |
384 | ||
385 | return 1; | |
386 | } | |
387 | ||
388 | /* | |
389 | * Task blocks on lock. | |
390 | * | |
391 | * Prepare waiter and propagate pi chain | |
392 | * | |
393 | * This must be called with lock->wait_lock held. | |
394 | */ | |
395 | static int task_blocks_on_rt_mutex(struct rt_mutex *lock, | |
396 | struct rt_mutex_waiter *waiter, | |
9a11b49a | 397 | int detect_deadlock) |
23f78d4a | 398 | { |
36c8b586 | 399 | struct task_struct *owner = rt_mutex_owner(lock); |
23f78d4a | 400 | struct rt_mutex_waiter *top_waiter = waiter; |
23f78d4a | 401 | unsigned long flags; |
db630637 | 402 | int chain_walk = 0, res; |
23f78d4a IM |
403 | |
404 | spin_lock_irqsave(¤t->pi_lock, flags); | |
405 | __rt_mutex_adjust_prio(current); | |
406 | waiter->task = current; | |
407 | waiter->lock = lock; | |
408 | plist_node_init(&waiter->list_entry, current->prio); | |
409 | plist_node_init(&waiter->pi_list_entry, current->prio); | |
410 | ||
411 | /* Get the top priority waiter on the lock */ | |
412 | if (rt_mutex_has_waiters(lock)) | |
413 | top_waiter = rt_mutex_top_waiter(lock); | |
414 | plist_add(&waiter->list_entry, &lock->wait_list); | |
415 | ||
416 | current->pi_blocked_on = waiter; | |
417 | ||
418 | spin_unlock_irqrestore(¤t->pi_lock, flags); | |
419 | ||
420 | if (waiter == rt_mutex_top_waiter(lock)) { | |
421 | spin_lock_irqsave(&owner->pi_lock, flags); | |
422 | plist_del(&top_waiter->pi_list_entry, &owner->pi_waiters); | |
423 | plist_add(&waiter->pi_list_entry, &owner->pi_waiters); | |
424 | ||
425 | __rt_mutex_adjust_prio(owner); | |
db630637 SR |
426 | if (owner->pi_blocked_on) |
427 | chain_walk = 1; | |
23f78d4a IM |
428 | spin_unlock_irqrestore(&owner->pi_lock, flags); |
429 | } | |
db630637 SR |
430 | else if (debug_rt_mutex_detect_deadlock(waiter, detect_deadlock)) |
431 | chain_walk = 1; | |
432 | ||
433 | if (!chain_walk) | |
23f78d4a IM |
434 | return 0; |
435 | ||
db630637 SR |
436 | /* |
437 | * The owner can't disappear while holding a lock, | |
438 | * so the owner struct is protected by wait_lock. | |
439 | * Gets dropped in rt_mutex_adjust_prio_chain()! | |
440 | */ | |
441 | get_task_struct(owner); | |
442 | ||
23f78d4a IM |
443 | spin_unlock(&lock->wait_lock); |
444 | ||
95e02ca9 | 445 | res = rt_mutex_adjust_prio_chain(owner, detect_deadlock, lock, waiter, |
9a11b49a | 446 | current); |
23f78d4a IM |
447 | |
448 | spin_lock(&lock->wait_lock); | |
449 | ||
450 | return res; | |
451 | } | |
452 | ||
453 | /* | |
454 | * Wake up the next waiter on the lock. | |
455 | * | |
456 | * Remove the top waiter from the current tasks waiter list and from | |
457 | * the lock waiter list. Set it as pending owner. Then wake it up. | |
458 | * | |
459 | * Called with lock->wait_lock held. | |
460 | */ | |
461 | static void wakeup_next_waiter(struct rt_mutex *lock) | |
462 | { | |
463 | struct rt_mutex_waiter *waiter; | |
464 | struct task_struct *pendowner; | |
465 | unsigned long flags; | |
466 | ||
467 | spin_lock_irqsave(¤t->pi_lock, flags); | |
468 | ||
469 | waiter = rt_mutex_top_waiter(lock); | |
470 | plist_del(&waiter->list_entry, &lock->wait_list); | |
471 | ||
472 | /* | |
473 | * Remove it from current->pi_waiters. We do not adjust a | |
474 | * possible priority boost right now. We execute wakeup in the | |
475 | * boosted mode and go back to normal after releasing | |
476 | * lock->wait_lock. | |
477 | */ | |
478 | plist_del(&waiter->pi_list_entry, ¤t->pi_waiters); | |
479 | pendowner = waiter->task; | |
480 | waiter->task = NULL; | |
481 | ||
482 | rt_mutex_set_owner(lock, pendowner, RT_MUTEX_OWNER_PENDING); | |
483 | ||
484 | spin_unlock_irqrestore(¤t->pi_lock, flags); | |
485 | ||
486 | /* | |
487 | * Clear the pi_blocked_on variable and enqueue a possible | |
488 | * waiter into the pi_waiters list of the pending owner. This | |
489 | * prevents that in case the pending owner gets unboosted a | |
490 | * waiter with higher priority than pending-owner->normal_prio | |
491 | * is blocked on the unboosted (pending) owner. | |
492 | */ | |
493 | spin_lock_irqsave(&pendowner->pi_lock, flags); | |
494 | ||
495 | WARN_ON(!pendowner->pi_blocked_on); | |
496 | WARN_ON(pendowner->pi_blocked_on != waiter); | |
497 | WARN_ON(pendowner->pi_blocked_on->lock != lock); | |
498 | ||
499 | pendowner->pi_blocked_on = NULL; | |
500 | ||
501 | if (rt_mutex_has_waiters(lock)) { | |
502 | struct rt_mutex_waiter *next; | |
503 | ||
504 | next = rt_mutex_top_waiter(lock); | |
505 | plist_add(&next->pi_list_entry, &pendowner->pi_waiters); | |
506 | } | |
507 | spin_unlock_irqrestore(&pendowner->pi_lock, flags); | |
508 | ||
509 | wake_up_process(pendowner); | |
510 | } | |
511 | ||
512 | /* | |
513 | * Remove a waiter from a lock | |
514 | * | |
515 | * Must be called with lock->wait_lock held | |
516 | */ | |
d0aa7a70 PP |
517 | void remove_waiter(struct rt_mutex *lock, |
518 | struct rt_mutex_waiter *waiter) | |
23f78d4a IM |
519 | { |
520 | int first = (waiter == rt_mutex_top_waiter(lock)); | |
36c8b586 | 521 | struct task_struct *owner = rt_mutex_owner(lock); |
23f78d4a | 522 | unsigned long flags; |
db630637 | 523 | int chain_walk = 0; |
23f78d4a IM |
524 | |
525 | spin_lock_irqsave(¤t->pi_lock, flags); | |
526 | plist_del(&waiter->list_entry, &lock->wait_list); | |
527 | waiter->task = NULL; | |
528 | current->pi_blocked_on = NULL; | |
529 | spin_unlock_irqrestore(¤t->pi_lock, flags); | |
530 | ||
531 | if (first && owner != current) { | |
532 | ||
533 | spin_lock_irqsave(&owner->pi_lock, flags); | |
534 | ||
535 | plist_del(&waiter->pi_list_entry, &owner->pi_waiters); | |
536 | ||
537 | if (rt_mutex_has_waiters(lock)) { | |
538 | struct rt_mutex_waiter *next; | |
539 | ||
540 | next = rt_mutex_top_waiter(lock); | |
541 | plist_add(&next->pi_list_entry, &owner->pi_waiters); | |
542 | } | |
543 | __rt_mutex_adjust_prio(owner); | |
544 | ||
db630637 SR |
545 | if (owner->pi_blocked_on) |
546 | chain_walk = 1; | |
547 | ||
23f78d4a IM |
548 | spin_unlock_irqrestore(&owner->pi_lock, flags); |
549 | } | |
550 | ||
551 | WARN_ON(!plist_node_empty(&waiter->pi_list_entry)); | |
552 | ||
db630637 | 553 | if (!chain_walk) |
23f78d4a IM |
554 | return; |
555 | ||
db630637 SR |
556 | /* gets dropped in rt_mutex_adjust_prio_chain()! */ |
557 | get_task_struct(owner); | |
558 | ||
23f78d4a IM |
559 | spin_unlock(&lock->wait_lock); |
560 | ||
9a11b49a | 561 | rt_mutex_adjust_prio_chain(owner, 0, lock, NULL, current); |
23f78d4a IM |
562 | |
563 | spin_lock(&lock->wait_lock); | |
564 | } | |
565 | ||
95e02ca9 TG |
566 | /* |
567 | * Recheck the pi chain, in case we got a priority setting | |
568 | * | |
569 | * Called from sched_setscheduler | |
570 | */ | |
571 | void rt_mutex_adjust_pi(struct task_struct *task) | |
572 | { | |
573 | struct rt_mutex_waiter *waiter; | |
574 | unsigned long flags; | |
575 | ||
576 | spin_lock_irqsave(&task->pi_lock, flags); | |
577 | ||
578 | waiter = task->pi_blocked_on; | |
579 | if (!waiter || waiter->list_entry.prio == task->prio) { | |
580 | spin_unlock_irqrestore(&task->pi_lock, flags); | |
581 | return; | |
582 | } | |
583 | ||
95e02ca9 TG |
584 | spin_unlock_irqrestore(&task->pi_lock, flags); |
585 | ||
db630637 SR |
586 | /* gets dropped in rt_mutex_adjust_prio_chain()! */ |
587 | get_task_struct(task); | |
9a11b49a | 588 | rt_mutex_adjust_prio_chain(task, 0, NULL, NULL, task); |
95e02ca9 TG |
589 | } |
590 | ||
23f78d4a IM |
591 | /* |
592 | * Slow path lock function: | |
593 | */ | |
594 | static int __sched | |
595 | rt_mutex_slowlock(struct rt_mutex *lock, int state, | |
596 | struct hrtimer_sleeper *timeout, | |
9a11b49a | 597 | int detect_deadlock) |
23f78d4a IM |
598 | { |
599 | struct rt_mutex_waiter waiter; | |
600 | int ret = 0; | |
601 | ||
602 | debug_rt_mutex_init_waiter(&waiter); | |
603 | waiter.task = NULL; | |
604 | ||
605 | spin_lock(&lock->wait_lock); | |
606 | ||
607 | /* Try to acquire the lock again: */ | |
9a11b49a | 608 | if (try_to_take_rt_mutex(lock)) { |
23f78d4a IM |
609 | spin_unlock(&lock->wait_lock); |
610 | return 0; | |
611 | } | |
612 | ||
613 | set_current_state(state); | |
614 | ||
615 | /* Setup the timer, when timeout != NULL */ | |
616 | if (unlikely(timeout)) | |
617 | hrtimer_start(&timeout->timer, timeout->timer.expires, | |
c9cb2e3d | 618 | HRTIMER_MODE_ABS); |
23f78d4a IM |
619 | |
620 | for (;;) { | |
621 | /* Try to acquire the lock: */ | |
9a11b49a | 622 | if (try_to_take_rt_mutex(lock)) |
23f78d4a IM |
623 | break; |
624 | ||
625 | /* | |
626 | * TASK_INTERRUPTIBLE checks for signals and | |
627 | * timeout. Ignored otherwise. | |
628 | */ | |
629 | if (unlikely(state == TASK_INTERRUPTIBLE)) { | |
630 | /* Signal pending? */ | |
631 | if (signal_pending(current)) | |
632 | ret = -EINTR; | |
633 | if (timeout && !timeout->task) | |
634 | ret = -ETIMEDOUT; | |
635 | if (ret) | |
636 | break; | |
637 | } | |
638 | ||
639 | /* | |
640 | * waiter.task is NULL the first time we come here and | |
641 | * when we have been woken up by the previous owner | |
642 | * but the lock got stolen by a higher prio task. | |
643 | */ | |
644 | if (!waiter.task) { | |
645 | ret = task_blocks_on_rt_mutex(lock, &waiter, | |
9a11b49a | 646 | detect_deadlock); |
23f78d4a IM |
647 | /* |
648 | * If we got woken up by the owner then start loop | |
649 | * all over without going into schedule to try | |
650 | * to get the lock now: | |
651 | */ | |
c0d1d2bf TG |
652 | if (unlikely(!waiter.task)) { |
653 | /* | |
654 | * Reset the return value. We might | |
655 | * have returned with -EDEADLK and the | |
656 | * owner released the lock while we | |
657 | * were walking the pi chain. | |
658 | */ | |
659 | ret = 0; | |
23f78d4a | 660 | continue; |
c0d1d2bf | 661 | } |
23f78d4a IM |
662 | if (unlikely(ret)) |
663 | break; | |
664 | } | |
95e02ca9 | 665 | |
23f78d4a IM |
666 | spin_unlock(&lock->wait_lock); |
667 | ||
668 | debug_rt_mutex_print_deadlock(&waiter); | |
669 | ||
61a87122 TG |
670 | if (waiter.task) |
671 | schedule_rt_mutex(lock); | |
23f78d4a IM |
672 | |
673 | spin_lock(&lock->wait_lock); | |
674 | set_current_state(state); | |
675 | } | |
676 | ||
677 | set_current_state(TASK_RUNNING); | |
678 | ||
679 | if (unlikely(waiter.task)) | |
9a11b49a | 680 | remove_waiter(lock, &waiter); |
23f78d4a IM |
681 | |
682 | /* | |
683 | * try_to_take_rt_mutex() sets the waiter bit | |
684 | * unconditionally. We might have to fix that up. | |
685 | */ | |
686 | fixup_rt_mutex_waiters(lock); | |
687 | ||
688 | spin_unlock(&lock->wait_lock); | |
689 | ||
690 | /* Remove pending timer: */ | |
691 | if (unlikely(timeout)) | |
692 | hrtimer_cancel(&timeout->timer); | |
693 | ||
694 | /* | |
695 | * Readjust priority, when we did not get the lock. We might | |
696 | * have been the pending owner and boosted. Since we did not | |
697 | * take the lock, the PI boost has to go. | |
698 | */ | |
699 | if (unlikely(ret)) | |
700 | rt_mutex_adjust_prio(current); | |
701 | ||
702 | debug_rt_mutex_free_waiter(&waiter); | |
703 | ||
704 | return ret; | |
705 | } | |
706 | ||
707 | /* | |
708 | * Slow path try-lock function: | |
709 | */ | |
710 | static inline int | |
9a11b49a | 711 | rt_mutex_slowtrylock(struct rt_mutex *lock) |
23f78d4a IM |
712 | { |
713 | int ret = 0; | |
714 | ||
715 | spin_lock(&lock->wait_lock); | |
716 | ||
717 | if (likely(rt_mutex_owner(lock) != current)) { | |
718 | ||
9a11b49a | 719 | ret = try_to_take_rt_mutex(lock); |
23f78d4a IM |
720 | /* |
721 | * try_to_take_rt_mutex() sets the lock waiters | |
722 | * bit unconditionally. Clean this up. | |
723 | */ | |
724 | fixup_rt_mutex_waiters(lock); | |
725 | } | |
726 | ||
727 | spin_unlock(&lock->wait_lock); | |
728 | ||
729 | return ret; | |
730 | } | |
731 | ||
732 | /* | |
733 | * Slow path to release a rt-mutex: | |
734 | */ | |
735 | static void __sched | |
736 | rt_mutex_slowunlock(struct rt_mutex *lock) | |
737 | { | |
738 | spin_lock(&lock->wait_lock); | |
739 | ||
740 | debug_rt_mutex_unlock(lock); | |
741 | ||
742 | rt_mutex_deadlock_account_unlock(current); | |
743 | ||
744 | if (!rt_mutex_has_waiters(lock)) { | |
745 | lock->owner = NULL; | |
746 | spin_unlock(&lock->wait_lock); | |
747 | return; | |
748 | } | |
749 | ||
750 | wakeup_next_waiter(lock); | |
751 | ||
752 | spin_unlock(&lock->wait_lock); | |
753 | ||
754 | /* Undo pi boosting if necessary: */ | |
755 | rt_mutex_adjust_prio(current); | |
756 | } | |
757 | ||
758 | /* | |
759 | * debug aware fast / slowpath lock,trylock,unlock | |
760 | * | |
761 | * The atomic acquire/release ops are compiled away, when either the | |
762 | * architecture does not support cmpxchg or when debugging is enabled. | |
763 | */ | |
764 | static inline int | |
765 | rt_mutex_fastlock(struct rt_mutex *lock, int state, | |
766 | int detect_deadlock, | |
767 | int (*slowfn)(struct rt_mutex *lock, int state, | |
768 | struct hrtimer_sleeper *timeout, | |
9a11b49a | 769 | int detect_deadlock)) |
23f78d4a IM |
770 | { |
771 | if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) { | |
772 | rt_mutex_deadlock_account_lock(lock, current); | |
773 | return 0; | |
774 | } else | |
9a11b49a | 775 | return slowfn(lock, state, NULL, detect_deadlock); |
23f78d4a IM |
776 | } |
777 | ||
778 | static inline int | |
779 | rt_mutex_timed_fastlock(struct rt_mutex *lock, int state, | |
780 | struct hrtimer_sleeper *timeout, int detect_deadlock, | |
781 | int (*slowfn)(struct rt_mutex *lock, int state, | |
782 | struct hrtimer_sleeper *timeout, | |
9a11b49a | 783 | int detect_deadlock)) |
23f78d4a IM |
784 | { |
785 | if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) { | |
786 | rt_mutex_deadlock_account_lock(lock, current); | |
787 | return 0; | |
788 | } else | |
9a11b49a | 789 | return slowfn(lock, state, timeout, detect_deadlock); |
23f78d4a IM |
790 | } |
791 | ||
792 | static inline int | |
793 | rt_mutex_fasttrylock(struct rt_mutex *lock, | |
9a11b49a | 794 | int (*slowfn)(struct rt_mutex *lock)) |
23f78d4a IM |
795 | { |
796 | if (likely(rt_mutex_cmpxchg(lock, NULL, current))) { | |
797 | rt_mutex_deadlock_account_lock(lock, current); | |
798 | return 1; | |
799 | } | |
9a11b49a | 800 | return slowfn(lock); |
23f78d4a IM |
801 | } |
802 | ||
803 | static inline void | |
804 | rt_mutex_fastunlock(struct rt_mutex *lock, | |
805 | void (*slowfn)(struct rt_mutex *lock)) | |
806 | { | |
807 | if (likely(rt_mutex_cmpxchg(lock, current, NULL))) | |
808 | rt_mutex_deadlock_account_unlock(current); | |
809 | else | |
810 | slowfn(lock); | |
811 | } | |
812 | ||
813 | /** | |
814 | * rt_mutex_lock - lock a rt_mutex | |
815 | * | |
816 | * @lock: the rt_mutex to be locked | |
817 | */ | |
818 | void __sched rt_mutex_lock(struct rt_mutex *lock) | |
819 | { | |
820 | might_sleep(); | |
821 | ||
822 | rt_mutex_fastlock(lock, TASK_UNINTERRUPTIBLE, 0, rt_mutex_slowlock); | |
823 | } | |
824 | EXPORT_SYMBOL_GPL(rt_mutex_lock); | |
825 | ||
826 | /** | |
827 | * rt_mutex_lock_interruptible - lock a rt_mutex interruptible | |
828 | * | |
829 | * @lock: the rt_mutex to be locked | |
830 | * @detect_deadlock: deadlock detection on/off | |
831 | * | |
832 | * Returns: | |
833 | * 0 on success | |
834 | * -EINTR when interrupted by a signal | |
835 | * -EDEADLK when the lock would deadlock (when deadlock detection is on) | |
836 | */ | |
837 | int __sched rt_mutex_lock_interruptible(struct rt_mutex *lock, | |
838 | int detect_deadlock) | |
839 | { | |
840 | might_sleep(); | |
841 | ||
842 | return rt_mutex_fastlock(lock, TASK_INTERRUPTIBLE, | |
843 | detect_deadlock, rt_mutex_slowlock); | |
844 | } | |
845 | EXPORT_SYMBOL_GPL(rt_mutex_lock_interruptible); | |
846 | ||
847 | /** | |
848 | * rt_mutex_lock_interruptible_ktime - lock a rt_mutex interruptible | |
849 | * the timeout structure is provided | |
850 | * by the caller | |
851 | * | |
852 | * @lock: the rt_mutex to be locked | |
853 | * @timeout: timeout structure or NULL (no timeout) | |
854 | * @detect_deadlock: deadlock detection on/off | |
855 | * | |
856 | * Returns: | |
857 | * 0 on success | |
858 | * -EINTR when interrupted by a signal | |
859 | * -ETIMEOUT when the timeout expired | |
860 | * -EDEADLK when the lock would deadlock (when deadlock detection is on) | |
861 | */ | |
862 | int | |
863 | rt_mutex_timed_lock(struct rt_mutex *lock, struct hrtimer_sleeper *timeout, | |
864 | int detect_deadlock) | |
865 | { | |
866 | might_sleep(); | |
867 | ||
868 | return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout, | |
869 | detect_deadlock, rt_mutex_slowlock); | |
870 | } | |
871 | EXPORT_SYMBOL_GPL(rt_mutex_timed_lock); | |
872 | ||
873 | /** | |
874 | * rt_mutex_trylock - try to lock a rt_mutex | |
875 | * | |
876 | * @lock: the rt_mutex to be locked | |
877 | * | |
878 | * Returns 1 on success and 0 on contention | |
879 | */ | |
880 | int __sched rt_mutex_trylock(struct rt_mutex *lock) | |
881 | { | |
882 | return rt_mutex_fasttrylock(lock, rt_mutex_slowtrylock); | |
883 | } | |
884 | EXPORT_SYMBOL_GPL(rt_mutex_trylock); | |
885 | ||
886 | /** | |
887 | * rt_mutex_unlock - unlock a rt_mutex | |
888 | * | |
889 | * @lock: the rt_mutex to be unlocked | |
890 | */ | |
891 | void __sched rt_mutex_unlock(struct rt_mutex *lock) | |
892 | { | |
893 | rt_mutex_fastunlock(lock, rt_mutex_slowunlock); | |
894 | } | |
895 | EXPORT_SYMBOL_GPL(rt_mutex_unlock); | |
896 | ||
897 | /*** | |
898 | * rt_mutex_destroy - mark a mutex unusable | |
899 | * @lock: the mutex to be destroyed | |
900 | * | |
901 | * This function marks the mutex uninitialized, and any subsequent | |
902 | * use of the mutex is forbidden. The mutex must not be locked when | |
903 | * this function is called. | |
904 | */ | |
905 | void rt_mutex_destroy(struct rt_mutex *lock) | |
906 | { | |
907 | WARN_ON(rt_mutex_is_locked(lock)); | |
908 | #ifdef CONFIG_DEBUG_RT_MUTEXES | |
909 | lock->magic = NULL; | |
910 | #endif | |
911 | } | |
912 | ||
913 | EXPORT_SYMBOL_GPL(rt_mutex_destroy); | |
914 | ||
915 | /** | |
916 | * __rt_mutex_init - initialize the rt lock | |
917 | * | |
918 | * @lock: the rt lock to be initialized | |
919 | * | |
920 | * Initialize the rt lock to unlocked state. | |
921 | * | |
922 | * Initializing of a locked rt lock is not allowed | |
923 | */ | |
924 | void __rt_mutex_init(struct rt_mutex *lock, const char *name) | |
925 | { | |
926 | lock->owner = NULL; | |
927 | spin_lock_init(&lock->wait_lock); | |
928 | plist_head_init(&lock->wait_list, &lock->wait_lock); | |
929 | ||
930 | debug_rt_mutex_init(lock, name); | |
931 | } | |
932 | EXPORT_SYMBOL_GPL(__rt_mutex_init); | |
0cdbee99 IM |
933 | |
934 | /** | |
935 | * rt_mutex_init_proxy_locked - initialize and lock a rt_mutex on behalf of a | |
936 | * proxy owner | |
937 | * | |
938 | * @lock: the rt_mutex to be locked | |
939 | * @proxy_owner:the task to set as owner | |
940 | * | |
941 | * No locking. Caller has to do serializing itself | |
942 | * Special API call for PI-futex support | |
943 | */ | |
944 | void rt_mutex_init_proxy_locked(struct rt_mutex *lock, | |
945 | struct task_struct *proxy_owner) | |
946 | { | |
947 | __rt_mutex_init(lock, NULL); | |
9a11b49a | 948 | debug_rt_mutex_proxy_lock(lock, proxy_owner); |
0cdbee99 IM |
949 | rt_mutex_set_owner(lock, proxy_owner, 0); |
950 | rt_mutex_deadlock_account_lock(lock, proxy_owner); | |
951 | } | |
952 | ||
953 | /** | |
954 | * rt_mutex_proxy_unlock - release a lock on behalf of owner | |
955 | * | |
956 | * @lock: the rt_mutex to be locked | |
957 | * | |
958 | * No locking. Caller has to do serializing itself | |
959 | * Special API call for PI-futex support | |
960 | */ | |
961 | void rt_mutex_proxy_unlock(struct rt_mutex *lock, | |
962 | struct task_struct *proxy_owner) | |
963 | { | |
964 | debug_rt_mutex_proxy_unlock(lock); | |
965 | rt_mutex_set_owner(lock, NULL, 0); | |
966 | rt_mutex_deadlock_account_unlock(proxy_owner); | |
967 | } | |
968 | ||
969 | /** | |
970 | * rt_mutex_next_owner - return the next owner of the lock | |
971 | * | |
972 | * @lock: the rt lock query | |
973 | * | |
974 | * Returns the next owner of the lock or NULL | |
975 | * | |
976 | * Caller has to serialize against other accessors to the lock | |
977 | * itself. | |
978 | * | |
979 | * Special API call for PI-futex support | |
980 | */ | |
981 | struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock) | |
982 | { | |
983 | if (!rt_mutex_has_waiters(lock)) | |
984 | return NULL; | |
985 | ||
986 | return rt_mutex_top_waiter(lock)->task; | |
987 | } |