Branch data Line data Source code
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 : : * See Documentation/rt-mutex-design.txt for details.
12 : : */
13 : : #include <linux/spinlock.h>
14 : : #include <linux/export.h>
15 : : #include <linux/sched.h>
16 : : #include <linux/sched/rt.h>
17 : : #include <linux/timer.h>
18 : :
19 : : #include "rtmutex_common.h"
20 : :
21 : : /*
22 : : * lock->owner state tracking:
23 : : *
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.
26 : : *
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**
33 : : *
34 : : * The fast atomic compare exchange based acquire and release is only
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.
41 : : *
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.
46 : : */
47 : :
48 : : static void
49 : : rt_mutex_set_owner(struct rt_mutex *lock, struct task_struct *owner)
50 : : {
51 : 0 : unsigned long val = (unsigned long)owner;
52 : :
53 [ # # ][ # # ]: 0 : if (rt_mutex_has_waiters(lock))
[ # # ]
54 : 0 : val |= RT_MUTEX_HAS_WAITERS;
55 : :
56 : 0 : lock->owner = (struct task_struct *)val;
57 : : }
58 : :
59 : : static inline void clear_rt_mutex_waiters(struct rt_mutex *lock)
60 : : {
61 : 0 : lock->owner = (struct task_struct *)
62 : 0 : ((unsigned long)lock->owner & ~RT_MUTEX_HAS_WAITERS);
63 : : }
64 : :
65 : 0 : static void fixup_rt_mutex_waiters(struct rt_mutex *lock)
66 : : {
67 [ # # ][ # # ]: 0 : if (!rt_mutex_has_waiters(lock))
[ # # ]
68 : : clear_rt_mutex_waiters(lock);
69 : 0 : }
70 : :
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 : : }
85 : : #else
86 : : # define rt_mutex_cmpxchg(l,c,n) (0)
87 : : static inline void mark_rt_mutex_waiters(struct rt_mutex *lock)
88 : : {
89 : 0 : lock->owner = (struct task_struct *)
90 : 0 : ((unsigned long)lock->owner | RT_MUTEX_HAS_WAITERS);
91 : : }
92 : : #endif
93 : :
94 : : /*
95 : : * Calculate task priority from the waiter list priority
96 : : *
97 : : * Return task->normal_prio when the waiter list is empty or when
98 : : * the waiter is not allowed to do priority boosting
99 : : */
100 : 0 : int rt_mutex_getprio(struct task_struct *task)
101 : : {
102 [ # # ][ + - ]: 77 : if (likely(!task_has_pi_waiters(task)))
103 : 77 : return task->normal_prio;
104 : :
105 : 0 : return min(task_top_pi_waiter(task)->pi_list_entry.prio,
106 : : task->normal_prio);
107 : : }
108 : :
109 : : /*
110 : : * Adjust the priority of a task, after its pi_waiters got modified.
111 : : *
112 : : * This can be both boosting and unboosting. task->pi_lock must be held.
113 : : */
114 : 0 : static void __rt_mutex_adjust_prio(struct task_struct *task)
115 : : {
116 : : int prio = rt_mutex_getprio(task);
117 : :
118 [ # # ]: 0 : if (task->prio != prio)
119 : 0 : rt_mutex_setprio(task, prio);
120 : 0 : }
121 : :
122 : : /*
123 : : * Adjust task priority (undo boosting). Called from the exit path of
124 : : * rt_mutex_slowunlock() and rt_mutex_slowlock().
125 : : *
126 : : * (Note: We do this outside of the protection of lock->wait_lock to
127 : : * allow the lock to be taken while or before we readjust the priority
128 : : * of task. We do not use the spin_xx_mutex() variants here as we are
129 : : * outside of the debug path.)
130 : : */
131 : 0 : static void rt_mutex_adjust_prio(struct task_struct *task)
132 : : {
133 : : unsigned long flags;
134 : :
135 : 0 : raw_spin_lock_irqsave(&task->pi_lock, flags);
136 : 0 : __rt_mutex_adjust_prio(task);
137 : 0 : raw_spin_unlock_irqrestore(&task->pi_lock, flags);
138 : 0 : }
139 : :
140 : : /*
141 : : * Max number of times we'll walk the boosting chain:
142 : : */
143 : : int max_lock_depth = 1024;
144 : :
145 : : /*
146 : : * Adjust the priority chain. Also used for deadlock detection.
147 : : * Decreases task's usage by one - may thus free the task.
148 : : *
149 : : * @task: the task owning the mutex (owner) for which a chain walk is probably
150 : : * needed
151 : : * @deadlock_detect: do we have to carry out deadlock detection?
152 : : * @orig_lock: the mutex (can be NULL if we are walking the chain to recheck
153 : : * things for a task that has just got its priority adjusted, and
154 : : * is waiting on a mutex)
155 : : * @orig_waiter: rt_mutex_waiter struct for the task that has just donated
156 : : * its priority to the mutex owner (can be NULL in the case
157 : : * depicted above or if the top waiter is gone away and we are
158 : : * actually deboosting the owner)
159 : : * @top_task: the current top waiter
160 : : *
161 : : * Returns 0 or -EDEADLK.
162 : : */
163 : 0 : static int rt_mutex_adjust_prio_chain(struct task_struct *task,
164 : : int deadlock_detect,
165 : 0 : struct rt_mutex *orig_lock,
166 : : struct rt_mutex_waiter *orig_waiter,
167 : : struct task_struct *top_task)
168 : : {
169 : 0 : struct rt_mutex *lock;
170 : : struct rt_mutex_waiter *waiter, *top_waiter = orig_waiter;
171 : : int detect_deadlock, ret = 0, depth = 0;
172 : : unsigned long flags;
173 : :
174 : : detect_deadlock = debug_rt_mutex_detect_deadlock(orig_waiter,
175 : : deadlock_detect);
176 : :
177 : : /*
178 : : * The (de)boosting is a step by step approach with a lot of
179 : : * pitfalls. We want this to be preemptible and we want hold a
180 : : * maximum of two locks per step. So we have to check
181 : : * carefully whether things change under us.
182 : : */
183 : : again:
184 [ # # ]: 0 : if (++depth > max_lock_depth) {
185 : : static int prev_max;
186 : :
187 : : /*
188 : : * Print this only once. If the admin changes the limit,
189 : : * print a new message when reaching the limit again.
190 : : */
191 [ # # ]: 0 : if (prev_max != max_lock_depth) {
192 : 0 : prev_max = max_lock_depth;
193 : 0 : printk(KERN_WARNING "Maximum lock depth %d reached "
194 : : "task: %s (%d)\n", max_lock_depth,
195 : 0 : top_task->comm, task_pid_nr(top_task));
196 : : }
197 : : put_task_struct(task);
198 : :
199 [ # # ]: 0 : return deadlock_detect ? -EDEADLK : 0;
200 : : }
201 : : retry:
202 : : /*
203 : : * Task can not go away as we did a get_task() before !
204 : : */
205 : 0 : raw_spin_lock_irqsave(&task->pi_lock, flags);
206 : :
207 : 0 : waiter = task->pi_blocked_on;
208 : : /*
209 : : * Check whether the end of the boosting chain has been
210 : : * reached or the state of the chain has changed while we
211 : : * dropped the locks.
212 : : */
213 [ # # ]: 0 : if (!waiter)
214 : : goto out_unlock_pi;
215 : :
216 : : /*
217 : : * Check the orig_waiter state. After we dropped the locks,
218 : : * the previous owner of the lock might have released the lock.
219 : : */
220 [ # # ][ # # ]: 0 : if (orig_waiter && !rt_mutex_owner(orig_lock))
221 : : goto out_unlock_pi;
222 : :
223 : : /*
224 : : * Drop out, when the task has no waiters. Note,
225 : : * top_waiter can be NULL, when we are in the deboosting
226 : : * mode!
227 : : */
228 [ # # ][ # # ]: 0 : if (top_waiter && (!task_has_pi_waiters(task) ||
[ # # ]
229 : 0 : top_waiter != task_top_pi_waiter(task)))
230 : : goto out_unlock_pi;
231 : :
232 : : /*
233 : : * When deadlock detection is off then we check, if further
234 : : * priority adjustment is necessary.
235 : : */
236 [ # # ][ # # ]: 0 : if (!detect_deadlock && waiter->list_entry.prio == task->prio)
237 : : goto out_unlock_pi;
238 : :
239 : 0 : lock = waiter->lock;
240 [ # # ]: 0 : if (!raw_spin_trylock(&lock->wait_lock)) {
241 : 0 : raw_spin_unlock_irqrestore(&task->pi_lock, flags);
242 : 0 : cpu_relax();
243 : 0 : goto retry;
244 : : }
245 : :
246 : : /* Deadlock detection */
247 [ # # ][ # # ]: 0 : if (lock == orig_lock || rt_mutex_owner(lock) == top_task) {
248 : : debug_rt_mutex_deadlock(deadlock_detect, orig_waiter, lock);
249 : : raw_spin_unlock(&lock->wait_lock);
250 [ # # ]: 0 : ret = deadlock_detect ? -EDEADLK : 0;
251 : 0 : goto out_unlock_pi;
252 : : }
253 : :
254 : 0 : top_waiter = rt_mutex_top_waiter(lock);
255 : :
256 : : /* Requeue the waiter */
257 : 0 : plist_del(&waiter->list_entry, &lock->wait_list);
258 : 0 : waiter->list_entry.prio = task->prio;
259 : 0 : plist_add(&waiter->list_entry, &lock->wait_list);
260 : :
261 : : /* Release the task */
262 : 0 : raw_spin_unlock_irqrestore(&task->pi_lock, flags);
263 [ # # ]: 0 : if (!rt_mutex_owner(lock)) {
264 : : /*
265 : : * If the requeue above changed the top waiter, then we need
266 : : * to wake the new top waiter up to try to get the lock.
267 : : */
268 : :
269 [ # # ]: 0 : if (top_waiter != rt_mutex_top_waiter(lock))
270 : 0 : wake_up_process(rt_mutex_top_waiter(lock)->task);
271 : : raw_spin_unlock(&lock->wait_lock);
272 : : goto out_put_task;
273 : : }
274 : : put_task_struct(task);
275 : :
276 : : /* Grab the next task */
277 : : task = rt_mutex_owner(lock);
278 : 0 : get_task_struct(task);
279 : 0 : raw_spin_lock_irqsave(&task->pi_lock, flags);
280 : :
281 [ # # ]: 0 : if (waiter == rt_mutex_top_waiter(lock)) {
282 : : /* Boost the owner */
283 : 0 : plist_del(&top_waiter->pi_list_entry, &task->pi_waiters);
284 : 0 : waiter->pi_list_entry.prio = waiter->list_entry.prio;
285 : 0 : plist_add(&waiter->pi_list_entry, &task->pi_waiters);
286 : 0 : __rt_mutex_adjust_prio(task);
287 : :
288 [ # # ]: 0 : } else if (top_waiter == waiter) {
289 : : /* Deboost the owner */
290 : 0 : plist_del(&waiter->pi_list_entry, &task->pi_waiters);
291 : 0 : waiter = rt_mutex_top_waiter(lock);
292 : 0 : waiter->pi_list_entry.prio = waiter->list_entry.prio;
293 : 0 : plist_add(&waiter->pi_list_entry, &task->pi_waiters);
294 : 0 : __rt_mutex_adjust_prio(task);
295 : : }
296 : :
297 : 0 : raw_spin_unlock_irqrestore(&task->pi_lock, flags);
298 : :
299 : 0 : top_waiter = rt_mutex_top_waiter(lock);
300 : : raw_spin_unlock(&lock->wait_lock);
301 : :
302 [ # # ]: 0 : if (!detect_deadlock && waiter != top_waiter)
303 : : goto out_put_task;
304 : :
305 : : goto again;
306 : :
307 : : out_unlock_pi:
308 : 0 : raw_spin_unlock_irqrestore(&task->pi_lock, flags);
309 : : out_put_task:
310 : : put_task_struct(task);
311 : :
312 : 0 : return ret;
313 : : }
314 : :
315 : : /*
316 : : * Try to take an rt-mutex
317 : : *
318 : : * Must be called with lock->wait_lock held.
319 : : *
320 : : * @lock: the lock to be acquired.
321 : : * @task: the task which wants to acquire the lock
322 : : * @waiter: the waiter that is queued to the lock's wait list. (could be NULL)
323 : : */
324 : 0 : static int try_to_take_rt_mutex(struct rt_mutex *lock, struct task_struct *task,
325 : : struct rt_mutex_waiter *waiter)
326 : : {
327 : : /*
328 : : * We have to be careful here if the atomic speedups are
329 : : * enabled, such that, when
330 : : * - no other waiter is on the lock
331 : : * - the lock has been released since we did the cmpxchg
332 : : * the lock can be released or taken while we are doing the
333 : : * checks and marking the lock with RT_MUTEX_HAS_WAITERS.
334 : : *
335 : : * The atomic acquire/release aware variant of
336 : : * mark_rt_mutex_waiters uses a cmpxchg loop. After setting
337 : : * the WAITERS bit, the atomic release / acquire can not
338 : : * happen anymore and lock->wait_lock protects us from the
339 : : * non-atomic case.
340 : : *
341 : : * Note, that this might set lock->owner =
342 : : * RT_MUTEX_HAS_WAITERS in the case the lock is not contended
343 : : * any more. This is fixed up when we take the ownership.
344 : : * This is the transitional state explained at the top of this file.
345 : : */
346 : : mark_rt_mutex_waiters(lock);
347 : :
348 [ # # ]: 0 : if (rt_mutex_owner(lock))
349 : : return 0;
350 : :
351 : : /*
352 : : * It will get the lock because of one of these conditions:
353 : : * 1) there is no waiter
354 : : * 2) higher priority than waiters
355 : : * 3) it is top waiter
356 : : */
357 [ # # ]: 0 : if (rt_mutex_has_waiters(lock)) {
358 [ # # ]: 0 : if (task->prio >= rt_mutex_top_waiter(lock)->list_entry.prio) {
359 [ # # ][ # # ]: 0 : if (!waiter || waiter != rt_mutex_top_waiter(lock))
360 : : return 0;
361 : : }
362 : : }
363 : :
364 [ # # ][ # # ]: 0 : if (waiter || rt_mutex_has_waiters(lock)) {
365 : : unsigned long flags;
366 : : struct rt_mutex_waiter *top;
367 : :
368 : 0 : raw_spin_lock_irqsave(&task->pi_lock, flags);
369 : :
370 : : /* remove the queued waiter. */
371 [ # # ]: 0 : if (waiter) {
372 : 0 : plist_del(&waiter->list_entry, &lock->wait_list);
373 : 0 : task->pi_blocked_on = NULL;
374 : : }
375 : :
376 : : /*
377 : : * We have to enqueue the top waiter(if it exists) into
378 : : * task->pi_waiters list.
379 : : */
380 [ # # ]: 0 : if (rt_mutex_has_waiters(lock)) {
381 : : top = rt_mutex_top_waiter(lock);
382 : 0 : top->pi_list_entry.prio = top->list_entry.prio;
383 : 0 : plist_add(&top->pi_list_entry, &task->pi_waiters);
384 : : }
385 : 0 : raw_spin_unlock_irqrestore(&task->pi_lock, flags);
386 : : }
387 : :
388 : : /* We got the lock. */
389 : : debug_rt_mutex_lock(lock);
390 : :
391 : : rt_mutex_set_owner(lock, task);
392 : :
393 : : rt_mutex_deadlock_account_lock(lock, task);
394 : :
395 : 0 : return 1;
396 : : }
397 : :
398 : : /*
399 : : * Task blocks on lock.
400 : : *
401 : : * Prepare waiter and propagate pi chain
402 : : *
403 : : * This must be called with lock->wait_lock held.
404 : : */
405 : 0 : static int task_blocks_on_rt_mutex(struct rt_mutex *lock,
406 : : struct rt_mutex_waiter *waiter,
407 : : struct task_struct *task,
408 : : int detect_deadlock)
409 : : {
410 : : struct task_struct *owner = rt_mutex_owner(lock);
411 : : struct rt_mutex_waiter *top_waiter = waiter;
412 : : unsigned long flags;
413 : : int chain_walk = 0, res;
414 : :
415 : 0 : raw_spin_lock_irqsave(&task->pi_lock, flags);
416 : 0 : __rt_mutex_adjust_prio(task);
417 : 0 : waiter->task = task;
418 : 0 : waiter->lock = lock;
419 : 0 : plist_node_init(&waiter->list_entry, task->prio);
420 : 0 : plist_node_init(&waiter->pi_list_entry, task->prio);
421 : :
422 : : /* Get the top priority waiter on the lock */
423 [ # # ]: 0 : if (rt_mutex_has_waiters(lock))
424 : 0 : top_waiter = rt_mutex_top_waiter(lock);
425 : 0 : plist_add(&waiter->list_entry, &lock->wait_list);
426 : :
427 : 0 : task->pi_blocked_on = waiter;
428 : :
429 : 0 : raw_spin_unlock_irqrestore(&task->pi_lock, flags);
430 : :
431 [ # # ]: 0 : if (!owner)
432 : : return 0;
433 : :
434 [ # # ]: 0 : if (waiter == rt_mutex_top_waiter(lock)) {
435 : 0 : raw_spin_lock_irqsave(&owner->pi_lock, flags);
436 : 0 : plist_del(&top_waiter->pi_list_entry, &owner->pi_waiters);
437 : 0 : plist_add(&waiter->pi_list_entry, &owner->pi_waiters);
438 : :
439 : 0 : __rt_mutex_adjust_prio(owner);
440 [ # # ]: 0 : if (owner->pi_blocked_on)
441 : : chain_walk = 1;
442 : 0 : raw_spin_unlock_irqrestore(&owner->pi_lock, flags);
443 : : }
444 [ # # ]: 0 : else if (debug_rt_mutex_detect_deadlock(waiter, detect_deadlock))
445 : : chain_walk = 1;
446 : :
447 [ # # ]: 0 : if (!chain_walk)
448 : : return 0;
449 : :
450 : : /*
451 : : * The owner can't disappear while holding a lock,
452 : : * so the owner struct is protected by wait_lock.
453 : : * Gets dropped in rt_mutex_adjust_prio_chain()!
454 : : */
455 : 0 : get_task_struct(owner);
456 : :
457 : : raw_spin_unlock(&lock->wait_lock);
458 : :
459 : 0 : res = rt_mutex_adjust_prio_chain(owner, detect_deadlock, lock, waiter,
460 : : task);
461 : :
462 : 0 : raw_spin_lock(&lock->wait_lock);
463 : :
464 : 0 : return res;
465 : : }
466 : :
467 : : /*
468 : : * Wake up the next waiter on the lock.
469 : : *
470 : : * Remove the top waiter from the current tasks waiter list and wake it up.
471 : : *
472 : : * Called with lock->wait_lock held.
473 : : */
474 : 0 : static void wakeup_next_waiter(struct rt_mutex *lock)
475 : : {
476 : : struct rt_mutex_waiter *waiter;
477 : : unsigned long flags;
478 : :
479 : 0 : raw_spin_lock_irqsave(¤t->pi_lock, flags);
480 : :
481 : : waiter = rt_mutex_top_waiter(lock);
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 : 0 : plist_del(&waiter->pi_list_entry, ¤t->pi_waiters);
490 : :
491 : : rt_mutex_set_owner(lock, NULL);
492 : :
493 : 0 : raw_spin_unlock_irqrestore(¤t->pi_lock, flags);
494 : :
495 : 0 : wake_up_process(waiter->task);
496 : 0 : }
497 : :
498 : : /*
499 : : * Remove a waiter from a lock and give up
500 : : *
501 : : * Must be called with lock->wait_lock held and
502 : : * have just failed to try_to_take_rt_mutex().
503 : : */
504 : 0 : static void remove_waiter(struct rt_mutex *lock,
505 : : struct rt_mutex_waiter *waiter)
506 : : {
507 : 0 : int first = (waiter == rt_mutex_top_waiter(lock));
508 : : struct task_struct *owner = rt_mutex_owner(lock);
509 : : unsigned long flags;
510 : : int chain_walk = 0;
511 : :
512 : 0 : raw_spin_lock_irqsave(¤t->pi_lock, flags);
513 : 0 : plist_del(&waiter->list_entry, &lock->wait_list);
514 : 0 : current->pi_blocked_on = NULL;
515 : 0 : raw_spin_unlock_irqrestore(¤t->pi_lock, flags);
516 : :
517 [ # # ]: 0 : if (!owner)
518 : : return;
519 : :
520 [ # # ]: 0 : if (first) {
521 : :
522 : 0 : raw_spin_lock_irqsave(&owner->pi_lock, flags);
523 : :
524 : 0 : plist_del(&waiter->pi_list_entry, &owner->pi_waiters);
525 : :
526 [ # # ]: 0 : if (rt_mutex_has_waiters(lock)) {
527 : : struct rt_mutex_waiter *next;
528 : :
529 : : next = rt_mutex_top_waiter(lock);
530 : 0 : plist_add(&next->pi_list_entry, &owner->pi_waiters);
531 : : }
532 : 0 : __rt_mutex_adjust_prio(owner);
533 : :
534 [ # # ]: 0 : if (owner->pi_blocked_on)
535 : : chain_walk = 1;
536 : :
537 : 0 : raw_spin_unlock_irqrestore(&owner->pi_lock, flags);
538 : : }
539 : :
540 [ # # ]: 0 : WARN_ON(!plist_node_empty(&waiter->pi_list_entry));
541 : :
542 [ # # ]: 0 : if (!chain_walk)
543 : : return;
544 : :
545 : : /* gets dropped in rt_mutex_adjust_prio_chain()! */
546 : 0 : get_task_struct(owner);
547 : :
548 : : raw_spin_unlock(&lock->wait_lock);
549 : :
550 : 0 : rt_mutex_adjust_prio_chain(owner, 0, lock, NULL, current);
551 : :
552 : 0 : raw_spin_lock(&lock->wait_lock);
553 : : }
554 : :
555 : : /*
556 : : * Recheck the pi chain, in case we got a priority setting
557 : : *
558 : : * Called from sched_setscheduler
559 : : */
560 : 0 : void rt_mutex_adjust_pi(struct task_struct *task)
561 : : {
562 : : struct rt_mutex_waiter *waiter;
563 : : unsigned long flags;
564 : :
565 : 77 : raw_spin_lock_irqsave(&task->pi_lock, flags);
566 : :
567 : 77 : waiter = task->pi_blocked_on;
568 [ - + ][ # # ]: 77 : if (!waiter || waiter->list_entry.prio == task->prio) {
569 : 77 : raw_spin_unlock_irqrestore(&task->pi_lock, flags);
570 : 77 : return;
571 : : }
572 : :
573 : 0 : raw_spin_unlock_irqrestore(&task->pi_lock, flags);
574 : :
575 : : /* gets dropped in rt_mutex_adjust_prio_chain()! */
576 : 0 : get_task_struct(task);
577 : 0 : rt_mutex_adjust_prio_chain(task, 0, NULL, NULL, task);
578 : : }
579 : :
580 : : /**
581 : : * __rt_mutex_slowlock() - Perform the wait-wake-try-to-take loop
582 : : * @lock: the rt_mutex to take
583 : : * @state: the state the task should block in (TASK_INTERRUPTIBLE
584 : : * or TASK_UNINTERRUPTIBLE)
585 : : * @timeout: the pre-initialized and started timer, or NULL for none
586 : : * @waiter: the pre-initialized rt_mutex_waiter
587 : : *
588 : : * lock->wait_lock must be held by the caller.
589 : : */
590 : : static int __sched
591 : 0 : __rt_mutex_slowlock(struct rt_mutex *lock, int state,
592 : : struct hrtimer_sleeper *timeout,
593 : : struct rt_mutex_waiter *waiter)
594 : : {
595 : : int ret = 0;
596 : :
597 : : for (;;) {
598 : : /* Try to acquire the lock: */
599 [ # # ]: 0 : if (try_to_take_rt_mutex(lock, current, waiter))
600 : : break;
601 : :
602 : : /*
603 : : * TASK_INTERRUPTIBLE checks for signals and
604 : : * timeout. Ignored otherwise.
605 : : */
606 [ # # ]: 0 : if (unlikely(state == TASK_INTERRUPTIBLE)) {
607 : : /* Signal pending? */
608 [ # # ]: 0 : if (signal_pending(current))
609 : : ret = -EINTR;
610 [ # # ][ # # ]: 0 : if (timeout && !timeout->task)
611 : : ret = -ETIMEDOUT;
612 [ # # ]: 0 : if (ret)
613 : : break;
614 : : }
615 : :
616 : : raw_spin_unlock(&lock->wait_lock);
617 : :
618 : : debug_rt_mutex_print_deadlock(waiter);
619 : :
620 : 0 : schedule_rt_mutex(lock);
621 : :
622 : 0 : raw_spin_lock(&lock->wait_lock);
623 : 0 : set_current_state(state);
624 : 0 : }
625 : :
626 : 0 : return ret;
627 : : }
628 : :
629 : : /*
630 : : * Slow path lock function:
631 : : */
632 : : static int __sched
633 : 0 : rt_mutex_slowlock(struct rt_mutex *lock, int state,
634 : : struct hrtimer_sleeper *timeout,
635 : : int detect_deadlock)
636 : : {
637 : : struct rt_mutex_waiter waiter;
638 : : int ret = 0;
639 : :
640 : : debug_rt_mutex_init_waiter(&waiter);
641 : :
642 : 0 : raw_spin_lock(&lock->wait_lock);
643 : :
644 : : /* Try to acquire the lock again: */
645 [ # # ]: 0 : if (try_to_take_rt_mutex(lock, current, NULL)) {
646 : : raw_spin_unlock(&lock->wait_lock);
647 : 0 : return 0;
648 : : }
649 : :
650 : 0 : set_current_state(state);
651 : :
652 : : /* Setup the timer, when timeout != NULL */
653 [ # # ]: 0 : if (unlikely(timeout)) {
654 : 0 : hrtimer_start_expires(&timeout->timer, HRTIMER_MODE_ABS);
655 [ # # ]: 0 : if (!hrtimer_active(&timeout->timer))
656 : 0 : timeout->task = NULL;
657 : : }
658 : :
659 : 0 : ret = task_blocks_on_rt_mutex(lock, &waiter, current, detect_deadlock);
660 : :
661 [ # # ]: 0 : if (likely(!ret))
662 : 0 : ret = __rt_mutex_slowlock(lock, state, timeout, &waiter);
663 : :
664 : 0 : set_current_state(TASK_RUNNING);
665 : :
666 [ # # ]: 0 : if (unlikely(ret))
667 : 0 : remove_waiter(lock, &waiter);
668 : :
669 : : /*
670 : : * try_to_take_rt_mutex() sets the waiter bit
671 : : * unconditionally. We might have to fix that up.
672 : : */
673 : : fixup_rt_mutex_waiters(lock);
674 : :
675 : : raw_spin_unlock(&lock->wait_lock);
676 : :
677 : : /* Remove pending timer: */
678 [ # # ]: 0 : if (unlikely(timeout))
679 : 0 : hrtimer_cancel(&timeout->timer);
680 : :
681 : : debug_rt_mutex_free_waiter(&waiter);
682 : :
683 : 0 : return ret;
684 : : }
685 : :
686 : : /*
687 : : * Slow path try-lock function:
688 : : */
689 : : static inline int
690 : 0 : rt_mutex_slowtrylock(struct rt_mutex *lock)
691 : : {
692 : : int ret = 0;
693 : :
694 : 0 : raw_spin_lock(&lock->wait_lock);
695 : :
696 [ # # ]: 0 : if (likely(rt_mutex_owner(lock) != current)) {
697 : :
698 : 0 : ret = try_to_take_rt_mutex(lock, current, NULL);
699 : : /*
700 : : * try_to_take_rt_mutex() sets the lock waiters
701 : : * bit unconditionally. Clean this up.
702 : : */
703 : 0 : fixup_rt_mutex_waiters(lock);
704 : : }
705 : :
706 : : raw_spin_unlock(&lock->wait_lock);
707 : :
708 : 0 : return ret;
709 : : }
710 : :
711 : : /*
712 : : * Slow path to release a rt-mutex:
713 : : */
714 : : static void __sched
715 : 0 : rt_mutex_slowunlock(struct rt_mutex *lock)
716 : : {
717 : 0 : raw_spin_lock(&lock->wait_lock);
718 : :
719 : : debug_rt_mutex_unlock(lock);
720 : :
721 : : rt_mutex_deadlock_account_unlock(current);
722 : :
723 [ # # ]: 0 : if (!rt_mutex_has_waiters(lock)) {
724 : 0 : lock->owner = NULL;
725 : : raw_spin_unlock(&lock->wait_lock);
726 : 0 : return;
727 : : }
728 : :
729 : 0 : wakeup_next_waiter(lock);
730 : :
731 : : raw_spin_unlock(&lock->wait_lock);
732 : :
733 : : /* Undo pi boosting if necessary: */
734 : 0 : rt_mutex_adjust_prio(current);
735 : : }
736 : :
737 : : /*
738 : : * debug aware fast / slowpath lock,trylock,unlock
739 : : *
740 : : * The atomic acquire/release ops are compiled away, when either the
741 : : * architecture does not support cmpxchg or when debugging is enabled.
742 : : */
743 : : static inline int
744 : : rt_mutex_fastlock(struct rt_mutex *lock, int state,
745 : : int detect_deadlock,
746 : : int (*slowfn)(struct rt_mutex *lock, int state,
747 : : struct hrtimer_sleeper *timeout,
748 : : int detect_deadlock))
749 : : {
750 : : if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) {
751 : : rt_mutex_deadlock_account_lock(lock, current);
752 : : return 0;
753 : : } else
754 : 0 : return slowfn(lock, state, NULL, detect_deadlock);
755 : : }
756 : :
757 : : static inline int
758 : : rt_mutex_timed_fastlock(struct rt_mutex *lock, int state,
759 : : struct hrtimer_sleeper *timeout, int detect_deadlock,
760 : : int (*slowfn)(struct rt_mutex *lock, int state,
761 : : struct hrtimer_sleeper *timeout,
762 : : int detect_deadlock))
763 : : {
764 : : if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) {
765 : : rt_mutex_deadlock_account_lock(lock, current);
766 : : return 0;
767 : : } else
768 : 0 : return slowfn(lock, state, timeout, detect_deadlock);
769 : : }
770 : :
771 : : static inline int
772 : : rt_mutex_fasttrylock(struct rt_mutex *lock,
773 : : int (*slowfn)(struct rt_mutex *lock))
774 : : {
775 : : if (likely(rt_mutex_cmpxchg(lock, NULL, current))) {
776 : : rt_mutex_deadlock_account_lock(lock, current);
777 : : return 1;
778 : : }
779 : 0 : return slowfn(lock);
780 : : }
781 : :
782 : : static inline void
783 : : rt_mutex_fastunlock(struct rt_mutex *lock,
784 : : void (*slowfn)(struct rt_mutex *lock))
785 : : {
786 : : if (likely(rt_mutex_cmpxchg(lock, current, NULL)))
787 : : rt_mutex_deadlock_account_unlock(current);
788 : : else
789 : 0 : slowfn(lock);
790 : : }
791 : :
792 : : /**
793 : : * rt_mutex_lock - lock a rt_mutex
794 : : *
795 : : * @lock: the rt_mutex to be locked
796 : : */
797 : 0 : void __sched rt_mutex_lock(struct rt_mutex *lock)
798 : : {
799 : : might_sleep();
800 : :
801 : : rt_mutex_fastlock(lock, TASK_UNINTERRUPTIBLE, 0, rt_mutex_slowlock);
802 : 0 : }
803 : : EXPORT_SYMBOL_GPL(rt_mutex_lock);
804 : :
805 : : /**
806 : : * rt_mutex_lock_interruptible - lock a rt_mutex interruptible
807 : : *
808 : : * @lock: the rt_mutex to be locked
809 : : * @detect_deadlock: deadlock detection on/off
810 : : *
811 : : * Returns:
812 : : * 0 on success
813 : : * -EINTR when interrupted by a signal
814 : : * -EDEADLK when the lock would deadlock (when deadlock detection is on)
815 : : */
816 : 0 : int __sched rt_mutex_lock_interruptible(struct rt_mutex *lock,
817 : : int detect_deadlock)
818 : : {
819 : : might_sleep();
820 : :
821 : 0 : return rt_mutex_fastlock(lock, TASK_INTERRUPTIBLE,
822 : : detect_deadlock, rt_mutex_slowlock);
823 : : }
824 : : EXPORT_SYMBOL_GPL(rt_mutex_lock_interruptible);
825 : :
826 : : /**
827 : : * rt_mutex_timed_lock - lock a rt_mutex interruptible
828 : : * the timeout structure is provided
829 : : * by the caller
830 : : *
831 : : * @lock: the rt_mutex to be locked
832 : : * @timeout: timeout structure or NULL (no timeout)
833 : : * @detect_deadlock: deadlock detection on/off
834 : : *
835 : : * Returns:
836 : : * 0 on success
837 : : * -EINTR when interrupted by a signal
838 : : * -ETIMEDOUT when the timeout expired
839 : : * -EDEADLK when the lock would deadlock (when deadlock detection is on)
840 : : */
841 : : int
842 : 0 : rt_mutex_timed_lock(struct rt_mutex *lock, struct hrtimer_sleeper *timeout,
843 : : int detect_deadlock)
844 : : {
845 : : might_sleep();
846 : :
847 : 0 : return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout,
848 : : detect_deadlock, rt_mutex_slowlock);
849 : : }
850 : : EXPORT_SYMBOL_GPL(rt_mutex_timed_lock);
851 : :
852 : : /**
853 : : * rt_mutex_trylock - try to lock a rt_mutex
854 : : *
855 : : * @lock: the rt_mutex to be locked
856 : : *
857 : : * Returns 1 on success and 0 on contention
858 : : */
859 : 0 : int __sched rt_mutex_trylock(struct rt_mutex *lock)
860 : : {
861 : 0 : return rt_mutex_fasttrylock(lock, rt_mutex_slowtrylock);
862 : : }
863 : : EXPORT_SYMBOL_GPL(rt_mutex_trylock);
864 : :
865 : : /**
866 : : * rt_mutex_unlock - unlock a rt_mutex
867 : : *
868 : : * @lock: the rt_mutex to be unlocked
869 : : */
870 : 0 : void __sched rt_mutex_unlock(struct rt_mutex *lock)
871 : : {
872 : : rt_mutex_fastunlock(lock, rt_mutex_slowunlock);
873 : 0 : }
874 : : EXPORT_SYMBOL_GPL(rt_mutex_unlock);
875 : :
876 : : /**
877 : : * rt_mutex_destroy - mark a mutex unusable
878 : : * @lock: the mutex to be destroyed
879 : : *
880 : : * This function marks the mutex uninitialized, and any subsequent
881 : : * use of the mutex is forbidden. The mutex must not be locked when
882 : : * this function is called.
883 : : */
884 : 0 : void rt_mutex_destroy(struct rt_mutex *lock)
885 : : {
886 [ # # ]: 0 : WARN_ON(rt_mutex_is_locked(lock));
887 : : #ifdef CONFIG_DEBUG_RT_MUTEXES
888 : : lock->magic = NULL;
889 : : #endif
890 : 0 : }
891 : :
892 : : EXPORT_SYMBOL_GPL(rt_mutex_destroy);
893 : :
894 : : /**
895 : : * __rt_mutex_init - initialize the rt lock
896 : : *
897 : : * @lock: the rt lock to be initialized
898 : : *
899 : : * Initialize the rt lock to unlocked state.
900 : : *
901 : : * Initializing of a locked rt lock is not allowed
902 : : */
903 : 0 : void __rt_mutex_init(struct rt_mutex *lock, const char *name)
904 : : {
905 : 0 : lock->owner = NULL;
906 : 0 : raw_spin_lock_init(&lock->wait_lock);
907 : : plist_head_init(&lock->wait_list);
908 : :
909 : : debug_rt_mutex_init(lock, name);
910 : 0 : }
911 : : EXPORT_SYMBOL_GPL(__rt_mutex_init);
912 : :
913 : : /**
914 : : * rt_mutex_init_proxy_locked - initialize and lock a rt_mutex on behalf of a
915 : : * proxy owner
916 : : *
917 : : * @lock: the rt_mutex to be locked
918 : : * @proxy_owner:the task to set as owner
919 : : *
920 : : * No locking. Caller has to do serializing itself
921 : : * Special API call for PI-futex support
922 : : */
923 : 0 : void rt_mutex_init_proxy_locked(struct rt_mutex *lock,
924 : : struct task_struct *proxy_owner)
925 : : {
926 : : __rt_mutex_init(lock, NULL);
927 : : debug_rt_mutex_proxy_lock(lock, proxy_owner);
928 : : rt_mutex_set_owner(lock, proxy_owner);
929 : : rt_mutex_deadlock_account_lock(lock, proxy_owner);
930 : 0 : }
931 : :
932 : : /**
933 : : * rt_mutex_proxy_unlock - release a lock on behalf of owner
934 : : *
935 : : * @lock: the rt_mutex to be locked
936 : : *
937 : : * No locking. Caller has to do serializing itself
938 : : * Special API call for PI-futex support
939 : : */
940 : 0 : void rt_mutex_proxy_unlock(struct rt_mutex *lock,
941 : : struct task_struct *proxy_owner)
942 : : {
943 : : debug_rt_mutex_proxy_unlock(lock);
944 : : rt_mutex_set_owner(lock, NULL);
945 : : rt_mutex_deadlock_account_unlock(proxy_owner);
946 : 0 : }
947 : :
948 : : /**
949 : : * rt_mutex_start_proxy_lock() - Start lock acquisition for another task
950 : : * @lock: the rt_mutex to take
951 : : * @waiter: the pre-initialized rt_mutex_waiter
952 : : * @task: the task to prepare
953 : : * @detect_deadlock: perform deadlock detection (1) or not (0)
954 : : *
955 : : * Returns:
956 : : * 0 - task blocked on lock
957 : : * 1 - acquired the lock for task, caller should wake it up
958 : : * <0 - error
959 : : *
960 : : * Special API call for FUTEX_REQUEUE_PI support.
961 : : */
962 : 0 : int rt_mutex_start_proxy_lock(struct rt_mutex *lock,
963 : : struct rt_mutex_waiter *waiter,
964 : : struct task_struct *task, int detect_deadlock)
965 : : {
966 : : int ret;
967 : :
968 : 0 : raw_spin_lock(&lock->wait_lock);
969 : :
970 [ # # ]: 0 : if (try_to_take_rt_mutex(lock, task, NULL)) {
971 : : raw_spin_unlock(&lock->wait_lock);
972 : 0 : return 1;
973 : : }
974 : :
975 : 0 : ret = task_blocks_on_rt_mutex(lock, waiter, task, detect_deadlock);
976 : :
977 [ # # ][ # # ]: 0 : if (ret && !rt_mutex_owner(lock)) {
978 : : /*
979 : : * Reset the return value. We might have
980 : : * returned with -EDEADLK and the owner
981 : : * released the lock while we were walking the
982 : : * pi chain. Let the waiter sort it out.
983 : : */
984 : : ret = 0;
985 : : }
986 : :
987 [ # # ]: 0 : if (unlikely(ret))
988 : 0 : remove_waiter(lock, waiter);
989 : :
990 : : raw_spin_unlock(&lock->wait_lock);
991 : :
992 : : debug_rt_mutex_print_deadlock(waiter);
993 : :
994 : 0 : return ret;
995 : : }
996 : :
997 : : /**
998 : : * rt_mutex_next_owner - return the next owner of the lock
999 : : *
1000 : : * @lock: the rt lock query
1001 : : *
1002 : : * Returns the next owner of the lock or NULL
1003 : : *
1004 : : * Caller has to serialize against other accessors to the lock
1005 : : * itself.
1006 : : *
1007 : : * Special API call for PI-futex support
1008 : : */
1009 : 0 : struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock)
1010 : : {
1011 [ # # ]: 0 : if (!rt_mutex_has_waiters(lock))
1012 : : return NULL;
1013 : :
1014 : 0 : return rt_mutex_top_waiter(lock)->task;
1015 : : }
1016 : :
1017 : : /**
1018 : : * rt_mutex_finish_proxy_lock() - Complete lock acquisition
1019 : : * @lock: the rt_mutex we were woken on
1020 : : * @to: the timeout, null if none. hrtimer should already have
1021 : : * been started.
1022 : : * @waiter: the pre-initialized rt_mutex_waiter
1023 : : * @detect_deadlock: perform deadlock detection (1) or not (0)
1024 : : *
1025 : : * Complete the lock acquisition started our behalf by another thread.
1026 : : *
1027 : : * Returns:
1028 : : * 0 - success
1029 : : * <0 - error, one of -EINTR, -ETIMEDOUT, or -EDEADLK
1030 : : *
1031 : : * Special API call for PI-futex requeue support
1032 : : */
1033 : 0 : int rt_mutex_finish_proxy_lock(struct rt_mutex *lock,
1034 : : struct hrtimer_sleeper *to,
1035 : : struct rt_mutex_waiter *waiter,
1036 : : int detect_deadlock)
1037 : : {
1038 : : int ret;
1039 : :
1040 : 0 : raw_spin_lock(&lock->wait_lock);
1041 : :
1042 : 0 : set_current_state(TASK_INTERRUPTIBLE);
1043 : :
1044 : 0 : ret = __rt_mutex_slowlock(lock, TASK_INTERRUPTIBLE, to, waiter);
1045 : :
1046 : 0 : set_current_state(TASK_RUNNING);
1047 : :
1048 [ # # ]: 0 : if (unlikely(ret))
1049 : 0 : remove_waiter(lock, waiter);
1050 : :
1051 : : /*
1052 : : * try_to_take_rt_mutex() sets the waiter bit unconditionally. We might
1053 : : * have to fix that up.
1054 : : */
1055 : : fixup_rt_mutex_waiters(lock);
1056 : :
1057 : : raw_spin_unlock(&lock->wait_lock);
1058 : :
1059 : 0 : return ret;
1060 : : }
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