Commit | Line | Data |
---|---|---|
23f78d4a IM |
1 | /* |
2 | * RT-Mutexes: simple blocking mutual exclusion locks with PI support | |
3 | * | |
4 | * started by Ingo Molnar and Thomas Gleixner. | |
5 | * | |
6 | * Copyright (C) 2004-2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com> | |
7 | * Copyright (C) 2005-2006 Timesys Corp., Thomas Gleixner <tglx@timesys.com> | |
8 | * Copyright (C) 2005 Kihon Technologies Inc., Steven Rostedt | |
9 | * Copyright (C) 2006 Esben Nielsen | |
d07fe82c | 10 | * |
214e0aed | 11 | * See Documentation/locking/rt-mutex-design.txt for details. |
23f78d4a IM |
12 | */ |
13 | #include <linux/spinlock.h> | |
9984de1a | 14 | #include <linux/export.h> |
23f78d4a | 15 | #include <linux/sched.h> |
8bd75c77 | 16 | #include <linux/sched/rt.h> |
fb00aca4 | 17 | #include <linux/sched/deadline.h> |
23f78d4a IM |
18 | #include <linux/timer.h> |
19 | ||
20 | #include "rtmutex_common.h" | |
21 | ||
23f78d4a IM |
22 | /* |
23 | * lock->owner state tracking: | |
24 | * | |
8161239a LJ |
25 | * lock->owner holds the task_struct pointer of the owner. Bit 0 |
26 | * is used to keep track of the "lock has waiters" state. | |
23f78d4a | 27 | * |
8161239a LJ |
28 | * owner bit0 |
29 | * NULL 0 lock is free (fast acquire possible) | |
30 | * NULL 1 lock is free and has waiters and the top waiter | |
31 | * is going to take the lock* | |
32 | * taskpointer 0 lock is held (fast release possible) | |
33 | * taskpointer 1 lock is held and has waiters** | |
23f78d4a IM |
34 | * |
35 | * The fast atomic compare exchange based acquire and release is only | |
8161239a LJ |
36 | * possible when bit 0 of lock->owner is 0. |
37 | * | |
38 | * (*) It also can be a transitional state when grabbing the lock | |
39 | * with ->wait_lock is held. To prevent any fast path cmpxchg to the lock, | |
40 | * we need to set the bit0 before looking at the lock, and the owner may be | |
41 | * NULL in this small time, hence this can be a transitional state. | |
23f78d4a | 42 | * |
8161239a LJ |
43 | * (**) There is a small time when bit 0 is set but there are no |
44 | * waiters. This can happen when grabbing the lock in the slow path. | |
45 | * To prevent a cmpxchg of the owner releasing the lock, we need to | |
46 | * set this bit before looking at the lock. | |
23f78d4a IM |
47 | */ |
48 | ||
bd197234 | 49 | static void |
8161239a | 50 | rt_mutex_set_owner(struct rt_mutex *lock, struct task_struct *owner) |
23f78d4a | 51 | { |
8161239a | 52 | unsigned long val = (unsigned long)owner; |
23f78d4a IM |
53 | |
54 | if (rt_mutex_has_waiters(lock)) | |
55 | val |= RT_MUTEX_HAS_WAITERS; | |
56 | ||
57 | lock->owner = (struct task_struct *)val; | |
58 | } | |
59 | ||
60 | static inline void clear_rt_mutex_waiters(struct rt_mutex *lock) | |
61 | { | |
62 | lock->owner = (struct task_struct *) | |
63 | ((unsigned long)lock->owner & ~RT_MUTEX_HAS_WAITERS); | |
64 | } | |
65 | ||
66 | static void fixup_rt_mutex_waiters(struct rt_mutex *lock) | |
67 | { | |
68 | if (!rt_mutex_has_waiters(lock)) | |
69 | clear_rt_mutex_waiters(lock); | |
70 | } | |
71 | ||
bd197234 | 72 | /* |
cede8841 SAS |
73 | * We can speed up the acquire/release, if there's no debugging state to be |
74 | * set up. | |
bd197234 | 75 | */ |
cede8841 | 76 | #ifndef CONFIG_DEBUG_RT_MUTEXES |
700318d1 DB |
77 | # define rt_mutex_cmpxchg_relaxed(l,c,n) (cmpxchg_relaxed(&l->owner, c, n) == c) |
78 | # define rt_mutex_cmpxchg_acquire(l,c,n) (cmpxchg_acquire(&l->owner, c, n) == c) | |
79 | # define rt_mutex_cmpxchg_release(l,c,n) (cmpxchg_release(&l->owner, c, n) == c) | |
80 | ||
81 | /* | |
82 | * Callers must hold the ->wait_lock -- which is the whole purpose as we force | |
83 | * all future threads that attempt to [Rmw] the lock to the slowpath. As such | |
84 | * relaxed semantics suffice. | |
85 | */ | |
bd197234 TG |
86 | static inline void mark_rt_mutex_waiters(struct rt_mutex *lock) |
87 | { | |
88 | unsigned long owner, *p = (unsigned long *) &lock->owner; | |
89 | ||
90 | do { | |
91 | owner = *p; | |
700318d1 DB |
92 | } while (cmpxchg_relaxed(p, owner, |
93 | owner | RT_MUTEX_HAS_WAITERS) != owner); | |
bd197234 | 94 | } |
27e35715 TG |
95 | |
96 | /* | |
97 | * Safe fastpath aware unlock: | |
98 | * 1) Clear the waiters bit | |
99 | * 2) Drop lock->wait_lock | |
100 | * 3) Try to unlock the lock with cmpxchg | |
101 | */ | |
102 | static inline bool unlock_rt_mutex_safe(struct rt_mutex *lock) | |
103 | __releases(lock->wait_lock) | |
104 | { | |
105 | struct task_struct *owner = rt_mutex_owner(lock); | |
106 | ||
107 | clear_rt_mutex_waiters(lock); | |
108 | raw_spin_unlock(&lock->wait_lock); | |
109 | /* | |
110 | * If a new waiter comes in between the unlock and the cmpxchg | |
111 | * we have two situations: | |
112 | * | |
113 | * unlock(wait_lock); | |
114 | * lock(wait_lock); | |
115 | * cmpxchg(p, owner, 0) == owner | |
116 | * mark_rt_mutex_waiters(lock); | |
117 | * acquire(lock); | |
118 | * or: | |
119 | * | |
120 | * unlock(wait_lock); | |
121 | * lock(wait_lock); | |
122 | * mark_rt_mutex_waiters(lock); | |
123 | * | |
124 | * cmpxchg(p, owner, 0) != owner | |
125 | * enqueue_waiter(); | |
126 | * unlock(wait_lock); | |
127 | * lock(wait_lock); | |
128 | * wake waiter(); | |
129 | * unlock(wait_lock); | |
130 | * lock(wait_lock); | |
131 | * acquire(lock); | |
132 | */ | |
700318d1 | 133 | return rt_mutex_cmpxchg_release(lock, owner, NULL); |
27e35715 TG |
134 | } |
135 | ||
bd197234 | 136 | #else |
700318d1 DB |
137 | # define rt_mutex_cmpxchg_relaxed(l,c,n) (0) |
138 | # define rt_mutex_cmpxchg_acquire(l,c,n) (0) | |
139 | # define rt_mutex_cmpxchg_release(l,c,n) (0) | |
140 | ||
bd197234 TG |
141 | static inline void mark_rt_mutex_waiters(struct rt_mutex *lock) |
142 | { | |
143 | lock->owner = (struct task_struct *) | |
144 | ((unsigned long)lock->owner | RT_MUTEX_HAS_WAITERS); | |
145 | } | |
27e35715 TG |
146 | |
147 | /* | |
148 | * Simple slow path only version: lock->owner is protected by lock->wait_lock. | |
149 | */ | |
150 | static inline bool unlock_rt_mutex_safe(struct rt_mutex *lock) | |
151 | __releases(lock->wait_lock) | |
152 | { | |
153 | lock->owner = NULL; | |
154 | raw_spin_unlock(&lock->wait_lock); | |
155 | return true; | |
156 | } | |
bd197234 TG |
157 | #endif |
158 | ||
fb00aca4 PZ |
159 | static inline int |
160 | rt_mutex_waiter_less(struct rt_mutex_waiter *left, | |
161 | struct rt_mutex_waiter *right) | |
162 | { | |
2d3d891d | 163 | if (left->prio < right->prio) |
fb00aca4 PZ |
164 | return 1; |
165 | ||
166 | /* | |
2d3d891d DF |
167 | * If both waiters have dl_prio(), we check the deadlines of the |
168 | * associated tasks. | |
169 | * If left waiter has a dl_prio(), and we didn't return 1 above, | |
170 | * then right waiter has a dl_prio() too. | |
fb00aca4 | 171 | */ |
2d3d891d | 172 | if (dl_prio(left->prio)) |
f5240575 JL |
173 | return dl_time_before(left->task->dl.deadline, |
174 | right->task->dl.deadline); | |
fb00aca4 PZ |
175 | |
176 | return 0; | |
177 | } | |
178 | ||
179 | static void | |
180 | rt_mutex_enqueue(struct rt_mutex *lock, struct rt_mutex_waiter *waiter) | |
181 | { | |
182 | struct rb_node **link = &lock->waiters.rb_node; | |
183 | struct rb_node *parent = NULL; | |
184 | struct rt_mutex_waiter *entry; | |
185 | int leftmost = 1; | |
186 | ||
187 | while (*link) { | |
188 | parent = *link; | |
189 | entry = rb_entry(parent, struct rt_mutex_waiter, tree_entry); | |
190 | if (rt_mutex_waiter_less(waiter, entry)) { | |
191 | link = &parent->rb_left; | |
192 | } else { | |
193 | link = &parent->rb_right; | |
194 | leftmost = 0; | |
195 | } | |
196 | } | |
197 | ||
198 | if (leftmost) | |
199 | lock->waiters_leftmost = &waiter->tree_entry; | |
200 | ||
201 | rb_link_node(&waiter->tree_entry, parent, link); | |
202 | rb_insert_color(&waiter->tree_entry, &lock->waiters); | |
203 | } | |
204 | ||
205 | static void | |
206 | rt_mutex_dequeue(struct rt_mutex *lock, struct rt_mutex_waiter *waiter) | |
207 | { | |
208 | if (RB_EMPTY_NODE(&waiter->tree_entry)) | |
209 | return; | |
210 | ||
211 | if (lock->waiters_leftmost == &waiter->tree_entry) | |
212 | lock->waiters_leftmost = rb_next(&waiter->tree_entry); | |
213 | ||
214 | rb_erase(&waiter->tree_entry, &lock->waiters); | |
215 | RB_CLEAR_NODE(&waiter->tree_entry); | |
216 | } | |
217 | ||
218 | static void | |
219 | rt_mutex_enqueue_pi(struct task_struct *task, struct rt_mutex_waiter *waiter) | |
220 | { | |
221 | struct rb_node **link = &task->pi_waiters.rb_node; | |
222 | struct rb_node *parent = NULL; | |
223 | struct rt_mutex_waiter *entry; | |
224 | int leftmost = 1; | |
225 | ||
226 | while (*link) { | |
227 | parent = *link; | |
228 | entry = rb_entry(parent, struct rt_mutex_waiter, pi_tree_entry); | |
229 | if (rt_mutex_waiter_less(waiter, entry)) { | |
230 | link = &parent->rb_left; | |
231 | } else { | |
232 | link = &parent->rb_right; | |
233 | leftmost = 0; | |
234 | } | |
235 | } | |
236 | ||
237 | if (leftmost) | |
238 | task->pi_waiters_leftmost = &waiter->pi_tree_entry; | |
239 | ||
240 | rb_link_node(&waiter->pi_tree_entry, parent, link); | |
241 | rb_insert_color(&waiter->pi_tree_entry, &task->pi_waiters); | |
242 | } | |
243 | ||
244 | static void | |
245 | rt_mutex_dequeue_pi(struct task_struct *task, struct rt_mutex_waiter *waiter) | |
246 | { | |
247 | if (RB_EMPTY_NODE(&waiter->pi_tree_entry)) | |
248 | return; | |
249 | ||
250 | if (task->pi_waiters_leftmost == &waiter->pi_tree_entry) | |
251 | task->pi_waiters_leftmost = rb_next(&waiter->pi_tree_entry); | |
252 | ||
253 | rb_erase(&waiter->pi_tree_entry, &task->pi_waiters); | |
254 | RB_CLEAR_NODE(&waiter->pi_tree_entry); | |
255 | } | |
256 | ||
23f78d4a | 257 | /* |
fb00aca4 | 258 | * Calculate task priority from the waiter tree priority |
23f78d4a | 259 | * |
fb00aca4 | 260 | * Return task->normal_prio when the waiter tree is empty or when |
23f78d4a IM |
261 | * the waiter is not allowed to do priority boosting |
262 | */ | |
263 | int rt_mutex_getprio(struct task_struct *task) | |
264 | { | |
265 | if (likely(!task_has_pi_waiters(task))) | |
266 | return task->normal_prio; | |
267 | ||
2d3d891d | 268 | return min(task_top_pi_waiter(task)->prio, |
23f78d4a IM |
269 | task->normal_prio); |
270 | } | |
271 | ||
2d3d891d DF |
272 | struct task_struct *rt_mutex_get_top_task(struct task_struct *task) |
273 | { | |
274 | if (likely(!task_has_pi_waiters(task))) | |
275 | return NULL; | |
276 | ||
277 | return task_top_pi_waiter(task)->task; | |
278 | } | |
279 | ||
c365c292 | 280 | /* |
0782e63b TG |
281 | * Called by sched_setscheduler() to get the priority which will be |
282 | * effective after the change. | |
c365c292 | 283 | */ |
0782e63b | 284 | int rt_mutex_get_effective_prio(struct task_struct *task, int newprio) |
c365c292 TG |
285 | { |
286 | if (!task_has_pi_waiters(task)) | |
0782e63b | 287 | return newprio; |
c365c292 | 288 | |
0782e63b TG |
289 | if (task_top_pi_waiter(task)->task->prio <= newprio) |
290 | return task_top_pi_waiter(task)->task->prio; | |
291 | return newprio; | |
c365c292 TG |
292 | } |
293 | ||
23f78d4a IM |
294 | /* |
295 | * Adjust the priority of a task, after its pi_waiters got modified. | |
296 | * | |
297 | * This can be both boosting and unboosting. task->pi_lock must be held. | |
298 | */ | |
bd197234 | 299 | static void __rt_mutex_adjust_prio(struct task_struct *task) |
23f78d4a IM |
300 | { |
301 | int prio = rt_mutex_getprio(task); | |
302 | ||
2d3d891d | 303 | if (task->prio != prio || dl_prio(prio)) |
23f78d4a IM |
304 | rt_mutex_setprio(task, prio); |
305 | } | |
306 | ||
307 | /* | |
308 | * Adjust task priority (undo boosting). Called from the exit path of | |
309 | * rt_mutex_slowunlock() and rt_mutex_slowlock(). | |
310 | * | |
311 | * (Note: We do this outside of the protection of lock->wait_lock to | |
312 | * allow the lock to be taken while or before we readjust the priority | |
313 | * of task. We do not use the spin_xx_mutex() variants here as we are | |
314 | * outside of the debug path.) | |
315 | */ | |
802ab58d | 316 | void rt_mutex_adjust_prio(struct task_struct *task) |
23f78d4a IM |
317 | { |
318 | unsigned long flags; | |
319 | ||
1d615482 | 320 | raw_spin_lock_irqsave(&task->pi_lock, flags); |
23f78d4a | 321 | __rt_mutex_adjust_prio(task); |
1d615482 | 322 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
23f78d4a IM |
323 | } |
324 | ||
8930ed80 TG |
325 | /* |
326 | * Deadlock detection is conditional: | |
327 | * | |
328 | * If CONFIG_DEBUG_RT_MUTEXES=n, deadlock detection is only conducted | |
329 | * if the detect argument is == RT_MUTEX_FULL_CHAINWALK. | |
330 | * | |
331 | * If CONFIG_DEBUG_RT_MUTEXES=y, deadlock detection is always | |
332 | * conducted independent of the detect argument. | |
333 | * | |
334 | * If the waiter argument is NULL this indicates the deboost path and | |
335 | * deadlock detection is disabled independent of the detect argument | |
336 | * and the config settings. | |
337 | */ | |
338 | static bool rt_mutex_cond_detect_deadlock(struct rt_mutex_waiter *waiter, | |
339 | enum rtmutex_chainwalk chwalk) | |
340 | { | |
341 | /* | |
342 | * This is just a wrapper function for the following call, | |
343 | * because debug_rt_mutex_detect_deadlock() smells like a magic | |
344 | * debug feature and I wanted to keep the cond function in the | |
345 | * main source file along with the comments instead of having | |
346 | * two of the same in the headers. | |
347 | */ | |
348 | return debug_rt_mutex_detect_deadlock(waiter, chwalk); | |
349 | } | |
350 | ||
23f78d4a IM |
351 | /* |
352 | * Max number of times we'll walk the boosting chain: | |
353 | */ | |
354 | int max_lock_depth = 1024; | |
355 | ||
82084984 TG |
356 | static inline struct rt_mutex *task_blocked_on_lock(struct task_struct *p) |
357 | { | |
358 | return p->pi_blocked_on ? p->pi_blocked_on->lock : NULL; | |
359 | } | |
360 | ||
23f78d4a IM |
361 | /* |
362 | * Adjust the priority chain. Also used for deadlock detection. | |
363 | * Decreases task's usage by one - may thus free the task. | |
0c106173 | 364 | * |
82084984 TG |
365 | * @task: the task owning the mutex (owner) for which a chain walk is |
366 | * probably needed | |
e6beaa36 | 367 | * @chwalk: do we have to carry out deadlock detection? |
82084984 TG |
368 | * @orig_lock: the mutex (can be NULL if we are walking the chain to recheck |
369 | * things for a task that has just got its priority adjusted, and | |
370 | * is waiting on a mutex) | |
371 | * @next_lock: the mutex on which the owner of @orig_lock was blocked before | |
372 | * we dropped its pi_lock. Is never dereferenced, only used for | |
373 | * comparison to detect lock chain changes. | |
0c106173 | 374 | * @orig_waiter: rt_mutex_waiter struct for the task that has just donated |
82084984 TG |
375 | * its priority to the mutex owner (can be NULL in the case |
376 | * depicted above or if the top waiter is gone away and we are | |
377 | * actually deboosting the owner) | |
378 | * @top_task: the current top waiter | |
0c106173 | 379 | * |
23f78d4a | 380 | * Returns 0 or -EDEADLK. |
3eb65aea TG |
381 | * |
382 | * Chain walk basics and protection scope | |
383 | * | |
384 | * [R] refcount on task | |
385 | * [P] task->pi_lock held | |
386 | * [L] rtmutex->wait_lock held | |
387 | * | |
388 | * Step Description Protected by | |
389 | * function arguments: | |
390 | * @task [R] | |
391 | * @orig_lock if != NULL @top_task is blocked on it | |
392 | * @next_lock Unprotected. Cannot be | |
393 | * dereferenced. Only used for | |
394 | * comparison. | |
395 | * @orig_waiter if != NULL @top_task is blocked on it | |
396 | * @top_task current, or in case of proxy | |
397 | * locking protected by calling | |
398 | * code | |
399 | * again: | |
400 | * loop_sanity_check(); | |
401 | * retry: | |
402 | * [1] lock(task->pi_lock); [R] acquire [P] | |
403 | * [2] waiter = task->pi_blocked_on; [P] | |
404 | * [3] check_exit_conditions_1(); [P] | |
405 | * [4] lock = waiter->lock; [P] | |
406 | * [5] if (!try_lock(lock->wait_lock)) { [P] try to acquire [L] | |
407 | * unlock(task->pi_lock); release [P] | |
408 | * goto retry; | |
409 | * } | |
410 | * [6] check_exit_conditions_2(); [P] + [L] | |
411 | * [7] requeue_lock_waiter(lock, waiter); [P] + [L] | |
412 | * [8] unlock(task->pi_lock); release [P] | |
413 | * put_task_struct(task); release [R] | |
414 | * [9] check_exit_conditions_3(); [L] | |
415 | * [10] task = owner(lock); [L] | |
416 | * get_task_struct(task); [L] acquire [R] | |
417 | * lock(task->pi_lock); [L] acquire [P] | |
418 | * [11] requeue_pi_waiter(tsk, waiters(lock));[P] + [L] | |
419 | * [12] check_exit_conditions_4(); [P] + [L] | |
420 | * [13] unlock(task->pi_lock); release [P] | |
421 | * unlock(lock->wait_lock); release [L] | |
422 | * goto again; | |
23f78d4a | 423 | */ |
bd197234 | 424 | static int rt_mutex_adjust_prio_chain(struct task_struct *task, |
8930ed80 | 425 | enum rtmutex_chainwalk chwalk, |
bd197234 | 426 | struct rt_mutex *orig_lock, |
82084984 | 427 | struct rt_mutex *next_lock, |
bd197234 TG |
428 | struct rt_mutex_waiter *orig_waiter, |
429 | struct task_struct *top_task) | |
23f78d4a | 430 | { |
23f78d4a | 431 | struct rt_mutex_waiter *waiter, *top_waiter = orig_waiter; |
a57594a1 | 432 | struct rt_mutex_waiter *prerequeue_top_waiter; |
8930ed80 | 433 | int ret = 0, depth = 0; |
a57594a1 | 434 | struct rt_mutex *lock; |
8930ed80 | 435 | bool detect_deadlock; |
23f78d4a | 436 | unsigned long flags; |
67792e2c | 437 | bool requeue = true; |
23f78d4a | 438 | |
8930ed80 | 439 | detect_deadlock = rt_mutex_cond_detect_deadlock(orig_waiter, chwalk); |
23f78d4a IM |
440 | |
441 | /* | |
442 | * The (de)boosting is a step by step approach with a lot of | |
443 | * pitfalls. We want this to be preemptible and we want hold a | |
444 | * maximum of two locks per step. So we have to check | |
445 | * carefully whether things change under us. | |
446 | */ | |
447 | again: | |
3eb65aea TG |
448 | /* |
449 | * We limit the lock chain length for each invocation. | |
450 | */ | |
23f78d4a IM |
451 | if (++depth > max_lock_depth) { |
452 | static int prev_max; | |
453 | ||
454 | /* | |
455 | * Print this only once. If the admin changes the limit, | |
456 | * print a new message when reaching the limit again. | |
457 | */ | |
458 | if (prev_max != max_lock_depth) { | |
459 | prev_max = max_lock_depth; | |
460 | printk(KERN_WARNING "Maximum lock depth %d reached " | |
461 | "task: %s (%d)\n", max_lock_depth, | |
ba25f9dc | 462 | top_task->comm, task_pid_nr(top_task)); |
23f78d4a IM |
463 | } |
464 | put_task_struct(task); | |
465 | ||
3d5c9340 | 466 | return -EDEADLK; |
23f78d4a | 467 | } |
3eb65aea TG |
468 | |
469 | /* | |
470 | * We are fully preemptible here and only hold the refcount on | |
471 | * @task. So everything can have changed under us since the | |
472 | * caller or our own code below (goto retry/again) dropped all | |
473 | * locks. | |
474 | */ | |
23f78d4a IM |
475 | retry: |
476 | /* | |
3eb65aea | 477 | * [1] Task cannot go away as we did a get_task() before ! |
23f78d4a | 478 | */ |
1d615482 | 479 | raw_spin_lock_irqsave(&task->pi_lock, flags); |
23f78d4a | 480 | |
3eb65aea TG |
481 | /* |
482 | * [2] Get the waiter on which @task is blocked on. | |
483 | */ | |
23f78d4a | 484 | waiter = task->pi_blocked_on; |
3eb65aea TG |
485 | |
486 | /* | |
487 | * [3] check_exit_conditions_1() protected by task->pi_lock. | |
488 | */ | |
489 | ||
23f78d4a IM |
490 | /* |
491 | * Check whether the end of the boosting chain has been | |
492 | * reached or the state of the chain has changed while we | |
493 | * dropped the locks. | |
494 | */ | |
8161239a | 495 | if (!waiter) |
23f78d4a IM |
496 | goto out_unlock_pi; |
497 | ||
1a539a87 TG |
498 | /* |
499 | * Check the orig_waiter state. After we dropped the locks, | |
8161239a | 500 | * the previous owner of the lock might have released the lock. |
1a539a87 | 501 | */ |
8161239a | 502 | if (orig_waiter && !rt_mutex_owner(orig_lock)) |
1a539a87 TG |
503 | goto out_unlock_pi; |
504 | ||
82084984 TG |
505 | /* |
506 | * We dropped all locks after taking a refcount on @task, so | |
507 | * the task might have moved on in the lock chain or even left | |
508 | * the chain completely and blocks now on an unrelated lock or | |
509 | * on @orig_lock. | |
510 | * | |
511 | * We stored the lock on which @task was blocked in @next_lock, | |
512 | * so we can detect the chain change. | |
513 | */ | |
514 | if (next_lock != waiter->lock) | |
515 | goto out_unlock_pi; | |
516 | ||
1a539a87 TG |
517 | /* |
518 | * Drop out, when the task has no waiters. Note, | |
519 | * top_waiter can be NULL, when we are in the deboosting | |
520 | * mode! | |
521 | */ | |
397335f0 TG |
522 | if (top_waiter) { |
523 | if (!task_has_pi_waiters(task)) | |
524 | goto out_unlock_pi; | |
525 | /* | |
526 | * If deadlock detection is off, we stop here if we | |
67792e2c TG |
527 | * are not the top pi waiter of the task. If deadlock |
528 | * detection is enabled we continue, but stop the | |
529 | * requeueing in the chain walk. | |
397335f0 | 530 | */ |
67792e2c TG |
531 | if (top_waiter != task_top_pi_waiter(task)) { |
532 | if (!detect_deadlock) | |
533 | goto out_unlock_pi; | |
534 | else | |
535 | requeue = false; | |
536 | } | |
397335f0 | 537 | } |
23f78d4a IM |
538 | |
539 | /* | |
67792e2c TG |
540 | * If the waiter priority is the same as the task priority |
541 | * then there is no further priority adjustment necessary. If | |
542 | * deadlock detection is off, we stop the chain walk. If its | |
543 | * enabled we continue, but stop the requeueing in the chain | |
544 | * walk. | |
23f78d4a | 545 | */ |
67792e2c TG |
546 | if (waiter->prio == task->prio) { |
547 | if (!detect_deadlock) | |
548 | goto out_unlock_pi; | |
549 | else | |
550 | requeue = false; | |
551 | } | |
23f78d4a | 552 | |
3eb65aea TG |
553 | /* |
554 | * [4] Get the next lock | |
555 | */ | |
23f78d4a | 556 | lock = waiter->lock; |
3eb65aea TG |
557 | /* |
558 | * [5] We need to trylock here as we are holding task->pi_lock, | |
559 | * which is the reverse lock order versus the other rtmutex | |
560 | * operations. | |
561 | */ | |
d209d74d | 562 | if (!raw_spin_trylock(&lock->wait_lock)) { |
1d615482 | 563 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
23f78d4a IM |
564 | cpu_relax(); |
565 | goto retry; | |
566 | } | |
567 | ||
397335f0 | 568 | /* |
3eb65aea TG |
569 | * [6] check_exit_conditions_2() protected by task->pi_lock and |
570 | * lock->wait_lock. | |
571 | * | |
397335f0 TG |
572 | * Deadlock detection. If the lock is the same as the original |
573 | * lock which caused us to walk the lock chain or if the | |
574 | * current lock is owned by the task which initiated the chain | |
575 | * walk, we detected a deadlock. | |
576 | */ | |
95e02ca9 | 577 | if (lock == orig_lock || rt_mutex_owner(lock) == top_task) { |
8930ed80 | 578 | debug_rt_mutex_deadlock(chwalk, orig_waiter, lock); |
d209d74d | 579 | raw_spin_unlock(&lock->wait_lock); |
3d5c9340 | 580 | ret = -EDEADLK; |
23f78d4a IM |
581 | goto out_unlock_pi; |
582 | } | |
583 | ||
67792e2c TG |
584 | /* |
585 | * If we just follow the lock chain for deadlock detection, no | |
586 | * need to do all the requeue operations. To avoid a truckload | |
587 | * of conditionals around the various places below, just do the | |
588 | * minimum chain walk checks. | |
589 | */ | |
590 | if (!requeue) { | |
591 | /* | |
592 | * No requeue[7] here. Just release @task [8] | |
593 | */ | |
594 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); | |
595 | put_task_struct(task); | |
596 | ||
597 | /* | |
598 | * [9] check_exit_conditions_3 protected by lock->wait_lock. | |
599 | * If there is no owner of the lock, end of chain. | |
600 | */ | |
601 | if (!rt_mutex_owner(lock)) { | |
602 | raw_spin_unlock(&lock->wait_lock); | |
603 | return 0; | |
604 | } | |
605 | ||
606 | /* [10] Grab the next task, i.e. owner of @lock */ | |
607 | task = rt_mutex_owner(lock); | |
608 | get_task_struct(task); | |
609 | raw_spin_lock_irqsave(&task->pi_lock, flags); | |
610 | ||
611 | /* | |
612 | * No requeue [11] here. We just do deadlock detection. | |
613 | * | |
614 | * [12] Store whether owner is blocked | |
615 | * itself. Decision is made after dropping the locks | |
616 | */ | |
617 | next_lock = task_blocked_on_lock(task); | |
618 | /* | |
619 | * Get the top waiter for the next iteration | |
620 | */ | |
621 | top_waiter = rt_mutex_top_waiter(lock); | |
622 | ||
623 | /* [13] Drop locks */ | |
624 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); | |
625 | raw_spin_unlock(&lock->wait_lock); | |
626 | ||
627 | /* If owner is not blocked, end of chain. */ | |
628 | if (!next_lock) | |
629 | goto out_put_task; | |
630 | goto again; | |
631 | } | |
632 | ||
a57594a1 TG |
633 | /* |
634 | * Store the current top waiter before doing the requeue | |
635 | * operation on @lock. We need it for the boost/deboost | |
636 | * decision below. | |
637 | */ | |
638 | prerequeue_top_waiter = rt_mutex_top_waiter(lock); | |
23f78d4a | 639 | |
9f40a51a | 640 | /* [7] Requeue the waiter in the lock waiter tree. */ |
fb00aca4 | 641 | rt_mutex_dequeue(lock, waiter); |
2d3d891d | 642 | waiter->prio = task->prio; |
fb00aca4 | 643 | rt_mutex_enqueue(lock, waiter); |
23f78d4a | 644 | |
3eb65aea | 645 | /* [8] Release the task */ |
1d615482 | 646 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
2ffa5a5c TG |
647 | put_task_struct(task); |
648 | ||
a57594a1 | 649 | /* |
3eb65aea TG |
650 | * [9] check_exit_conditions_3 protected by lock->wait_lock. |
651 | * | |
a57594a1 TG |
652 | * We must abort the chain walk if there is no lock owner even |
653 | * in the dead lock detection case, as we have nothing to | |
654 | * follow here. This is the end of the chain we are walking. | |
655 | */ | |
8161239a LJ |
656 | if (!rt_mutex_owner(lock)) { |
657 | /* | |
3eb65aea TG |
658 | * If the requeue [7] above changed the top waiter, |
659 | * then we need to wake the new top waiter up to try | |
660 | * to get the lock. | |
8161239a | 661 | */ |
a57594a1 | 662 | if (prerequeue_top_waiter != rt_mutex_top_waiter(lock)) |
8161239a LJ |
663 | wake_up_process(rt_mutex_top_waiter(lock)->task); |
664 | raw_spin_unlock(&lock->wait_lock); | |
2ffa5a5c | 665 | return 0; |
8161239a | 666 | } |
23f78d4a | 667 | |
3eb65aea | 668 | /* [10] Grab the next task, i.e. the owner of @lock */ |
23f78d4a | 669 | task = rt_mutex_owner(lock); |
db630637 | 670 | get_task_struct(task); |
1d615482 | 671 | raw_spin_lock_irqsave(&task->pi_lock, flags); |
23f78d4a | 672 | |
3eb65aea | 673 | /* [11] requeue the pi waiters if necessary */ |
23f78d4a | 674 | if (waiter == rt_mutex_top_waiter(lock)) { |
a57594a1 TG |
675 | /* |
676 | * The waiter became the new top (highest priority) | |
677 | * waiter on the lock. Replace the previous top waiter | |
9f40a51a | 678 | * in the owner tasks pi waiters tree with this waiter |
a57594a1 TG |
679 | * and adjust the priority of the owner. |
680 | */ | |
681 | rt_mutex_dequeue_pi(task, prerequeue_top_waiter); | |
fb00aca4 | 682 | rt_mutex_enqueue_pi(task, waiter); |
23f78d4a IM |
683 | __rt_mutex_adjust_prio(task); |
684 | ||
a57594a1 TG |
685 | } else if (prerequeue_top_waiter == waiter) { |
686 | /* | |
687 | * The waiter was the top waiter on the lock, but is | |
688 | * no longer the top prority waiter. Replace waiter in | |
9f40a51a | 689 | * the owner tasks pi waiters tree with the new top |
a57594a1 TG |
690 | * (highest priority) waiter and adjust the priority |
691 | * of the owner. | |
692 | * The new top waiter is stored in @waiter so that | |
693 | * @waiter == @top_waiter evaluates to true below and | |
694 | * we continue to deboost the rest of the chain. | |
695 | */ | |
fb00aca4 | 696 | rt_mutex_dequeue_pi(task, waiter); |
23f78d4a | 697 | waiter = rt_mutex_top_waiter(lock); |
fb00aca4 | 698 | rt_mutex_enqueue_pi(task, waiter); |
23f78d4a | 699 | __rt_mutex_adjust_prio(task); |
a57594a1 TG |
700 | } else { |
701 | /* | |
702 | * Nothing changed. No need to do any priority | |
703 | * adjustment. | |
704 | */ | |
23f78d4a IM |
705 | } |
706 | ||
82084984 | 707 | /* |
3eb65aea TG |
708 | * [12] check_exit_conditions_4() protected by task->pi_lock |
709 | * and lock->wait_lock. The actual decisions are made after we | |
710 | * dropped the locks. | |
711 | * | |
82084984 TG |
712 | * Check whether the task which owns the current lock is pi |
713 | * blocked itself. If yes we store a pointer to the lock for | |
714 | * the lock chain change detection above. After we dropped | |
715 | * task->pi_lock next_lock cannot be dereferenced anymore. | |
716 | */ | |
717 | next_lock = task_blocked_on_lock(task); | |
a57594a1 TG |
718 | /* |
719 | * Store the top waiter of @lock for the end of chain walk | |
720 | * decision below. | |
721 | */ | |
23f78d4a | 722 | top_waiter = rt_mutex_top_waiter(lock); |
3eb65aea TG |
723 | |
724 | /* [13] Drop the locks */ | |
725 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); | |
d209d74d | 726 | raw_spin_unlock(&lock->wait_lock); |
23f78d4a | 727 | |
82084984 | 728 | /* |
3eb65aea TG |
729 | * Make the actual exit decisions [12], based on the stored |
730 | * values. | |
731 | * | |
82084984 TG |
732 | * We reached the end of the lock chain. Stop right here. No |
733 | * point to go back just to figure that out. | |
734 | */ | |
735 | if (!next_lock) | |
736 | goto out_put_task; | |
737 | ||
a57594a1 TG |
738 | /* |
739 | * If the current waiter is not the top waiter on the lock, | |
740 | * then we can stop the chain walk here if we are not in full | |
741 | * deadlock detection mode. | |
742 | */ | |
23f78d4a IM |
743 | if (!detect_deadlock && waiter != top_waiter) |
744 | goto out_put_task; | |
745 | ||
746 | goto again; | |
747 | ||
748 | out_unlock_pi: | |
1d615482 | 749 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
23f78d4a IM |
750 | out_put_task: |
751 | put_task_struct(task); | |
36c8b586 | 752 | |
23f78d4a IM |
753 | return ret; |
754 | } | |
755 | ||
23f78d4a IM |
756 | /* |
757 | * Try to take an rt-mutex | |
758 | * | |
23f78d4a | 759 | * Must be called with lock->wait_lock held. |
8161239a | 760 | * |
358c331f TG |
761 | * @lock: The lock to be acquired. |
762 | * @task: The task which wants to acquire the lock | |
9f40a51a | 763 | * @waiter: The waiter that is queued to the lock's wait tree if the |
358c331f | 764 | * callsite called task_blocked_on_lock(), otherwise NULL |
23f78d4a | 765 | */ |
8161239a | 766 | static int try_to_take_rt_mutex(struct rt_mutex *lock, struct task_struct *task, |
358c331f | 767 | struct rt_mutex_waiter *waiter) |
23f78d4a | 768 | { |
358c331f TG |
769 | unsigned long flags; |
770 | ||
23f78d4a | 771 | /* |
358c331f TG |
772 | * Before testing whether we can acquire @lock, we set the |
773 | * RT_MUTEX_HAS_WAITERS bit in @lock->owner. This forces all | |
774 | * other tasks which try to modify @lock into the slow path | |
775 | * and they serialize on @lock->wait_lock. | |
23f78d4a | 776 | * |
358c331f TG |
777 | * The RT_MUTEX_HAS_WAITERS bit can have a transitional state |
778 | * as explained at the top of this file if and only if: | |
23f78d4a | 779 | * |
358c331f TG |
780 | * - There is a lock owner. The caller must fixup the |
781 | * transient state if it does a trylock or leaves the lock | |
782 | * function due to a signal or timeout. | |
783 | * | |
784 | * - @task acquires the lock and there are no other | |
785 | * waiters. This is undone in rt_mutex_set_owner(@task) at | |
786 | * the end of this function. | |
23f78d4a IM |
787 | */ |
788 | mark_rt_mutex_waiters(lock); | |
789 | ||
358c331f TG |
790 | /* |
791 | * If @lock has an owner, give up. | |
792 | */ | |
8161239a | 793 | if (rt_mutex_owner(lock)) |
23f78d4a IM |
794 | return 0; |
795 | ||
8161239a | 796 | /* |
358c331f | 797 | * If @waiter != NULL, @task has already enqueued the waiter |
9f40a51a | 798 | * into @lock waiter tree. If @waiter == NULL then this is a |
358c331f | 799 | * trylock attempt. |
8161239a | 800 | */ |
358c331f TG |
801 | if (waiter) { |
802 | /* | |
803 | * If waiter is not the highest priority waiter of | |
804 | * @lock, give up. | |
805 | */ | |
806 | if (waiter != rt_mutex_top_waiter(lock)) | |
807 | return 0; | |
8161239a | 808 | |
358c331f TG |
809 | /* |
810 | * We can acquire the lock. Remove the waiter from the | |
9f40a51a | 811 | * lock waiters tree. |
358c331f TG |
812 | */ |
813 | rt_mutex_dequeue(lock, waiter); | |
8161239a | 814 | |
358c331f | 815 | } else { |
8161239a | 816 | /* |
358c331f TG |
817 | * If the lock has waiters already we check whether @task is |
818 | * eligible to take over the lock. | |
819 | * | |
820 | * If there are no other waiters, @task can acquire | |
821 | * the lock. @task->pi_blocked_on is NULL, so it does | |
822 | * not need to be dequeued. | |
8161239a LJ |
823 | */ |
824 | if (rt_mutex_has_waiters(lock)) { | |
358c331f TG |
825 | /* |
826 | * If @task->prio is greater than or equal to | |
827 | * the top waiter priority (kernel view), | |
828 | * @task lost. | |
829 | */ | |
830 | if (task->prio >= rt_mutex_top_waiter(lock)->prio) | |
831 | return 0; | |
832 | ||
833 | /* | |
834 | * The current top waiter stays enqueued. We | |
835 | * don't have to change anything in the lock | |
836 | * waiters order. | |
837 | */ | |
838 | } else { | |
839 | /* | |
840 | * No waiters. Take the lock without the | |
841 | * pi_lock dance.@task->pi_blocked_on is NULL | |
842 | * and we have no waiters to enqueue in @task | |
9f40a51a | 843 | * pi waiters tree. |
358c331f TG |
844 | */ |
845 | goto takeit; | |
8161239a | 846 | } |
8161239a LJ |
847 | } |
848 | ||
358c331f TG |
849 | /* |
850 | * Clear @task->pi_blocked_on. Requires protection by | |
851 | * @task->pi_lock. Redundant operation for the @waiter == NULL | |
852 | * case, but conditionals are more expensive than a redundant | |
853 | * store. | |
854 | */ | |
855 | raw_spin_lock_irqsave(&task->pi_lock, flags); | |
856 | task->pi_blocked_on = NULL; | |
857 | /* | |
858 | * Finish the lock acquisition. @task is the new owner. If | |
859 | * other waiters exist we have to insert the highest priority | |
9f40a51a | 860 | * waiter into @task->pi_waiters tree. |
358c331f TG |
861 | */ |
862 | if (rt_mutex_has_waiters(lock)) | |
863 | rt_mutex_enqueue_pi(task, rt_mutex_top_waiter(lock)); | |
864 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); | |
865 | ||
866 | takeit: | |
23f78d4a | 867 | /* We got the lock. */ |
9a11b49a | 868 | debug_rt_mutex_lock(lock); |
23f78d4a | 869 | |
358c331f TG |
870 | /* |
871 | * This either preserves the RT_MUTEX_HAS_WAITERS bit if there | |
872 | * are still waiters or clears it. | |
873 | */ | |
8161239a | 874 | rt_mutex_set_owner(lock, task); |
23f78d4a | 875 | |
8161239a | 876 | rt_mutex_deadlock_account_lock(lock, task); |
23f78d4a IM |
877 | |
878 | return 1; | |
879 | } | |
880 | ||
881 | /* | |
882 | * Task blocks on lock. | |
883 | * | |
884 | * Prepare waiter and propagate pi chain | |
885 | * | |
886 | * This must be called with lock->wait_lock held. | |
887 | */ | |
888 | static int task_blocks_on_rt_mutex(struct rt_mutex *lock, | |
889 | struct rt_mutex_waiter *waiter, | |
8dac456a | 890 | struct task_struct *task, |
8930ed80 | 891 | enum rtmutex_chainwalk chwalk) |
23f78d4a | 892 | { |
36c8b586 | 893 | struct task_struct *owner = rt_mutex_owner(lock); |
23f78d4a | 894 | struct rt_mutex_waiter *top_waiter = waiter; |
82084984 | 895 | struct rt_mutex *next_lock; |
db630637 | 896 | int chain_walk = 0, res; |
82084984 | 897 | unsigned long flags; |
23f78d4a | 898 | |
397335f0 TG |
899 | /* |
900 | * Early deadlock detection. We really don't want the task to | |
901 | * enqueue on itself just to untangle the mess later. It's not | |
902 | * only an optimization. We drop the locks, so another waiter | |
903 | * can come in before the chain walk detects the deadlock. So | |
904 | * the other will detect the deadlock and return -EDEADLOCK, | |
905 | * which is wrong, as the other waiter is not in a deadlock | |
906 | * situation. | |
907 | */ | |
3d5c9340 | 908 | if (owner == task) |
397335f0 TG |
909 | return -EDEADLK; |
910 | ||
1d615482 | 911 | raw_spin_lock_irqsave(&task->pi_lock, flags); |
8dac456a DH |
912 | __rt_mutex_adjust_prio(task); |
913 | waiter->task = task; | |
23f78d4a | 914 | waiter->lock = lock; |
2d3d891d | 915 | waiter->prio = task->prio; |
23f78d4a IM |
916 | |
917 | /* Get the top priority waiter on the lock */ | |
918 | if (rt_mutex_has_waiters(lock)) | |
919 | top_waiter = rt_mutex_top_waiter(lock); | |
fb00aca4 | 920 | rt_mutex_enqueue(lock, waiter); |
23f78d4a | 921 | |
8dac456a | 922 | task->pi_blocked_on = waiter; |
23f78d4a | 923 | |
1d615482 | 924 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
23f78d4a | 925 | |
8161239a LJ |
926 | if (!owner) |
927 | return 0; | |
928 | ||
82084984 | 929 | raw_spin_lock_irqsave(&owner->pi_lock, flags); |
23f78d4a | 930 | if (waiter == rt_mutex_top_waiter(lock)) { |
fb00aca4 PZ |
931 | rt_mutex_dequeue_pi(owner, top_waiter); |
932 | rt_mutex_enqueue_pi(owner, waiter); | |
23f78d4a IM |
933 | |
934 | __rt_mutex_adjust_prio(owner); | |
db630637 SR |
935 | if (owner->pi_blocked_on) |
936 | chain_walk = 1; | |
8930ed80 | 937 | } else if (rt_mutex_cond_detect_deadlock(waiter, chwalk)) { |
db630637 | 938 | chain_walk = 1; |
82084984 | 939 | } |
db630637 | 940 | |
82084984 TG |
941 | /* Store the lock on which owner is blocked or NULL */ |
942 | next_lock = task_blocked_on_lock(owner); | |
943 | ||
944 | raw_spin_unlock_irqrestore(&owner->pi_lock, flags); | |
945 | /* | |
946 | * Even if full deadlock detection is on, if the owner is not | |
947 | * blocked itself, we can avoid finding this out in the chain | |
948 | * walk. | |
949 | */ | |
950 | if (!chain_walk || !next_lock) | |
23f78d4a IM |
951 | return 0; |
952 | ||
db630637 SR |
953 | /* |
954 | * The owner can't disappear while holding a lock, | |
955 | * so the owner struct is protected by wait_lock. | |
956 | * Gets dropped in rt_mutex_adjust_prio_chain()! | |
957 | */ | |
958 | get_task_struct(owner); | |
959 | ||
d209d74d | 960 | raw_spin_unlock(&lock->wait_lock); |
23f78d4a | 961 | |
8930ed80 | 962 | res = rt_mutex_adjust_prio_chain(owner, chwalk, lock, |
82084984 | 963 | next_lock, waiter, task); |
23f78d4a | 964 | |
d209d74d | 965 | raw_spin_lock(&lock->wait_lock); |
23f78d4a IM |
966 | |
967 | return res; | |
968 | } | |
969 | ||
970 | /* | |
9f40a51a | 971 | * Remove the top waiter from the current tasks pi waiter tree and |
45ab4eff | 972 | * queue it up. |
23f78d4a IM |
973 | * |
974 | * Called with lock->wait_lock held. | |
975 | */ | |
45ab4eff DB |
976 | static void mark_wakeup_next_waiter(struct wake_q_head *wake_q, |
977 | struct rt_mutex *lock) | |
23f78d4a IM |
978 | { |
979 | struct rt_mutex_waiter *waiter; | |
23f78d4a IM |
980 | unsigned long flags; |
981 | ||
1d615482 | 982 | raw_spin_lock_irqsave(¤t->pi_lock, flags); |
23f78d4a IM |
983 | |
984 | waiter = rt_mutex_top_waiter(lock); | |
23f78d4a IM |
985 | |
986 | /* | |
987 | * Remove it from current->pi_waiters. We do not adjust a | |
988 | * possible priority boost right now. We execute wakeup in the | |
989 | * boosted mode and go back to normal after releasing | |
990 | * lock->wait_lock. | |
991 | */ | |
fb00aca4 | 992 | rt_mutex_dequeue_pi(current, waiter); |
23f78d4a | 993 | |
27e35715 TG |
994 | /* |
995 | * As we are waking up the top waiter, and the waiter stays | |
996 | * queued on the lock until it gets the lock, this lock | |
997 | * obviously has waiters. Just set the bit here and this has | |
998 | * the added benefit of forcing all new tasks into the | |
999 | * slow path making sure no task of lower priority than | |
1000 | * the top waiter can steal this lock. | |
1001 | */ | |
1002 | lock->owner = (void *) RT_MUTEX_HAS_WAITERS; | |
23f78d4a | 1003 | |
1d615482 | 1004 | raw_spin_unlock_irqrestore(¤t->pi_lock, flags); |
23f78d4a | 1005 | |
45ab4eff | 1006 | wake_q_add(wake_q, waiter->task); |
23f78d4a IM |
1007 | } |
1008 | ||
1009 | /* | |
8161239a | 1010 | * Remove a waiter from a lock and give up |
23f78d4a | 1011 | * |
8161239a LJ |
1012 | * Must be called with lock->wait_lock held and |
1013 | * have just failed to try_to_take_rt_mutex(). | |
23f78d4a | 1014 | */ |
bd197234 TG |
1015 | static void remove_waiter(struct rt_mutex *lock, |
1016 | struct rt_mutex_waiter *waiter) | |
23f78d4a | 1017 | { |
1ca7b860 | 1018 | bool is_top_waiter = (waiter == rt_mutex_top_waiter(lock)); |
36c8b586 | 1019 | struct task_struct *owner = rt_mutex_owner(lock); |
1ca7b860 | 1020 | struct rt_mutex *next_lock; |
23f78d4a IM |
1021 | unsigned long flags; |
1022 | ||
1d615482 | 1023 | raw_spin_lock_irqsave(¤t->pi_lock, flags); |
fb00aca4 | 1024 | rt_mutex_dequeue(lock, waiter); |
23f78d4a | 1025 | current->pi_blocked_on = NULL; |
1d615482 | 1026 | raw_spin_unlock_irqrestore(¤t->pi_lock, flags); |
23f78d4a | 1027 | |
1ca7b860 TG |
1028 | /* |
1029 | * Only update priority if the waiter was the highest priority | |
1030 | * waiter of the lock and there is an owner to update. | |
1031 | */ | |
1032 | if (!owner || !is_top_waiter) | |
8161239a LJ |
1033 | return; |
1034 | ||
1ca7b860 | 1035 | raw_spin_lock_irqsave(&owner->pi_lock, flags); |
23f78d4a | 1036 | |
1ca7b860 | 1037 | rt_mutex_dequeue_pi(owner, waiter); |
23f78d4a | 1038 | |
1ca7b860 TG |
1039 | if (rt_mutex_has_waiters(lock)) |
1040 | rt_mutex_enqueue_pi(owner, rt_mutex_top_waiter(lock)); | |
23f78d4a | 1041 | |
1ca7b860 | 1042 | __rt_mutex_adjust_prio(owner); |
23f78d4a | 1043 | |
1ca7b860 TG |
1044 | /* Store the lock on which owner is blocked or NULL */ |
1045 | next_lock = task_blocked_on_lock(owner); | |
db630637 | 1046 | |
1ca7b860 | 1047 | raw_spin_unlock_irqrestore(&owner->pi_lock, flags); |
23f78d4a | 1048 | |
1ca7b860 TG |
1049 | /* |
1050 | * Don't walk the chain, if the owner task is not blocked | |
1051 | * itself. | |
1052 | */ | |
82084984 | 1053 | if (!next_lock) |
23f78d4a IM |
1054 | return; |
1055 | ||
db630637 SR |
1056 | /* gets dropped in rt_mutex_adjust_prio_chain()! */ |
1057 | get_task_struct(owner); | |
1058 | ||
d209d74d | 1059 | raw_spin_unlock(&lock->wait_lock); |
23f78d4a | 1060 | |
8930ed80 TG |
1061 | rt_mutex_adjust_prio_chain(owner, RT_MUTEX_MIN_CHAINWALK, lock, |
1062 | next_lock, NULL, current); | |
23f78d4a | 1063 | |
d209d74d | 1064 | raw_spin_lock(&lock->wait_lock); |
23f78d4a IM |
1065 | } |
1066 | ||
95e02ca9 TG |
1067 | /* |
1068 | * Recheck the pi chain, in case we got a priority setting | |
1069 | * | |
1070 | * Called from sched_setscheduler | |
1071 | */ | |
1072 | void rt_mutex_adjust_pi(struct task_struct *task) | |
1073 | { | |
1074 | struct rt_mutex_waiter *waiter; | |
82084984 | 1075 | struct rt_mutex *next_lock; |
95e02ca9 TG |
1076 | unsigned long flags; |
1077 | ||
1d615482 | 1078 | raw_spin_lock_irqsave(&task->pi_lock, flags); |
95e02ca9 TG |
1079 | |
1080 | waiter = task->pi_blocked_on; | |
2d3d891d DF |
1081 | if (!waiter || (waiter->prio == task->prio && |
1082 | !dl_prio(task->prio))) { | |
1d615482 | 1083 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
95e02ca9 TG |
1084 | return; |
1085 | } | |
82084984 | 1086 | next_lock = waiter->lock; |
1d615482 | 1087 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
95e02ca9 | 1088 | |
db630637 SR |
1089 | /* gets dropped in rt_mutex_adjust_prio_chain()! */ |
1090 | get_task_struct(task); | |
82084984 | 1091 | |
8930ed80 TG |
1092 | rt_mutex_adjust_prio_chain(task, RT_MUTEX_MIN_CHAINWALK, NULL, |
1093 | next_lock, NULL, task); | |
95e02ca9 TG |
1094 | } |
1095 | ||
8dac456a DH |
1096 | /** |
1097 | * __rt_mutex_slowlock() - Perform the wait-wake-try-to-take loop | |
1098 | * @lock: the rt_mutex to take | |
1099 | * @state: the state the task should block in (TASK_INTERRUPTIBLE | |
1100 | * or TASK_UNINTERRUPTIBLE) | |
1101 | * @timeout: the pre-initialized and started timer, or NULL for none | |
1102 | * @waiter: the pre-initialized rt_mutex_waiter | |
8dac456a DH |
1103 | * |
1104 | * lock->wait_lock must be held by the caller. | |
23f78d4a IM |
1105 | */ |
1106 | static int __sched | |
8dac456a DH |
1107 | __rt_mutex_slowlock(struct rt_mutex *lock, int state, |
1108 | struct hrtimer_sleeper *timeout, | |
8161239a | 1109 | struct rt_mutex_waiter *waiter) |
23f78d4a | 1110 | { |
23f78d4a IM |
1111 | int ret = 0; |
1112 | ||
23f78d4a IM |
1113 | for (;;) { |
1114 | /* Try to acquire the lock: */ | |
8161239a | 1115 | if (try_to_take_rt_mutex(lock, current, waiter)) |
23f78d4a IM |
1116 | break; |
1117 | ||
1118 | /* | |
1119 | * TASK_INTERRUPTIBLE checks for signals and | |
1120 | * timeout. Ignored otherwise. | |
1121 | */ | |
1122 | if (unlikely(state == TASK_INTERRUPTIBLE)) { | |
1123 | /* Signal pending? */ | |
1124 | if (signal_pending(current)) | |
1125 | ret = -EINTR; | |
1126 | if (timeout && !timeout->task) | |
1127 | ret = -ETIMEDOUT; | |
1128 | if (ret) | |
1129 | break; | |
1130 | } | |
1131 | ||
d209d74d | 1132 | raw_spin_unlock(&lock->wait_lock); |
23f78d4a | 1133 | |
8dac456a | 1134 | debug_rt_mutex_print_deadlock(waiter); |
23f78d4a | 1135 | |
1b0b7c17 | 1136 | schedule(); |
23f78d4a | 1137 | |
d209d74d | 1138 | raw_spin_lock(&lock->wait_lock); |
23f78d4a IM |
1139 | set_current_state(state); |
1140 | } | |
1141 | ||
afffc6c1 | 1142 | __set_current_state(TASK_RUNNING); |
8dac456a DH |
1143 | return ret; |
1144 | } | |
1145 | ||
3d5c9340 TG |
1146 | static void rt_mutex_handle_deadlock(int res, int detect_deadlock, |
1147 | struct rt_mutex_waiter *w) | |
1148 | { | |
1149 | /* | |
1150 | * If the result is not -EDEADLOCK or the caller requested | |
1151 | * deadlock detection, nothing to do here. | |
1152 | */ | |
1153 | if (res != -EDEADLOCK || detect_deadlock) | |
1154 | return; | |
1155 | ||
1156 | /* | |
1157 | * Yell lowdly and stop the task right here. | |
1158 | */ | |
1159 | rt_mutex_print_deadlock(w); | |
1160 | while (1) { | |
1161 | set_current_state(TASK_INTERRUPTIBLE); | |
1162 | schedule(); | |
1163 | } | |
1164 | } | |
1165 | ||
8dac456a DH |
1166 | /* |
1167 | * Slow path lock function: | |
1168 | */ | |
1169 | static int __sched | |
1170 | rt_mutex_slowlock(struct rt_mutex *lock, int state, | |
1171 | struct hrtimer_sleeper *timeout, | |
8930ed80 | 1172 | enum rtmutex_chainwalk chwalk) |
8dac456a DH |
1173 | { |
1174 | struct rt_mutex_waiter waiter; | |
1175 | int ret = 0; | |
1176 | ||
1177 | debug_rt_mutex_init_waiter(&waiter); | |
fb00aca4 PZ |
1178 | RB_CLEAR_NODE(&waiter.pi_tree_entry); |
1179 | RB_CLEAR_NODE(&waiter.tree_entry); | |
8dac456a | 1180 | |
d209d74d | 1181 | raw_spin_lock(&lock->wait_lock); |
8dac456a DH |
1182 | |
1183 | /* Try to acquire the lock again: */ | |
8161239a | 1184 | if (try_to_take_rt_mutex(lock, current, NULL)) { |
d209d74d | 1185 | raw_spin_unlock(&lock->wait_lock); |
8dac456a DH |
1186 | return 0; |
1187 | } | |
1188 | ||
1189 | set_current_state(state); | |
1190 | ||
1191 | /* Setup the timer, when timeout != NULL */ | |
ccdd92c1 | 1192 | if (unlikely(timeout)) |
8dac456a | 1193 | hrtimer_start_expires(&timeout->timer, HRTIMER_MODE_ABS); |
8dac456a | 1194 | |
8930ed80 | 1195 | ret = task_blocks_on_rt_mutex(lock, &waiter, current, chwalk); |
8161239a LJ |
1196 | |
1197 | if (likely(!ret)) | |
afffc6c1 | 1198 | /* sleep on the mutex */ |
8161239a | 1199 | ret = __rt_mutex_slowlock(lock, state, timeout, &waiter); |
8dac456a | 1200 | |
3d5c9340 | 1201 | if (unlikely(ret)) { |
9d3e2d02 | 1202 | __set_current_state(TASK_RUNNING); |
8d1e5a1a SAS |
1203 | if (rt_mutex_has_waiters(lock)) |
1204 | remove_waiter(lock, &waiter); | |
8930ed80 | 1205 | rt_mutex_handle_deadlock(ret, chwalk, &waiter); |
3d5c9340 | 1206 | } |
23f78d4a IM |
1207 | |
1208 | /* | |
1209 | * try_to_take_rt_mutex() sets the waiter bit | |
1210 | * unconditionally. We might have to fix that up. | |
1211 | */ | |
1212 | fixup_rt_mutex_waiters(lock); | |
1213 | ||
d209d74d | 1214 | raw_spin_unlock(&lock->wait_lock); |
23f78d4a IM |
1215 | |
1216 | /* Remove pending timer: */ | |
1217 | if (unlikely(timeout)) | |
1218 | hrtimer_cancel(&timeout->timer); | |
1219 | ||
23f78d4a IM |
1220 | debug_rt_mutex_free_waiter(&waiter); |
1221 | ||
1222 | return ret; | |
1223 | } | |
1224 | ||
1225 | /* | |
1226 | * Slow path try-lock function: | |
1227 | */ | |
88f2b4c1 | 1228 | static inline int rt_mutex_slowtrylock(struct rt_mutex *lock) |
23f78d4a | 1229 | { |
88f2b4c1 TG |
1230 | int ret; |
1231 | ||
1232 | /* | |
1233 | * If the lock already has an owner we fail to get the lock. | |
1234 | * This can be done without taking the @lock->wait_lock as | |
1235 | * it is only being read, and this is a trylock anyway. | |
1236 | */ | |
1237 | if (rt_mutex_owner(lock)) | |
1238 | return 0; | |
23f78d4a | 1239 | |
88f2b4c1 TG |
1240 | /* |
1241 | * The mutex has currently no owner. Lock the wait lock and | |
1242 | * try to acquire the lock. | |
1243 | */ | |
d209d74d | 1244 | raw_spin_lock(&lock->wait_lock); |
23f78d4a | 1245 | |
88f2b4c1 | 1246 | ret = try_to_take_rt_mutex(lock, current, NULL); |
23f78d4a | 1247 | |
88f2b4c1 TG |
1248 | /* |
1249 | * try_to_take_rt_mutex() sets the lock waiters bit | |
1250 | * unconditionally. Clean this up. | |
1251 | */ | |
1252 | fixup_rt_mutex_waiters(lock); | |
23f78d4a | 1253 | |
d209d74d | 1254 | raw_spin_unlock(&lock->wait_lock); |
23f78d4a IM |
1255 | |
1256 | return ret; | |
1257 | } | |
1258 | ||
1259 | /* | |
802ab58d SAS |
1260 | * Slow path to release a rt-mutex. |
1261 | * Return whether the current task needs to undo a potential priority boosting. | |
23f78d4a | 1262 | */ |
802ab58d SAS |
1263 | static bool __sched rt_mutex_slowunlock(struct rt_mutex *lock, |
1264 | struct wake_q_head *wake_q) | |
23f78d4a | 1265 | { |
d209d74d | 1266 | raw_spin_lock(&lock->wait_lock); |
23f78d4a IM |
1267 | |
1268 | debug_rt_mutex_unlock(lock); | |
1269 | ||
1270 | rt_mutex_deadlock_account_unlock(current); | |
1271 | ||
27e35715 TG |
1272 | /* |
1273 | * We must be careful here if the fast path is enabled. If we | |
1274 | * have no waiters queued we cannot set owner to NULL here | |
1275 | * because of: | |
1276 | * | |
1277 | * foo->lock->owner = NULL; | |
1278 | * rtmutex_lock(foo->lock); <- fast path | |
1279 | * free = atomic_dec_and_test(foo->refcnt); | |
1280 | * rtmutex_unlock(foo->lock); <- fast path | |
1281 | * if (free) | |
1282 | * kfree(foo); | |
1283 | * raw_spin_unlock(foo->lock->wait_lock); | |
1284 | * | |
1285 | * So for the fastpath enabled kernel: | |
1286 | * | |
1287 | * Nothing can set the waiters bit as long as we hold | |
1288 | * lock->wait_lock. So we do the following sequence: | |
1289 | * | |
1290 | * owner = rt_mutex_owner(lock); | |
1291 | * clear_rt_mutex_waiters(lock); | |
1292 | * raw_spin_unlock(&lock->wait_lock); | |
1293 | * if (cmpxchg(&lock->owner, owner, 0) == owner) | |
1294 | * return; | |
1295 | * goto retry; | |
1296 | * | |
1297 | * The fastpath disabled variant is simple as all access to | |
1298 | * lock->owner is serialized by lock->wait_lock: | |
1299 | * | |
1300 | * lock->owner = NULL; | |
1301 | * raw_spin_unlock(&lock->wait_lock); | |
1302 | */ | |
1303 | while (!rt_mutex_has_waiters(lock)) { | |
1304 | /* Drops lock->wait_lock ! */ | |
1305 | if (unlock_rt_mutex_safe(lock) == true) | |
802ab58d | 1306 | return false; |
27e35715 TG |
1307 | /* Relock the rtmutex and try again */ |
1308 | raw_spin_lock(&lock->wait_lock); | |
23f78d4a IM |
1309 | } |
1310 | ||
27e35715 TG |
1311 | /* |
1312 | * The wakeup next waiter path does not suffer from the above | |
1313 | * race. See the comments there. | |
45ab4eff DB |
1314 | * |
1315 | * Queue the next waiter for wakeup once we release the wait_lock. | |
27e35715 | 1316 | */ |
802ab58d | 1317 | mark_wakeup_next_waiter(wake_q, lock); |
23f78d4a | 1318 | |
d209d74d | 1319 | raw_spin_unlock(&lock->wait_lock); |
23f78d4a | 1320 | |
802ab58d SAS |
1321 | /* check PI boosting */ |
1322 | return true; | |
23f78d4a IM |
1323 | } |
1324 | ||
1325 | /* | |
1326 | * debug aware fast / slowpath lock,trylock,unlock | |
1327 | * | |
1328 | * The atomic acquire/release ops are compiled away, when either the | |
1329 | * architecture does not support cmpxchg or when debugging is enabled. | |
1330 | */ | |
1331 | static inline int | |
1332 | rt_mutex_fastlock(struct rt_mutex *lock, int state, | |
23f78d4a IM |
1333 | int (*slowfn)(struct rt_mutex *lock, int state, |
1334 | struct hrtimer_sleeper *timeout, | |
8930ed80 | 1335 | enum rtmutex_chainwalk chwalk)) |
23f78d4a | 1336 | { |
700318d1 | 1337 | if (likely(rt_mutex_cmpxchg_acquire(lock, NULL, current))) { |
23f78d4a IM |
1338 | rt_mutex_deadlock_account_lock(lock, current); |
1339 | return 0; | |
1340 | } else | |
8930ed80 | 1341 | return slowfn(lock, state, NULL, RT_MUTEX_MIN_CHAINWALK); |
23f78d4a IM |
1342 | } |
1343 | ||
1344 | static inline int | |
1345 | rt_mutex_timed_fastlock(struct rt_mutex *lock, int state, | |
8930ed80 TG |
1346 | struct hrtimer_sleeper *timeout, |
1347 | enum rtmutex_chainwalk chwalk, | |
23f78d4a IM |
1348 | int (*slowfn)(struct rt_mutex *lock, int state, |
1349 | struct hrtimer_sleeper *timeout, | |
8930ed80 | 1350 | enum rtmutex_chainwalk chwalk)) |
23f78d4a | 1351 | { |
8930ed80 | 1352 | if (chwalk == RT_MUTEX_MIN_CHAINWALK && |
700318d1 | 1353 | likely(rt_mutex_cmpxchg_acquire(lock, NULL, current))) { |
23f78d4a IM |
1354 | rt_mutex_deadlock_account_lock(lock, current); |
1355 | return 0; | |
1356 | } else | |
8930ed80 | 1357 | return slowfn(lock, state, timeout, chwalk); |
23f78d4a IM |
1358 | } |
1359 | ||
1360 | static inline int | |
1361 | rt_mutex_fasttrylock(struct rt_mutex *lock, | |
9a11b49a | 1362 | int (*slowfn)(struct rt_mutex *lock)) |
23f78d4a | 1363 | { |
700318d1 | 1364 | if (likely(rt_mutex_cmpxchg_acquire(lock, NULL, current))) { |
23f78d4a IM |
1365 | rt_mutex_deadlock_account_lock(lock, current); |
1366 | return 1; | |
1367 | } | |
9a11b49a | 1368 | return slowfn(lock); |
23f78d4a IM |
1369 | } |
1370 | ||
1371 | static inline void | |
1372 | rt_mutex_fastunlock(struct rt_mutex *lock, | |
802ab58d SAS |
1373 | bool (*slowfn)(struct rt_mutex *lock, |
1374 | struct wake_q_head *wqh)) | |
23f78d4a | 1375 | { |
802ab58d SAS |
1376 | WAKE_Q(wake_q); |
1377 | ||
700318d1 | 1378 | if (likely(rt_mutex_cmpxchg_release(lock, current, NULL))) { |
23f78d4a | 1379 | rt_mutex_deadlock_account_unlock(current); |
802ab58d SAS |
1380 | |
1381 | } else { | |
1382 | bool deboost = slowfn(lock, &wake_q); | |
1383 | ||
1384 | wake_up_q(&wake_q); | |
1385 | ||
1386 | /* Undo pi boosting if necessary: */ | |
1387 | if (deboost) | |
1388 | rt_mutex_adjust_prio(current); | |
1389 | } | |
23f78d4a IM |
1390 | } |
1391 | ||
1392 | /** | |
1393 | * rt_mutex_lock - lock a rt_mutex | |
1394 | * | |
1395 | * @lock: the rt_mutex to be locked | |
1396 | */ | |
1397 | void __sched rt_mutex_lock(struct rt_mutex *lock) | |
1398 | { | |
1399 | might_sleep(); | |
1400 | ||
c051b21f | 1401 | rt_mutex_fastlock(lock, TASK_UNINTERRUPTIBLE, rt_mutex_slowlock); |
23f78d4a IM |
1402 | } |
1403 | EXPORT_SYMBOL_GPL(rt_mutex_lock); | |
1404 | ||
1405 | /** | |
1406 | * rt_mutex_lock_interruptible - lock a rt_mutex interruptible | |
1407 | * | |
c051b21f | 1408 | * @lock: the rt_mutex to be locked |
23f78d4a IM |
1409 | * |
1410 | * Returns: | |
c051b21f TG |
1411 | * 0 on success |
1412 | * -EINTR when interrupted by a signal | |
23f78d4a | 1413 | */ |
c051b21f | 1414 | int __sched rt_mutex_lock_interruptible(struct rt_mutex *lock) |
23f78d4a IM |
1415 | { |
1416 | might_sleep(); | |
1417 | ||
c051b21f | 1418 | return rt_mutex_fastlock(lock, TASK_INTERRUPTIBLE, rt_mutex_slowlock); |
23f78d4a IM |
1419 | } |
1420 | EXPORT_SYMBOL_GPL(rt_mutex_lock_interruptible); | |
1421 | ||
c051b21f TG |
1422 | /* |
1423 | * Futex variant with full deadlock detection. | |
1424 | */ | |
1425 | int rt_mutex_timed_futex_lock(struct rt_mutex *lock, | |
1426 | struct hrtimer_sleeper *timeout) | |
1427 | { | |
1428 | might_sleep(); | |
1429 | ||
8930ed80 TG |
1430 | return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout, |
1431 | RT_MUTEX_FULL_CHAINWALK, | |
c051b21f TG |
1432 | rt_mutex_slowlock); |
1433 | } | |
1434 | ||
23f78d4a | 1435 | /** |
23b94b96 LH |
1436 | * rt_mutex_timed_lock - lock a rt_mutex interruptible |
1437 | * the timeout structure is provided | |
1438 | * by the caller | |
23f78d4a | 1439 | * |
c051b21f | 1440 | * @lock: the rt_mutex to be locked |
23f78d4a | 1441 | * @timeout: timeout structure or NULL (no timeout) |
23f78d4a IM |
1442 | * |
1443 | * Returns: | |
c051b21f TG |
1444 | * 0 on success |
1445 | * -EINTR when interrupted by a signal | |
3ac49a1c | 1446 | * -ETIMEDOUT when the timeout expired |
23f78d4a IM |
1447 | */ |
1448 | int | |
c051b21f | 1449 | rt_mutex_timed_lock(struct rt_mutex *lock, struct hrtimer_sleeper *timeout) |
23f78d4a IM |
1450 | { |
1451 | might_sleep(); | |
1452 | ||
8930ed80 TG |
1453 | return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout, |
1454 | RT_MUTEX_MIN_CHAINWALK, | |
c051b21f | 1455 | rt_mutex_slowlock); |
23f78d4a IM |
1456 | } |
1457 | EXPORT_SYMBOL_GPL(rt_mutex_timed_lock); | |
1458 | ||
1459 | /** | |
1460 | * rt_mutex_trylock - try to lock a rt_mutex | |
1461 | * | |
1462 | * @lock: the rt_mutex to be locked | |
1463 | * | |
6ce47fd9 TG |
1464 | * This function can only be called in thread context. It's safe to |
1465 | * call it from atomic regions, but not from hard interrupt or soft | |
1466 | * interrupt context. | |
1467 | * | |
23f78d4a IM |
1468 | * Returns 1 on success and 0 on contention |
1469 | */ | |
1470 | int __sched rt_mutex_trylock(struct rt_mutex *lock) | |
1471 | { | |
6ce47fd9 TG |
1472 | if (WARN_ON(in_irq() || in_nmi() || in_serving_softirq())) |
1473 | return 0; | |
1474 | ||
23f78d4a IM |
1475 | return rt_mutex_fasttrylock(lock, rt_mutex_slowtrylock); |
1476 | } | |
1477 | EXPORT_SYMBOL_GPL(rt_mutex_trylock); | |
1478 | ||
1479 | /** | |
1480 | * rt_mutex_unlock - unlock a rt_mutex | |
1481 | * | |
1482 | * @lock: the rt_mutex to be unlocked | |
1483 | */ | |
1484 | void __sched rt_mutex_unlock(struct rt_mutex *lock) | |
1485 | { | |
1486 | rt_mutex_fastunlock(lock, rt_mutex_slowunlock); | |
1487 | } | |
1488 | EXPORT_SYMBOL_GPL(rt_mutex_unlock); | |
1489 | ||
802ab58d SAS |
1490 | /** |
1491 | * rt_mutex_futex_unlock - Futex variant of rt_mutex_unlock | |
1492 | * @lock: the rt_mutex to be unlocked | |
1493 | * | |
1494 | * Returns: true/false indicating whether priority adjustment is | |
1495 | * required or not. | |
1496 | */ | |
1497 | bool __sched rt_mutex_futex_unlock(struct rt_mutex *lock, | |
1498 | struct wake_q_head *wqh) | |
1499 | { | |
700318d1 | 1500 | if (likely(rt_mutex_cmpxchg_release(lock, current, NULL))) { |
802ab58d SAS |
1501 | rt_mutex_deadlock_account_unlock(current); |
1502 | return false; | |
1503 | } | |
1504 | return rt_mutex_slowunlock(lock, wqh); | |
1505 | } | |
1506 | ||
23b94b96 | 1507 | /** |
23f78d4a IM |
1508 | * rt_mutex_destroy - mark a mutex unusable |
1509 | * @lock: the mutex to be destroyed | |
1510 | * | |
1511 | * This function marks the mutex uninitialized, and any subsequent | |
1512 | * use of the mutex is forbidden. The mutex must not be locked when | |
1513 | * this function is called. | |
1514 | */ | |
1515 | void rt_mutex_destroy(struct rt_mutex *lock) | |
1516 | { | |
1517 | WARN_ON(rt_mutex_is_locked(lock)); | |
1518 | #ifdef CONFIG_DEBUG_RT_MUTEXES | |
1519 | lock->magic = NULL; | |
1520 | #endif | |
1521 | } | |
1522 | ||
1523 | EXPORT_SYMBOL_GPL(rt_mutex_destroy); | |
1524 | ||
1525 | /** | |
1526 | * __rt_mutex_init - initialize the rt lock | |
1527 | * | |
1528 | * @lock: the rt lock to be initialized | |
1529 | * | |
1530 | * Initialize the rt lock to unlocked state. | |
1531 | * | |
1532 | * Initializing of a locked rt lock is not allowed | |
1533 | */ | |
1534 | void __rt_mutex_init(struct rt_mutex *lock, const char *name) | |
1535 | { | |
1536 | lock->owner = NULL; | |
d209d74d | 1537 | raw_spin_lock_init(&lock->wait_lock); |
fb00aca4 PZ |
1538 | lock->waiters = RB_ROOT; |
1539 | lock->waiters_leftmost = NULL; | |
23f78d4a IM |
1540 | |
1541 | debug_rt_mutex_init(lock, name); | |
1542 | } | |
1543 | EXPORT_SYMBOL_GPL(__rt_mutex_init); | |
0cdbee99 IM |
1544 | |
1545 | /** | |
1546 | * rt_mutex_init_proxy_locked - initialize and lock a rt_mutex on behalf of a | |
1547 | * proxy owner | |
1548 | * | |
1549 | * @lock: the rt_mutex to be locked | |
1550 | * @proxy_owner:the task to set as owner | |
1551 | * | |
1552 | * No locking. Caller has to do serializing itself | |
1553 | * Special API call for PI-futex support | |
1554 | */ | |
1555 | void rt_mutex_init_proxy_locked(struct rt_mutex *lock, | |
1556 | struct task_struct *proxy_owner) | |
1557 | { | |
1558 | __rt_mutex_init(lock, NULL); | |
9a11b49a | 1559 | debug_rt_mutex_proxy_lock(lock, proxy_owner); |
8161239a | 1560 | rt_mutex_set_owner(lock, proxy_owner); |
0cdbee99 IM |
1561 | rt_mutex_deadlock_account_lock(lock, proxy_owner); |
1562 | } | |
1563 | ||
1564 | /** | |
1565 | * rt_mutex_proxy_unlock - release a lock on behalf of owner | |
1566 | * | |
1567 | * @lock: the rt_mutex to be locked | |
1568 | * | |
1569 | * No locking. Caller has to do serializing itself | |
1570 | * Special API call for PI-futex support | |
1571 | */ | |
1572 | void rt_mutex_proxy_unlock(struct rt_mutex *lock, | |
1573 | struct task_struct *proxy_owner) | |
1574 | { | |
1575 | debug_rt_mutex_proxy_unlock(lock); | |
8161239a | 1576 | rt_mutex_set_owner(lock, NULL); |
0cdbee99 IM |
1577 | rt_mutex_deadlock_account_unlock(proxy_owner); |
1578 | } | |
1579 | ||
8dac456a DH |
1580 | /** |
1581 | * rt_mutex_start_proxy_lock() - Start lock acquisition for another task | |
1582 | * @lock: the rt_mutex to take | |
1583 | * @waiter: the pre-initialized rt_mutex_waiter | |
1584 | * @task: the task to prepare | |
8dac456a DH |
1585 | * |
1586 | * Returns: | |
1587 | * 0 - task blocked on lock | |
1588 | * 1 - acquired the lock for task, caller should wake it up | |
1589 | * <0 - error | |
1590 | * | |
1591 | * Special API call for FUTEX_REQUEUE_PI support. | |
1592 | */ | |
1593 | int rt_mutex_start_proxy_lock(struct rt_mutex *lock, | |
1594 | struct rt_mutex_waiter *waiter, | |
c051b21f | 1595 | struct task_struct *task) |
8dac456a DH |
1596 | { |
1597 | int ret; | |
1598 | ||
d209d74d | 1599 | raw_spin_lock(&lock->wait_lock); |
8dac456a | 1600 | |
8161239a | 1601 | if (try_to_take_rt_mutex(lock, task, NULL)) { |
d209d74d | 1602 | raw_spin_unlock(&lock->wait_lock); |
8dac456a DH |
1603 | return 1; |
1604 | } | |
1605 | ||
3d5c9340 | 1606 | /* We enforce deadlock detection for futexes */ |
8930ed80 TG |
1607 | ret = task_blocks_on_rt_mutex(lock, waiter, task, |
1608 | RT_MUTEX_FULL_CHAINWALK); | |
8dac456a | 1609 | |
8161239a | 1610 | if (ret && !rt_mutex_owner(lock)) { |
8dac456a DH |
1611 | /* |
1612 | * Reset the return value. We might have | |
1613 | * returned with -EDEADLK and the owner | |
1614 | * released the lock while we were walking the | |
1615 | * pi chain. Let the waiter sort it out. | |
1616 | */ | |
1617 | ret = 0; | |
1618 | } | |
8161239a LJ |
1619 | |
1620 | if (unlikely(ret)) | |
1621 | remove_waiter(lock, waiter); | |
1622 | ||
d209d74d | 1623 | raw_spin_unlock(&lock->wait_lock); |
8dac456a DH |
1624 | |
1625 | debug_rt_mutex_print_deadlock(waiter); | |
1626 | ||
1627 | return ret; | |
1628 | } | |
1629 | ||
0cdbee99 IM |
1630 | /** |
1631 | * rt_mutex_next_owner - return the next owner of the lock | |
1632 | * | |
1633 | * @lock: the rt lock query | |
1634 | * | |
1635 | * Returns the next owner of the lock or NULL | |
1636 | * | |
1637 | * Caller has to serialize against other accessors to the lock | |
1638 | * itself. | |
1639 | * | |
1640 | * Special API call for PI-futex support | |
1641 | */ | |
1642 | struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock) | |
1643 | { | |
1644 | if (!rt_mutex_has_waiters(lock)) | |
1645 | return NULL; | |
1646 | ||
1647 | return rt_mutex_top_waiter(lock)->task; | |
1648 | } | |
8dac456a DH |
1649 | |
1650 | /** | |
1651 | * rt_mutex_finish_proxy_lock() - Complete lock acquisition | |
1652 | * @lock: the rt_mutex we were woken on | |
1653 | * @to: the timeout, null if none. hrtimer should already have | |
c051b21f | 1654 | * been started. |
8dac456a | 1655 | * @waiter: the pre-initialized rt_mutex_waiter |
8dac456a DH |
1656 | * |
1657 | * Complete the lock acquisition started our behalf by another thread. | |
1658 | * | |
1659 | * Returns: | |
1660 | * 0 - success | |
c051b21f | 1661 | * <0 - error, one of -EINTR, -ETIMEDOUT |
8dac456a DH |
1662 | * |
1663 | * Special API call for PI-futex requeue support | |
1664 | */ | |
1665 | int rt_mutex_finish_proxy_lock(struct rt_mutex *lock, | |
1666 | struct hrtimer_sleeper *to, | |
c051b21f | 1667 | struct rt_mutex_waiter *waiter) |
8dac456a DH |
1668 | { |
1669 | int ret; | |
1670 | ||
d209d74d | 1671 | raw_spin_lock(&lock->wait_lock); |
8dac456a DH |
1672 | |
1673 | set_current_state(TASK_INTERRUPTIBLE); | |
1674 | ||
afffc6c1 | 1675 | /* sleep on the mutex */ |
8161239a | 1676 | ret = __rt_mutex_slowlock(lock, TASK_INTERRUPTIBLE, to, waiter); |
8dac456a | 1677 | |
8161239a | 1678 | if (unlikely(ret)) |
8dac456a DH |
1679 | remove_waiter(lock, waiter); |
1680 | ||
1681 | /* | |
1682 | * try_to_take_rt_mutex() sets the waiter bit unconditionally. We might | |
1683 | * have to fix that up. | |
1684 | */ | |
1685 | fixup_rt_mutex_waiters(lock); | |
1686 | ||
d209d74d | 1687 | raw_spin_unlock(&lock->wait_lock); |
8dac456a | 1688 | |
8dac456a DH |
1689 | return ret; |
1690 | } |