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 | */ | |
b4abf910 TG |
102 | static inline bool unlock_rt_mutex_safe(struct rt_mutex *lock, |
103 | unsigned long flags) | |
27e35715 TG |
104 | __releases(lock->wait_lock) |
105 | { | |
106 | struct task_struct *owner = rt_mutex_owner(lock); | |
107 | ||
108 | clear_rt_mutex_waiters(lock); | |
b4abf910 | 109 | raw_spin_unlock_irqrestore(&lock->wait_lock, flags); |
27e35715 TG |
110 | /* |
111 | * If a new waiter comes in between the unlock and the cmpxchg | |
112 | * we have two situations: | |
113 | * | |
114 | * unlock(wait_lock); | |
115 | * lock(wait_lock); | |
116 | * cmpxchg(p, owner, 0) == owner | |
117 | * mark_rt_mutex_waiters(lock); | |
118 | * acquire(lock); | |
119 | * or: | |
120 | * | |
121 | * unlock(wait_lock); | |
122 | * lock(wait_lock); | |
123 | * mark_rt_mutex_waiters(lock); | |
124 | * | |
125 | * cmpxchg(p, owner, 0) != owner | |
126 | * enqueue_waiter(); | |
127 | * unlock(wait_lock); | |
128 | * lock(wait_lock); | |
129 | * wake waiter(); | |
130 | * unlock(wait_lock); | |
131 | * lock(wait_lock); | |
132 | * acquire(lock); | |
133 | */ | |
700318d1 | 134 | return rt_mutex_cmpxchg_release(lock, owner, NULL); |
27e35715 TG |
135 | } |
136 | ||
bd197234 | 137 | #else |
700318d1 DB |
138 | # define rt_mutex_cmpxchg_relaxed(l,c,n) (0) |
139 | # define rt_mutex_cmpxchg_acquire(l,c,n) (0) | |
140 | # define rt_mutex_cmpxchg_release(l,c,n) (0) | |
141 | ||
bd197234 TG |
142 | static inline void mark_rt_mutex_waiters(struct rt_mutex *lock) |
143 | { | |
144 | lock->owner = (struct task_struct *) | |
145 | ((unsigned long)lock->owner | RT_MUTEX_HAS_WAITERS); | |
146 | } | |
27e35715 TG |
147 | |
148 | /* | |
149 | * Simple slow path only version: lock->owner is protected by lock->wait_lock. | |
150 | */ | |
b4abf910 TG |
151 | static inline bool unlock_rt_mutex_safe(struct rt_mutex *lock, |
152 | unsigned long flags) | |
27e35715 TG |
153 | __releases(lock->wait_lock) |
154 | { | |
155 | lock->owner = NULL; | |
b4abf910 | 156 | raw_spin_unlock_irqrestore(&lock->wait_lock, flags); |
27e35715 TG |
157 | return true; |
158 | } | |
bd197234 TG |
159 | #endif |
160 | ||
fb00aca4 PZ |
161 | static inline int |
162 | rt_mutex_waiter_less(struct rt_mutex_waiter *left, | |
163 | struct rt_mutex_waiter *right) | |
164 | { | |
2d3d891d | 165 | if (left->prio < right->prio) |
fb00aca4 PZ |
166 | return 1; |
167 | ||
168 | /* | |
2d3d891d DF |
169 | * If both waiters have dl_prio(), we check the deadlines of the |
170 | * associated tasks. | |
171 | * If left waiter has a dl_prio(), and we didn't return 1 above, | |
172 | * then right waiter has a dl_prio() too. | |
fb00aca4 | 173 | */ |
2d3d891d | 174 | if (dl_prio(left->prio)) |
f5240575 JL |
175 | return dl_time_before(left->task->dl.deadline, |
176 | right->task->dl.deadline); | |
fb00aca4 PZ |
177 | |
178 | return 0; | |
179 | } | |
180 | ||
181 | static void | |
182 | rt_mutex_enqueue(struct rt_mutex *lock, struct rt_mutex_waiter *waiter) | |
183 | { | |
184 | struct rb_node **link = &lock->waiters.rb_node; | |
185 | struct rb_node *parent = NULL; | |
186 | struct rt_mutex_waiter *entry; | |
187 | int leftmost = 1; | |
188 | ||
189 | while (*link) { | |
190 | parent = *link; | |
191 | entry = rb_entry(parent, struct rt_mutex_waiter, tree_entry); | |
192 | if (rt_mutex_waiter_less(waiter, entry)) { | |
193 | link = &parent->rb_left; | |
194 | } else { | |
195 | link = &parent->rb_right; | |
196 | leftmost = 0; | |
197 | } | |
198 | } | |
199 | ||
200 | if (leftmost) | |
201 | lock->waiters_leftmost = &waiter->tree_entry; | |
202 | ||
203 | rb_link_node(&waiter->tree_entry, parent, link); | |
204 | rb_insert_color(&waiter->tree_entry, &lock->waiters); | |
205 | } | |
206 | ||
207 | static void | |
208 | rt_mutex_dequeue(struct rt_mutex *lock, struct rt_mutex_waiter *waiter) | |
209 | { | |
210 | if (RB_EMPTY_NODE(&waiter->tree_entry)) | |
211 | return; | |
212 | ||
213 | if (lock->waiters_leftmost == &waiter->tree_entry) | |
214 | lock->waiters_leftmost = rb_next(&waiter->tree_entry); | |
215 | ||
216 | rb_erase(&waiter->tree_entry, &lock->waiters); | |
217 | RB_CLEAR_NODE(&waiter->tree_entry); | |
218 | } | |
219 | ||
220 | static void | |
221 | rt_mutex_enqueue_pi(struct task_struct *task, struct rt_mutex_waiter *waiter) | |
222 | { | |
223 | struct rb_node **link = &task->pi_waiters.rb_node; | |
224 | struct rb_node *parent = NULL; | |
225 | struct rt_mutex_waiter *entry; | |
226 | int leftmost = 1; | |
227 | ||
228 | while (*link) { | |
229 | parent = *link; | |
230 | entry = rb_entry(parent, struct rt_mutex_waiter, pi_tree_entry); | |
231 | if (rt_mutex_waiter_less(waiter, entry)) { | |
232 | link = &parent->rb_left; | |
233 | } else { | |
234 | link = &parent->rb_right; | |
235 | leftmost = 0; | |
236 | } | |
237 | } | |
238 | ||
239 | if (leftmost) | |
240 | task->pi_waiters_leftmost = &waiter->pi_tree_entry; | |
241 | ||
242 | rb_link_node(&waiter->pi_tree_entry, parent, link); | |
243 | rb_insert_color(&waiter->pi_tree_entry, &task->pi_waiters); | |
244 | } | |
245 | ||
246 | static void | |
247 | rt_mutex_dequeue_pi(struct task_struct *task, struct rt_mutex_waiter *waiter) | |
248 | { | |
249 | if (RB_EMPTY_NODE(&waiter->pi_tree_entry)) | |
250 | return; | |
251 | ||
252 | if (task->pi_waiters_leftmost == &waiter->pi_tree_entry) | |
253 | task->pi_waiters_leftmost = rb_next(&waiter->pi_tree_entry); | |
254 | ||
255 | rb_erase(&waiter->pi_tree_entry, &task->pi_waiters); | |
256 | RB_CLEAR_NODE(&waiter->pi_tree_entry); | |
257 | } | |
258 | ||
23f78d4a | 259 | /* |
fb00aca4 | 260 | * Calculate task priority from the waiter tree priority |
23f78d4a | 261 | * |
fb00aca4 | 262 | * Return task->normal_prio when the waiter tree is empty or when |
23f78d4a IM |
263 | * the waiter is not allowed to do priority boosting |
264 | */ | |
265 | int rt_mutex_getprio(struct task_struct *task) | |
266 | { | |
267 | if (likely(!task_has_pi_waiters(task))) | |
268 | return task->normal_prio; | |
269 | ||
2d3d891d | 270 | return min(task_top_pi_waiter(task)->prio, |
23f78d4a IM |
271 | task->normal_prio); |
272 | } | |
273 | ||
2d3d891d DF |
274 | struct task_struct *rt_mutex_get_top_task(struct task_struct *task) |
275 | { | |
276 | if (likely(!task_has_pi_waiters(task))) | |
277 | return NULL; | |
278 | ||
279 | return task_top_pi_waiter(task)->task; | |
280 | } | |
281 | ||
c365c292 | 282 | /* |
0782e63b TG |
283 | * Called by sched_setscheduler() to get the priority which will be |
284 | * effective after the change. | |
c365c292 | 285 | */ |
0782e63b | 286 | int rt_mutex_get_effective_prio(struct task_struct *task, int newprio) |
c365c292 TG |
287 | { |
288 | if (!task_has_pi_waiters(task)) | |
0782e63b | 289 | return newprio; |
c365c292 | 290 | |
0782e63b TG |
291 | if (task_top_pi_waiter(task)->task->prio <= newprio) |
292 | return task_top_pi_waiter(task)->task->prio; | |
293 | return newprio; | |
c365c292 TG |
294 | } |
295 | ||
23f78d4a IM |
296 | /* |
297 | * Adjust the priority of a task, after its pi_waiters got modified. | |
298 | * | |
299 | * This can be both boosting and unboosting. task->pi_lock must be held. | |
300 | */ | |
bd197234 | 301 | static void __rt_mutex_adjust_prio(struct task_struct *task) |
23f78d4a IM |
302 | { |
303 | int prio = rt_mutex_getprio(task); | |
304 | ||
2d3d891d | 305 | if (task->prio != prio || dl_prio(prio)) |
23f78d4a IM |
306 | rt_mutex_setprio(task, prio); |
307 | } | |
308 | ||
309 | /* | |
310 | * Adjust task priority (undo boosting). Called from the exit path of | |
311 | * rt_mutex_slowunlock() and rt_mutex_slowlock(). | |
312 | * | |
313 | * (Note: We do this outside of the protection of lock->wait_lock to | |
314 | * allow the lock to be taken while or before we readjust the priority | |
315 | * of task. We do not use the spin_xx_mutex() variants here as we are | |
316 | * outside of the debug path.) | |
317 | */ | |
802ab58d | 318 | void rt_mutex_adjust_prio(struct task_struct *task) |
23f78d4a IM |
319 | { |
320 | unsigned long flags; | |
321 | ||
1d615482 | 322 | raw_spin_lock_irqsave(&task->pi_lock, flags); |
23f78d4a | 323 | __rt_mutex_adjust_prio(task); |
1d615482 | 324 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
23f78d4a IM |
325 | } |
326 | ||
8930ed80 TG |
327 | /* |
328 | * Deadlock detection is conditional: | |
329 | * | |
330 | * If CONFIG_DEBUG_RT_MUTEXES=n, deadlock detection is only conducted | |
331 | * if the detect argument is == RT_MUTEX_FULL_CHAINWALK. | |
332 | * | |
333 | * If CONFIG_DEBUG_RT_MUTEXES=y, deadlock detection is always | |
334 | * conducted independent of the detect argument. | |
335 | * | |
336 | * If the waiter argument is NULL this indicates the deboost path and | |
337 | * deadlock detection is disabled independent of the detect argument | |
338 | * and the config settings. | |
339 | */ | |
340 | static bool rt_mutex_cond_detect_deadlock(struct rt_mutex_waiter *waiter, | |
341 | enum rtmutex_chainwalk chwalk) | |
342 | { | |
343 | /* | |
344 | * This is just a wrapper function for the following call, | |
345 | * because debug_rt_mutex_detect_deadlock() smells like a magic | |
346 | * debug feature and I wanted to keep the cond function in the | |
347 | * main source file along with the comments instead of having | |
348 | * two of the same in the headers. | |
349 | */ | |
350 | return debug_rt_mutex_detect_deadlock(waiter, chwalk); | |
351 | } | |
352 | ||
23f78d4a IM |
353 | /* |
354 | * Max number of times we'll walk the boosting chain: | |
355 | */ | |
356 | int max_lock_depth = 1024; | |
357 | ||
82084984 TG |
358 | static inline struct rt_mutex *task_blocked_on_lock(struct task_struct *p) |
359 | { | |
360 | return p->pi_blocked_on ? p->pi_blocked_on->lock : NULL; | |
361 | } | |
362 | ||
23f78d4a IM |
363 | /* |
364 | * Adjust the priority chain. Also used for deadlock detection. | |
365 | * Decreases task's usage by one - may thus free the task. | |
0c106173 | 366 | * |
82084984 TG |
367 | * @task: the task owning the mutex (owner) for which a chain walk is |
368 | * probably needed | |
e6beaa36 | 369 | * @chwalk: do we have to carry out deadlock detection? |
82084984 TG |
370 | * @orig_lock: the mutex (can be NULL if we are walking the chain to recheck |
371 | * things for a task that has just got its priority adjusted, and | |
372 | * is waiting on a mutex) | |
373 | * @next_lock: the mutex on which the owner of @orig_lock was blocked before | |
374 | * we dropped its pi_lock. Is never dereferenced, only used for | |
375 | * comparison to detect lock chain changes. | |
0c106173 | 376 | * @orig_waiter: rt_mutex_waiter struct for the task that has just donated |
82084984 TG |
377 | * its priority to the mutex owner (can be NULL in the case |
378 | * depicted above or if the top waiter is gone away and we are | |
379 | * actually deboosting the owner) | |
380 | * @top_task: the current top waiter | |
0c106173 | 381 | * |
23f78d4a | 382 | * Returns 0 or -EDEADLK. |
3eb65aea TG |
383 | * |
384 | * Chain walk basics and protection scope | |
385 | * | |
386 | * [R] refcount on task | |
387 | * [P] task->pi_lock held | |
388 | * [L] rtmutex->wait_lock held | |
389 | * | |
390 | * Step Description Protected by | |
391 | * function arguments: | |
392 | * @task [R] | |
393 | * @orig_lock if != NULL @top_task is blocked on it | |
394 | * @next_lock Unprotected. Cannot be | |
395 | * dereferenced. Only used for | |
396 | * comparison. | |
397 | * @orig_waiter if != NULL @top_task is blocked on it | |
398 | * @top_task current, or in case of proxy | |
399 | * locking protected by calling | |
400 | * code | |
401 | * again: | |
402 | * loop_sanity_check(); | |
403 | * retry: | |
404 | * [1] lock(task->pi_lock); [R] acquire [P] | |
405 | * [2] waiter = task->pi_blocked_on; [P] | |
406 | * [3] check_exit_conditions_1(); [P] | |
407 | * [4] lock = waiter->lock; [P] | |
408 | * [5] if (!try_lock(lock->wait_lock)) { [P] try to acquire [L] | |
409 | * unlock(task->pi_lock); release [P] | |
410 | * goto retry; | |
411 | * } | |
412 | * [6] check_exit_conditions_2(); [P] + [L] | |
413 | * [7] requeue_lock_waiter(lock, waiter); [P] + [L] | |
414 | * [8] unlock(task->pi_lock); release [P] | |
415 | * put_task_struct(task); release [R] | |
416 | * [9] check_exit_conditions_3(); [L] | |
417 | * [10] task = owner(lock); [L] | |
418 | * get_task_struct(task); [L] acquire [R] | |
419 | * lock(task->pi_lock); [L] acquire [P] | |
420 | * [11] requeue_pi_waiter(tsk, waiters(lock));[P] + [L] | |
421 | * [12] check_exit_conditions_4(); [P] + [L] | |
422 | * [13] unlock(task->pi_lock); release [P] | |
423 | * unlock(lock->wait_lock); release [L] | |
424 | * goto again; | |
23f78d4a | 425 | */ |
bd197234 | 426 | static int rt_mutex_adjust_prio_chain(struct task_struct *task, |
8930ed80 | 427 | enum rtmutex_chainwalk chwalk, |
bd197234 | 428 | struct rt_mutex *orig_lock, |
82084984 | 429 | struct rt_mutex *next_lock, |
bd197234 TG |
430 | struct rt_mutex_waiter *orig_waiter, |
431 | struct task_struct *top_task) | |
23f78d4a | 432 | { |
23f78d4a | 433 | struct rt_mutex_waiter *waiter, *top_waiter = orig_waiter; |
a57594a1 | 434 | struct rt_mutex_waiter *prerequeue_top_waiter; |
8930ed80 | 435 | int ret = 0, depth = 0; |
a57594a1 | 436 | struct rt_mutex *lock; |
8930ed80 | 437 | bool detect_deadlock; |
67792e2c | 438 | bool requeue = true; |
23f78d4a | 439 | |
8930ed80 | 440 | detect_deadlock = rt_mutex_cond_detect_deadlock(orig_waiter, chwalk); |
23f78d4a IM |
441 | |
442 | /* | |
443 | * The (de)boosting is a step by step approach with a lot of | |
444 | * pitfalls. We want this to be preemptible and we want hold a | |
445 | * maximum of two locks per step. So we have to check | |
446 | * carefully whether things change under us. | |
447 | */ | |
448 | again: | |
3eb65aea TG |
449 | /* |
450 | * We limit the lock chain length for each invocation. | |
451 | */ | |
23f78d4a IM |
452 | if (++depth > max_lock_depth) { |
453 | static int prev_max; | |
454 | ||
455 | /* | |
456 | * Print this only once. If the admin changes the limit, | |
457 | * print a new message when reaching the limit again. | |
458 | */ | |
459 | if (prev_max != max_lock_depth) { | |
460 | prev_max = max_lock_depth; | |
461 | printk(KERN_WARNING "Maximum lock depth %d reached " | |
462 | "task: %s (%d)\n", max_lock_depth, | |
ba25f9dc | 463 | top_task->comm, task_pid_nr(top_task)); |
23f78d4a IM |
464 | } |
465 | put_task_struct(task); | |
466 | ||
3d5c9340 | 467 | return -EDEADLK; |
23f78d4a | 468 | } |
3eb65aea TG |
469 | |
470 | /* | |
471 | * We are fully preemptible here and only hold the refcount on | |
472 | * @task. So everything can have changed under us since the | |
473 | * caller or our own code below (goto retry/again) dropped all | |
474 | * locks. | |
475 | */ | |
23f78d4a IM |
476 | retry: |
477 | /* | |
3eb65aea | 478 | * [1] Task cannot go away as we did a get_task() before ! |
23f78d4a | 479 | */ |
b4abf910 | 480 | raw_spin_lock_irq(&task->pi_lock); |
23f78d4a | 481 | |
3eb65aea TG |
482 | /* |
483 | * [2] Get the waiter on which @task is blocked on. | |
484 | */ | |
23f78d4a | 485 | waiter = task->pi_blocked_on; |
3eb65aea TG |
486 | |
487 | /* | |
488 | * [3] check_exit_conditions_1() protected by task->pi_lock. | |
489 | */ | |
490 | ||
23f78d4a IM |
491 | /* |
492 | * Check whether the end of the boosting chain has been | |
493 | * reached or the state of the chain has changed while we | |
494 | * dropped the locks. | |
495 | */ | |
8161239a | 496 | if (!waiter) |
23f78d4a IM |
497 | goto out_unlock_pi; |
498 | ||
1a539a87 TG |
499 | /* |
500 | * Check the orig_waiter state. After we dropped the locks, | |
8161239a | 501 | * the previous owner of the lock might have released the lock. |
1a539a87 | 502 | */ |
8161239a | 503 | if (orig_waiter && !rt_mutex_owner(orig_lock)) |
1a539a87 TG |
504 | goto out_unlock_pi; |
505 | ||
82084984 TG |
506 | /* |
507 | * We dropped all locks after taking a refcount on @task, so | |
508 | * the task might have moved on in the lock chain or even left | |
509 | * the chain completely and blocks now on an unrelated lock or | |
510 | * on @orig_lock. | |
511 | * | |
512 | * We stored the lock on which @task was blocked in @next_lock, | |
513 | * so we can detect the chain change. | |
514 | */ | |
515 | if (next_lock != waiter->lock) | |
516 | goto out_unlock_pi; | |
517 | ||
1a539a87 TG |
518 | /* |
519 | * Drop out, when the task has no waiters. Note, | |
520 | * top_waiter can be NULL, when we are in the deboosting | |
521 | * mode! | |
522 | */ | |
397335f0 TG |
523 | if (top_waiter) { |
524 | if (!task_has_pi_waiters(task)) | |
525 | goto out_unlock_pi; | |
526 | /* | |
527 | * If deadlock detection is off, we stop here if we | |
67792e2c TG |
528 | * are not the top pi waiter of the task. If deadlock |
529 | * detection is enabled we continue, but stop the | |
530 | * requeueing in the chain walk. | |
397335f0 | 531 | */ |
67792e2c TG |
532 | if (top_waiter != task_top_pi_waiter(task)) { |
533 | if (!detect_deadlock) | |
534 | goto out_unlock_pi; | |
535 | else | |
536 | requeue = false; | |
537 | } | |
397335f0 | 538 | } |
23f78d4a IM |
539 | |
540 | /* | |
67792e2c TG |
541 | * If the waiter priority is the same as the task priority |
542 | * then there is no further priority adjustment necessary. If | |
543 | * deadlock detection is off, we stop the chain walk. If its | |
544 | * enabled we continue, but stop the requeueing in the chain | |
545 | * walk. | |
23f78d4a | 546 | */ |
67792e2c TG |
547 | if (waiter->prio == task->prio) { |
548 | if (!detect_deadlock) | |
549 | goto out_unlock_pi; | |
550 | else | |
551 | requeue = false; | |
552 | } | |
23f78d4a | 553 | |
3eb65aea TG |
554 | /* |
555 | * [4] Get the next lock | |
556 | */ | |
23f78d4a | 557 | lock = waiter->lock; |
3eb65aea TG |
558 | /* |
559 | * [5] We need to trylock here as we are holding task->pi_lock, | |
560 | * which is the reverse lock order versus the other rtmutex | |
561 | * operations. | |
562 | */ | |
d209d74d | 563 | if (!raw_spin_trylock(&lock->wait_lock)) { |
b4abf910 | 564 | raw_spin_unlock_irq(&task->pi_lock); |
23f78d4a IM |
565 | cpu_relax(); |
566 | goto retry; | |
567 | } | |
568 | ||
397335f0 | 569 | /* |
3eb65aea TG |
570 | * [6] check_exit_conditions_2() protected by task->pi_lock and |
571 | * lock->wait_lock. | |
572 | * | |
397335f0 TG |
573 | * Deadlock detection. If the lock is the same as the original |
574 | * lock which caused us to walk the lock chain or if the | |
575 | * current lock is owned by the task which initiated the chain | |
576 | * walk, we detected a deadlock. | |
577 | */ | |
95e02ca9 | 578 | if (lock == orig_lock || rt_mutex_owner(lock) == top_task) { |
8930ed80 | 579 | debug_rt_mutex_deadlock(chwalk, orig_waiter, lock); |
d209d74d | 580 | raw_spin_unlock(&lock->wait_lock); |
3d5c9340 | 581 | ret = -EDEADLK; |
23f78d4a IM |
582 | goto out_unlock_pi; |
583 | } | |
584 | ||
67792e2c TG |
585 | /* |
586 | * If we just follow the lock chain for deadlock detection, no | |
587 | * need to do all the requeue operations. To avoid a truckload | |
588 | * of conditionals around the various places below, just do the | |
589 | * minimum chain walk checks. | |
590 | */ | |
591 | if (!requeue) { | |
592 | /* | |
593 | * No requeue[7] here. Just release @task [8] | |
594 | */ | |
b4abf910 | 595 | raw_spin_unlock(&task->pi_lock); |
67792e2c TG |
596 | put_task_struct(task); |
597 | ||
598 | /* | |
599 | * [9] check_exit_conditions_3 protected by lock->wait_lock. | |
600 | * If there is no owner of the lock, end of chain. | |
601 | */ | |
602 | if (!rt_mutex_owner(lock)) { | |
b4abf910 | 603 | raw_spin_unlock_irq(&lock->wait_lock); |
67792e2c TG |
604 | return 0; |
605 | } | |
606 | ||
607 | /* [10] Grab the next task, i.e. owner of @lock */ | |
608 | task = rt_mutex_owner(lock); | |
609 | get_task_struct(task); | |
b4abf910 | 610 | raw_spin_lock(&task->pi_lock); |
67792e2c TG |
611 | |
612 | /* | |
613 | * No requeue [11] here. We just do deadlock detection. | |
614 | * | |
615 | * [12] Store whether owner is blocked | |
616 | * itself. Decision is made after dropping the locks | |
617 | */ | |
618 | next_lock = task_blocked_on_lock(task); | |
619 | /* | |
620 | * Get the top waiter for the next iteration | |
621 | */ | |
622 | top_waiter = rt_mutex_top_waiter(lock); | |
623 | ||
624 | /* [13] Drop locks */ | |
b4abf910 TG |
625 | raw_spin_unlock(&task->pi_lock); |
626 | raw_spin_unlock_irq(&lock->wait_lock); | |
67792e2c TG |
627 | |
628 | /* If owner is not blocked, end of chain. */ | |
629 | if (!next_lock) | |
630 | goto out_put_task; | |
631 | goto again; | |
632 | } | |
633 | ||
a57594a1 TG |
634 | /* |
635 | * Store the current top waiter before doing the requeue | |
636 | * operation on @lock. We need it for the boost/deboost | |
637 | * decision below. | |
638 | */ | |
639 | prerequeue_top_waiter = rt_mutex_top_waiter(lock); | |
23f78d4a | 640 | |
9f40a51a | 641 | /* [7] Requeue the waiter in the lock waiter tree. */ |
fb00aca4 | 642 | rt_mutex_dequeue(lock, waiter); |
2d3d891d | 643 | waiter->prio = task->prio; |
fb00aca4 | 644 | rt_mutex_enqueue(lock, waiter); |
23f78d4a | 645 | |
3eb65aea | 646 | /* [8] Release the task */ |
b4abf910 | 647 | raw_spin_unlock(&task->pi_lock); |
2ffa5a5c TG |
648 | put_task_struct(task); |
649 | ||
a57594a1 | 650 | /* |
3eb65aea TG |
651 | * [9] check_exit_conditions_3 protected by lock->wait_lock. |
652 | * | |
a57594a1 TG |
653 | * We must abort the chain walk if there is no lock owner even |
654 | * in the dead lock detection case, as we have nothing to | |
655 | * follow here. This is the end of the chain we are walking. | |
656 | */ | |
8161239a LJ |
657 | if (!rt_mutex_owner(lock)) { |
658 | /* | |
3eb65aea TG |
659 | * If the requeue [7] above changed the top waiter, |
660 | * then we need to wake the new top waiter up to try | |
661 | * to get the lock. | |
8161239a | 662 | */ |
a57594a1 | 663 | if (prerequeue_top_waiter != rt_mutex_top_waiter(lock)) |
8161239a | 664 | wake_up_process(rt_mutex_top_waiter(lock)->task); |
b4abf910 | 665 | raw_spin_unlock_irq(&lock->wait_lock); |
2ffa5a5c | 666 | return 0; |
8161239a | 667 | } |
23f78d4a | 668 | |
3eb65aea | 669 | /* [10] Grab the next task, i.e. the owner of @lock */ |
23f78d4a | 670 | task = rt_mutex_owner(lock); |
db630637 | 671 | get_task_struct(task); |
b4abf910 | 672 | raw_spin_lock(&task->pi_lock); |
23f78d4a | 673 | |
3eb65aea | 674 | /* [11] requeue the pi waiters if necessary */ |
23f78d4a | 675 | if (waiter == rt_mutex_top_waiter(lock)) { |
a57594a1 TG |
676 | /* |
677 | * The waiter became the new top (highest priority) | |
678 | * waiter on the lock. Replace the previous top waiter | |
9f40a51a | 679 | * in the owner tasks pi waiters tree with this waiter |
a57594a1 TG |
680 | * and adjust the priority of the owner. |
681 | */ | |
682 | rt_mutex_dequeue_pi(task, prerequeue_top_waiter); | |
fb00aca4 | 683 | rt_mutex_enqueue_pi(task, waiter); |
23f78d4a IM |
684 | __rt_mutex_adjust_prio(task); |
685 | ||
a57594a1 TG |
686 | } else if (prerequeue_top_waiter == waiter) { |
687 | /* | |
688 | * The waiter was the top waiter on the lock, but is | |
689 | * no longer the top prority waiter. Replace waiter in | |
9f40a51a | 690 | * the owner tasks pi waiters tree with the new top |
a57594a1 TG |
691 | * (highest priority) waiter and adjust the priority |
692 | * of the owner. | |
693 | * The new top waiter is stored in @waiter so that | |
694 | * @waiter == @top_waiter evaluates to true below and | |
695 | * we continue to deboost the rest of the chain. | |
696 | */ | |
fb00aca4 | 697 | rt_mutex_dequeue_pi(task, waiter); |
23f78d4a | 698 | waiter = rt_mutex_top_waiter(lock); |
fb00aca4 | 699 | rt_mutex_enqueue_pi(task, waiter); |
23f78d4a | 700 | __rt_mutex_adjust_prio(task); |
a57594a1 TG |
701 | } else { |
702 | /* | |
703 | * Nothing changed. No need to do any priority | |
704 | * adjustment. | |
705 | */ | |
23f78d4a IM |
706 | } |
707 | ||
82084984 | 708 | /* |
3eb65aea TG |
709 | * [12] check_exit_conditions_4() protected by task->pi_lock |
710 | * and lock->wait_lock. The actual decisions are made after we | |
711 | * dropped the locks. | |
712 | * | |
82084984 TG |
713 | * Check whether the task which owns the current lock is pi |
714 | * blocked itself. If yes we store a pointer to the lock for | |
715 | * the lock chain change detection above. After we dropped | |
716 | * task->pi_lock next_lock cannot be dereferenced anymore. | |
717 | */ | |
718 | next_lock = task_blocked_on_lock(task); | |
a57594a1 TG |
719 | /* |
720 | * Store the top waiter of @lock for the end of chain walk | |
721 | * decision below. | |
722 | */ | |
23f78d4a | 723 | top_waiter = rt_mutex_top_waiter(lock); |
3eb65aea TG |
724 | |
725 | /* [13] Drop the locks */ | |
b4abf910 TG |
726 | raw_spin_unlock(&task->pi_lock); |
727 | raw_spin_unlock_irq(&lock->wait_lock); | |
23f78d4a | 728 | |
82084984 | 729 | /* |
3eb65aea TG |
730 | * Make the actual exit decisions [12], based on the stored |
731 | * values. | |
732 | * | |
82084984 TG |
733 | * We reached the end of the lock chain. Stop right here. No |
734 | * point to go back just to figure that out. | |
735 | */ | |
736 | if (!next_lock) | |
737 | goto out_put_task; | |
738 | ||
a57594a1 TG |
739 | /* |
740 | * If the current waiter is not the top waiter on the lock, | |
741 | * then we can stop the chain walk here if we are not in full | |
742 | * deadlock detection mode. | |
743 | */ | |
23f78d4a IM |
744 | if (!detect_deadlock && waiter != top_waiter) |
745 | goto out_put_task; | |
746 | ||
747 | goto again; | |
748 | ||
749 | out_unlock_pi: | |
b4abf910 | 750 | raw_spin_unlock_irq(&task->pi_lock); |
23f78d4a IM |
751 | out_put_task: |
752 | put_task_struct(task); | |
36c8b586 | 753 | |
23f78d4a IM |
754 | return ret; |
755 | } | |
756 | ||
23f78d4a IM |
757 | /* |
758 | * Try to take an rt-mutex | |
759 | * | |
b4abf910 | 760 | * Must be called with lock->wait_lock held and interrupts disabled |
8161239a | 761 | * |
358c331f TG |
762 | * @lock: The lock to be acquired. |
763 | * @task: The task which wants to acquire the lock | |
9f40a51a | 764 | * @waiter: The waiter that is queued to the lock's wait tree if the |
358c331f | 765 | * callsite called task_blocked_on_lock(), otherwise NULL |
23f78d4a | 766 | */ |
8161239a | 767 | static int try_to_take_rt_mutex(struct rt_mutex *lock, struct task_struct *task, |
358c331f | 768 | struct rt_mutex_waiter *waiter) |
23f78d4a IM |
769 | { |
770 | /* | |
358c331f TG |
771 | * Before testing whether we can acquire @lock, we set the |
772 | * RT_MUTEX_HAS_WAITERS bit in @lock->owner. This forces all | |
773 | * other tasks which try to modify @lock into the slow path | |
774 | * and they serialize on @lock->wait_lock. | |
23f78d4a | 775 | * |
358c331f TG |
776 | * The RT_MUTEX_HAS_WAITERS bit can have a transitional state |
777 | * as explained at the top of this file if and only if: | |
23f78d4a | 778 | * |
358c331f TG |
779 | * - There is a lock owner. The caller must fixup the |
780 | * transient state if it does a trylock or leaves the lock | |
781 | * function due to a signal or timeout. | |
782 | * | |
783 | * - @task acquires the lock and there are no other | |
784 | * waiters. This is undone in rt_mutex_set_owner(@task) at | |
785 | * the end of this function. | |
23f78d4a IM |
786 | */ |
787 | mark_rt_mutex_waiters(lock); | |
788 | ||
358c331f TG |
789 | /* |
790 | * If @lock has an owner, give up. | |
791 | */ | |
8161239a | 792 | if (rt_mutex_owner(lock)) |
23f78d4a IM |
793 | return 0; |
794 | ||
8161239a | 795 | /* |
358c331f | 796 | * If @waiter != NULL, @task has already enqueued the waiter |
9f40a51a | 797 | * into @lock waiter tree. If @waiter == NULL then this is a |
358c331f | 798 | * trylock attempt. |
8161239a | 799 | */ |
358c331f TG |
800 | if (waiter) { |
801 | /* | |
802 | * If waiter is not the highest priority waiter of | |
803 | * @lock, give up. | |
804 | */ | |
805 | if (waiter != rt_mutex_top_waiter(lock)) | |
806 | return 0; | |
8161239a | 807 | |
358c331f TG |
808 | /* |
809 | * We can acquire the lock. Remove the waiter from the | |
9f40a51a | 810 | * lock waiters tree. |
358c331f TG |
811 | */ |
812 | rt_mutex_dequeue(lock, waiter); | |
8161239a | 813 | |
358c331f | 814 | } else { |
8161239a | 815 | /* |
358c331f TG |
816 | * If the lock has waiters already we check whether @task is |
817 | * eligible to take over the lock. | |
818 | * | |
819 | * If there are no other waiters, @task can acquire | |
820 | * the lock. @task->pi_blocked_on is NULL, so it does | |
821 | * not need to be dequeued. | |
8161239a LJ |
822 | */ |
823 | if (rt_mutex_has_waiters(lock)) { | |
358c331f TG |
824 | /* |
825 | * If @task->prio is greater than or equal to | |
826 | * the top waiter priority (kernel view), | |
827 | * @task lost. | |
828 | */ | |
829 | if (task->prio >= rt_mutex_top_waiter(lock)->prio) | |
830 | return 0; | |
831 | ||
832 | /* | |
833 | * The current top waiter stays enqueued. We | |
834 | * don't have to change anything in the lock | |
835 | * waiters order. | |
836 | */ | |
837 | } else { | |
838 | /* | |
839 | * No waiters. Take the lock without the | |
840 | * pi_lock dance.@task->pi_blocked_on is NULL | |
841 | * and we have no waiters to enqueue in @task | |
9f40a51a | 842 | * pi waiters tree. |
358c331f TG |
843 | */ |
844 | goto takeit; | |
8161239a | 845 | } |
8161239a LJ |
846 | } |
847 | ||
358c331f TG |
848 | /* |
849 | * Clear @task->pi_blocked_on. Requires protection by | |
850 | * @task->pi_lock. Redundant operation for the @waiter == NULL | |
851 | * case, but conditionals are more expensive than a redundant | |
852 | * store. | |
853 | */ | |
b4abf910 | 854 | raw_spin_lock(&task->pi_lock); |
358c331f TG |
855 | task->pi_blocked_on = NULL; |
856 | /* | |
857 | * Finish the lock acquisition. @task is the new owner. If | |
858 | * other waiters exist we have to insert the highest priority | |
9f40a51a | 859 | * waiter into @task->pi_waiters tree. |
358c331f TG |
860 | */ |
861 | if (rt_mutex_has_waiters(lock)) | |
862 | rt_mutex_enqueue_pi(task, rt_mutex_top_waiter(lock)); | |
b4abf910 | 863 | raw_spin_unlock(&task->pi_lock); |
358c331f TG |
864 | |
865 | takeit: | |
23f78d4a | 866 | /* We got the lock. */ |
9a11b49a | 867 | debug_rt_mutex_lock(lock); |
23f78d4a | 868 | |
358c331f TG |
869 | /* |
870 | * This either preserves the RT_MUTEX_HAS_WAITERS bit if there | |
871 | * are still waiters or clears it. | |
872 | */ | |
8161239a | 873 | rt_mutex_set_owner(lock, task); |
23f78d4a | 874 | |
8161239a | 875 | rt_mutex_deadlock_account_lock(lock, task); |
23f78d4a IM |
876 | |
877 | return 1; | |
878 | } | |
879 | ||
880 | /* | |
881 | * Task blocks on lock. | |
882 | * | |
883 | * Prepare waiter and propagate pi chain | |
884 | * | |
b4abf910 | 885 | * This must be called with lock->wait_lock held and interrupts disabled |
23f78d4a IM |
886 | */ |
887 | static int task_blocks_on_rt_mutex(struct rt_mutex *lock, | |
888 | struct rt_mutex_waiter *waiter, | |
8dac456a | 889 | struct task_struct *task, |
8930ed80 | 890 | enum rtmutex_chainwalk chwalk) |
23f78d4a | 891 | { |
36c8b586 | 892 | struct task_struct *owner = rt_mutex_owner(lock); |
23f78d4a | 893 | struct rt_mutex_waiter *top_waiter = waiter; |
82084984 | 894 | struct rt_mutex *next_lock; |
db630637 | 895 | int chain_walk = 0, res; |
23f78d4a | 896 | |
397335f0 TG |
897 | /* |
898 | * Early deadlock detection. We really don't want the task to | |
899 | * enqueue on itself just to untangle the mess later. It's not | |
900 | * only an optimization. We drop the locks, so another waiter | |
901 | * can come in before the chain walk detects the deadlock. So | |
902 | * the other will detect the deadlock and return -EDEADLOCK, | |
903 | * which is wrong, as the other waiter is not in a deadlock | |
904 | * situation. | |
905 | */ | |
3d5c9340 | 906 | if (owner == task) |
397335f0 TG |
907 | return -EDEADLK; |
908 | ||
b4abf910 | 909 | raw_spin_lock(&task->pi_lock); |
8dac456a DH |
910 | __rt_mutex_adjust_prio(task); |
911 | waiter->task = task; | |
23f78d4a | 912 | waiter->lock = lock; |
2d3d891d | 913 | waiter->prio = task->prio; |
23f78d4a IM |
914 | |
915 | /* Get the top priority waiter on the lock */ | |
916 | if (rt_mutex_has_waiters(lock)) | |
917 | top_waiter = rt_mutex_top_waiter(lock); | |
fb00aca4 | 918 | rt_mutex_enqueue(lock, waiter); |
23f78d4a | 919 | |
8dac456a | 920 | task->pi_blocked_on = waiter; |
23f78d4a | 921 | |
b4abf910 | 922 | raw_spin_unlock(&task->pi_lock); |
23f78d4a | 923 | |
8161239a LJ |
924 | if (!owner) |
925 | return 0; | |
926 | ||
b4abf910 | 927 | raw_spin_lock(&owner->pi_lock); |
23f78d4a | 928 | if (waiter == rt_mutex_top_waiter(lock)) { |
fb00aca4 PZ |
929 | rt_mutex_dequeue_pi(owner, top_waiter); |
930 | rt_mutex_enqueue_pi(owner, waiter); | |
23f78d4a IM |
931 | |
932 | __rt_mutex_adjust_prio(owner); | |
db630637 SR |
933 | if (owner->pi_blocked_on) |
934 | chain_walk = 1; | |
8930ed80 | 935 | } else if (rt_mutex_cond_detect_deadlock(waiter, chwalk)) { |
db630637 | 936 | chain_walk = 1; |
82084984 | 937 | } |
db630637 | 938 | |
82084984 TG |
939 | /* Store the lock on which owner is blocked or NULL */ |
940 | next_lock = task_blocked_on_lock(owner); | |
941 | ||
b4abf910 | 942 | raw_spin_unlock(&owner->pi_lock); |
82084984 TG |
943 | /* |
944 | * Even if full deadlock detection is on, if the owner is not | |
945 | * blocked itself, we can avoid finding this out in the chain | |
946 | * walk. | |
947 | */ | |
948 | if (!chain_walk || !next_lock) | |
23f78d4a IM |
949 | return 0; |
950 | ||
db630637 SR |
951 | /* |
952 | * The owner can't disappear while holding a lock, | |
953 | * so the owner struct is protected by wait_lock. | |
954 | * Gets dropped in rt_mutex_adjust_prio_chain()! | |
955 | */ | |
956 | get_task_struct(owner); | |
957 | ||
b4abf910 | 958 | raw_spin_unlock_irq(&lock->wait_lock); |
23f78d4a | 959 | |
8930ed80 | 960 | res = rt_mutex_adjust_prio_chain(owner, chwalk, lock, |
82084984 | 961 | next_lock, waiter, task); |
23f78d4a | 962 | |
b4abf910 | 963 | raw_spin_lock_irq(&lock->wait_lock); |
23f78d4a IM |
964 | |
965 | return res; | |
966 | } | |
967 | ||
968 | /* | |
9f40a51a | 969 | * Remove the top waiter from the current tasks pi waiter tree and |
45ab4eff | 970 | * queue it up. |
23f78d4a | 971 | * |
b4abf910 | 972 | * Called with lock->wait_lock held and interrupts disabled. |
23f78d4a | 973 | */ |
45ab4eff DB |
974 | static void mark_wakeup_next_waiter(struct wake_q_head *wake_q, |
975 | struct rt_mutex *lock) | |
23f78d4a IM |
976 | { |
977 | struct rt_mutex_waiter *waiter; | |
23f78d4a | 978 | |
b4abf910 | 979 | raw_spin_lock(¤t->pi_lock); |
23f78d4a IM |
980 | |
981 | waiter = rt_mutex_top_waiter(lock); | |
23f78d4a IM |
982 | |
983 | /* | |
984 | * Remove it from current->pi_waiters. We do not adjust a | |
985 | * possible priority boost right now. We execute wakeup in the | |
986 | * boosted mode and go back to normal after releasing | |
987 | * lock->wait_lock. | |
988 | */ | |
fb00aca4 | 989 | rt_mutex_dequeue_pi(current, waiter); |
23f78d4a | 990 | |
27e35715 TG |
991 | /* |
992 | * As we are waking up the top waiter, and the waiter stays | |
993 | * queued on the lock until it gets the lock, this lock | |
994 | * obviously has waiters. Just set the bit here and this has | |
995 | * the added benefit of forcing all new tasks into the | |
996 | * slow path making sure no task of lower priority than | |
997 | * the top waiter can steal this lock. | |
998 | */ | |
999 | lock->owner = (void *) RT_MUTEX_HAS_WAITERS; | |
23f78d4a | 1000 | |
b4abf910 | 1001 | raw_spin_unlock(¤t->pi_lock); |
23f78d4a | 1002 | |
45ab4eff | 1003 | wake_q_add(wake_q, waiter->task); |
23f78d4a IM |
1004 | } |
1005 | ||
1006 | /* | |
8161239a | 1007 | * Remove a waiter from a lock and give up |
23f78d4a | 1008 | * |
b4abf910 | 1009 | * Must be called with lock->wait_lock held and interrupts disabled. I must |
8161239a | 1010 | * have just failed to try_to_take_rt_mutex(). |
23f78d4a | 1011 | */ |
bd197234 TG |
1012 | static void remove_waiter(struct rt_mutex *lock, |
1013 | struct rt_mutex_waiter *waiter) | |
23f78d4a | 1014 | { |
1ca7b860 | 1015 | bool is_top_waiter = (waiter == rt_mutex_top_waiter(lock)); |
36c8b586 | 1016 | struct task_struct *owner = rt_mutex_owner(lock); |
1ca7b860 | 1017 | struct rt_mutex *next_lock; |
23f78d4a | 1018 | |
b4abf910 | 1019 | raw_spin_lock(¤t->pi_lock); |
fb00aca4 | 1020 | rt_mutex_dequeue(lock, waiter); |
23f78d4a | 1021 | current->pi_blocked_on = NULL; |
b4abf910 | 1022 | raw_spin_unlock(¤t->pi_lock); |
23f78d4a | 1023 | |
1ca7b860 TG |
1024 | /* |
1025 | * Only update priority if the waiter was the highest priority | |
1026 | * waiter of the lock and there is an owner to update. | |
1027 | */ | |
1028 | if (!owner || !is_top_waiter) | |
8161239a LJ |
1029 | return; |
1030 | ||
b4abf910 | 1031 | raw_spin_lock(&owner->pi_lock); |
23f78d4a | 1032 | |
1ca7b860 | 1033 | rt_mutex_dequeue_pi(owner, waiter); |
23f78d4a | 1034 | |
1ca7b860 TG |
1035 | if (rt_mutex_has_waiters(lock)) |
1036 | rt_mutex_enqueue_pi(owner, rt_mutex_top_waiter(lock)); | |
23f78d4a | 1037 | |
1ca7b860 | 1038 | __rt_mutex_adjust_prio(owner); |
23f78d4a | 1039 | |
1ca7b860 TG |
1040 | /* Store the lock on which owner is blocked or NULL */ |
1041 | next_lock = task_blocked_on_lock(owner); | |
db630637 | 1042 | |
b4abf910 | 1043 | raw_spin_unlock(&owner->pi_lock); |
23f78d4a | 1044 | |
1ca7b860 TG |
1045 | /* |
1046 | * Don't walk the chain, if the owner task is not blocked | |
1047 | * itself. | |
1048 | */ | |
82084984 | 1049 | if (!next_lock) |
23f78d4a IM |
1050 | return; |
1051 | ||
db630637 SR |
1052 | /* gets dropped in rt_mutex_adjust_prio_chain()! */ |
1053 | get_task_struct(owner); | |
1054 | ||
b4abf910 | 1055 | raw_spin_unlock_irq(&lock->wait_lock); |
23f78d4a | 1056 | |
8930ed80 TG |
1057 | rt_mutex_adjust_prio_chain(owner, RT_MUTEX_MIN_CHAINWALK, lock, |
1058 | next_lock, NULL, current); | |
23f78d4a | 1059 | |
b4abf910 | 1060 | raw_spin_lock_irq(&lock->wait_lock); |
23f78d4a IM |
1061 | } |
1062 | ||
95e02ca9 TG |
1063 | /* |
1064 | * Recheck the pi chain, in case we got a priority setting | |
1065 | * | |
1066 | * Called from sched_setscheduler | |
1067 | */ | |
1068 | void rt_mutex_adjust_pi(struct task_struct *task) | |
1069 | { | |
1070 | struct rt_mutex_waiter *waiter; | |
82084984 | 1071 | struct rt_mutex *next_lock; |
95e02ca9 TG |
1072 | unsigned long flags; |
1073 | ||
1d615482 | 1074 | raw_spin_lock_irqsave(&task->pi_lock, flags); |
95e02ca9 TG |
1075 | |
1076 | waiter = task->pi_blocked_on; | |
2d3d891d DF |
1077 | if (!waiter || (waiter->prio == task->prio && |
1078 | !dl_prio(task->prio))) { | |
1d615482 | 1079 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
95e02ca9 TG |
1080 | return; |
1081 | } | |
82084984 | 1082 | next_lock = waiter->lock; |
1d615482 | 1083 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
95e02ca9 | 1084 | |
db630637 SR |
1085 | /* gets dropped in rt_mutex_adjust_prio_chain()! */ |
1086 | get_task_struct(task); | |
82084984 | 1087 | |
8930ed80 TG |
1088 | rt_mutex_adjust_prio_chain(task, RT_MUTEX_MIN_CHAINWALK, NULL, |
1089 | next_lock, NULL, task); | |
95e02ca9 TG |
1090 | } |
1091 | ||
8dac456a DH |
1092 | /** |
1093 | * __rt_mutex_slowlock() - Perform the wait-wake-try-to-take loop | |
1094 | * @lock: the rt_mutex to take | |
1095 | * @state: the state the task should block in (TASK_INTERRUPTIBLE | |
b4abf910 | 1096 | * or TASK_UNINTERRUPTIBLE) |
8dac456a DH |
1097 | * @timeout: the pre-initialized and started timer, or NULL for none |
1098 | * @waiter: the pre-initialized rt_mutex_waiter | |
8dac456a | 1099 | * |
b4abf910 | 1100 | * Must be called with lock->wait_lock held and interrupts disabled |
23f78d4a IM |
1101 | */ |
1102 | static int __sched | |
8dac456a DH |
1103 | __rt_mutex_slowlock(struct rt_mutex *lock, int state, |
1104 | struct hrtimer_sleeper *timeout, | |
8161239a | 1105 | struct rt_mutex_waiter *waiter) |
23f78d4a | 1106 | { |
23f78d4a IM |
1107 | int ret = 0; |
1108 | ||
23f78d4a IM |
1109 | for (;;) { |
1110 | /* Try to acquire the lock: */ | |
8161239a | 1111 | if (try_to_take_rt_mutex(lock, current, waiter)) |
23f78d4a IM |
1112 | break; |
1113 | ||
1114 | /* | |
1115 | * TASK_INTERRUPTIBLE checks for signals and | |
1116 | * timeout. Ignored otherwise. | |
1117 | */ | |
1118 | if (unlikely(state == TASK_INTERRUPTIBLE)) { | |
1119 | /* Signal pending? */ | |
1120 | if (signal_pending(current)) | |
1121 | ret = -EINTR; | |
1122 | if (timeout && !timeout->task) | |
1123 | ret = -ETIMEDOUT; | |
1124 | if (ret) | |
1125 | break; | |
1126 | } | |
1127 | ||
b4abf910 | 1128 | raw_spin_unlock_irq(&lock->wait_lock); |
23f78d4a | 1129 | |
8dac456a | 1130 | debug_rt_mutex_print_deadlock(waiter); |
23f78d4a | 1131 | |
1b0b7c17 | 1132 | schedule(); |
23f78d4a | 1133 | |
b4abf910 | 1134 | raw_spin_lock_irq(&lock->wait_lock); |
23f78d4a IM |
1135 | set_current_state(state); |
1136 | } | |
1137 | ||
afffc6c1 | 1138 | __set_current_state(TASK_RUNNING); |
8dac456a DH |
1139 | return ret; |
1140 | } | |
1141 | ||
3d5c9340 TG |
1142 | static void rt_mutex_handle_deadlock(int res, int detect_deadlock, |
1143 | struct rt_mutex_waiter *w) | |
1144 | { | |
1145 | /* | |
1146 | * If the result is not -EDEADLOCK or the caller requested | |
1147 | * deadlock detection, nothing to do here. | |
1148 | */ | |
1149 | if (res != -EDEADLOCK || detect_deadlock) | |
1150 | return; | |
1151 | ||
1152 | /* | |
1153 | * Yell lowdly and stop the task right here. | |
1154 | */ | |
1155 | rt_mutex_print_deadlock(w); | |
1156 | while (1) { | |
1157 | set_current_state(TASK_INTERRUPTIBLE); | |
1158 | schedule(); | |
1159 | } | |
1160 | } | |
1161 | ||
8dac456a DH |
1162 | /* |
1163 | * Slow path lock function: | |
1164 | */ | |
1165 | static int __sched | |
1166 | rt_mutex_slowlock(struct rt_mutex *lock, int state, | |
1167 | struct hrtimer_sleeper *timeout, | |
8930ed80 | 1168 | enum rtmutex_chainwalk chwalk) |
8dac456a DH |
1169 | { |
1170 | struct rt_mutex_waiter waiter; | |
b4abf910 | 1171 | unsigned long flags; |
8dac456a DH |
1172 | int ret = 0; |
1173 | ||
1174 | debug_rt_mutex_init_waiter(&waiter); | |
fb00aca4 PZ |
1175 | RB_CLEAR_NODE(&waiter.pi_tree_entry); |
1176 | RB_CLEAR_NODE(&waiter.tree_entry); | |
8dac456a | 1177 | |
b4abf910 TG |
1178 | /* |
1179 | * Technically we could use raw_spin_[un]lock_irq() here, but this can | |
1180 | * be called in early boot if the cmpxchg() fast path is disabled | |
1181 | * (debug, no architecture support). In this case we will acquire the | |
1182 | * rtmutex with lock->wait_lock held. But we cannot unconditionally | |
1183 | * enable interrupts in that early boot case. So we need to use the | |
1184 | * irqsave/restore variants. | |
1185 | */ | |
1186 | raw_spin_lock_irqsave(&lock->wait_lock, flags); | |
8dac456a DH |
1187 | |
1188 | /* Try to acquire the lock again: */ | |
8161239a | 1189 | if (try_to_take_rt_mutex(lock, current, NULL)) { |
b4abf910 | 1190 | raw_spin_unlock_irqrestore(&lock->wait_lock, flags); |
8dac456a DH |
1191 | return 0; |
1192 | } | |
1193 | ||
1194 | set_current_state(state); | |
1195 | ||
1196 | /* Setup the timer, when timeout != NULL */ | |
ccdd92c1 | 1197 | if (unlikely(timeout)) |
8dac456a | 1198 | hrtimer_start_expires(&timeout->timer, HRTIMER_MODE_ABS); |
8dac456a | 1199 | |
8930ed80 | 1200 | ret = task_blocks_on_rt_mutex(lock, &waiter, current, chwalk); |
8161239a LJ |
1201 | |
1202 | if (likely(!ret)) | |
afffc6c1 | 1203 | /* sleep on the mutex */ |
8161239a | 1204 | ret = __rt_mutex_slowlock(lock, state, timeout, &waiter); |
8dac456a | 1205 | |
3d5c9340 | 1206 | if (unlikely(ret)) { |
9d3e2d02 | 1207 | __set_current_state(TASK_RUNNING); |
8d1e5a1a SAS |
1208 | if (rt_mutex_has_waiters(lock)) |
1209 | remove_waiter(lock, &waiter); | |
8930ed80 | 1210 | rt_mutex_handle_deadlock(ret, chwalk, &waiter); |
3d5c9340 | 1211 | } |
23f78d4a IM |
1212 | |
1213 | /* | |
1214 | * try_to_take_rt_mutex() sets the waiter bit | |
1215 | * unconditionally. We might have to fix that up. | |
1216 | */ | |
1217 | fixup_rt_mutex_waiters(lock); | |
1218 | ||
b4abf910 | 1219 | raw_spin_unlock_irqrestore(&lock->wait_lock, flags); |
23f78d4a IM |
1220 | |
1221 | /* Remove pending timer: */ | |
1222 | if (unlikely(timeout)) | |
1223 | hrtimer_cancel(&timeout->timer); | |
1224 | ||
23f78d4a IM |
1225 | debug_rt_mutex_free_waiter(&waiter); |
1226 | ||
1227 | return ret; | |
1228 | } | |
1229 | ||
1230 | /* | |
1231 | * Slow path try-lock function: | |
1232 | */ | |
88f2b4c1 | 1233 | static inline int rt_mutex_slowtrylock(struct rt_mutex *lock) |
23f78d4a | 1234 | { |
b4abf910 | 1235 | unsigned long flags; |
88f2b4c1 TG |
1236 | int ret; |
1237 | ||
1238 | /* | |
1239 | * If the lock already has an owner we fail to get the lock. | |
1240 | * This can be done without taking the @lock->wait_lock as | |
1241 | * it is only being read, and this is a trylock anyway. | |
1242 | */ | |
1243 | if (rt_mutex_owner(lock)) | |
1244 | return 0; | |
23f78d4a | 1245 | |
88f2b4c1 | 1246 | /* |
b4abf910 TG |
1247 | * The mutex has currently no owner. Lock the wait lock and try to |
1248 | * acquire the lock. We use irqsave here to support early boot calls. | |
88f2b4c1 | 1249 | */ |
b4abf910 | 1250 | raw_spin_lock_irqsave(&lock->wait_lock, flags); |
23f78d4a | 1251 | |
88f2b4c1 | 1252 | ret = try_to_take_rt_mutex(lock, current, NULL); |
23f78d4a | 1253 | |
88f2b4c1 TG |
1254 | /* |
1255 | * try_to_take_rt_mutex() sets the lock waiters bit | |
1256 | * unconditionally. Clean this up. | |
1257 | */ | |
1258 | fixup_rt_mutex_waiters(lock); | |
23f78d4a | 1259 | |
b4abf910 | 1260 | raw_spin_unlock_irqrestore(&lock->wait_lock, flags); |
23f78d4a IM |
1261 | |
1262 | return ret; | |
1263 | } | |
1264 | ||
1265 | /* | |
802ab58d SAS |
1266 | * Slow path to release a rt-mutex. |
1267 | * Return whether the current task needs to undo a potential priority boosting. | |
23f78d4a | 1268 | */ |
802ab58d SAS |
1269 | static bool __sched rt_mutex_slowunlock(struct rt_mutex *lock, |
1270 | struct wake_q_head *wake_q) | |
23f78d4a | 1271 | { |
b4abf910 TG |
1272 | unsigned long flags; |
1273 | ||
1274 | /* irqsave required to support early boot calls */ | |
1275 | raw_spin_lock_irqsave(&lock->wait_lock, flags); | |
23f78d4a IM |
1276 | |
1277 | debug_rt_mutex_unlock(lock); | |
1278 | ||
1279 | rt_mutex_deadlock_account_unlock(current); | |
1280 | ||
27e35715 TG |
1281 | /* |
1282 | * We must be careful here if the fast path is enabled. If we | |
1283 | * have no waiters queued we cannot set owner to NULL here | |
1284 | * because of: | |
1285 | * | |
1286 | * foo->lock->owner = NULL; | |
1287 | * rtmutex_lock(foo->lock); <- fast path | |
1288 | * free = atomic_dec_and_test(foo->refcnt); | |
1289 | * rtmutex_unlock(foo->lock); <- fast path | |
1290 | * if (free) | |
1291 | * kfree(foo); | |
1292 | * raw_spin_unlock(foo->lock->wait_lock); | |
1293 | * | |
1294 | * So for the fastpath enabled kernel: | |
1295 | * | |
1296 | * Nothing can set the waiters bit as long as we hold | |
1297 | * lock->wait_lock. So we do the following sequence: | |
1298 | * | |
1299 | * owner = rt_mutex_owner(lock); | |
1300 | * clear_rt_mutex_waiters(lock); | |
1301 | * raw_spin_unlock(&lock->wait_lock); | |
1302 | * if (cmpxchg(&lock->owner, owner, 0) == owner) | |
1303 | * return; | |
1304 | * goto retry; | |
1305 | * | |
1306 | * The fastpath disabled variant is simple as all access to | |
1307 | * lock->owner is serialized by lock->wait_lock: | |
1308 | * | |
1309 | * lock->owner = NULL; | |
1310 | * raw_spin_unlock(&lock->wait_lock); | |
1311 | */ | |
1312 | while (!rt_mutex_has_waiters(lock)) { | |
1313 | /* Drops lock->wait_lock ! */ | |
b4abf910 | 1314 | if (unlock_rt_mutex_safe(lock, flags) == true) |
802ab58d | 1315 | return false; |
27e35715 | 1316 | /* Relock the rtmutex and try again */ |
b4abf910 | 1317 | raw_spin_lock_irqsave(&lock->wait_lock, flags); |
23f78d4a IM |
1318 | } |
1319 | ||
27e35715 TG |
1320 | /* |
1321 | * The wakeup next waiter path does not suffer from the above | |
1322 | * race. See the comments there. | |
45ab4eff DB |
1323 | * |
1324 | * Queue the next waiter for wakeup once we release the wait_lock. | |
27e35715 | 1325 | */ |
802ab58d | 1326 | mark_wakeup_next_waiter(wake_q, lock); |
23f78d4a | 1327 | |
b4abf910 | 1328 | raw_spin_unlock_irqrestore(&lock->wait_lock, flags); |
23f78d4a | 1329 | |
802ab58d SAS |
1330 | /* check PI boosting */ |
1331 | return true; | |
23f78d4a IM |
1332 | } |
1333 | ||
1334 | /* | |
1335 | * debug aware fast / slowpath lock,trylock,unlock | |
1336 | * | |
1337 | * The atomic acquire/release ops are compiled away, when either the | |
1338 | * architecture does not support cmpxchg or when debugging is enabled. | |
1339 | */ | |
1340 | static inline int | |
1341 | rt_mutex_fastlock(struct rt_mutex *lock, int state, | |
23f78d4a IM |
1342 | int (*slowfn)(struct rt_mutex *lock, int state, |
1343 | struct hrtimer_sleeper *timeout, | |
8930ed80 | 1344 | enum rtmutex_chainwalk chwalk)) |
23f78d4a | 1345 | { |
700318d1 | 1346 | if (likely(rt_mutex_cmpxchg_acquire(lock, NULL, current))) { |
23f78d4a IM |
1347 | rt_mutex_deadlock_account_lock(lock, current); |
1348 | return 0; | |
1349 | } else | |
8930ed80 | 1350 | return slowfn(lock, state, NULL, RT_MUTEX_MIN_CHAINWALK); |
23f78d4a IM |
1351 | } |
1352 | ||
1353 | static inline int | |
1354 | rt_mutex_timed_fastlock(struct rt_mutex *lock, int state, | |
8930ed80 TG |
1355 | struct hrtimer_sleeper *timeout, |
1356 | enum rtmutex_chainwalk chwalk, | |
23f78d4a IM |
1357 | int (*slowfn)(struct rt_mutex *lock, int state, |
1358 | struct hrtimer_sleeper *timeout, | |
8930ed80 | 1359 | enum rtmutex_chainwalk chwalk)) |
23f78d4a | 1360 | { |
8930ed80 | 1361 | if (chwalk == RT_MUTEX_MIN_CHAINWALK && |
700318d1 | 1362 | likely(rt_mutex_cmpxchg_acquire(lock, NULL, current))) { |
23f78d4a IM |
1363 | rt_mutex_deadlock_account_lock(lock, current); |
1364 | return 0; | |
1365 | } else | |
8930ed80 | 1366 | return slowfn(lock, state, timeout, chwalk); |
23f78d4a IM |
1367 | } |
1368 | ||
1369 | static inline int | |
1370 | rt_mutex_fasttrylock(struct rt_mutex *lock, | |
9a11b49a | 1371 | int (*slowfn)(struct rt_mutex *lock)) |
23f78d4a | 1372 | { |
700318d1 | 1373 | if (likely(rt_mutex_cmpxchg_acquire(lock, NULL, current))) { |
23f78d4a IM |
1374 | rt_mutex_deadlock_account_lock(lock, current); |
1375 | return 1; | |
1376 | } | |
9a11b49a | 1377 | return slowfn(lock); |
23f78d4a IM |
1378 | } |
1379 | ||
1380 | static inline void | |
1381 | rt_mutex_fastunlock(struct rt_mutex *lock, | |
802ab58d SAS |
1382 | bool (*slowfn)(struct rt_mutex *lock, |
1383 | struct wake_q_head *wqh)) | |
23f78d4a | 1384 | { |
802ab58d SAS |
1385 | WAKE_Q(wake_q); |
1386 | ||
700318d1 | 1387 | if (likely(rt_mutex_cmpxchg_release(lock, current, NULL))) { |
23f78d4a | 1388 | rt_mutex_deadlock_account_unlock(current); |
802ab58d SAS |
1389 | |
1390 | } else { | |
1391 | bool deboost = slowfn(lock, &wake_q); | |
1392 | ||
1393 | wake_up_q(&wake_q); | |
1394 | ||
1395 | /* Undo pi boosting if necessary: */ | |
1396 | if (deboost) | |
1397 | rt_mutex_adjust_prio(current); | |
1398 | } | |
23f78d4a IM |
1399 | } |
1400 | ||
1401 | /** | |
1402 | * rt_mutex_lock - lock a rt_mutex | |
1403 | * | |
1404 | * @lock: the rt_mutex to be locked | |
1405 | */ | |
1406 | void __sched rt_mutex_lock(struct rt_mutex *lock) | |
1407 | { | |
1408 | might_sleep(); | |
1409 | ||
c051b21f | 1410 | rt_mutex_fastlock(lock, TASK_UNINTERRUPTIBLE, rt_mutex_slowlock); |
23f78d4a IM |
1411 | } |
1412 | EXPORT_SYMBOL_GPL(rt_mutex_lock); | |
1413 | ||
1414 | /** | |
1415 | * rt_mutex_lock_interruptible - lock a rt_mutex interruptible | |
1416 | * | |
c051b21f | 1417 | * @lock: the rt_mutex to be locked |
23f78d4a IM |
1418 | * |
1419 | * Returns: | |
c051b21f TG |
1420 | * 0 on success |
1421 | * -EINTR when interrupted by a signal | |
23f78d4a | 1422 | */ |
c051b21f | 1423 | int __sched rt_mutex_lock_interruptible(struct rt_mutex *lock) |
23f78d4a IM |
1424 | { |
1425 | might_sleep(); | |
1426 | ||
c051b21f | 1427 | return rt_mutex_fastlock(lock, TASK_INTERRUPTIBLE, rt_mutex_slowlock); |
23f78d4a IM |
1428 | } |
1429 | EXPORT_SYMBOL_GPL(rt_mutex_lock_interruptible); | |
1430 | ||
c051b21f TG |
1431 | /* |
1432 | * Futex variant with full deadlock detection. | |
1433 | */ | |
1434 | int rt_mutex_timed_futex_lock(struct rt_mutex *lock, | |
1435 | struct hrtimer_sleeper *timeout) | |
1436 | { | |
1437 | might_sleep(); | |
1438 | ||
8930ed80 TG |
1439 | return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout, |
1440 | RT_MUTEX_FULL_CHAINWALK, | |
c051b21f TG |
1441 | rt_mutex_slowlock); |
1442 | } | |
1443 | ||
23f78d4a | 1444 | /** |
23b94b96 LH |
1445 | * rt_mutex_timed_lock - lock a rt_mutex interruptible |
1446 | * the timeout structure is provided | |
1447 | * by the caller | |
23f78d4a | 1448 | * |
c051b21f | 1449 | * @lock: the rt_mutex to be locked |
23f78d4a | 1450 | * @timeout: timeout structure or NULL (no timeout) |
23f78d4a IM |
1451 | * |
1452 | * Returns: | |
c051b21f TG |
1453 | * 0 on success |
1454 | * -EINTR when interrupted by a signal | |
3ac49a1c | 1455 | * -ETIMEDOUT when the timeout expired |
23f78d4a IM |
1456 | */ |
1457 | int | |
c051b21f | 1458 | rt_mutex_timed_lock(struct rt_mutex *lock, struct hrtimer_sleeper *timeout) |
23f78d4a IM |
1459 | { |
1460 | might_sleep(); | |
1461 | ||
8930ed80 TG |
1462 | return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout, |
1463 | RT_MUTEX_MIN_CHAINWALK, | |
c051b21f | 1464 | rt_mutex_slowlock); |
23f78d4a IM |
1465 | } |
1466 | EXPORT_SYMBOL_GPL(rt_mutex_timed_lock); | |
1467 | ||
1468 | /** | |
1469 | * rt_mutex_trylock - try to lock a rt_mutex | |
1470 | * | |
1471 | * @lock: the rt_mutex to be locked | |
1472 | * | |
6ce47fd9 TG |
1473 | * This function can only be called in thread context. It's safe to |
1474 | * call it from atomic regions, but not from hard interrupt or soft | |
1475 | * interrupt context. | |
1476 | * | |
23f78d4a IM |
1477 | * Returns 1 on success and 0 on contention |
1478 | */ | |
1479 | int __sched rt_mutex_trylock(struct rt_mutex *lock) | |
1480 | { | |
a461d587 | 1481 | if (WARN_ON_ONCE(in_irq() || in_nmi() || in_serving_softirq())) |
6ce47fd9 TG |
1482 | return 0; |
1483 | ||
23f78d4a IM |
1484 | return rt_mutex_fasttrylock(lock, rt_mutex_slowtrylock); |
1485 | } | |
1486 | EXPORT_SYMBOL_GPL(rt_mutex_trylock); | |
1487 | ||
1488 | /** | |
1489 | * rt_mutex_unlock - unlock a rt_mutex | |
1490 | * | |
1491 | * @lock: the rt_mutex to be unlocked | |
1492 | */ | |
1493 | void __sched rt_mutex_unlock(struct rt_mutex *lock) | |
1494 | { | |
1495 | rt_mutex_fastunlock(lock, rt_mutex_slowunlock); | |
1496 | } | |
1497 | EXPORT_SYMBOL_GPL(rt_mutex_unlock); | |
1498 | ||
802ab58d SAS |
1499 | /** |
1500 | * rt_mutex_futex_unlock - Futex variant of rt_mutex_unlock | |
1501 | * @lock: the rt_mutex to be unlocked | |
1502 | * | |
1503 | * Returns: true/false indicating whether priority adjustment is | |
1504 | * required or not. | |
1505 | */ | |
1506 | bool __sched rt_mutex_futex_unlock(struct rt_mutex *lock, | |
1507 | struct wake_q_head *wqh) | |
1508 | { | |
700318d1 | 1509 | if (likely(rt_mutex_cmpxchg_release(lock, current, NULL))) { |
802ab58d SAS |
1510 | rt_mutex_deadlock_account_unlock(current); |
1511 | return false; | |
1512 | } | |
1513 | return rt_mutex_slowunlock(lock, wqh); | |
1514 | } | |
1515 | ||
23b94b96 | 1516 | /** |
23f78d4a IM |
1517 | * rt_mutex_destroy - mark a mutex unusable |
1518 | * @lock: the mutex to be destroyed | |
1519 | * | |
1520 | * This function marks the mutex uninitialized, and any subsequent | |
1521 | * use of the mutex is forbidden. The mutex must not be locked when | |
1522 | * this function is called. | |
1523 | */ | |
1524 | void rt_mutex_destroy(struct rt_mutex *lock) | |
1525 | { | |
1526 | WARN_ON(rt_mutex_is_locked(lock)); | |
1527 | #ifdef CONFIG_DEBUG_RT_MUTEXES | |
1528 | lock->magic = NULL; | |
1529 | #endif | |
1530 | } | |
1531 | ||
1532 | EXPORT_SYMBOL_GPL(rt_mutex_destroy); | |
1533 | ||
1534 | /** | |
1535 | * __rt_mutex_init - initialize the rt lock | |
1536 | * | |
1537 | * @lock: the rt lock to be initialized | |
1538 | * | |
1539 | * Initialize the rt lock to unlocked state. | |
1540 | * | |
1541 | * Initializing of a locked rt lock is not allowed | |
1542 | */ | |
1543 | void __rt_mutex_init(struct rt_mutex *lock, const char *name) | |
1544 | { | |
1545 | lock->owner = NULL; | |
d209d74d | 1546 | raw_spin_lock_init(&lock->wait_lock); |
fb00aca4 PZ |
1547 | lock->waiters = RB_ROOT; |
1548 | lock->waiters_leftmost = NULL; | |
23f78d4a IM |
1549 | |
1550 | debug_rt_mutex_init(lock, name); | |
1551 | } | |
1552 | EXPORT_SYMBOL_GPL(__rt_mutex_init); | |
0cdbee99 IM |
1553 | |
1554 | /** | |
1555 | * rt_mutex_init_proxy_locked - initialize and lock a rt_mutex on behalf of a | |
1556 | * proxy owner | |
1557 | * | |
1558 | * @lock: the rt_mutex to be locked | |
1559 | * @proxy_owner:the task to set as owner | |
1560 | * | |
1561 | * No locking. Caller has to do serializing itself | |
1562 | * Special API call for PI-futex support | |
1563 | */ | |
1564 | void rt_mutex_init_proxy_locked(struct rt_mutex *lock, | |
1565 | struct task_struct *proxy_owner) | |
1566 | { | |
1567 | __rt_mutex_init(lock, NULL); | |
9a11b49a | 1568 | debug_rt_mutex_proxy_lock(lock, proxy_owner); |
8161239a | 1569 | rt_mutex_set_owner(lock, proxy_owner); |
0cdbee99 IM |
1570 | rt_mutex_deadlock_account_lock(lock, proxy_owner); |
1571 | } | |
1572 | ||
1573 | /** | |
1574 | * rt_mutex_proxy_unlock - release a lock on behalf of owner | |
1575 | * | |
1576 | * @lock: the rt_mutex to be locked | |
1577 | * | |
1578 | * No locking. Caller has to do serializing itself | |
1579 | * Special API call for PI-futex support | |
1580 | */ | |
1581 | void rt_mutex_proxy_unlock(struct rt_mutex *lock, | |
1582 | struct task_struct *proxy_owner) | |
1583 | { | |
1584 | debug_rt_mutex_proxy_unlock(lock); | |
8161239a | 1585 | rt_mutex_set_owner(lock, NULL); |
0cdbee99 IM |
1586 | rt_mutex_deadlock_account_unlock(proxy_owner); |
1587 | } | |
1588 | ||
8dac456a DH |
1589 | /** |
1590 | * rt_mutex_start_proxy_lock() - Start lock acquisition for another task | |
1591 | * @lock: the rt_mutex to take | |
1592 | * @waiter: the pre-initialized rt_mutex_waiter | |
1593 | * @task: the task to prepare | |
8dac456a DH |
1594 | * |
1595 | * Returns: | |
1596 | * 0 - task blocked on lock | |
1597 | * 1 - acquired the lock for task, caller should wake it up | |
1598 | * <0 - error | |
1599 | * | |
1600 | * Special API call for FUTEX_REQUEUE_PI support. | |
1601 | */ | |
1602 | int rt_mutex_start_proxy_lock(struct rt_mutex *lock, | |
1603 | struct rt_mutex_waiter *waiter, | |
c051b21f | 1604 | struct task_struct *task) |
8dac456a DH |
1605 | { |
1606 | int ret; | |
1607 | ||
b4abf910 | 1608 | raw_spin_lock_irq(&lock->wait_lock); |
8dac456a | 1609 | |
8161239a | 1610 | if (try_to_take_rt_mutex(lock, task, NULL)) { |
b4abf910 | 1611 | raw_spin_unlock_irq(&lock->wait_lock); |
8dac456a DH |
1612 | return 1; |
1613 | } | |
1614 | ||
3d5c9340 | 1615 | /* We enforce deadlock detection for futexes */ |
8930ed80 TG |
1616 | ret = task_blocks_on_rt_mutex(lock, waiter, task, |
1617 | RT_MUTEX_FULL_CHAINWALK); | |
8dac456a | 1618 | |
8161239a | 1619 | if (ret && !rt_mutex_owner(lock)) { |
8dac456a DH |
1620 | /* |
1621 | * Reset the return value. We might have | |
1622 | * returned with -EDEADLK and the owner | |
1623 | * released the lock while we were walking the | |
1624 | * pi chain. Let the waiter sort it out. | |
1625 | */ | |
1626 | ret = 0; | |
1627 | } | |
8161239a LJ |
1628 | |
1629 | if (unlikely(ret)) | |
1630 | remove_waiter(lock, waiter); | |
1631 | ||
b4abf910 | 1632 | raw_spin_unlock_irq(&lock->wait_lock); |
8dac456a DH |
1633 | |
1634 | debug_rt_mutex_print_deadlock(waiter); | |
1635 | ||
1636 | return ret; | |
1637 | } | |
1638 | ||
0cdbee99 IM |
1639 | /** |
1640 | * rt_mutex_next_owner - return the next owner of the lock | |
1641 | * | |
1642 | * @lock: the rt lock query | |
1643 | * | |
1644 | * Returns the next owner of the lock or NULL | |
1645 | * | |
1646 | * Caller has to serialize against other accessors to the lock | |
1647 | * itself. | |
1648 | * | |
1649 | * Special API call for PI-futex support | |
1650 | */ | |
1651 | struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock) | |
1652 | { | |
1653 | if (!rt_mutex_has_waiters(lock)) | |
1654 | return NULL; | |
1655 | ||
1656 | return rt_mutex_top_waiter(lock)->task; | |
1657 | } | |
8dac456a DH |
1658 | |
1659 | /** | |
1660 | * rt_mutex_finish_proxy_lock() - Complete lock acquisition | |
1661 | * @lock: the rt_mutex we were woken on | |
1662 | * @to: the timeout, null if none. hrtimer should already have | |
c051b21f | 1663 | * been started. |
8dac456a | 1664 | * @waiter: the pre-initialized rt_mutex_waiter |
8dac456a DH |
1665 | * |
1666 | * Complete the lock acquisition started our behalf by another thread. | |
1667 | * | |
1668 | * Returns: | |
1669 | * 0 - success | |
c051b21f | 1670 | * <0 - error, one of -EINTR, -ETIMEDOUT |
8dac456a DH |
1671 | * |
1672 | * Special API call for PI-futex requeue support | |
1673 | */ | |
1674 | int rt_mutex_finish_proxy_lock(struct rt_mutex *lock, | |
1675 | struct hrtimer_sleeper *to, | |
c051b21f | 1676 | struct rt_mutex_waiter *waiter) |
8dac456a DH |
1677 | { |
1678 | int ret; | |
1679 | ||
b4abf910 | 1680 | raw_spin_lock_irq(&lock->wait_lock); |
8dac456a DH |
1681 | |
1682 | set_current_state(TASK_INTERRUPTIBLE); | |
1683 | ||
afffc6c1 | 1684 | /* sleep on the mutex */ |
8161239a | 1685 | ret = __rt_mutex_slowlock(lock, TASK_INTERRUPTIBLE, to, waiter); |
8dac456a | 1686 | |
8161239a | 1687 | if (unlikely(ret)) |
8dac456a DH |
1688 | remove_waiter(lock, waiter); |
1689 | ||
1690 | /* | |
1691 | * try_to_take_rt_mutex() sets the waiter bit unconditionally. We might | |
1692 | * have to fix that up. | |
1693 | */ | |
1694 | fixup_rt_mutex_waiters(lock); | |
1695 | ||
b4abf910 | 1696 | raw_spin_unlock_irq(&lock->wait_lock); |
8dac456a | 1697 | |
8dac456a DH |
1698 | return ret; |
1699 | } |