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Commit | Line | Data |
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23f78d4a IM |
1 | /* |
2 | * RT-Mutexes: simple blocking mutual exclusion locks with PI support | |
3 | * | |
4 | * started by Ingo Molnar and Thomas Gleixner. | |
5 | * | |
6 | * Copyright (C) 2004-2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com> | |
7 | * Copyright (C) 2005-2006 Timesys Corp., Thomas Gleixner <tglx@timesys.com> | |
8 | * Copyright (C) 2005 Kihon Technologies Inc., Steven Rostedt | |
9 | * Copyright (C) 2006 Esben Nielsen | |
d07fe82c | 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> |
174cd4b1 | 15 | #include <linux/sched/signal.h> |
8bd75c77 | 16 | #include <linux/sched/rt.h> |
fb00aca4 | 17 | #include <linux/sched/deadline.h> |
84f001e1 | 18 | #include <linux/sched/wake_q.h> |
b17b0153 | 19 | #include <linux/sched/debug.h> |
23f78d4a IM |
20 | #include <linux/timer.h> |
21 | ||
22 | #include "rtmutex_common.h" | |
23 | ||
23f78d4a IM |
24 | /* |
25 | * lock->owner state tracking: | |
26 | * | |
8161239a LJ |
27 | * lock->owner holds the task_struct pointer of the owner. Bit 0 |
28 | * is used to keep track of the "lock has waiters" state. | |
23f78d4a | 29 | * |
8161239a LJ |
30 | * owner bit0 |
31 | * NULL 0 lock is free (fast acquire possible) | |
32 | * NULL 1 lock is free and has waiters and the top waiter | |
33 | * is going to take the lock* | |
34 | * taskpointer 0 lock is held (fast release possible) | |
35 | * taskpointer 1 lock is held and has waiters** | |
23f78d4a IM |
36 | * |
37 | * The fast atomic compare exchange based acquire and release is only | |
8161239a LJ |
38 | * possible when bit 0 of lock->owner is 0. |
39 | * | |
40 | * (*) It also can be a transitional state when grabbing the lock | |
41 | * with ->wait_lock is held. To prevent any fast path cmpxchg to the lock, | |
42 | * we need to set the bit0 before looking at the lock, and the owner may be | |
43 | * NULL in this small time, hence this can be a transitional state. | |
23f78d4a | 44 | * |
8161239a LJ |
45 | * (**) There is a small time when bit 0 is set but there are no |
46 | * waiters. This can happen when grabbing the lock in the slow path. | |
47 | * To prevent a cmpxchg of the owner releasing the lock, we need to | |
48 | * set this bit before looking at the lock. | |
23f78d4a IM |
49 | */ |
50 | ||
bd197234 | 51 | static void |
8161239a | 52 | rt_mutex_set_owner(struct rt_mutex *lock, struct task_struct *owner) |
23f78d4a | 53 | { |
8161239a | 54 | unsigned long val = (unsigned long)owner; |
23f78d4a IM |
55 | |
56 | if (rt_mutex_has_waiters(lock)) | |
57 | val |= RT_MUTEX_HAS_WAITERS; | |
58 | ||
59 | lock->owner = (struct task_struct *)val; | |
60 | } | |
61 | ||
62 | static inline void clear_rt_mutex_waiters(struct rt_mutex *lock) | |
63 | { | |
64 | lock->owner = (struct task_struct *) | |
65 | ((unsigned long)lock->owner & ~RT_MUTEX_HAS_WAITERS); | |
66 | } | |
67 | ||
68 | static void fixup_rt_mutex_waiters(struct rt_mutex *lock) | |
69 | { | |
dbb26055 TG |
70 | unsigned long owner, *p = (unsigned long *) &lock->owner; |
71 | ||
72 | if (rt_mutex_has_waiters(lock)) | |
73 | return; | |
74 | ||
75 | /* | |
76 | * The rbtree has no waiters enqueued, now make sure that the | |
77 | * lock->owner still has the waiters bit set, otherwise the | |
78 | * following can happen: | |
79 | * | |
80 | * CPU 0 CPU 1 CPU2 | |
81 | * l->owner=T1 | |
82 | * rt_mutex_lock(l) | |
83 | * lock(l->lock) | |
84 | * l->owner = T1 | HAS_WAITERS; | |
85 | * enqueue(T2) | |
86 | * boost() | |
87 | * unlock(l->lock) | |
88 | * block() | |
89 | * | |
90 | * rt_mutex_lock(l) | |
91 | * lock(l->lock) | |
92 | * l->owner = T1 | HAS_WAITERS; | |
93 | * enqueue(T3) | |
94 | * boost() | |
95 | * unlock(l->lock) | |
96 | * block() | |
97 | * signal(->T2) signal(->T3) | |
98 | * lock(l->lock) | |
99 | * dequeue(T2) | |
100 | * deboost() | |
101 | * unlock(l->lock) | |
102 | * lock(l->lock) | |
103 | * dequeue(T3) | |
104 | * ==> wait list is empty | |
105 | * deboost() | |
106 | * unlock(l->lock) | |
107 | * lock(l->lock) | |
108 | * fixup_rt_mutex_waiters() | |
109 | * if (wait_list_empty(l) { | |
110 | * l->owner = owner | |
111 | * owner = l->owner & ~HAS_WAITERS; | |
112 | * ==> l->owner = T1 | |
113 | * } | |
114 | * lock(l->lock) | |
115 | * rt_mutex_unlock(l) fixup_rt_mutex_waiters() | |
116 | * if (wait_list_empty(l) { | |
117 | * owner = l->owner & ~HAS_WAITERS; | |
118 | * cmpxchg(l->owner, T1, NULL) | |
119 | * ===> Success (l->owner = NULL) | |
120 | * | |
121 | * l->owner = owner | |
122 | * ==> l->owner = T1 | |
123 | * } | |
124 | * | |
125 | * With the check for the waiter bit in place T3 on CPU2 will not | |
126 | * overwrite. All tasks fiddling with the waiters bit are | |
127 | * serialized by l->lock, so nothing else can modify the waiters | |
128 | * bit. If the bit is set then nothing can change l->owner either | |
129 | * so the simple RMW is safe. The cmpxchg() will simply fail if it | |
130 | * happens in the middle of the RMW because the waiters bit is | |
131 | * still set. | |
132 | */ | |
133 | owner = READ_ONCE(*p); | |
134 | if (owner & RT_MUTEX_HAS_WAITERS) | |
135 | WRITE_ONCE(*p, owner & ~RT_MUTEX_HAS_WAITERS); | |
23f78d4a IM |
136 | } |
137 | ||
bd197234 | 138 | /* |
cede8841 SAS |
139 | * We can speed up the acquire/release, if there's no debugging state to be |
140 | * set up. | |
bd197234 | 141 | */ |
cede8841 | 142 | #ifndef CONFIG_DEBUG_RT_MUTEXES |
700318d1 DB |
143 | # define rt_mutex_cmpxchg_relaxed(l,c,n) (cmpxchg_relaxed(&l->owner, c, n) == c) |
144 | # define rt_mutex_cmpxchg_acquire(l,c,n) (cmpxchg_acquire(&l->owner, c, n) == c) | |
145 | # define rt_mutex_cmpxchg_release(l,c,n) (cmpxchg_release(&l->owner, c, n) == c) | |
146 | ||
147 | /* | |
148 | * Callers must hold the ->wait_lock -- which is the whole purpose as we force | |
149 | * all future threads that attempt to [Rmw] the lock to the slowpath. As such | |
150 | * relaxed semantics suffice. | |
151 | */ | |
bd197234 TG |
152 | static inline void mark_rt_mutex_waiters(struct rt_mutex *lock) |
153 | { | |
154 | unsigned long owner, *p = (unsigned long *) &lock->owner; | |
155 | ||
156 | do { | |
157 | owner = *p; | |
700318d1 DB |
158 | } while (cmpxchg_relaxed(p, owner, |
159 | owner | RT_MUTEX_HAS_WAITERS) != owner); | |
bd197234 | 160 | } |
27e35715 TG |
161 | |
162 | /* | |
163 | * Safe fastpath aware unlock: | |
164 | * 1) Clear the waiters bit | |
165 | * 2) Drop lock->wait_lock | |
166 | * 3) Try to unlock the lock with cmpxchg | |
167 | */ | |
b4abf910 TG |
168 | static inline bool unlock_rt_mutex_safe(struct rt_mutex *lock, |
169 | unsigned long flags) | |
27e35715 TG |
170 | __releases(lock->wait_lock) |
171 | { | |
172 | struct task_struct *owner = rt_mutex_owner(lock); | |
173 | ||
174 | clear_rt_mutex_waiters(lock); | |
b4abf910 | 175 | raw_spin_unlock_irqrestore(&lock->wait_lock, flags); |
27e35715 TG |
176 | /* |
177 | * If a new waiter comes in between the unlock and the cmpxchg | |
178 | * we have two situations: | |
179 | * | |
180 | * unlock(wait_lock); | |
181 | * lock(wait_lock); | |
182 | * cmpxchg(p, owner, 0) == owner | |
183 | * mark_rt_mutex_waiters(lock); | |
184 | * acquire(lock); | |
185 | * or: | |
186 | * | |
187 | * unlock(wait_lock); | |
188 | * lock(wait_lock); | |
189 | * mark_rt_mutex_waiters(lock); | |
190 | * | |
191 | * cmpxchg(p, owner, 0) != owner | |
192 | * enqueue_waiter(); | |
193 | * unlock(wait_lock); | |
194 | * lock(wait_lock); | |
195 | * wake waiter(); | |
196 | * unlock(wait_lock); | |
197 | * lock(wait_lock); | |
198 | * acquire(lock); | |
199 | */ | |
700318d1 | 200 | return rt_mutex_cmpxchg_release(lock, owner, NULL); |
27e35715 TG |
201 | } |
202 | ||
bd197234 | 203 | #else |
700318d1 DB |
204 | # define rt_mutex_cmpxchg_relaxed(l,c,n) (0) |
205 | # define rt_mutex_cmpxchg_acquire(l,c,n) (0) | |
206 | # define rt_mutex_cmpxchg_release(l,c,n) (0) | |
207 | ||
bd197234 TG |
208 | static inline void mark_rt_mutex_waiters(struct rt_mutex *lock) |
209 | { | |
210 | lock->owner = (struct task_struct *) | |
211 | ((unsigned long)lock->owner | RT_MUTEX_HAS_WAITERS); | |
212 | } | |
27e35715 TG |
213 | |
214 | /* | |
215 | * Simple slow path only version: lock->owner is protected by lock->wait_lock. | |
216 | */ | |
b4abf910 TG |
217 | static inline bool unlock_rt_mutex_safe(struct rt_mutex *lock, |
218 | unsigned long flags) | |
27e35715 TG |
219 | __releases(lock->wait_lock) |
220 | { | |
221 | lock->owner = NULL; | |
b4abf910 | 222 | raw_spin_unlock_irqrestore(&lock->wait_lock, flags); |
27e35715 TG |
223 | return true; |
224 | } | |
bd197234 TG |
225 | #endif |
226 | ||
19830e55 PZ |
227 | /* |
228 | * Only use with rt_mutex_waiter_{less,equal}() | |
229 | */ | |
230 | #define task_to_waiter(p) \ | |
231 | &(struct rt_mutex_waiter){ .prio = (p)->prio, .deadline = (p)->dl.deadline } | |
232 | ||
fb00aca4 PZ |
233 | static inline int |
234 | rt_mutex_waiter_less(struct rt_mutex_waiter *left, | |
235 | struct rt_mutex_waiter *right) | |
236 | { | |
2d3d891d | 237 | if (left->prio < right->prio) |
fb00aca4 PZ |
238 | return 1; |
239 | ||
240 | /* | |
2d3d891d DF |
241 | * If both waiters have dl_prio(), we check the deadlines of the |
242 | * associated tasks. | |
243 | * If left waiter has a dl_prio(), and we didn't return 1 above, | |
244 | * then right waiter has a dl_prio() too. | |
fb00aca4 | 245 | */ |
2d3d891d | 246 | if (dl_prio(left->prio)) |
e0aad5b4 | 247 | return dl_time_before(left->deadline, right->deadline); |
fb00aca4 PZ |
248 | |
249 | return 0; | |
250 | } | |
251 | ||
19830e55 PZ |
252 | static inline int |
253 | rt_mutex_waiter_equal(struct rt_mutex_waiter *left, | |
254 | struct rt_mutex_waiter *right) | |
255 | { | |
256 | if (left->prio != right->prio) | |
257 | return 0; | |
258 | ||
259 | /* | |
260 | * If both waiters have dl_prio(), we check the deadlines of the | |
261 | * associated tasks. | |
262 | * If left waiter has a dl_prio(), and we didn't return 0 above, | |
263 | * then right waiter has a dl_prio() too. | |
264 | */ | |
265 | if (dl_prio(left->prio)) | |
266 | return left->deadline == right->deadline; | |
267 | ||
268 | return 1; | |
269 | } | |
270 | ||
fb00aca4 PZ |
271 | static void |
272 | rt_mutex_enqueue(struct rt_mutex *lock, struct rt_mutex_waiter *waiter) | |
273 | { | |
274 | struct rb_node **link = &lock->waiters.rb_node; | |
275 | struct rb_node *parent = NULL; | |
276 | struct rt_mutex_waiter *entry; | |
277 | int leftmost = 1; | |
278 | ||
279 | while (*link) { | |
280 | parent = *link; | |
281 | entry = rb_entry(parent, struct rt_mutex_waiter, tree_entry); | |
282 | if (rt_mutex_waiter_less(waiter, entry)) { | |
283 | link = &parent->rb_left; | |
284 | } else { | |
285 | link = &parent->rb_right; | |
286 | leftmost = 0; | |
287 | } | |
288 | } | |
289 | ||
290 | if (leftmost) | |
291 | lock->waiters_leftmost = &waiter->tree_entry; | |
292 | ||
293 | rb_link_node(&waiter->tree_entry, parent, link); | |
294 | rb_insert_color(&waiter->tree_entry, &lock->waiters); | |
295 | } | |
296 | ||
297 | static void | |
298 | rt_mutex_dequeue(struct rt_mutex *lock, struct rt_mutex_waiter *waiter) | |
299 | { | |
300 | if (RB_EMPTY_NODE(&waiter->tree_entry)) | |
301 | return; | |
302 | ||
303 | if (lock->waiters_leftmost == &waiter->tree_entry) | |
304 | lock->waiters_leftmost = rb_next(&waiter->tree_entry); | |
305 | ||
306 | rb_erase(&waiter->tree_entry, &lock->waiters); | |
307 | RB_CLEAR_NODE(&waiter->tree_entry); | |
308 | } | |
309 | ||
310 | static void | |
311 | rt_mutex_enqueue_pi(struct task_struct *task, struct rt_mutex_waiter *waiter) | |
312 | { | |
313 | struct rb_node **link = &task->pi_waiters.rb_node; | |
314 | struct rb_node *parent = NULL; | |
315 | struct rt_mutex_waiter *entry; | |
316 | int leftmost = 1; | |
317 | ||
318 | while (*link) { | |
319 | parent = *link; | |
320 | entry = rb_entry(parent, struct rt_mutex_waiter, pi_tree_entry); | |
321 | if (rt_mutex_waiter_less(waiter, entry)) { | |
322 | link = &parent->rb_left; | |
323 | } else { | |
324 | link = &parent->rb_right; | |
325 | leftmost = 0; | |
326 | } | |
327 | } | |
328 | ||
329 | if (leftmost) | |
330 | task->pi_waiters_leftmost = &waiter->pi_tree_entry; | |
331 | ||
332 | rb_link_node(&waiter->pi_tree_entry, parent, link); | |
333 | rb_insert_color(&waiter->pi_tree_entry, &task->pi_waiters); | |
334 | } | |
335 | ||
336 | static void | |
337 | rt_mutex_dequeue_pi(struct task_struct *task, struct rt_mutex_waiter *waiter) | |
338 | { | |
339 | if (RB_EMPTY_NODE(&waiter->pi_tree_entry)) | |
340 | return; | |
341 | ||
342 | if (task->pi_waiters_leftmost == &waiter->pi_tree_entry) | |
343 | task->pi_waiters_leftmost = rb_next(&waiter->pi_tree_entry); | |
344 | ||
345 | rb_erase(&waiter->pi_tree_entry, &task->pi_waiters); | |
346 | RB_CLEAR_NODE(&waiter->pi_tree_entry); | |
347 | } | |
348 | ||
acd58620 | 349 | static void rt_mutex_adjust_prio(struct task_struct *p) |
c365c292 | 350 | { |
acd58620 | 351 | struct task_struct *pi_task = NULL; |
e96a7705 | 352 | |
acd58620 | 353 | lockdep_assert_held(&p->pi_lock); |
c365c292 | 354 | |
acd58620 PZ |
355 | if (task_has_pi_waiters(p)) |
356 | pi_task = task_top_pi_waiter(p)->task; | |
c365c292 | 357 | |
acd58620 | 358 | rt_mutex_setprio(p, pi_task); |
23f78d4a IM |
359 | } |
360 | ||
8930ed80 TG |
361 | /* |
362 | * Deadlock detection is conditional: | |
363 | * | |
364 | * If CONFIG_DEBUG_RT_MUTEXES=n, deadlock detection is only conducted | |
365 | * if the detect argument is == RT_MUTEX_FULL_CHAINWALK. | |
366 | * | |
367 | * If CONFIG_DEBUG_RT_MUTEXES=y, deadlock detection is always | |
368 | * conducted independent of the detect argument. | |
369 | * | |
370 | * If the waiter argument is NULL this indicates the deboost path and | |
371 | * deadlock detection is disabled independent of the detect argument | |
372 | * and the config settings. | |
373 | */ | |
374 | static bool rt_mutex_cond_detect_deadlock(struct rt_mutex_waiter *waiter, | |
375 | enum rtmutex_chainwalk chwalk) | |
376 | { | |
377 | /* | |
378 | * This is just a wrapper function for the following call, | |
379 | * because debug_rt_mutex_detect_deadlock() smells like a magic | |
380 | * debug feature and I wanted to keep the cond function in the | |
381 | * main source file along with the comments instead of having | |
382 | * two of the same in the headers. | |
383 | */ | |
384 | return debug_rt_mutex_detect_deadlock(waiter, chwalk); | |
385 | } | |
386 | ||
23f78d4a IM |
387 | /* |
388 | * Max number of times we'll walk the boosting chain: | |
389 | */ | |
390 | int max_lock_depth = 1024; | |
391 | ||
82084984 TG |
392 | static inline struct rt_mutex *task_blocked_on_lock(struct task_struct *p) |
393 | { | |
394 | return p->pi_blocked_on ? p->pi_blocked_on->lock : NULL; | |
395 | } | |
396 | ||
23f78d4a IM |
397 | /* |
398 | * Adjust the priority chain. Also used for deadlock detection. | |
399 | * Decreases task's usage by one - may thus free the task. | |
0c106173 | 400 | * |
82084984 TG |
401 | * @task: the task owning the mutex (owner) for which a chain walk is |
402 | * probably needed | |
e6beaa36 | 403 | * @chwalk: do we have to carry out deadlock detection? |
82084984 TG |
404 | * @orig_lock: the mutex (can be NULL if we are walking the chain to recheck |
405 | * things for a task that has just got its priority adjusted, and | |
406 | * is waiting on a mutex) | |
407 | * @next_lock: the mutex on which the owner of @orig_lock was blocked before | |
408 | * we dropped its pi_lock. Is never dereferenced, only used for | |
409 | * comparison to detect lock chain changes. | |
0c106173 | 410 | * @orig_waiter: rt_mutex_waiter struct for the task that has just donated |
82084984 TG |
411 | * its priority to the mutex owner (can be NULL in the case |
412 | * depicted above or if the top waiter is gone away and we are | |
413 | * actually deboosting the owner) | |
414 | * @top_task: the current top waiter | |
0c106173 | 415 | * |
23f78d4a | 416 | * Returns 0 or -EDEADLK. |
3eb65aea TG |
417 | * |
418 | * Chain walk basics and protection scope | |
419 | * | |
420 | * [R] refcount on task | |
421 | * [P] task->pi_lock held | |
422 | * [L] rtmutex->wait_lock held | |
423 | * | |
424 | * Step Description Protected by | |
425 | * function arguments: | |
426 | * @task [R] | |
427 | * @orig_lock if != NULL @top_task is blocked on it | |
428 | * @next_lock Unprotected. Cannot be | |
429 | * dereferenced. Only used for | |
430 | * comparison. | |
431 | * @orig_waiter if != NULL @top_task is blocked on it | |
432 | * @top_task current, or in case of proxy | |
433 | * locking protected by calling | |
434 | * code | |
435 | * again: | |
436 | * loop_sanity_check(); | |
437 | * retry: | |
438 | * [1] lock(task->pi_lock); [R] acquire [P] | |
439 | * [2] waiter = task->pi_blocked_on; [P] | |
440 | * [3] check_exit_conditions_1(); [P] | |
441 | * [4] lock = waiter->lock; [P] | |
442 | * [5] if (!try_lock(lock->wait_lock)) { [P] try to acquire [L] | |
443 | * unlock(task->pi_lock); release [P] | |
444 | * goto retry; | |
445 | * } | |
446 | * [6] check_exit_conditions_2(); [P] + [L] | |
447 | * [7] requeue_lock_waiter(lock, waiter); [P] + [L] | |
448 | * [8] unlock(task->pi_lock); release [P] | |
449 | * put_task_struct(task); release [R] | |
450 | * [9] check_exit_conditions_3(); [L] | |
451 | * [10] task = owner(lock); [L] | |
452 | * get_task_struct(task); [L] acquire [R] | |
453 | * lock(task->pi_lock); [L] acquire [P] | |
454 | * [11] requeue_pi_waiter(tsk, waiters(lock));[P] + [L] | |
455 | * [12] check_exit_conditions_4(); [P] + [L] | |
456 | * [13] unlock(task->pi_lock); release [P] | |
457 | * unlock(lock->wait_lock); release [L] | |
458 | * goto again; | |
23f78d4a | 459 | */ |
bd197234 | 460 | static int rt_mutex_adjust_prio_chain(struct task_struct *task, |
8930ed80 | 461 | enum rtmutex_chainwalk chwalk, |
bd197234 | 462 | struct rt_mutex *orig_lock, |
82084984 | 463 | struct rt_mutex *next_lock, |
bd197234 TG |
464 | struct rt_mutex_waiter *orig_waiter, |
465 | struct task_struct *top_task) | |
23f78d4a | 466 | { |
23f78d4a | 467 | struct rt_mutex_waiter *waiter, *top_waiter = orig_waiter; |
a57594a1 | 468 | struct rt_mutex_waiter *prerequeue_top_waiter; |
8930ed80 | 469 | int ret = 0, depth = 0; |
a57594a1 | 470 | struct rt_mutex *lock; |
8930ed80 | 471 | bool detect_deadlock; |
67792e2c | 472 | bool requeue = true; |
23f78d4a | 473 | |
8930ed80 | 474 | detect_deadlock = rt_mutex_cond_detect_deadlock(orig_waiter, chwalk); |
23f78d4a IM |
475 | |
476 | /* | |
477 | * The (de)boosting is a step by step approach with a lot of | |
478 | * pitfalls. We want this to be preemptible and we want hold a | |
479 | * maximum of two locks per step. So we have to check | |
480 | * carefully whether things change under us. | |
481 | */ | |
482 | again: | |
3eb65aea TG |
483 | /* |
484 | * We limit the lock chain length for each invocation. | |
485 | */ | |
23f78d4a IM |
486 | if (++depth > max_lock_depth) { |
487 | static int prev_max; | |
488 | ||
489 | /* | |
490 | * Print this only once. If the admin changes the limit, | |
491 | * print a new message when reaching the limit again. | |
492 | */ | |
493 | if (prev_max != max_lock_depth) { | |
494 | prev_max = max_lock_depth; | |
495 | printk(KERN_WARNING "Maximum lock depth %d reached " | |
496 | "task: %s (%d)\n", max_lock_depth, | |
ba25f9dc | 497 | top_task->comm, task_pid_nr(top_task)); |
23f78d4a IM |
498 | } |
499 | put_task_struct(task); | |
500 | ||
3d5c9340 | 501 | return -EDEADLK; |
23f78d4a | 502 | } |
3eb65aea TG |
503 | |
504 | /* | |
505 | * We are fully preemptible here and only hold the refcount on | |
506 | * @task. So everything can have changed under us since the | |
507 | * caller or our own code below (goto retry/again) dropped all | |
508 | * locks. | |
509 | */ | |
23f78d4a IM |
510 | retry: |
511 | /* | |
3eb65aea | 512 | * [1] Task cannot go away as we did a get_task() before ! |
23f78d4a | 513 | */ |
b4abf910 | 514 | raw_spin_lock_irq(&task->pi_lock); |
23f78d4a | 515 | |
3eb65aea TG |
516 | /* |
517 | * [2] Get the waiter on which @task is blocked on. | |
518 | */ | |
23f78d4a | 519 | waiter = task->pi_blocked_on; |
3eb65aea TG |
520 | |
521 | /* | |
522 | * [3] check_exit_conditions_1() protected by task->pi_lock. | |
523 | */ | |
524 | ||
23f78d4a IM |
525 | /* |
526 | * Check whether the end of the boosting chain has been | |
527 | * reached or the state of the chain has changed while we | |
528 | * dropped the locks. | |
529 | */ | |
8161239a | 530 | if (!waiter) |
23f78d4a IM |
531 | goto out_unlock_pi; |
532 | ||
1a539a87 TG |
533 | /* |
534 | * Check the orig_waiter state. After we dropped the locks, | |
8161239a | 535 | * the previous owner of the lock might have released the lock. |
1a539a87 | 536 | */ |
8161239a | 537 | if (orig_waiter && !rt_mutex_owner(orig_lock)) |
1a539a87 TG |
538 | goto out_unlock_pi; |
539 | ||
82084984 TG |
540 | /* |
541 | * We dropped all locks after taking a refcount on @task, so | |
542 | * the task might have moved on in the lock chain or even left | |
543 | * the chain completely and blocks now on an unrelated lock or | |
544 | * on @orig_lock. | |
545 | * | |
546 | * We stored the lock on which @task was blocked in @next_lock, | |
547 | * so we can detect the chain change. | |
548 | */ | |
549 | if (next_lock != waiter->lock) | |
550 | goto out_unlock_pi; | |
551 | ||
1a539a87 TG |
552 | /* |
553 | * Drop out, when the task has no waiters. Note, | |
554 | * top_waiter can be NULL, when we are in the deboosting | |
555 | * mode! | |
556 | */ | |
397335f0 TG |
557 | if (top_waiter) { |
558 | if (!task_has_pi_waiters(task)) | |
559 | goto out_unlock_pi; | |
560 | /* | |
561 | * If deadlock detection is off, we stop here if we | |
67792e2c TG |
562 | * are not the top pi waiter of the task. If deadlock |
563 | * detection is enabled we continue, but stop the | |
564 | * requeueing in the chain walk. | |
397335f0 | 565 | */ |
67792e2c TG |
566 | if (top_waiter != task_top_pi_waiter(task)) { |
567 | if (!detect_deadlock) | |
568 | goto out_unlock_pi; | |
569 | else | |
570 | requeue = false; | |
571 | } | |
397335f0 | 572 | } |
23f78d4a IM |
573 | |
574 | /* | |
67792e2c TG |
575 | * If the waiter priority is the same as the task priority |
576 | * then there is no further priority adjustment necessary. If | |
577 | * deadlock detection is off, we stop the chain walk. If its | |
578 | * enabled we continue, but stop the requeueing in the chain | |
579 | * walk. | |
23f78d4a | 580 | */ |
19830e55 | 581 | if (rt_mutex_waiter_equal(waiter, task_to_waiter(task))) { |
67792e2c TG |
582 | if (!detect_deadlock) |
583 | goto out_unlock_pi; | |
584 | else | |
585 | requeue = false; | |
586 | } | |
23f78d4a | 587 | |
3eb65aea TG |
588 | /* |
589 | * [4] Get the next lock | |
590 | */ | |
23f78d4a | 591 | lock = waiter->lock; |
3eb65aea TG |
592 | /* |
593 | * [5] We need to trylock here as we are holding task->pi_lock, | |
594 | * which is the reverse lock order versus the other rtmutex | |
595 | * operations. | |
596 | */ | |
d209d74d | 597 | if (!raw_spin_trylock(&lock->wait_lock)) { |
b4abf910 | 598 | raw_spin_unlock_irq(&task->pi_lock); |
23f78d4a IM |
599 | cpu_relax(); |
600 | goto retry; | |
601 | } | |
602 | ||
397335f0 | 603 | /* |
3eb65aea TG |
604 | * [6] check_exit_conditions_2() protected by task->pi_lock and |
605 | * lock->wait_lock. | |
606 | * | |
397335f0 TG |
607 | * Deadlock detection. If the lock is the same as the original |
608 | * lock which caused us to walk the lock chain or if the | |
609 | * current lock is owned by the task which initiated the chain | |
610 | * walk, we detected a deadlock. | |
611 | */ | |
95e02ca9 | 612 | if (lock == orig_lock || rt_mutex_owner(lock) == top_task) { |
8930ed80 | 613 | debug_rt_mutex_deadlock(chwalk, orig_waiter, lock); |
d209d74d | 614 | raw_spin_unlock(&lock->wait_lock); |
3d5c9340 | 615 | ret = -EDEADLK; |
23f78d4a IM |
616 | goto out_unlock_pi; |
617 | } | |
618 | ||
67792e2c TG |
619 | /* |
620 | * If we just follow the lock chain for deadlock detection, no | |
621 | * need to do all the requeue operations. To avoid a truckload | |
622 | * of conditionals around the various places below, just do the | |
623 | * minimum chain walk checks. | |
624 | */ | |
625 | if (!requeue) { | |
626 | /* | |
627 | * No requeue[7] here. Just release @task [8] | |
628 | */ | |
b4abf910 | 629 | raw_spin_unlock(&task->pi_lock); |
67792e2c TG |
630 | put_task_struct(task); |
631 | ||
632 | /* | |
633 | * [9] check_exit_conditions_3 protected by lock->wait_lock. | |
634 | * If there is no owner of the lock, end of chain. | |
635 | */ | |
636 | if (!rt_mutex_owner(lock)) { | |
b4abf910 | 637 | raw_spin_unlock_irq(&lock->wait_lock); |
67792e2c TG |
638 | return 0; |
639 | } | |
640 | ||
641 | /* [10] Grab the next task, i.e. owner of @lock */ | |
642 | task = rt_mutex_owner(lock); | |
643 | get_task_struct(task); | |
b4abf910 | 644 | raw_spin_lock(&task->pi_lock); |
67792e2c TG |
645 | |
646 | /* | |
647 | * No requeue [11] here. We just do deadlock detection. | |
648 | * | |
649 | * [12] Store whether owner is blocked | |
650 | * itself. Decision is made after dropping the locks | |
651 | */ | |
652 | next_lock = task_blocked_on_lock(task); | |
653 | /* | |
654 | * Get the top waiter for the next iteration | |
655 | */ | |
656 | top_waiter = rt_mutex_top_waiter(lock); | |
657 | ||
658 | /* [13] Drop locks */ | |
b4abf910 TG |
659 | raw_spin_unlock(&task->pi_lock); |
660 | raw_spin_unlock_irq(&lock->wait_lock); | |
67792e2c TG |
661 | |
662 | /* If owner is not blocked, end of chain. */ | |
663 | if (!next_lock) | |
664 | goto out_put_task; | |
665 | goto again; | |
666 | } | |
667 | ||
a57594a1 TG |
668 | /* |
669 | * Store the current top waiter before doing the requeue | |
670 | * operation on @lock. We need it for the boost/deboost | |
671 | * decision below. | |
672 | */ | |
673 | prerequeue_top_waiter = rt_mutex_top_waiter(lock); | |
23f78d4a | 674 | |
9f40a51a | 675 | /* [7] Requeue the waiter in the lock waiter tree. */ |
fb00aca4 | 676 | rt_mutex_dequeue(lock, waiter); |
e0aad5b4 PZ |
677 | |
678 | /* | |
679 | * Update the waiter prio fields now that we're dequeued. | |
680 | * | |
681 | * These values can have changed through either: | |
682 | * | |
683 | * sys_sched_set_scheduler() / sys_sched_setattr() | |
684 | * | |
685 | * or | |
686 | * | |
687 | * DL CBS enforcement advancing the effective deadline. | |
688 | * | |
689 | * Even though pi_waiters also uses these fields, and that tree is only | |
690 | * updated in [11], we can do this here, since we hold [L], which | |
691 | * serializes all pi_waiters access and rb_erase() does not care about | |
692 | * the values of the node being removed. | |
693 | */ | |
2d3d891d | 694 | waiter->prio = task->prio; |
e0aad5b4 PZ |
695 | waiter->deadline = task->dl.deadline; |
696 | ||
fb00aca4 | 697 | rt_mutex_enqueue(lock, waiter); |
23f78d4a | 698 | |
3eb65aea | 699 | /* [8] Release the task */ |
b4abf910 | 700 | raw_spin_unlock(&task->pi_lock); |
2ffa5a5c TG |
701 | put_task_struct(task); |
702 | ||
a57594a1 | 703 | /* |
3eb65aea TG |
704 | * [9] check_exit_conditions_3 protected by lock->wait_lock. |
705 | * | |
a57594a1 TG |
706 | * We must abort the chain walk if there is no lock owner even |
707 | * in the dead lock detection case, as we have nothing to | |
708 | * follow here. This is the end of the chain we are walking. | |
709 | */ | |
8161239a LJ |
710 | if (!rt_mutex_owner(lock)) { |
711 | /* | |
3eb65aea TG |
712 | * If the requeue [7] above changed the top waiter, |
713 | * then we need to wake the new top waiter up to try | |
714 | * to get the lock. | |
8161239a | 715 | */ |
a57594a1 | 716 | if (prerequeue_top_waiter != rt_mutex_top_waiter(lock)) |
8161239a | 717 | wake_up_process(rt_mutex_top_waiter(lock)->task); |
b4abf910 | 718 | raw_spin_unlock_irq(&lock->wait_lock); |
2ffa5a5c | 719 | return 0; |
8161239a | 720 | } |
23f78d4a | 721 | |
3eb65aea | 722 | /* [10] Grab the next task, i.e. the owner of @lock */ |
23f78d4a | 723 | task = rt_mutex_owner(lock); |
db630637 | 724 | get_task_struct(task); |
b4abf910 | 725 | raw_spin_lock(&task->pi_lock); |
23f78d4a | 726 | |
3eb65aea | 727 | /* [11] requeue the pi waiters if necessary */ |
23f78d4a | 728 | if (waiter == rt_mutex_top_waiter(lock)) { |
a57594a1 TG |
729 | /* |
730 | * The waiter became the new top (highest priority) | |
731 | * waiter on the lock. Replace the previous top waiter | |
9f40a51a | 732 | * in the owner tasks pi waiters tree with this waiter |
a57594a1 TG |
733 | * and adjust the priority of the owner. |
734 | */ | |
735 | rt_mutex_dequeue_pi(task, prerequeue_top_waiter); | |
fb00aca4 | 736 | rt_mutex_enqueue_pi(task, waiter); |
acd58620 | 737 | rt_mutex_adjust_prio(task); |
23f78d4a | 738 | |
a57594a1 TG |
739 | } else if (prerequeue_top_waiter == waiter) { |
740 | /* | |
741 | * The waiter was the top waiter on the lock, but is | |
742 | * no longer the top prority waiter. Replace waiter in | |
9f40a51a | 743 | * the owner tasks pi waiters tree with the new top |
a57594a1 TG |
744 | * (highest priority) waiter and adjust the priority |
745 | * of the owner. | |
746 | * The new top waiter is stored in @waiter so that | |
747 | * @waiter == @top_waiter evaluates to true below and | |
748 | * we continue to deboost the rest of the chain. | |
749 | */ | |
fb00aca4 | 750 | rt_mutex_dequeue_pi(task, waiter); |
23f78d4a | 751 | waiter = rt_mutex_top_waiter(lock); |
fb00aca4 | 752 | rt_mutex_enqueue_pi(task, waiter); |
acd58620 | 753 | rt_mutex_adjust_prio(task); |
a57594a1 TG |
754 | } else { |
755 | /* | |
756 | * Nothing changed. No need to do any priority | |
757 | * adjustment. | |
758 | */ | |
23f78d4a IM |
759 | } |
760 | ||
82084984 | 761 | /* |
3eb65aea TG |
762 | * [12] check_exit_conditions_4() protected by task->pi_lock |
763 | * and lock->wait_lock. The actual decisions are made after we | |
764 | * dropped the locks. | |
765 | * | |
82084984 TG |
766 | * Check whether the task which owns the current lock is pi |
767 | * blocked itself. If yes we store a pointer to the lock for | |
768 | * the lock chain change detection above. After we dropped | |
769 | * task->pi_lock next_lock cannot be dereferenced anymore. | |
770 | */ | |
771 | next_lock = task_blocked_on_lock(task); | |
a57594a1 TG |
772 | /* |
773 | * Store the top waiter of @lock for the end of chain walk | |
774 | * decision below. | |
775 | */ | |
23f78d4a | 776 | top_waiter = rt_mutex_top_waiter(lock); |
3eb65aea TG |
777 | |
778 | /* [13] Drop the locks */ | |
b4abf910 TG |
779 | raw_spin_unlock(&task->pi_lock); |
780 | raw_spin_unlock_irq(&lock->wait_lock); | |
23f78d4a | 781 | |
82084984 | 782 | /* |
3eb65aea TG |
783 | * Make the actual exit decisions [12], based on the stored |
784 | * values. | |
785 | * | |
82084984 TG |
786 | * We reached the end of the lock chain. Stop right here. No |
787 | * point to go back just to figure that out. | |
788 | */ | |
789 | if (!next_lock) | |
790 | goto out_put_task; | |
791 | ||
a57594a1 TG |
792 | /* |
793 | * If the current waiter is not the top waiter on the lock, | |
794 | * then we can stop the chain walk here if we are not in full | |
795 | * deadlock detection mode. | |
796 | */ | |
23f78d4a IM |
797 | if (!detect_deadlock && waiter != top_waiter) |
798 | goto out_put_task; | |
799 | ||
800 | goto again; | |
801 | ||
802 | out_unlock_pi: | |
b4abf910 | 803 | raw_spin_unlock_irq(&task->pi_lock); |
23f78d4a IM |
804 | out_put_task: |
805 | put_task_struct(task); | |
36c8b586 | 806 | |
23f78d4a IM |
807 | return ret; |
808 | } | |
809 | ||
23f78d4a IM |
810 | /* |
811 | * Try to take an rt-mutex | |
812 | * | |
b4abf910 | 813 | * Must be called with lock->wait_lock held and interrupts disabled |
8161239a | 814 | * |
358c331f TG |
815 | * @lock: The lock to be acquired. |
816 | * @task: The task which wants to acquire the lock | |
9f40a51a | 817 | * @waiter: The waiter that is queued to the lock's wait tree if the |
358c331f | 818 | * callsite called task_blocked_on_lock(), otherwise NULL |
23f78d4a | 819 | */ |
8161239a | 820 | static int try_to_take_rt_mutex(struct rt_mutex *lock, struct task_struct *task, |
358c331f | 821 | struct rt_mutex_waiter *waiter) |
23f78d4a | 822 | { |
e0aad5b4 PZ |
823 | lockdep_assert_held(&lock->wait_lock); |
824 | ||
23f78d4a | 825 | /* |
358c331f TG |
826 | * Before testing whether we can acquire @lock, we set the |
827 | * RT_MUTEX_HAS_WAITERS bit in @lock->owner. This forces all | |
828 | * other tasks which try to modify @lock into the slow path | |
829 | * and they serialize on @lock->wait_lock. | |
23f78d4a | 830 | * |
358c331f TG |
831 | * The RT_MUTEX_HAS_WAITERS bit can have a transitional state |
832 | * as explained at the top of this file if and only if: | |
23f78d4a | 833 | * |
358c331f TG |
834 | * - There is a lock owner. The caller must fixup the |
835 | * transient state if it does a trylock or leaves the lock | |
836 | * function due to a signal or timeout. | |
837 | * | |
838 | * - @task acquires the lock and there are no other | |
839 | * waiters. This is undone in rt_mutex_set_owner(@task) at | |
840 | * the end of this function. | |
23f78d4a IM |
841 | */ |
842 | mark_rt_mutex_waiters(lock); | |
843 | ||
358c331f TG |
844 | /* |
845 | * If @lock has an owner, give up. | |
846 | */ | |
8161239a | 847 | if (rt_mutex_owner(lock)) |
23f78d4a IM |
848 | return 0; |
849 | ||
8161239a | 850 | /* |
358c331f | 851 | * If @waiter != NULL, @task has already enqueued the waiter |
9f40a51a | 852 | * into @lock waiter tree. If @waiter == NULL then this is a |
358c331f | 853 | * trylock attempt. |
8161239a | 854 | */ |
358c331f TG |
855 | if (waiter) { |
856 | /* | |
857 | * If waiter is not the highest priority waiter of | |
858 | * @lock, give up. | |
859 | */ | |
860 | if (waiter != rt_mutex_top_waiter(lock)) | |
861 | return 0; | |
8161239a | 862 | |
358c331f TG |
863 | /* |
864 | * We can acquire the lock. Remove the waiter from the | |
9f40a51a | 865 | * lock waiters tree. |
358c331f TG |
866 | */ |
867 | rt_mutex_dequeue(lock, waiter); | |
8161239a | 868 | |
358c331f | 869 | } else { |
8161239a | 870 | /* |
358c331f TG |
871 | * If the lock has waiters already we check whether @task is |
872 | * eligible to take over the lock. | |
873 | * | |
874 | * If there are no other waiters, @task can acquire | |
875 | * the lock. @task->pi_blocked_on is NULL, so it does | |
876 | * not need to be dequeued. | |
8161239a LJ |
877 | */ |
878 | if (rt_mutex_has_waiters(lock)) { | |
358c331f TG |
879 | /* |
880 | * If @task->prio is greater than or equal to | |
881 | * the top waiter priority (kernel view), | |
882 | * @task lost. | |
883 | */ | |
19830e55 PZ |
884 | if (!rt_mutex_waiter_less(task_to_waiter(task), |
885 | rt_mutex_top_waiter(lock))) | |
358c331f TG |
886 | return 0; |
887 | ||
888 | /* | |
889 | * The current top waiter stays enqueued. We | |
890 | * don't have to change anything in the lock | |
891 | * waiters order. | |
892 | */ | |
893 | } else { | |
894 | /* | |
895 | * No waiters. Take the lock without the | |
896 | * pi_lock dance.@task->pi_blocked_on is NULL | |
897 | * and we have no waiters to enqueue in @task | |
9f40a51a | 898 | * pi waiters tree. |
358c331f TG |
899 | */ |
900 | goto takeit; | |
8161239a | 901 | } |
8161239a LJ |
902 | } |
903 | ||
358c331f TG |
904 | /* |
905 | * Clear @task->pi_blocked_on. Requires protection by | |
906 | * @task->pi_lock. Redundant operation for the @waiter == NULL | |
907 | * case, but conditionals are more expensive than a redundant | |
908 | * store. | |
909 | */ | |
b4abf910 | 910 | raw_spin_lock(&task->pi_lock); |
358c331f TG |
911 | task->pi_blocked_on = NULL; |
912 | /* | |
913 | * Finish the lock acquisition. @task is the new owner. If | |
914 | * other waiters exist we have to insert the highest priority | |
9f40a51a | 915 | * waiter into @task->pi_waiters tree. |
358c331f TG |
916 | */ |
917 | if (rt_mutex_has_waiters(lock)) | |
918 | rt_mutex_enqueue_pi(task, rt_mutex_top_waiter(lock)); | |
b4abf910 | 919 | raw_spin_unlock(&task->pi_lock); |
358c331f TG |
920 | |
921 | takeit: | |
23f78d4a | 922 | /* We got the lock. */ |
9a11b49a | 923 | debug_rt_mutex_lock(lock); |
23f78d4a | 924 | |
358c331f TG |
925 | /* |
926 | * This either preserves the RT_MUTEX_HAS_WAITERS bit if there | |
927 | * are still waiters or clears it. | |
928 | */ | |
8161239a | 929 | rt_mutex_set_owner(lock, task); |
23f78d4a | 930 | |
23f78d4a IM |
931 | return 1; |
932 | } | |
933 | ||
934 | /* | |
935 | * Task blocks on lock. | |
936 | * | |
937 | * Prepare waiter and propagate pi chain | |
938 | * | |
b4abf910 | 939 | * This must be called with lock->wait_lock held and interrupts disabled |
23f78d4a IM |
940 | */ |
941 | static int task_blocks_on_rt_mutex(struct rt_mutex *lock, | |
942 | struct rt_mutex_waiter *waiter, | |
8dac456a | 943 | struct task_struct *task, |
8930ed80 | 944 | enum rtmutex_chainwalk chwalk) |
23f78d4a | 945 | { |
36c8b586 | 946 | struct task_struct *owner = rt_mutex_owner(lock); |
23f78d4a | 947 | struct rt_mutex_waiter *top_waiter = waiter; |
82084984 | 948 | struct rt_mutex *next_lock; |
db630637 | 949 | int chain_walk = 0, res; |
23f78d4a | 950 | |
e0aad5b4 PZ |
951 | lockdep_assert_held(&lock->wait_lock); |
952 | ||
397335f0 TG |
953 | /* |
954 | * Early deadlock detection. We really don't want the task to | |
955 | * enqueue on itself just to untangle the mess later. It's not | |
956 | * only an optimization. We drop the locks, so another waiter | |
957 | * can come in before the chain walk detects the deadlock. So | |
958 | * the other will detect the deadlock and return -EDEADLOCK, | |
959 | * which is wrong, as the other waiter is not in a deadlock | |
960 | * situation. | |
961 | */ | |
3d5c9340 | 962 | if (owner == task) |
397335f0 TG |
963 | return -EDEADLK; |
964 | ||
b4abf910 | 965 | raw_spin_lock(&task->pi_lock); |
acd58620 | 966 | rt_mutex_adjust_prio(task); |
8dac456a | 967 | waiter->task = task; |
23f78d4a | 968 | waiter->lock = lock; |
2d3d891d | 969 | waiter->prio = task->prio; |
e0aad5b4 | 970 | waiter->deadline = task->dl.deadline; |
23f78d4a IM |
971 | |
972 | /* Get the top priority waiter on the lock */ | |
973 | if (rt_mutex_has_waiters(lock)) | |
974 | top_waiter = rt_mutex_top_waiter(lock); | |
fb00aca4 | 975 | rt_mutex_enqueue(lock, waiter); |
23f78d4a | 976 | |
8dac456a | 977 | task->pi_blocked_on = waiter; |
23f78d4a | 978 | |
b4abf910 | 979 | raw_spin_unlock(&task->pi_lock); |
23f78d4a | 980 | |
8161239a LJ |
981 | if (!owner) |
982 | return 0; | |
983 | ||
b4abf910 | 984 | raw_spin_lock(&owner->pi_lock); |
23f78d4a | 985 | if (waiter == rt_mutex_top_waiter(lock)) { |
fb00aca4 PZ |
986 | rt_mutex_dequeue_pi(owner, top_waiter); |
987 | rt_mutex_enqueue_pi(owner, waiter); | |
23f78d4a | 988 | |
acd58620 | 989 | rt_mutex_adjust_prio(owner); |
db630637 SR |
990 | if (owner->pi_blocked_on) |
991 | chain_walk = 1; | |
8930ed80 | 992 | } else if (rt_mutex_cond_detect_deadlock(waiter, chwalk)) { |
db630637 | 993 | chain_walk = 1; |
82084984 | 994 | } |
db630637 | 995 | |
82084984 TG |
996 | /* Store the lock on which owner is blocked or NULL */ |
997 | next_lock = task_blocked_on_lock(owner); | |
998 | ||
b4abf910 | 999 | raw_spin_unlock(&owner->pi_lock); |
82084984 TG |
1000 | /* |
1001 | * Even if full deadlock detection is on, if the owner is not | |
1002 | * blocked itself, we can avoid finding this out in the chain | |
1003 | * walk. | |
1004 | */ | |
1005 | if (!chain_walk || !next_lock) | |
23f78d4a IM |
1006 | return 0; |
1007 | ||
db630637 SR |
1008 | /* |
1009 | * The owner can't disappear while holding a lock, | |
1010 | * so the owner struct is protected by wait_lock. | |
1011 | * Gets dropped in rt_mutex_adjust_prio_chain()! | |
1012 | */ | |
1013 | get_task_struct(owner); | |
1014 | ||
b4abf910 | 1015 | raw_spin_unlock_irq(&lock->wait_lock); |
23f78d4a | 1016 | |
8930ed80 | 1017 | res = rt_mutex_adjust_prio_chain(owner, chwalk, lock, |
82084984 | 1018 | next_lock, waiter, task); |
23f78d4a | 1019 | |
b4abf910 | 1020 | raw_spin_lock_irq(&lock->wait_lock); |
23f78d4a IM |
1021 | |
1022 | return res; | |
1023 | } | |
1024 | ||
1025 | /* | |
9f40a51a | 1026 | * Remove the top waiter from the current tasks pi waiter tree and |
45ab4eff | 1027 | * queue it up. |
23f78d4a | 1028 | * |
b4abf910 | 1029 | * Called with lock->wait_lock held and interrupts disabled. |
23f78d4a | 1030 | */ |
45ab4eff DB |
1031 | static void mark_wakeup_next_waiter(struct wake_q_head *wake_q, |
1032 | struct rt_mutex *lock) | |
23f78d4a IM |
1033 | { |
1034 | struct rt_mutex_waiter *waiter; | |
23f78d4a | 1035 | |
b4abf910 | 1036 | raw_spin_lock(¤t->pi_lock); |
23f78d4a IM |
1037 | |
1038 | waiter = rt_mutex_top_waiter(lock); | |
23f78d4a IM |
1039 | |
1040 | /* | |
acd58620 PZ |
1041 | * Remove it from current->pi_waiters and deboost. |
1042 | * | |
1043 | * We must in fact deboost here in order to ensure we call | |
1044 | * rt_mutex_setprio() to update p->pi_top_task before the | |
1045 | * task unblocks. | |
23f78d4a | 1046 | */ |
fb00aca4 | 1047 | rt_mutex_dequeue_pi(current, waiter); |
acd58620 | 1048 | rt_mutex_adjust_prio(current); |
23f78d4a | 1049 | |
27e35715 TG |
1050 | /* |
1051 | * As we are waking up the top waiter, and the waiter stays | |
1052 | * queued on the lock until it gets the lock, this lock | |
1053 | * obviously has waiters. Just set the bit here and this has | |
1054 | * the added benefit of forcing all new tasks into the | |
1055 | * slow path making sure no task of lower priority than | |
1056 | * the top waiter can steal this lock. | |
1057 | */ | |
1058 | lock->owner = (void *) RT_MUTEX_HAS_WAITERS; | |
23f78d4a | 1059 | |
acd58620 PZ |
1060 | /* |
1061 | * We deboosted before waking the top waiter task such that we don't | |
1062 | * run two tasks with the 'same' priority (and ensure the | |
1063 | * p->pi_top_task pointer points to a blocked task). This however can | |
1064 | * lead to priority inversion if we would get preempted after the | |
1065 | * deboost but before waking our donor task, hence the preempt_disable() | |
1066 | * before unlock. | |
1067 | * | |
1068 | * Pairs with preempt_enable() in rt_mutex_postunlock(); | |
1069 | */ | |
1070 | preempt_disable(); | |
45ab4eff | 1071 | wake_q_add(wake_q, waiter->task); |
acd58620 | 1072 | raw_spin_unlock(¤t->pi_lock); |
23f78d4a IM |
1073 | } |
1074 | ||
1075 | /* | |
8161239a | 1076 | * Remove a waiter from a lock and give up |
23f78d4a | 1077 | * |
b4abf910 | 1078 | * Must be called with lock->wait_lock held and interrupts disabled. I must |
8161239a | 1079 | * have just failed to try_to_take_rt_mutex(). |
23f78d4a | 1080 | */ |
bd197234 TG |
1081 | static void remove_waiter(struct rt_mutex *lock, |
1082 | struct rt_mutex_waiter *waiter) | |
23f78d4a | 1083 | { |
1ca7b860 | 1084 | bool is_top_waiter = (waiter == rt_mutex_top_waiter(lock)); |
36c8b586 | 1085 | struct task_struct *owner = rt_mutex_owner(lock); |
1ca7b860 | 1086 | struct rt_mutex *next_lock; |
23f78d4a | 1087 | |
e0aad5b4 PZ |
1088 | lockdep_assert_held(&lock->wait_lock); |
1089 | ||
b4abf910 | 1090 | raw_spin_lock(¤t->pi_lock); |
fb00aca4 | 1091 | rt_mutex_dequeue(lock, waiter); |
23f78d4a | 1092 | current->pi_blocked_on = NULL; |
b4abf910 | 1093 | raw_spin_unlock(¤t->pi_lock); |
23f78d4a | 1094 | |
1ca7b860 TG |
1095 | /* |
1096 | * Only update priority if the waiter was the highest priority | |
1097 | * waiter of the lock and there is an owner to update. | |
1098 | */ | |
1099 | if (!owner || !is_top_waiter) | |
8161239a LJ |
1100 | return; |
1101 | ||
b4abf910 | 1102 | raw_spin_lock(&owner->pi_lock); |
23f78d4a | 1103 | |
1ca7b860 | 1104 | rt_mutex_dequeue_pi(owner, waiter); |
23f78d4a | 1105 | |
1ca7b860 TG |
1106 | if (rt_mutex_has_waiters(lock)) |
1107 | rt_mutex_enqueue_pi(owner, rt_mutex_top_waiter(lock)); | |
23f78d4a | 1108 | |
acd58620 | 1109 | rt_mutex_adjust_prio(owner); |
23f78d4a | 1110 | |
1ca7b860 TG |
1111 | /* Store the lock on which owner is blocked or NULL */ |
1112 | next_lock = task_blocked_on_lock(owner); | |
db630637 | 1113 | |
b4abf910 | 1114 | raw_spin_unlock(&owner->pi_lock); |
23f78d4a | 1115 | |
1ca7b860 TG |
1116 | /* |
1117 | * Don't walk the chain, if the owner task is not blocked | |
1118 | * itself. | |
1119 | */ | |
82084984 | 1120 | if (!next_lock) |
23f78d4a IM |
1121 | return; |
1122 | ||
db630637 SR |
1123 | /* gets dropped in rt_mutex_adjust_prio_chain()! */ |
1124 | get_task_struct(owner); | |
1125 | ||
b4abf910 | 1126 | raw_spin_unlock_irq(&lock->wait_lock); |
23f78d4a | 1127 | |
8930ed80 TG |
1128 | rt_mutex_adjust_prio_chain(owner, RT_MUTEX_MIN_CHAINWALK, lock, |
1129 | next_lock, NULL, current); | |
23f78d4a | 1130 | |
b4abf910 | 1131 | raw_spin_lock_irq(&lock->wait_lock); |
23f78d4a IM |
1132 | } |
1133 | ||
95e02ca9 TG |
1134 | /* |
1135 | * Recheck the pi chain, in case we got a priority setting | |
1136 | * | |
1137 | * Called from sched_setscheduler | |
1138 | */ | |
1139 | void rt_mutex_adjust_pi(struct task_struct *task) | |
1140 | { | |
1141 | struct rt_mutex_waiter *waiter; | |
82084984 | 1142 | struct rt_mutex *next_lock; |
95e02ca9 TG |
1143 | unsigned long flags; |
1144 | ||
1d615482 | 1145 | raw_spin_lock_irqsave(&task->pi_lock, flags); |
95e02ca9 TG |
1146 | |
1147 | waiter = task->pi_blocked_on; | |
19830e55 | 1148 | if (!waiter || rt_mutex_waiter_equal(waiter, task_to_waiter(task))) { |
1d615482 | 1149 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
95e02ca9 TG |
1150 | return; |
1151 | } | |
82084984 | 1152 | next_lock = waiter->lock; |
1d615482 | 1153 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
95e02ca9 | 1154 | |
db630637 SR |
1155 | /* gets dropped in rt_mutex_adjust_prio_chain()! */ |
1156 | get_task_struct(task); | |
82084984 | 1157 | |
8930ed80 TG |
1158 | rt_mutex_adjust_prio_chain(task, RT_MUTEX_MIN_CHAINWALK, NULL, |
1159 | next_lock, NULL, task); | |
95e02ca9 TG |
1160 | } |
1161 | ||
50809358 PZ |
1162 | void rt_mutex_init_waiter(struct rt_mutex_waiter *waiter) |
1163 | { | |
1164 | debug_rt_mutex_init_waiter(waiter); | |
1165 | RB_CLEAR_NODE(&waiter->pi_tree_entry); | |
1166 | RB_CLEAR_NODE(&waiter->tree_entry); | |
1167 | waiter->task = NULL; | |
1168 | } | |
1169 | ||
8dac456a DH |
1170 | /** |
1171 | * __rt_mutex_slowlock() - Perform the wait-wake-try-to-take loop | |
1172 | * @lock: the rt_mutex to take | |
1173 | * @state: the state the task should block in (TASK_INTERRUPTIBLE | |
b4abf910 | 1174 | * or TASK_UNINTERRUPTIBLE) |
8dac456a DH |
1175 | * @timeout: the pre-initialized and started timer, or NULL for none |
1176 | * @waiter: the pre-initialized rt_mutex_waiter | |
8dac456a | 1177 | * |
b4abf910 | 1178 | * Must be called with lock->wait_lock held and interrupts disabled |
23f78d4a IM |
1179 | */ |
1180 | static int __sched | |
8dac456a DH |
1181 | __rt_mutex_slowlock(struct rt_mutex *lock, int state, |
1182 | struct hrtimer_sleeper *timeout, | |
8161239a | 1183 | struct rt_mutex_waiter *waiter) |
23f78d4a | 1184 | { |
23f78d4a IM |
1185 | int ret = 0; |
1186 | ||
23f78d4a IM |
1187 | for (;;) { |
1188 | /* Try to acquire the lock: */ | |
8161239a | 1189 | if (try_to_take_rt_mutex(lock, current, waiter)) |
23f78d4a IM |
1190 | break; |
1191 | ||
1192 | /* | |
1193 | * TASK_INTERRUPTIBLE checks for signals and | |
1194 | * timeout. Ignored otherwise. | |
1195 | */ | |
4009f4b3 | 1196 | if (likely(state == TASK_INTERRUPTIBLE)) { |
23f78d4a IM |
1197 | /* Signal pending? */ |
1198 | if (signal_pending(current)) | |
1199 | ret = -EINTR; | |
1200 | if (timeout && !timeout->task) | |
1201 | ret = -ETIMEDOUT; | |
1202 | if (ret) | |
1203 | break; | |
1204 | } | |
1205 | ||
b4abf910 | 1206 | raw_spin_unlock_irq(&lock->wait_lock); |
23f78d4a | 1207 | |
8dac456a | 1208 | debug_rt_mutex_print_deadlock(waiter); |
23f78d4a | 1209 | |
1b0b7c17 | 1210 | schedule(); |
23f78d4a | 1211 | |
b4abf910 | 1212 | raw_spin_lock_irq(&lock->wait_lock); |
23f78d4a IM |
1213 | set_current_state(state); |
1214 | } | |
1215 | ||
afffc6c1 | 1216 | __set_current_state(TASK_RUNNING); |
8dac456a DH |
1217 | return ret; |
1218 | } | |
1219 | ||
3d5c9340 TG |
1220 | static void rt_mutex_handle_deadlock(int res, int detect_deadlock, |
1221 | struct rt_mutex_waiter *w) | |
1222 | { | |
1223 | /* | |
1224 | * If the result is not -EDEADLOCK or the caller requested | |
1225 | * deadlock detection, nothing to do here. | |
1226 | */ | |
1227 | if (res != -EDEADLOCK || detect_deadlock) | |
1228 | return; | |
1229 | ||
1230 | /* | |
1231 | * Yell lowdly and stop the task right here. | |
1232 | */ | |
1233 | rt_mutex_print_deadlock(w); | |
1234 | while (1) { | |
1235 | set_current_state(TASK_INTERRUPTIBLE); | |
1236 | schedule(); | |
1237 | } | |
1238 | } | |
1239 | ||
8dac456a DH |
1240 | /* |
1241 | * Slow path lock function: | |
1242 | */ | |
1243 | static int __sched | |
1244 | rt_mutex_slowlock(struct rt_mutex *lock, int state, | |
1245 | struct hrtimer_sleeper *timeout, | |
8930ed80 | 1246 | enum rtmutex_chainwalk chwalk) |
8dac456a DH |
1247 | { |
1248 | struct rt_mutex_waiter waiter; | |
b4abf910 | 1249 | unsigned long flags; |
8dac456a DH |
1250 | int ret = 0; |
1251 | ||
50809358 | 1252 | rt_mutex_init_waiter(&waiter); |
8dac456a | 1253 | |
b4abf910 TG |
1254 | /* |
1255 | * Technically we could use raw_spin_[un]lock_irq() here, but this can | |
1256 | * be called in early boot if the cmpxchg() fast path is disabled | |
1257 | * (debug, no architecture support). In this case we will acquire the | |
1258 | * rtmutex with lock->wait_lock held. But we cannot unconditionally | |
1259 | * enable interrupts in that early boot case. So we need to use the | |
1260 | * irqsave/restore variants. | |
1261 | */ | |
1262 | raw_spin_lock_irqsave(&lock->wait_lock, flags); | |
8dac456a DH |
1263 | |
1264 | /* Try to acquire the lock again: */ | |
8161239a | 1265 | if (try_to_take_rt_mutex(lock, current, NULL)) { |
b4abf910 | 1266 | raw_spin_unlock_irqrestore(&lock->wait_lock, flags); |
8dac456a DH |
1267 | return 0; |
1268 | } | |
1269 | ||
1270 | set_current_state(state); | |
1271 | ||
1272 | /* Setup the timer, when timeout != NULL */ | |
ccdd92c1 | 1273 | if (unlikely(timeout)) |
8dac456a | 1274 | hrtimer_start_expires(&timeout->timer, HRTIMER_MODE_ABS); |
8dac456a | 1275 | |
8930ed80 | 1276 | ret = task_blocks_on_rt_mutex(lock, &waiter, current, chwalk); |
8161239a LJ |
1277 | |
1278 | if (likely(!ret)) | |
afffc6c1 | 1279 | /* sleep on the mutex */ |
8161239a | 1280 | ret = __rt_mutex_slowlock(lock, state, timeout, &waiter); |
8dac456a | 1281 | |
3d5c9340 | 1282 | if (unlikely(ret)) { |
9d3e2d02 | 1283 | __set_current_state(TASK_RUNNING); |
8d1e5a1a SAS |
1284 | if (rt_mutex_has_waiters(lock)) |
1285 | remove_waiter(lock, &waiter); | |
8930ed80 | 1286 | rt_mutex_handle_deadlock(ret, chwalk, &waiter); |
3d5c9340 | 1287 | } |
23f78d4a IM |
1288 | |
1289 | /* | |
1290 | * try_to_take_rt_mutex() sets the waiter bit | |
1291 | * unconditionally. We might have to fix that up. | |
1292 | */ | |
1293 | fixup_rt_mutex_waiters(lock); | |
1294 | ||
b4abf910 | 1295 | raw_spin_unlock_irqrestore(&lock->wait_lock, flags); |
23f78d4a IM |
1296 | |
1297 | /* Remove pending timer: */ | |
1298 | if (unlikely(timeout)) | |
1299 | hrtimer_cancel(&timeout->timer); | |
1300 | ||
23f78d4a IM |
1301 | debug_rt_mutex_free_waiter(&waiter); |
1302 | ||
1303 | return ret; | |
1304 | } | |
1305 | ||
1306 | /* | |
1307 | * Slow path try-lock function: | |
1308 | */ | |
88f2b4c1 | 1309 | static inline int rt_mutex_slowtrylock(struct rt_mutex *lock) |
23f78d4a | 1310 | { |
b4abf910 | 1311 | unsigned long flags; |
88f2b4c1 TG |
1312 | int ret; |
1313 | ||
1314 | /* | |
1315 | * If the lock already has an owner we fail to get the lock. | |
1316 | * This can be done without taking the @lock->wait_lock as | |
1317 | * it is only being read, and this is a trylock anyway. | |
1318 | */ | |
1319 | if (rt_mutex_owner(lock)) | |
1320 | return 0; | |
23f78d4a | 1321 | |
88f2b4c1 | 1322 | /* |
b4abf910 TG |
1323 | * The mutex has currently no owner. Lock the wait lock and try to |
1324 | * acquire the lock. We use irqsave here to support early boot calls. | |
88f2b4c1 | 1325 | */ |
b4abf910 | 1326 | raw_spin_lock_irqsave(&lock->wait_lock, flags); |
23f78d4a | 1327 | |
88f2b4c1 | 1328 | ret = try_to_take_rt_mutex(lock, current, NULL); |
23f78d4a | 1329 | |
88f2b4c1 TG |
1330 | /* |
1331 | * try_to_take_rt_mutex() sets the lock waiters bit | |
1332 | * unconditionally. Clean this up. | |
1333 | */ | |
1334 | fixup_rt_mutex_waiters(lock); | |
23f78d4a | 1335 | |
b4abf910 | 1336 | raw_spin_unlock_irqrestore(&lock->wait_lock, flags); |
23f78d4a IM |
1337 | |
1338 | return ret; | |
1339 | } | |
1340 | ||
1341 | /* | |
802ab58d | 1342 | * Slow path to release a rt-mutex. |
aa2bfe55 PZ |
1343 | * |
1344 | * Return whether the current task needs to call rt_mutex_postunlock(). | |
23f78d4a | 1345 | */ |
802ab58d SAS |
1346 | static bool __sched rt_mutex_slowunlock(struct rt_mutex *lock, |
1347 | struct wake_q_head *wake_q) | |
23f78d4a | 1348 | { |
b4abf910 TG |
1349 | unsigned long flags; |
1350 | ||
1351 | /* irqsave required to support early boot calls */ | |
1352 | raw_spin_lock_irqsave(&lock->wait_lock, flags); | |
23f78d4a IM |
1353 | |
1354 | debug_rt_mutex_unlock(lock); | |
1355 | ||
27e35715 TG |
1356 | /* |
1357 | * We must be careful here if the fast path is enabled. If we | |
1358 | * have no waiters queued we cannot set owner to NULL here | |
1359 | * because of: | |
1360 | * | |
1361 | * foo->lock->owner = NULL; | |
1362 | * rtmutex_lock(foo->lock); <- fast path | |
1363 | * free = atomic_dec_and_test(foo->refcnt); | |
1364 | * rtmutex_unlock(foo->lock); <- fast path | |
1365 | * if (free) | |
1366 | * kfree(foo); | |
1367 | * raw_spin_unlock(foo->lock->wait_lock); | |
1368 | * | |
1369 | * So for the fastpath enabled kernel: | |
1370 | * | |
1371 | * Nothing can set the waiters bit as long as we hold | |
1372 | * lock->wait_lock. So we do the following sequence: | |
1373 | * | |
1374 | * owner = rt_mutex_owner(lock); | |
1375 | * clear_rt_mutex_waiters(lock); | |
1376 | * raw_spin_unlock(&lock->wait_lock); | |
1377 | * if (cmpxchg(&lock->owner, owner, 0) == owner) | |
1378 | * return; | |
1379 | * goto retry; | |
1380 | * | |
1381 | * The fastpath disabled variant is simple as all access to | |
1382 | * lock->owner is serialized by lock->wait_lock: | |
1383 | * | |
1384 | * lock->owner = NULL; | |
1385 | * raw_spin_unlock(&lock->wait_lock); | |
1386 | */ | |
1387 | while (!rt_mutex_has_waiters(lock)) { | |
1388 | /* Drops lock->wait_lock ! */ | |
b4abf910 | 1389 | if (unlock_rt_mutex_safe(lock, flags) == true) |
802ab58d | 1390 | return false; |
27e35715 | 1391 | /* Relock the rtmutex and try again */ |
b4abf910 | 1392 | raw_spin_lock_irqsave(&lock->wait_lock, flags); |
23f78d4a IM |
1393 | } |
1394 | ||
27e35715 TG |
1395 | /* |
1396 | * The wakeup next waiter path does not suffer from the above | |
1397 | * race. See the comments there. | |
45ab4eff DB |
1398 | * |
1399 | * Queue the next waiter for wakeup once we release the wait_lock. | |
27e35715 | 1400 | */ |
802ab58d | 1401 | mark_wakeup_next_waiter(wake_q, lock); |
b4abf910 | 1402 | raw_spin_unlock_irqrestore(&lock->wait_lock, flags); |
23f78d4a | 1403 | |
aa2bfe55 | 1404 | return true; /* call rt_mutex_postunlock() */ |
23f78d4a IM |
1405 | } |
1406 | ||
1407 | /* | |
1408 | * debug aware fast / slowpath lock,trylock,unlock | |
1409 | * | |
1410 | * The atomic acquire/release ops are compiled away, when either the | |
1411 | * architecture does not support cmpxchg or when debugging is enabled. | |
1412 | */ | |
1413 | static inline int | |
1414 | rt_mutex_fastlock(struct rt_mutex *lock, int state, | |
23f78d4a IM |
1415 | int (*slowfn)(struct rt_mutex *lock, int state, |
1416 | struct hrtimer_sleeper *timeout, | |
8930ed80 | 1417 | enum rtmutex_chainwalk chwalk)) |
23f78d4a | 1418 | { |
fffa954f | 1419 | if (likely(rt_mutex_cmpxchg_acquire(lock, NULL, current))) |
23f78d4a | 1420 | return 0; |
fffa954f PZ |
1421 | |
1422 | return slowfn(lock, state, NULL, RT_MUTEX_MIN_CHAINWALK); | |
23f78d4a IM |
1423 | } |
1424 | ||
1425 | static inline int | |
1426 | rt_mutex_timed_fastlock(struct rt_mutex *lock, int state, | |
8930ed80 TG |
1427 | struct hrtimer_sleeper *timeout, |
1428 | enum rtmutex_chainwalk chwalk, | |
23f78d4a IM |
1429 | int (*slowfn)(struct rt_mutex *lock, int state, |
1430 | struct hrtimer_sleeper *timeout, | |
8930ed80 | 1431 | enum rtmutex_chainwalk chwalk)) |
23f78d4a | 1432 | { |
8930ed80 | 1433 | if (chwalk == RT_MUTEX_MIN_CHAINWALK && |
fffa954f | 1434 | likely(rt_mutex_cmpxchg_acquire(lock, NULL, current))) |
23f78d4a | 1435 | return 0; |
fffa954f PZ |
1436 | |
1437 | return slowfn(lock, state, timeout, chwalk); | |
23f78d4a IM |
1438 | } |
1439 | ||
1440 | static inline int | |
1441 | rt_mutex_fasttrylock(struct rt_mutex *lock, | |
9a11b49a | 1442 | int (*slowfn)(struct rt_mutex *lock)) |
23f78d4a | 1443 | { |
fffa954f | 1444 | if (likely(rt_mutex_cmpxchg_acquire(lock, NULL, current))) |
23f78d4a | 1445 | return 1; |
fffa954f | 1446 | |
9a11b49a | 1447 | return slowfn(lock); |
23f78d4a IM |
1448 | } |
1449 | ||
2a1c6029 | 1450 | /* |
aa2bfe55 | 1451 | * Performs the wakeup of the the top-waiter and re-enables preemption. |
2a1c6029 | 1452 | */ |
aa2bfe55 | 1453 | void rt_mutex_postunlock(struct wake_q_head *wake_q) |
2a1c6029 XP |
1454 | { |
1455 | wake_up_q(wake_q); | |
1456 | ||
1457 | /* Pairs with preempt_disable() in rt_mutex_slowunlock() */ | |
aa2bfe55 | 1458 | preempt_enable(); |
2a1c6029 XP |
1459 | } |
1460 | ||
23f78d4a IM |
1461 | static inline void |
1462 | rt_mutex_fastunlock(struct rt_mutex *lock, | |
802ab58d SAS |
1463 | bool (*slowfn)(struct rt_mutex *lock, |
1464 | struct wake_q_head *wqh)) | |
23f78d4a | 1465 | { |
194a6b5b | 1466 | DEFINE_WAKE_Q(wake_q); |
802ab58d | 1467 | |
fffa954f PZ |
1468 | if (likely(rt_mutex_cmpxchg_release(lock, current, NULL))) |
1469 | return; | |
802ab58d | 1470 | |
aa2bfe55 PZ |
1471 | if (slowfn(lock, &wake_q)) |
1472 | rt_mutex_postunlock(&wake_q); | |
23f78d4a IM |
1473 | } |
1474 | ||
1475 | /** | |
1476 | * rt_mutex_lock - lock a rt_mutex | |
1477 | * | |
1478 | * @lock: the rt_mutex to be locked | |
1479 | */ | |
1480 | void __sched rt_mutex_lock(struct rt_mutex *lock) | |
1481 | { | |
1482 | might_sleep(); | |
1483 | ||
f5694788 | 1484 | mutex_acquire(&lock->dep_map, 0, 0, _RET_IP_); |
c051b21f | 1485 | rt_mutex_fastlock(lock, TASK_UNINTERRUPTIBLE, rt_mutex_slowlock); |
23f78d4a IM |
1486 | } |
1487 | EXPORT_SYMBOL_GPL(rt_mutex_lock); | |
1488 | ||
1489 | /** | |
1490 | * rt_mutex_lock_interruptible - lock a rt_mutex interruptible | |
1491 | * | |
c051b21f | 1492 | * @lock: the rt_mutex to be locked |
23f78d4a IM |
1493 | * |
1494 | * Returns: | |
c051b21f TG |
1495 | * 0 on success |
1496 | * -EINTR when interrupted by a signal | |
23f78d4a | 1497 | */ |
c051b21f | 1498 | int __sched rt_mutex_lock_interruptible(struct rt_mutex *lock) |
23f78d4a | 1499 | { |
f5694788 PZ |
1500 | int ret; |
1501 | ||
23f78d4a IM |
1502 | might_sleep(); |
1503 | ||
f5694788 PZ |
1504 | mutex_acquire(&lock->dep_map, 0, 0, _RET_IP_); |
1505 | ret = rt_mutex_fastlock(lock, TASK_INTERRUPTIBLE, rt_mutex_slowlock); | |
1506 | if (ret) | |
1507 | mutex_release(&lock->dep_map, 1, _RET_IP_); | |
1508 | ||
1509 | return ret; | |
23f78d4a IM |
1510 | } |
1511 | EXPORT_SYMBOL_GPL(rt_mutex_lock_interruptible); | |
1512 | ||
5293c2ef PZ |
1513 | /* |
1514 | * Futex variant, must not use fastpath. | |
1515 | */ | |
1516 | int __sched rt_mutex_futex_trylock(struct rt_mutex *lock) | |
1517 | { | |
1518 | return rt_mutex_slowtrylock(lock); | |
c051b21f TG |
1519 | } |
1520 | ||
23f78d4a | 1521 | /** |
23b94b96 LH |
1522 | * rt_mutex_timed_lock - lock a rt_mutex interruptible |
1523 | * the timeout structure is provided | |
1524 | * by the caller | |
23f78d4a | 1525 | * |
c051b21f | 1526 | * @lock: the rt_mutex to be locked |
23f78d4a | 1527 | * @timeout: timeout structure or NULL (no timeout) |
23f78d4a IM |
1528 | * |
1529 | * Returns: | |
c051b21f TG |
1530 | * 0 on success |
1531 | * -EINTR when interrupted by a signal | |
3ac49a1c | 1532 | * -ETIMEDOUT when the timeout expired |
23f78d4a IM |
1533 | */ |
1534 | int | |
c051b21f | 1535 | rt_mutex_timed_lock(struct rt_mutex *lock, struct hrtimer_sleeper *timeout) |
23f78d4a | 1536 | { |
f5694788 PZ |
1537 | int ret; |
1538 | ||
23f78d4a IM |
1539 | might_sleep(); |
1540 | ||
f5694788 PZ |
1541 | mutex_acquire(&lock->dep_map, 0, 0, _RET_IP_); |
1542 | ret = rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout, | |
8930ed80 | 1543 | RT_MUTEX_MIN_CHAINWALK, |
c051b21f | 1544 | rt_mutex_slowlock); |
f5694788 PZ |
1545 | if (ret) |
1546 | mutex_release(&lock->dep_map, 1, _RET_IP_); | |
1547 | ||
1548 | return ret; | |
23f78d4a IM |
1549 | } |
1550 | EXPORT_SYMBOL_GPL(rt_mutex_timed_lock); | |
1551 | ||
1552 | /** | |
1553 | * rt_mutex_trylock - try to lock a rt_mutex | |
1554 | * | |
1555 | * @lock: the rt_mutex to be locked | |
1556 | * | |
6ce47fd9 TG |
1557 | * This function can only be called in thread context. It's safe to |
1558 | * call it from atomic regions, but not from hard interrupt or soft | |
1559 | * interrupt context. | |
1560 | * | |
23f78d4a IM |
1561 | * Returns 1 on success and 0 on contention |
1562 | */ | |
1563 | int __sched rt_mutex_trylock(struct rt_mutex *lock) | |
1564 | { | |
f5694788 PZ |
1565 | int ret; |
1566 | ||
a461d587 | 1567 | if (WARN_ON_ONCE(in_irq() || in_nmi() || in_serving_softirq())) |
6ce47fd9 TG |
1568 | return 0; |
1569 | ||
f5694788 PZ |
1570 | ret = rt_mutex_fasttrylock(lock, rt_mutex_slowtrylock); |
1571 | if (ret) | |
1572 | mutex_acquire(&lock->dep_map, 0, 1, _RET_IP_); | |
1573 | ||
1574 | return ret; | |
23f78d4a IM |
1575 | } |
1576 | EXPORT_SYMBOL_GPL(rt_mutex_trylock); | |
1577 | ||
1578 | /** | |
1579 | * rt_mutex_unlock - unlock a rt_mutex | |
1580 | * | |
1581 | * @lock: the rt_mutex to be unlocked | |
1582 | */ | |
1583 | void __sched rt_mutex_unlock(struct rt_mutex *lock) | |
1584 | { | |
f5694788 | 1585 | mutex_release(&lock->dep_map, 1, _RET_IP_); |
23f78d4a IM |
1586 | rt_mutex_fastunlock(lock, rt_mutex_slowunlock); |
1587 | } | |
1588 | EXPORT_SYMBOL_GPL(rt_mutex_unlock); | |
1589 | ||
802ab58d | 1590 | /** |
5293c2ef PZ |
1591 | * Futex variant, that since futex variants do not use the fast-path, can be |
1592 | * simple and will not need to retry. | |
802ab58d | 1593 | */ |
5293c2ef PZ |
1594 | bool __sched __rt_mutex_futex_unlock(struct rt_mutex *lock, |
1595 | struct wake_q_head *wake_q) | |
802ab58d | 1596 | { |
5293c2ef PZ |
1597 | lockdep_assert_held(&lock->wait_lock); |
1598 | ||
1599 | debug_rt_mutex_unlock(lock); | |
1600 | ||
1601 | if (!rt_mutex_has_waiters(lock)) { | |
1602 | lock->owner = NULL; | |
1603 | return false; /* done */ | |
1604 | } | |
1605 | ||
2a1c6029 | 1606 | /* |
def34eaa MG |
1607 | * We've already deboosted, mark_wakeup_next_waiter() will |
1608 | * retain preempt_disabled when we drop the wait_lock, to | |
1609 | * avoid inversion prior to the wakeup. preempt_disable() | |
1610 | * therein pairs with rt_mutex_postunlock(). | |
2a1c6029 | 1611 | */ |
def34eaa | 1612 | mark_wakeup_next_waiter(wake_q, lock); |
2a1c6029 | 1613 | |
aa2bfe55 | 1614 | return true; /* call postunlock() */ |
5293c2ef | 1615 | } |
fffa954f | 1616 | |
5293c2ef PZ |
1617 | void __sched rt_mutex_futex_unlock(struct rt_mutex *lock) |
1618 | { | |
1619 | DEFINE_WAKE_Q(wake_q); | |
aa2bfe55 | 1620 | bool postunlock; |
5293c2ef PZ |
1621 | |
1622 | raw_spin_lock_irq(&lock->wait_lock); | |
aa2bfe55 | 1623 | postunlock = __rt_mutex_futex_unlock(lock, &wake_q); |
5293c2ef PZ |
1624 | raw_spin_unlock_irq(&lock->wait_lock); |
1625 | ||
aa2bfe55 PZ |
1626 | if (postunlock) |
1627 | rt_mutex_postunlock(&wake_q); | |
802ab58d SAS |
1628 | } |
1629 | ||
23b94b96 | 1630 | /** |
23f78d4a IM |
1631 | * rt_mutex_destroy - mark a mutex unusable |
1632 | * @lock: the mutex to be destroyed | |
1633 | * | |
1634 | * This function marks the mutex uninitialized, and any subsequent | |
1635 | * use of the mutex is forbidden. The mutex must not be locked when | |
1636 | * this function is called. | |
1637 | */ | |
1638 | void rt_mutex_destroy(struct rt_mutex *lock) | |
1639 | { | |
1640 | WARN_ON(rt_mutex_is_locked(lock)); | |
1641 | #ifdef CONFIG_DEBUG_RT_MUTEXES | |
1642 | lock->magic = NULL; | |
1643 | #endif | |
1644 | } | |
23f78d4a IM |
1645 | EXPORT_SYMBOL_GPL(rt_mutex_destroy); |
1646 | ||
1647 | /** | |
1648 | * __rt_mutex_init - initialize the rt lock | |
1649 | * | |
1650 | * @lock: the rt lock to be initialized | |
1651 | * | |
1652 | * Initialize the rt lock to unlocked state. | |
1653 | * | |
1654 | * Initializing of a locked rt lock is not allowed | |
1655 | */ | |
f5694788 PZ |
1656 | void __rt_mutex_init(struct rt_mutex *lock, const char *name, |
1657 | struct lock_class_key *key) | |
23f78d4a IM |
1658 | { |
1659 | lock->owner = NULL; | |
d209d74d | 1660 | raw_spin_lock_init(&lock->wait_lock); |
fb00aca4 PZ |
1661 | lock->waiters = RB_ROOT; |
1662 | lock->waiters_leftmost = NULL; | |
23f78d4a | 1663 | |
cde50a67 LASL |
1664 | if (name && key) |
1665 | debug_rt_mutex_init(lock, name, key); | |
23f78d4a IM |
1666 | } |
1667 | EXPORT_SYMBOL_GPL(__rt_mutex_init); | |
0cdbee99 IM |
1668 | |
1669 | /** | |
1670 | * rt_mutex_init_proxy_locked - initialize and lock a rt_mutex on behalf of a | |
1671 | * proxy owner | |
1672 | * | |
84d82ec5 | 1673 | * @lock: the rt_mutex to be locked |
0cdbee99 IM |
1674 | * @proxy_owner:the task to set as owner |
1675 | * | |
1676 | * No locking. Caller has to do serializing itself | |
84d82ec5 TG |
1677 | * |
1678 | * Special API call for PI-futex support. This initializes the rtmutex and | |
1679 | * assigns it to @proxy_owner. Concurrent operations on the rtmutex are not | |
1680 | * possible at this point because the pi_state which contains the rtmutex | |
1681 | * is not yet visible to other tasks. | |
0cdbee99 IM |
1682 | */ |
1683 | void rt_mutex_init_proxy_locked(struct rt_mutex *lock, | |
1684 | struct task_struct *proxy_owner) | |
1685 | { | |
f5694788 | 1686 | __rt_mutex_init(lock, NULL, NULL); |
9a11b49a | 1687 | debug_rt_mutex_proxy_lock(lock, proxy_owner); |
8161239a | 1688 | rt_mutex_set_owner(lock, proxy_owner); |
0cdbee99 IM |
1689 | } |
1690 | ||
1691 | /** | |
1692 | * rt_mutex_proxy_unlock - release a lock on behalf of owner | |
1693 | * | |
84d82ec5 | 1694 | * @lock: the rt_mutex to be locked |
0cdbee99 IM |
1695 | * |
1696 | * No locking. Caller has to do serializing itself | |
84d82ec5 TG |
1697 | * |
1698 | * Special API call for PI-futex support. This merrily cleans up the rtmutex | |
1699 | * (debugging) state. Concurrent operations on this rt_mutex are not | |
1700 | * possible because it belongs to the pi_state which is about to be freed | |
1701 | * and it is not longer visible to other tasks. | |
0cdbee99 IM |
1702 | */ |
1703 | void rt_mutex_proxy_unlock(struct rt_mutex *lock, | |
1704 | struct task_struct *proxy_owner) | |
1705 | { | |
1706 | debug_rt_mutex_proxy_unlock(lock); | |
8161239a | 1707 | rt_mutex_set_owner(lock, NULL); |
0cdbee99 IM |
1708 | } |
1709 | ||
56222b21 | 1710 | int __rt_mutex_start_proxy_lock(struct rt_mutex *lock, |
8dac456a | 1711 | struct rt_mutex_waiter *waiter, |
c051b21f | 1712 | struct task_struct *task) |
8dac456a DH |
1713 | { |
1714 | int ret; | |
1715 | ||
56222b21 | 1716 | if (try_to_take_rt_mutex(lock, task, NULL)) |
8dac456a | 1717 | return 1; |
8dac456a | 1718 | |
3d5c9340 | 1719 | /* We enforce deadlock detection for futexes */ |
8930ed80 TG |
1720 | ret = task_blocks_on_rt_mutex(lock, waiter, task, |
1721 | RT_MUTEX_FULL_CHAINWALK); | |
8dac456a | 1722 | |
8161239a | 1723 | if (ret && !rt_mutex_owner(lock)) { |
8dac456a DH |
1724 | /* |
1725 | * Reset the return value. We might have | |
1726 | * returned with -EDEADLK and the owner | |
1727 | * released the lock while we were walking the | |
1728 | * pi chain. Let the waiter sort it out. | |
1729 | */ | |
1730 | ret = 0; | |
1731 | } | |
8161239a LJ |
1732 | |
1733 | if (unlikely(ret)) | |
1734 | remove_waiter(lock, waiter); | |
1735 | ||
8dac456a DH |
1736 | debug_rt_mutex_print_deadlock(waiter); |
1737 | ||
1738 | return ret; | |
1739 | } | |
1740 | ||
56222b21 PZ |
1741 | /** |
1742 | * rt_mutex_start_proxy_lock() - Start lock acquisition for another task | |
1743 | * @lock: the rt_mutex to take | |
1744 | * @waiter: the pre-initialized rt_mutex_waiter | |
1745 | * @task: the task to prepare | |
1746 | * | |
1747 | * Returns: | |
1748 | * 0 - task blocked on lock | |
1749 | * 1 - acquired the lock for task, caller should wake it up | |
1750 | * <0 - error | |
1751 | * | |
1752 | * Special API call for FUTEX_REQUEUE_PI support. | |
1753 | */ | |
1754 | int rt_mutex_start_proxy_lock(struct rt_mutex *lock, | |
1755 | struct rt_mutex_waiter *waiter, | |
1756 | struct task_struct *task) | |
1757 | { | |
1758 | int ret; | |
1759 | ||
1760 | raw_spin_lock_irq(&lock->wait_lock); | |
1761 | ret = __rt_mutex_start_proxy_lock(lock, waiter, task); | |
1762 | raw_spin_unlock_irq(&lock->wait_lock); | |
1763 | ||
1764 | return ret; | |
1765 | } | |
1766 | ||
0cdbee99 IM |
1767 | /** |
1768 | * rt_mutex_next_owner - return the next owner of the lock | |
1769 | * | |
1770 | * @lock: the rt lock query | |
1771 | * | |
1772 | * Returns the next owner of the lock or NULL | |
1773 | * | |
1774 | * Caller has to serialize against other accessors to the lock | |
1775 | * itself. | |
1776 | * | |
1777 | * Special API call for PI-futex support | |
1778 | */ | |
1779 | struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock) | |
1780 | { | |
1781 | if (!rt_mutex_has_waiters(lock)) | |
1782 | return NULL; | |
1783 | ||
1784 | return rt_mutex_top_waiter(lock)->task; | |
1785 | } | |
8dac456a DH |
1786 | |
1787 | /** | |
38d589f2 | 1788 | * rt_mutex_wait_proxy_lock() - Wait for lock acquisition |
8dac456a DH |
1789 | * @lock: the rt_mutex we were woken on |
1790 | * @to: the timeout, null if none. hrtimer should already have | |
c051b21f | 1791 | * been started. |
8dac456a | 1792 | * @waiter: the pre-initialized rt_mutex_waiter |
8dac456a | 1793 | * |
38d589f2 PZ |
1794 | * Wait for the the lock acquisition started on our behalf by |
1795 | * rt_mutex_start_proxy_lock(). Upon failure, the caller must call | |
1796 | * rt_mutex_cleanup_proxy_lock(). | |
8dac456a DH |
1797 | * |
1798 | * Returns: | |
1799 | * 0 - success | |
c051b21f | 1800 | * <0 - error, one of -EINTR, -ETIMEDOUT |
8dac456a | 1801 | * |
38d589f2 | 1802 | * Special API call for PI-futex support |
8dac456a | 1803 | */ |
38d589f2 | 1804 | int rt_mutex_wait_proxy_lock(struct rt_mutex *lock, |
8dac456a | 1805 | struct hrtimer_sleeper *to, |
c051b21f | 1806 | struct rt_mutex_waiter *waiter) |
8dac456a DH |
1807 | { |
1808 | int ret; | |
1809 | ||
b4abf910 | 1810 | raw_spin_lock_irq(&lock->wait_lock); |
afffc6c1 | 1811 | /* sleep on the mutex */ |
04dc1b2f | 1812 | set_current_state(TASK_INTERRUPTIBLE); |
8161239a | 1813 | ret = __rt_mutex_slowlock(lock, TASK_INTERRUPTIBLE, to, waiter); |
04dc1b2f PZ |
1814 | /* |
1815 | * try_to_take_rt_mutex() sets the waiter bit unconditionally. We might | |
1816 | * have to fix that up. | |
1817 | */ | |
1818 | fixup_rt_mutex_waiters(lock); | |
b4abf910 | 1819 | raw_spin_unlock_irq(&lock->wait_lock); |
8dac456a | 1820 | |
8dac456a DH |
1821 | return ret; |
1822 | } | |
38d589f2 PZ |
1823 | |
1824 | /** | |
1825 | * rt_mutex_cleanup_proxy_lock() - Cleanup failed lock acquisition | |
1826 | * @lock: the rt_mutex we were woken on | |
1827 | * @waiter: the pre-initialized rt_mutex_waiter | |
1828 | * | |
1829 | * Attempt to clean up after a failed rt_mutex_wait_proxy_lock(). | |
1830 | * | |
1831 | * Unless we acquired the lock; we're still enqueued on the wait-list and can | |
1832 | * in fact still be granted ownership until we're removed. Therefore we can | |
1833 | * find we are in fact the owner and must disregard the | |
1834 | * rt_mutex_wait_proxy_lock() failure. | |
1835 | * | |
1836 | * Returns: | |
1837 | * true - did the cleanup, we done. | |
1838 | * false - we acquired the lock after rt_mutex_wait_proxy_lock() returned, | |
1839 | * caller should disregards its return value. | |
1840 | * | |
1841 | * Special API call for PI-futex support | |
1842 | */ | |
1843 | bool rt_mutex_cleanup_proxy_lock(struct rt_mutex *lock, | |
1844 | struct rt_mutex_waiter *waiter) | |
1845 | { | |
1846 | bool cleanup = false; | |
1847 | ||
1848 | raw_spin_lock_irq(&lock->wait_lock); | |
04dc1b2f PZ |
1849 | /* |
1850 | * Do an unconditional try-lock, this deals with the lock stealing | |
1851 | * state where __rt_mutex_futex_unlock() -> mark_wakeup_next_waiter() | |
1852 | * sets a NULL owner. | |
1853 | * | |
1854 | * We're not interested in the return value, because the subsequent | |
1855 | * test on rt_mutex_owner() will infer that. If the trylock succeeded, | |
1856 | * we will own the lock and it will have removed the waiter. If we | |
1857 | * failed the trylock, we're still not owner and we need to remove | |
1858 | * ourselves. | |
1859 | */ | |
1860 | try_to_take_rt_mutex(lock, current, waiter); | |
38d589f2 PZ |
1861 | /* |
1862 | * Unless we're the owner; we're still enqueued on the wait_list. | |
1863 | * So check if we became owner, if not, take us off the wait_list. | |
1864 | */ | |
1865 | if (rt_mutex_owner(lock) != current) { | |
1866 | remove_waiter(lock, waiter); | |
38d589f2 PZ |
1867 | cleanup = true; |
1868 | } | |
cfafcd11 PZ |
1869 | /* |
1870 | * try_to_take_rt_mutex() sets the waiter bit unconditionally. We might | |
1871 | * have to fix that up. | |
1872 | */ | |
1873 | fixup_rt_mutex_waiters(lock); | |
1874 | ||
38d589f2 PZ |
1875 | raw_spin_unlock_irq(&lock->wait_lock); |
1876 | ||
1877 | return cleanup; | |
1878 | } |