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457c8996 | 1 | // SPDX-License-Identifier: GPL-2.0-only |
23f78d4a IM |
2 | /* |
3 | * RT-Mutexes: simple blocking mutual exclusion locks with PI support | |
4 | * | |
5 | * started by Ingo Molnar and Thomas Gleixner. | |
6 | * | |
7 | * Copyright (C) 2004-2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com> | |
8 | * Copyright (C) 2005-2006 Timesys Corp., Thomas Gleixner <tglx@timesys.com> | |
9 | * Copyright (C) 2005 Kihon Technologies Inc., Steven Rostedt | |
10 | * Copyright (C) 2006 Esben Nielsen | |
992caf7f SR |
11 | * Adaptive Spinlocks: |
12 | * Copyright (C) 2008 Novell, Inc., Gregory Haskins, Sven Dietrich, | |
13 | * and Peter Morreale, | |
14 | * Adaptive Spinlocks simplification: | |
15 | * Copyright (C) 2008 Red Hat, Inc., Steven Rostedt <srostedt@redhat.com> | |
d07fe82c | 16 | * |
387b1468 | 17 | * See Documentation/locking/rt-mutex-design.rst for details. |
23f78d4a | 18 | */ |
531ae4b0 TG |
19 | #include <linux/sched.h> |
20 | #include <linux/sched/debug.h> | |
21 | #include <linux/sched/deadline.h> | |
174cd4b1 | 22 | #include <linux/sched/signal.h> |
8bd75c77 | 23 | #include <linux/sched/rt.h> |
84f001e1 | 24 | #include <linux/sched/wake_q.h> |
add46132 | 25 | #include <linux/ww_mutex.h> |
23f78d4a IM |
26 | |
27 | #include "rtmutex_common.h" | |
28 | ||
add46132 PZ |
29 | #ifndef WW_RT |
30 | # define build_ww_mutex() (false) | |
31 | # define ww_container_of(rtm) NULL | |
32 | ||
33 | static inline int __ww_mutex_add_waiter(struct rt_mutex_waiter *waiter, | |
34 | struct rt_mutex *lock, | |
35 | struct ww_acquire_ctx *ww_ctx) | |
36 | { | |
37 | return 0; | |
38 | } | |
39 | ||
40 | static inline void __ww_mutex_check_waiters(struct rt_mutex *lock, | |
41 | struct ww_acquire_ctx *ww_ctx) | |
42 | { | |
43 | } | |
44 | ||
45 | static inline void ww_mutex_lock_acquired(struct ww_mutex *lock, | |
46 | struct ww_acquire_ctx *ww_ctx) | |
47 | { | |
48 | } | |
49 | ||
50 | static inline int __ww_mutex_check_kill(struct rt_mutex *lock, | |
51 | struct rt_mutex_waiter *waiter, | |
52 | struct ww_acquire_ctx *ww_ctx) | |
53 | { | |
54 | return 0; | |
55 | } | |
56 | ||
57 | #else | |
58 | # define build_ww_mutex() (true) | |
59 | # define ww_container_of(rtm) container_of(rtm, struct ww_mutex, base) | |
60 | # include "ww_mutex.h" | |
61 | #endif | |
62 | ||
23f78d4a IM |
63 | /* |
64 | * lock->owner state tracking: | |
65 | * | |
8161239a LJ |
66 | * lock->owner holds the task_struct pointer of the owner. Bit 0 |
67 | * is used to keep track of the "lock has waiters" state. | |
23f78d4a | 68 | * |
8161239a LJ |
69 | * owner bit0 |
70 | * NULL 0 lock is free (fast acquire possible) | |
71 | * NULL 1 lock is free and has waiters and the top waiter | |
72 | * is going to take the lock* | |
73 | * taskpointer 0 lock is held (fast release possible) | |
74 | * taskpointer 1 lock is held and has waiters** | |
23f78d4a IM |
75 | * |
76 | * The fast atomic compare exchange based acquire and release is only | |
8161239a LJ |
77 | * possible when bit 0 of lock->owner is 0. |
78 | * | |
79 | * (*) It also can be a transitional state when grabbing the lock | |
80 | * with ->wait_lock is held. To prevent any fast path cmpxchg to the lock, | |
81 | * we need to set the bit0 before looking at the lock, and the owner may be | |
82 | * NULL in this small time, hence this can be a transitional state. | |
23f78d4a | 83 | * |
8161239a LJ |
84 | * (**) There is a small time when bit 0 is set but there are no |
85 | * waiters. This can happen when grabbing the lock in the slow path. | |
86 | * To prevent a cmpxchg of the owner releasing the lock, we need to | |
87 | * set this bit before looking at the lock. | |
23f78d4a IM |
88 | */ |
89 | ||
d7a2edb8 | 90 | static __always_inline void |
830e6acc | 91 | rt_mutex_set_owner(struct rt_mutex_base *lock, struct task_struct *owner) |
23f78d4a | 92 | { |
8161239a | 93 | unsigned long val = (unsigned long)owner; |
23f78d4a IM |
94 | |
95 | if (rt_mutex_has_waiters(lock)) | |
96 | val |= RT_MUTEX_HAS_WAITERS; | |
97 | ||
0050c7b2 | 98 | WRITE_ONCE(lock->owner, (struct task_struct *)val); |
23f78d4a IM |
99 | } |
100 | ||
830e6acc | 101 | static __always_inline void clear_rt_mutex_waiters(struct rt_mutex_base *lock) |
23f78d4a IM |
102 | { |
103 | lock->owner = (struct task_struct *) | |
104 | ((unsigned long)lock->owner & ~RT_MUTEX_HAS_WAITERS); | |
105 | } | |
106 | ||
830e6acc | 107 | static __always_inline void fixup_rt_mutex_waiters(struct rt_mutex_base *lock) |
23f78d4a | 108 | { |
dbb26055 TG |
109 | unsigned long owner, *p = (unsigned long *) &lock->owner; |
110 | ||
111 | if (rt_mutex_has_waiters(lock)) | |
112 | return; | |
113 | ||
114 | /* | |
115 | * The rbtree has no waiters enqueued, now make sure that the | |
116 | * lock->owner still has the waiters bit set, otherwise the | |
117 | * following can happen: | |
118 | * | |
119 | * CPU 0 CPU 1 CPU2 | |
120 | * l->owner=T1 | |
121 | * rt_mutex_lock(l) | |
122 | * lock(l->lock) | |
123 | * l->owner = T1 | HAS_WAITERS; | |
124 | * enqueue(T2) | |
125 | * boost() | |
126 | * unlock(l->lock) | |
127 | * block() | |
128 | * | |
129 | * rt_mutex_lock(l) | |
130 | * lock(l->lock) | |
131 | * l->owner = T1 | HAS_WAITERS; | |
132 | * enqueue(T3) | |
133 | * boost() | |
134 | * unlock(l->lock) | |
135 | * block() | |
136 | * signal(->T2) signal(->T3) | |
137 | * lock(l->lock) | |
138 | * dequeue(T2) | |
139 | * deboost() | |
140 | * unlock(l->lock) | |
141 | * lock(l->lock) | |
142 | * dequeue(T3) | |
143 | * ==> wait list is empty | |
144 | * deboost() | |
145 | * unlock(l->lock) | |
146 | * lock(l->lock) | |
147 | * fixup_rt_mutex_waiters() | |
148 | * if (wait_list_empty(l) { | |
149 | * l->owner = owner | |
150 | * owner = l->owner & ~HAS_WAITERS; | |
151 | * ==> l->owner = T1 | |
152 | * } | |
153 | * lock(l->lock) | |
154 | * rt_mutex_unlock(l) fixup_rt_mutex_waiters() | |
155 | * if (wait_list_empty(l) { | |
156 | * owner = l->owner & ~HAS_WAITERS; | |
157 | * cmpxchg(l->owner, T1, NULL) | |
158 | * ===> Success (l->owner = NULL) | |
159 | * | |
160 | * l->owner = owner | |
161 | * ==> l->owner = T1 | |
162 | * } | |
163 | * | |
164 | * With the check for the waiter bit in place T3 on CPU2 will not | |
165 | * overwrite. All tasks fiddling with the waiters bit are | |
166 | * serialized by l->lock, so nothing else can modify the waiters | |
167 | * bit. If the bit is set then nothing can change l->owner either | |
168 | * so the simple RMW is safe. The cmpxchg() will simply fail if it | |
169 | * happens in the middle of the RMW because the waiters bit is | |
170 | * still set. | |
171 | */ | |
172 | owner = READ_ONCE(*p); | |
173 | if (owner & RT_MUTEX_HAS_WAITERS) | |
174 | WRITE_ONCE(*p, owner & ~RT_MUTEX_HAS_WAITERS); | |
23f78d4a IM |
175 | } |
176 | ||
bd197234 | 177 | /* |
cede8841 SAS |
178 | * We can speed up the acquire/release, if there's no debugging state to be |
179 | * set up. | |
bd197234 | 180 | */ |
cede8841 | 181 | #ifndef CONFIG_DEBUG_RT_MUTEXES |
830e6acc | 182 | static __always_inline bool rt_mutex_cmpxchg_acquire(struct rt_mutex_base *lock, |
78515930 SAS |
183 | struct task_struct *old, |
184 | struct task_struct *new) | |
185 | { | |
709e0b62 | 186 | return try_cmpxchg_acquire(&lock->owner, &old, new); |
78515930 SAS |
187 | } |
188 | ||
830e6acc | 189 | static __always_inline bool rt_mutex_cmpxchg_release(struct rt_mutex_base *lock, |
78515930 SAS |
190 | struct task_struct *old, |
191 | struct task_struct *new) | |
192 | { | |
709e0b62 | 193 | return try_cmpxchg_release(&lock->owner, &old, new); |
78515930 | 194 | } |
700318d1 DB |
195 | |
196 | /* | |
197 | * Callers must hold the ->wait_lock -- which is the whole purpose as we force | |
198 | * all future threads that attempt to [Rmw] the lock to the slowpath. As such | |
199 | * relaxed semantics suffice. | |
200 | */ | |
830e6acc | 201 | static __always_inline void mark_rt_mutex_waiters(struct rt_mutex_base *lock) |
bd197234 TG |
202 | { |
203 | unsigned long owner, *p = (unsigned long *) &lock->owner; | |
204 | ||
205 | do { | |
206 | owner = *p; | |
700318d1 DB |
207 | } while (cmpxchg_relaxed(p, owner, |
208 | owner | RT_MUTEX_HAS_WAITERS) != owner); | |
bd197234 | 209 | } |
27e35715 TG |
210 | |
211 | /* | |
212 | * Safe fastpath aware unlock: | |
213 | * 1) Clear the waiters bit | |
214 | * 2) Drop lock->wait_lock | |
215 | * 3) Try to unlock the lock with cmpxchg | |
216 | */ | |
830e6acc | 217 | static __always_inline bool unlock_rt_mutex_safe(struct rt_mutex_base *lock, |
d7a2edb8 | 218 | unsigned long flags) |
27e35715 TG |
219 | __releases(lock->wait_lock) |
220 | { | |
221 | struct task_struct *owner = rt_mutex_owner(lock); | |
222 | ||
223 | clear_rt_mutex_waiters(lock); | |
b4abf910 | 224 | raw_spin_unlock_irqrestore(&lock->wait_lock, flags); |
27e35715 TG |
225 | /* |
226 | * If a new waiter comes in between the unlock and the cmpxchg | |
227 | * we have two situations: | |
228 | * | |
229 | * unlock(wait_lock); | |
230 | * lock(wait_lock); | |
231 | * cmpxchg(p, owner, 0) == owner | |
232 | * mark_rt_mutex_waiters(lock); | |
233 | * acquire(lock); | |
234 | * or: | |
235 | * | |
236 | * unlock(wait_lock); | |
237 | * lock(wait_lock); | |
238 | * mark_rt_mutex_waiters(lock); | |
239 | * | |
240 | * cmpxchg(p, owner, 0) != owner | |
241 | * enqueue_waiter(); | |
242 | * unlock(wait_lock); | |
243 | * lock(wait_lock); | |
244 | * wake waiter(); | |
245 | * unlock(wait_lock); | |
246 | * lock(wait_lock); | |
247 | * acquire(lock); | |
248 | */ | |
700318d1 | 249 | return rt_mutex_cmpxchg_release(lock, owner, NULL); |
27e35715 TG |
250 | } |
251 | ||
bd197234 | 252 | #else |
830e6acc | 253 | static __always_inline bool rt_mutex_cmpxchg_acquire(struct rt_mutex_base *lock, |
78515930 SAS |
254 | struct task_struct *old, |
255 | struct task_struct *new) | |
256 | { | |
257 | return false; | |
258 | ||
259 | } | |
260 | ||
830e6acc | 261 | static __always_inline bool rt_mutex_cmpxchg_release(struct rt_mutex_base *lock, |
78515930 SAS |
262 | struct task_struct *old, |
263 | struct task_struct *new) | |
264 | { | |
265 | return false; | |
266 | } | |
700318d1 | 267 | |
830e6acc | 268 | static __always_inline void mark_rt_mutex_waiters(struct rt_mutex_base *lock) |
bd197234 TG |
269 | { |
270 | lock->owner = (struct task_struct *) | |
271 | ((unsigned long)lock->owner | RT_MUTEX_HAS_WAITERS); | |
272 | } | |
27e35715 TG |
273 | |
274 | /* | |
275 | * Simple slow path only version: lock->owner is protected by lock->wait_lock. | |
276 | */ | |
830e6acc | 277 | static __always_inline bool unlock_rt_mutex_safe(struct rt_mutex_base *lock, |
d7a2edb8 | 278 | unsigned long flags) |
27e35715 TG |
279 | __releases(lock->wait_lock) |
280 | { | |
281 | lock->owner = NULL; | |
b4abf910 | 282 | raw_spin_unlock_irqrestore(&lock->wait_lock, flags); |
27e35715 TG |
283 | return true; |
284 | } | |
bd197234 TG |
285 | #endif |
286 | ||
715f7f9e PZ |
287 | static __always_inline int __waiter_prio(struct task_struct *task) |
288 | { | |
289 | int prio = task->prio; | |
290 | ||
291 | if (!rt_prio(prio)) | |
292 | return DEFAULT_PRIO; | |
293 | ||
294 | return prio; | |
295 | } | |
296 | ||
297 | static __always_inline void | |
298 | waiter_update_prio(struct rt_mutex_waiter *waiter, struct task_struct *task) | |
299 | { | |
300 | waiter->prio = __waiter_prio(task); | |
301 | waiter->deadline = task->dl.deadline; | |
302 | } | |
303 | ||
19830e55 PZ |
304 | /* |
305 | * Only use with rt_mutex_waiter_{less,equal}() | |
306 | */ | |
307 | #define task_to_waiter(p) \ | |
715f7f9e | 308 | &(struct rt_mutex_waiter){ .prio = __waiter_prio(p), .deadline = (p)->dl.deadline } |
19830e55 | 309 | |
d7a2edb8 TG |
310 | static __always_inline int rt_mutex_waiter_less(struct rt_mutex_waiter *left, |
311 | struct rt_mutex_waiter *right) | |
fb00aca4 | 312 | { |
2d3d891d | 313 | if (left->prio < right->prio) |
fb00aca4 PZ |
314 | return 1; |
315 | ||
316 | /* | |
2d3d891d DF |
317 | * If both waiters have dl_prio(), we check the deadlines of the |
318 | * associated tasks. | |
319 | * If left waiter has a dl_prio(), and we didn't return 1 above, | |
320 | * then right waiter has a dl_prio() too. | |
fb00aca4 | 321 | */ |
2d3d891d | 322 | if (dl_prio(left->prio)) |
e0aad5b4 | 323 | return dl_time_before(left->deadline, right->deadline); |
fb00aca4 PZ |
324 | |
325 | return 0; | |
326 | } | |
327 | ||
d7a2edb8 TG |
328 | static __always_inline int rt_mutex_waiter_equal(struct rt_mutex_waiter *left, |
329 | struct rt_mutex_waiter *right) | |
19830e55 PZ |
330 | { |
331 | if (left->prio != right->prio) | |
332 | return 0; | |
333 | ||
334 | /* | |
335 | * If both waiters have dl_prio(), we check the deadlines of the | |
336 | * associated tasks. | |
337 | * If left waiter has a dl_prio(), and we didn't return 0 above, | |
338 | * then right waiter has a dl_prio() too. | |
339 | */ | |
340 | if (dl_prio(left->prio)) | |
341 | return left->deadline == right->deadline; | |
342 | ||
343 | return 1; | |
344 | } | |
345 | ||
48eb3f4f GH |
346 | static inline bool rt_mutex_steal(struct rt_mutex_waiter *waiter, |
347 | struct rt_mutex_waiter *top_waiter) | |
348 | { | |
349 | if (rt_mutex_waiter_less(waiter, top_waiter)) | |
350 | return true; | |
351 | ||
352 | #ifdef RT_MUTEX_BUILD_SPINLOCKS | |
353 | /* | |
354 | * Note that RT tasks are excluded from same priority (lateral) | |
355 | * steals to prevent the introduction of an unbounded latency. | |
356 | */ | |
357 | if (rt_prio(waiter->prio) || dl_prio(waiter->prio)) | |
358 | return false; | |
359 | ||
360 | return rt_mutex_waiter_equal(waiter, top_waiter); | |
361 | #else | |
362 | return false; | |
363 | #endif | |
364 | } | |
365 | ||
5a798725 PZ |
366 | #define __node_2_waiter(node) \ |
367 | rb_entry((node), struct rt_mutex_waiter, tree_entry) | |
368 | ||
d7a2edb8 | 369 | static __always_inline bool __waiter_less(struct rb_node *a, const struct rb_node *b) |
5a798725 | 370 | { |
add46132 PZ |
371 | struct rt_mutex_waiter *aw = __node_2_waiter(a); |
372 | struct rt_mutex_waiter *bw = __node_2_waiter(b); | |
373 | ||
374 | if (rt_mutex_waiter_less(aw, bw)) | |
375 | return 1; | |
376 | ||
377 | if (!build_ww_mutex()) | |
378 | return 0; | |
379 | ||
380 | if (rt_mutex_waiter_less(bw, aw)) | |
381 | return 0; | |
382 | ||
383 | /* NOTE: relies on waiter->ww_ctx being set before insertion */ | |
384 | if (aw->ww_ctx) { | |
385 | if (!bw->ww_ctx) | |
386 | return 1; | |
387 | ||
388 | return (signed long)(aw->ww_ctx->stamp - | |
389 | bw->ww_ctx->stamp) < 0; | |
390 | } | |
391 | ||
392 | return 0; | |
5a798725 PZ |
393 | } |
394 | ||
d7a2edb8 | 395 | static __always_inline void |
830e6acc | 396 | rt_mutex_enqueue(struct rt_mutex_base *lock, struct rt_mutex_waiter *waiter) |
fb00aca4 | 397 | { |
5a798725 | 398 | rb_add_cached(&waiter->tree_entry, &lock->waiters, __waiter_less); |
fb00aca4 PZ |
399 | } |
400 | ||
d7a2edb8 | 401 | static __always_inline void |
830e6acc | 402 | rt_mutex_dequeue(struct rt_mutex_base *lock, struct rt_mutex_waiter *waiter) |
fb00aca4 PZ |
403 | { |
404 | if (RB_EMPTY_NODE(&waiter->tree_entry)) | |
405 | return; | |
406 | ||
a23ba907 | 407 | rb_erase_cached(&waiter->tree_entry, &lock->waiters); |
fb00aca4 PZ |
408 | RB_CLEAR_NODE(&waiter->tree_entry); |
409 | } | |
410 | ||
5a798725 PZ |
411 | #define __node_2_pi_waiter(node) \ |
412 | rb_entry((node), struct rt_mutex_waiter, pi_tree_entry) | |
413 | ||
d7a2edb8 TG |
414 | static __always_inline bool |
415 | __pi_waiter_less(struct rb_node *a, const struct rb_node *b) | |
5a798725 PZ |
416 | { |
417 | return rt_mutex_waiter_less(__node_2_pi_waiter(a), __node_2_pi_waiter(b)); | |
418 | } | |
419 | ||
d7a2edb8 | 420 | static __always_inline void |
fb00aca4 PZ |
421 | rt_mutex_enqueue_pi(struct task_struct *task, struct rt_mutex_waiter *waiter) |
422 | { | |
5a798725 | 423 | rb_add_cached(&waiter->pi_tree_entry, &task->pi_waiters, __pi_waiter_less); |
fb00aca4 PZ |
424 | } |
425 | ||
d7a2edb8 | 426 | static __always_inline void |
fb00aca4 PZ |
427 | rt_mutex_dequeue_pi(struct task_struct *task, struct rt_mutex_waiter *waiter) |
428 | { | |
429 | if (RB_EMPTY_NODE(&waiter->pi_tree_entry)) | |
430 | return; | |
431 | ||
a23ba907 | 432 | rb_erase_cached(&waiter->pi_tree_entry, &task->pi_waiters); |
fb00aca4 PZ |
433 | RB_CLEAR_NODE(&waiter->pi_tree_entry); |
434 | } | |
435 | ||
d7a2edb8 | 436 | static __always_inline void rt_mutex_adjust_prio(struct task_struct *p) |
c365c292 | 437 | { |
acd58620 | 438 | struct task_struct *pi_task = NULL; |
e96a7705 | 439 | |
acd58620 | 440 | lockdep_assert_held(&p->pi_lock); |
c365c292 | 441 | |
acd58620 PZ |
442 | if (task_has_pi_waiters(p)) |
443 | pi_task = task_top_pi_waiter(p)->task; | |
c365c292 | 444 | |
acd58620 | 445 | rt_mutex_setprio(p, pi_task); |
23f78d4a IM |
446 | } |
447 | ||
b576e640 | 448 | /* RT mutex specific wake_q wrappers */ |
9321f815 TG |
449 | static __always_inline void rt_mutex_wake_q_add_task(struct rt_wake_q_head *wqh, |
450 | struct task_struct *task, | |
451 | unsigned int wake_state) | |
b576e640 | 452 | { |
9321f815 | 453 | if (IS_ENABLED(CONFIG_PREEMPT_RT) && wake_state == TASK_RTLOCK_WAIT) { |
456cfbc6 TG |
454 | if (IS_ENABLED(CONFIG_PROVE_LOCKING)) |
455 | WARN_ON_ONCE(wqh->rtlock_task); | |
9321f815 TG |
456 | get_task_struct(task); |
457 | wqh->rtlock_task = task; | |
456cfbc6 | 458 | } else { |
9321f815 | 459 | wake_q_add(&wqh->head, task); |
456cfbc6 | 460 | } |
b576e640 TG |
461 | } |
462 | ||
9321f815 TG |
463 | static __always_inline void rt_mutex_wake_q_add(struct rt_wake_q_head *wqh, |
464 | struct rt_mutex_waiter *w) | |
465 | { | |
466 | rt_mutex_wake_q_add_task(wqh, w->task, w->wake_state); | |
467 | } | |
468 | ||
b576e640 TG |
469 | static __always_inline void rt_mutex_wake_up_q(struct rt_wake_q_head *wqh) |
470 | { | |
456cfbc6 TG |
471 | if (IS_ENABLED(CONFIG_PREEMPT_RT) && wqh->rtlock_task) { |
472 | wake_up_state(wqh->rtlock_task, TASK_RTLOCK_WAIT); | |
473 | put_task_struct(wqh->rtlock_task); | |
474 | wqh->rtlock_task = NULL; | |
475 | } | |
476 | ||
477 | if (!wake_q_empty(&wqh->head)) | |
478 | wake_up_q(&wqh->head); | |
b576e640 TG |
479 | |
480 | /* Pairs with preempt_disable() in mark_wakeup_next_waiter() */ | |
481 | preempt_enable(); | |
482 | } | |
483 | ||
8930ed80 TG |
484 | /* |
485 | * Deadlock detection is conditional: | |
486 | * | |
487 | * If CONFIG_DEBUG_RT_MUTEXES=n, deadlock detection is only conducted | |
488 | * if the detect argument is == RT_MUTEX_FULL_CHAINWALK. | |
489 | * | |
490 | * If CONFIG_DEBUG_RT_MUTEXES=y, deadlock detection is always | |
491 | * conducted independent of the detect argument. | |
492 | * | |
493 | * If the waiter argument is NULL this indicates the deboost path and | |
494 | * deadlock detection is disabled independent of the detect argument | |
495 | * and the config settings. | |
496 | */ | |
d7a2edb8 TG |
497 | static __always_inline bool |
498 | rt_mutex_cond_detect_deadlock(struct rt_mutex_waiter *waiter, | |
499 | enum rtmutex_chainwalk chwalk) | |
8930ed80 | 500 | { |
07d25971 | 501 | if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES)) |
f7efc479 TG |
502 | return waiter != NULL; |
503 | return chwalk == RT_MUTEX_FULL_CHAINWALK; | |
8930ed80 TG |
504 | } |
505 | ||
830e6acc | 506 | static __always_inline struct rt_mutex_base *task_blocked_on_lock(struct task_struct *p) |
82084984 TG |
507 | { |
508 | return p->pi_blocked_on ? p->pi_blocked_on->lock : NULL; | |
509 | } | |
510 | ||
23f78d4a IM |
511 | /* |
512 | * Adjust the priority chain. Also used for deadlock detection. | |
513 | * Decreases task's usage by one - may thus free the task. | |
0c106173 | 514 | * |
82084984 TG |
515 | * @task: the task owning the mutex (owner) for which a chain walk is |
516 | * probably needed | |
e6beaa36 | 517 | * @chwalk: do we have to carry out deadlock detection? |
82084984 TG |
518 | * @orig_lock: the mutex (can be NULL if we are walking the chain to recheck |
519 | * things for a task that has just got its priority adjusted, and | |
520 | * is waiting on a mutex) | |
521 | * @next_lock: the mutex on which the owner of @orig_lock was blocked before | |
522 | * we dropped its pi_lock. Is never dereferenced, only used for | |
523 | * comparison to detect lock chain changes. | |
0c106173 | 524 | * @orig_waiter: rt_mutex_waiter struct for the task that has just donated |
82084984 TG |
525 | * its priority to the mutex owner (can be NULL in the case |
526 | * depicted above or if the top waiter is gone away and we are | |
527 | * actually deboosting the owner) | |
528 | * @top_task: the current top waiter | |
0c106173 | 529 | * |
23f78d4a | 530 | * Returns 0 or -EDEADLK. |
3eb65aea TG |
531 | * |
532 | * Chain walk basics and protection scope | |
533 | * | |
534 | * [R] refcount on task | |
535 | * [P] task->pi_lock held | |
536 | * [L] rtmutex->wait_lock held | |
537 | * | |
538 | * Step Description Protected by | |
539 | * function arguments: | |
540 | * @task [R] | |
541 | * @orig_lock if != NULL @top_task is blocked on it | |
542 | * @next_lock Unprotected. Cannot be | |
543 | * dereferenced. Only used for | |
544 | * comparison. | |
545 | * @orig_waiter if != NULL @top_task is blocked on it | |
546 | * @top_task current, or in case of proxy | |
547 | * locking protected by calling | |
548 | * code | |
549 | * again: | |
550 | * loop_sanity_check(); | |
551 | * retry: | |
552 | * [1] lock(task->pi_lock); [R] acquire [P] | |
553 | * [2] waiter = task->pi_blocked_on; [P] | |
554 | * [3] check_exit_conditions_1(); [P] | |
555 | * [4] lock = waiter->lock; [P] | |
556 | * [5] if (!try_lock(lock->wait_lock)) { [P] try to acquire [L] | |
557 | * unlock(task->pi_lock); release [P] | |
558 | * goto retry; | |
559 | * } | |
560 | * [6] check_exit_conditions_2(); [P] + [L] | |
561 | * [7] requeue_lock_waiter(lock, waiter); [P] + [L] | |
562 | * [8] unlock(task->pi_lock); release [P] | |
563 | * put_task_struct(task); release [R] | |
564 | * [9] check_exit_conditions_3(); [L] | |
565 | * [10] task = owner(lock); [L] | |
566 | * get_task_struct(task); [L] acquire [R] | |
567 | * lock(task->pi_lock); [L] acquire [P] | |
568 | * [11] requeue_pi_waiter(tsk, waiters(lock));[P] + [L] | |
569 | * [12] check_exit_conditions_4(); [P] + [L] | |
570 | * [13] unlock(task->pi_lock); release [P] | |
571 | * unlock(lock->wait_lock); release [L] | |
572 | * goto again; | |
23f78d4a | 573 | */ |
d7a2edb8 TG |
574 | static int __sched rt_mutex_adjust_prio_chain(struct task_struct *task, |
575 | enum rtmutex_chainwalk chwalk, | |
830e6acc PZ |
576 | struct rt_mutex_base *orig_lock, |
577 | struct rt_mutex_base *next_lock, | |
d7a2edb8 TG |
578 | struct rt_mutex_waiter *orig_waiter, |
579 | struct task_struct *top_task) | |
23f78d4a | 580 | { |
23f78d4a | 581 | struct rt_mutex_waiter *waiter, *top_waiter = orig_waiter; |
a57594a1 | 582 | struct rt_mutex_waiter *prerequeue_top_waiter; |
8930ed80 | 583 | int ret = 0, depth = 0; |
830e6acc | 584 | struct rt_mutex_base *lock; |
8930ed80 | 585 | bool detect_deadlock; |
67792e2c | 586 | bool requeue = true; |
23f78d4a | 587 | |
8930ed80 | 588 | detect_deadlock = rt_mutex_cond_detect_deadlock(orig_waiter, chwalk); |
23f78d4a IM |
589 | |
590 | /* | |
591 | * The (de)boosting is a step by step approach with a lot of | |
592 | * pitfalls. We want this to be preemptible and we want hold a | |
593 | * maximum of two locks per step. So we have to check | |
594 | * carefully whether things change under us. | |
595 | */ | |
596 | again: | |
3eb65aea TG |
597 | /* |
598 | * We limit the lock chain length for each invocation. | |
599 | */ | |
23f78d4a IM |
600 | if (++depth > max_lock_depth) { |
601 | static int prev_max; | |
602 | ||
603 | /* | |
604 | * Print this only once. If the admin changes the limit, | |
605 | * print a new message when reaching the limit again. | |
606 | */ | |
607 | if (prev_max != max_lock_depth) { | |
608 | prev_max = max_lock_depth; | |
609 | printk(KERN_WARNING "Maximum lock depth %d reached " | |
610 | "task: %s (%d)\n", max_lock_depth, | |
ba25f9dc | 611 | top_task->comm, task_pid_nr(top_task)); |
23f78d4a IM |
612 | } |
613 | put_task_struct(task); | |
614 | ||
3d5c9340 | 615 | return -EDEADLK; |
23f78d4a | 616 | } |
3eb65aea TG |
617 | |
618 | /* | |
619 | * We are fully preemptible here and only hold the refcount on | |
620 | * @task. So everything can have changed under us since the | |
621 | * caller or our own code below (goto retry/again) dropped all | |
622 | * locks. | |
623 | */ | |
23f78d4a IM |
624 | retry: |
625 | /* | |
3eb65aea | 626 | * [1] Task cannot go away as we did a get_task() before ! |
23f78d4a | 627 | */ |
b4abf910 | 628 | raw_spin_lock_irq(&task->pi_lock); |
23f78d4a | 629 | |
3eb65aea TG |
630 | /* |
631 | * [2] Get the waiter on which @task is blocked on. | |
632 | */ | |
23f78d4a | 633 | waiter = task->pi_blocked_on; |
3eb65aea TG |
634 | |
635 | /* | |
636 | * [3] check_exit_conditions_1() protected by task->pi_lock. | |
637 | */ | |
638 | ||
23f78d4a IM |
639 | /* |
640 | * Check whether the end of the boosting chain has been | |
641 | * reached or the state of the chain has changed while we | |
642 | * dropped the locks. | |
643 | */ | |
8161239a | 644 | if (!waiter) |
23f78d4a IM |
645 | goto out_unlock_pi; |
646 | ||
1a539a87 TG |
647 | /* |
648 | * Check the orig_waiter state. After we dropped the locks, | |
8161239a | 649 | * the previous owner of the lock might have released the lock. |
1a539a87 | 650 | */ |
8161239a | 651 | if (orig_waiter && !rt_mutex_owner(orig_lock)) |
1a539a87 TG |
652 | goto out_unlock_pi; |
653 | ||
82084984 TG |
654 | /* |
655 | * We dropped all locks after taking a refcount on @task, so | |
656 | * the task might have moved on in the lock chain or even left | |
657 | * the chain completely and blocks now on an unrelated lock or | |
658 | * on @orig_lock. | |
659 | * | |
660 | * We stored the lock on which @task was blocked in @next_lock, | |
661 | * so we can detect the chain change. | |
662 | */ | |
663 | if (next_lock != waiter->lock) | |
664 | goto out_unlock_pi; | |
665 | ||
6467822b PZ |
666 | /* |
667 | * There could be 'spurious' loops in the lock graph due to ww_mutex, | |
668 | * consider: | |
669 | * | |
670 | * P1: A, ww_A, ww_B | |
671 | * P2: ww_B, ww_A | |
672 | * P3: A | |
673 | * | |
674 | * P3 should not return -EDEADLK because it gets trapped in the cycle | |
675 | * created by P1 and P2 (which will resolve -- and runs into | |
676 | * max_lock_depth above). Therefore disable detect_deadlock such that | |
677 | * the below termination condition can trigger once all relevant tasks | |
678 | * are boosted. | |
679 | * | |
680 | * Even when we start with ww_mutex we can disable deadlock detection, | |
681 | * since we would supress a ww_mutex induced deadlock at [6] anyway. | |
682 | * Supressing it here however is not sufficient since we might still | |
683 | * hit [6] due to adjustment driven iteration. | |
684 | * | |
685 | * NOTE: if someone were to create a deadlock between 2 ww_classes we'd | |
686 | * utterly fail to report it; lockdep should. | |
687 | */ | |
688 | if (IS_ENABLED(CONFIG_PREEMPT_RT) && waiter->ww_ctx && detect_deadlock) | |
689 | detect_deadlock = false; | |
690 | ||
1a539a87 TG |
691 | /* |
692 | * Drop out, when the task has no waiters. Note, | |
693 | * top_waiter can be NULL, when we are in the deboosting | |
694 | * mode! | |
695 | */ | |
397335f0 TG |
696 | if (top_waiter) { |
697 | if (!task_has_pi_waiters(task)) | |
698 | goto out_unlock_pi; | |
699 | /* | |
700 | * If deadlock detection is off, we stop here if we | |
67792e2c TG |
701 | * are not the top pi waiter of the task. If deadlock |
702 | * detection is enabled we continue, but stop the | |
703 | * requeueing in the chain walk. | |
397335f0 | 704 | */ |
67792e2c TG |
705 | if (top_waiter != task_top_pi_waiter(task)) { |
706 | if (!detect_deadlock) | |
707 | goto out_unlock_pi; | |
708 | else | |
709 | requeue = false; | |
710 | } | |
397335f0 | 711 | } |
23f78d4a IM |
712 | |
713 | /* | |
67792e2c TG |
714 | * If the waiter priority is the same as the task priority |
715 | * then there is no further priority adjustment necessary. If | |
716 | * deadlock detection is off, we stop the chain walk. If its | |
717 | * enabled we continue, but stop the requeueing in the chain | |
718 | * walk. | |
23f78d4a | 719 | */ |
19830e55 | 720 | if (rt_mutex_waiter_equal(waiter, task_to_waiter(task))) { |
67792e2c TG |
721 | if (!detect_deadlock) |
722 | goto out_unlock_pi; | |
723 | else | |
724 | requeue = false; | |
725 | } | |
23f78d4a | 726 | |
3eb65aea TG |
727 | /* |
728 | * [4] Get the next lock | |
729 | */ | |
23f78d4a | 730 | lock = waiter->lock; |
3eb65aea TG |
731 | /* |
732 | * [5] We need to trylock here as we are holding task->pi_lock, | |
733 | * which is the reverse lock order versus the other rtmutex | |
734 | * operations. | |
735 | */ | |
d209d74d | 736 | if (!raw_spin_trylock(&lock->wait_lock)) { |
b4abf910 | 737 | raw_spin_unlock_irq(&task->pi_lock); |
23f78d4a IM |
738 | cpu_relax(); |
739 | goto retry; | |
740 | } | |
741 | ||
397335f0 | 742 | /* |
3eb65aea TG |
743 | * [6] check_exit_conditions_2() protected by task->pi_lock and |
744 | * lock->wait_lock. | |
745 | * | |
397335f0 TG |
746 | * Deadlock detection. If the lock is the same as the original |
747 | * lock which caused us to walk the lock chain or if the | |
748 | * current lock is owned by the task which initiated the chain | |
749 | * walk, we detected a deadlock. | |
750 | */ | |
95e02ca9 | 751 | if (lock == orig_lock || rt_mutex_owner(lock) == top_task) { |
3d5c9340 | 752 | ret = -EDEADLK; |
a055fcc1 PZ |
753 | |
754 | /* | |
755 | * When the deadlock is due to ww_mutex; also see above. Don't | |
756 | * report the deadlock and instead let the ww_mutex wound/die | |
757 | * logic pick which of the contending threads gets -EDEADLK. | |
758 | * | |
759 | * NOTE: assumes the cycle only contains a single ww_class; any | |
760 | * other configuration and we fail to report; also, see | |
761 | * lockdep. | |
762 | */ | |
e5480572 | 763 | if (IS_ENABLED(CONFIG_PREEMPT_RT) && orig_waiter && orig_waiter->ww_ctx) |
a055fcc1 PZ |
764 | ret = 0; |
765 | ||
766 | raw_spin_unlock(&lock->wait_lock); | |
23f78d4a IM |
767 | goto out_unlock_pi; |
768 | } | |
769 | ||
67792e2c TG |
770 | /* |
771 | * If we just follow the lock chain for deadlock detection, no | |
772 | * need to do all the requeue operations. To avoid a truckload | |
773 | * of conditionals around the various places below, just do the | |
774 | * minimum chain walk checks. | |
775 | */ | |
776 | if (!requeue) { | |
777 | /* | |
778 | * No requeue[7] here. Just release @task [8] | |
779 | */ | |
b4abf910 | 780 | raw_spin_unlock(&task->pi_lock); |
67792e2c TG |
781 | put_task_struct(task); |
782 | ||
783 | /* | |
784 | * [9] check_exit_conditions_3 protected by lock->wait_lock. | |
785 | * If there is no owner of the lock, end of chain. | |
786 | */ | |
787 | if (!rt_mutex_owner(lock)) { | |
b4abf910 | 788 | raw_spin_unlock_irq(&lock->wait_lock); |
67792e2c TG |
789 | return 0; |
790 | } | |
791 | ||
792 | /* [10] Grab the next task, i.e. owner of @lock */ | |
7b3c92b8 | 793 | task = get_task_struct(rt_mutex_owner(lock)); |
b4abf910 | 794 | raw_spin_lock(&task->pi_lock); |
67792e2c TG |
795 | |
796 | /* | |
797 | * No requeue [11] here. We just do deadlock detection. | |
798 | * | |
799 | * [12] Store whether owner is blocked | |
800 | * itself. Decision is made after dropping the locks | |
801 | */ | |
802 | next_lock = task_blocked_on_lock(task); | |
803 | /* | |
804 | * Get the top waiter for the next iteration | |
805 | */ | |
806 | top_waiter = rt_mutex_top_waiter(lock); | |
807 | ||
808 | /* [13] Drop locks */ | |
b4abf910 TG |
809 | raw_spin_unlock(&task->pi_lock); |
810 | raw_spin_unlock_irq(&lock->wait_lock); | |
67792e2c TG |
811 | |
812 | /* If owner is not blocked, end of chain. */ | |
813 | if (!next_lock) | |
814 | goto out_put_task; | |
815 | goto again; | |
816 | } | |
817 | ||
a57594a1 TG |
818 | /* |
819 | * Store the current top waiter before doing the requeue | |
820 | * operation on @lock. We need it for the boost/deboost | |
821 | * decision below. | |
822 | */ | |
823 | prerequeue_top_waiter = rt_mutex_top_waiter(lock); | |
23f78d4a | 824 | |
9f40a51a | 825 | /* [7] Requeue the waiter in the lock waiter tree. */ |
fb00aca4 | 826 | rt_mutex_dequeue(lock, waiter); |
e0aad5b4 PZ |
827 | |
828 | /* | |
829 | * Update the waiter prio fields now that we're dequeued. | |
830 | * | |
831 | * These values can have changed through either: | |
832 | * | |
833 | * sys_sched_set_scheduler() / sys_sched_setattr() | |
834 | * | |
835 | * or | |
836 | * | |
837 | * DL CBS enforcement advancing the effective deadline. | |
838 | * | |
839 | * Even though pi_waiters also uses these fields, and that tree is only | |
840 | * updated in [11], we can do this here, since we hold [L], which | |
841 | * serializes all pi_waiters access and rb_erase() does not care about | |
842 | * the values of the node being removed. | |
843 | */ | |
715f7f9e | 844 | waiter_update_prio(waiter, task); |
e0aad5b4 | 845 | |
fb00aca4 | 846 | rt_mutex_enqueue(lock, waiter); |
23f78d4a | 847 | |
3eb65aea | 848 | /* [8] Release the task */ |
b4abf910 | 849 | raw_spin_unlock(&task->pi_lock); |
2ffa5a5c TG |
850 | put_task_struct(task); |
851 | ||
a57594a1 | 852 | /* |
3eb65aea TG |
853 | * [9] check_exit_conditions_3 protected by lock->wait_lock. |
854 | * | |
a57594a1 TG |
855 | * We must abort the chain walk if there is no lock owner even |
856 | * in the dead lock detection case, as we have nothing to | |
857 | * follow here. This is the end of the chain we are walking. | |
858 | */ | |
8161239a LJ |
859 | if (!rt_mutex_owner(lock)) { |
860 | /* | |
3eb65aea TG |
861 | * If the requeue [7] above changed the top waiter, |
862 | * then we need to wake the new top waiter up to try | |
863 | * to get the lock. | |
8161239a | 864 | */ |
a57594a1 | 865 | if (prerequeue_top_waiter != rt_mutex_top_waiter(lock)) |
c014ef69 | 866 | wake_up_state(waiter->task, waiter->wake_state); |
b4abf910 | 867 | raw_spin_unlock_irq(&lock->wait_lock); |
2ffa5a5c | 868 | return 0; |
8161239a | 869 | } |
23f78d4a | 870 | |
3eb65aea | 871 | /* [10] Grab the next task, i.e. the owner of @lock */ |
7b3c92b8 | 872 | task = get_task_struct(rt_mutex_owner(lock)); |
b4abf910 | 873 | raw_spin_lock(&task->pi_lock); |
23f78d4a | 874 | |
3eb65aea | 875 | /* [11] requeue the pi waiters if necessary */ |
23f78d4a | 876 | if (waiter == rt_mutex_top_waiter(lock)) { |
a57594a1 TG |
877 | /* |
878 | * The waiter became the new top (highest priority) | |
879 | * waiter on the lock. Replace the previous top waiter | |
9f40a51a | 880 | * in the owner tasks pi waiters tree with this waiter |
a57594a1 TG |
881 | * and adjust the priority of the owner. |
882 | */ | |
883 | rt_mutex_dequeue_pi(task, prerequeue_top_waiter); | |
fb00aca4 | 884 | rt_mutex_enqueue_pi(task, waiter); |
acd58620 | 885 | rt_mutex_adjust_prio(task); |
23f78d4a | 886 | |
a57594a1 TG |
887 | } else if (prerequeue_top_waiter == waiter) { |
888 | /* | |
889 | * The waiter was the top waiter on the lock, but is | |
e2db7592 | 890 | * no longer the top priority waiter. Replace waiter in |
9f40a51a | 891 | * the owner tasks pi waiters tree with the new top |
a57594a1 TG |
892 | * (highest priority) waiter and adjust the priority |
893 | * of the owner. | |
894 | * The new top waiter is stored in @waiter so that | |
895 | * @waiter == @top_waiter evaluates to true below and | |
896 | * we continue to deboost the rest of the chain. | |
897 | */ | |
fb00aca4 | 898 | rt_mutex_dequeue_pi(task, waiter); |
23f78d4a | 899 | waiter = rt_mutex_top_waiter(lock); |
fb00aca4 | 900 | rt_mutex_enqueue_pi(task, waiter); |
acd58620 | 901 | rt_mutex_adjust_prio(task); |
a57594a1 TG |
902 | } else { |
903 | /* | |
904 | * Nothing changed. No need to do any priority | |
905 | * adjustment. | |
906 | */ | |
23f78d4a IM |
907 | } |
908 | ||
82084984 | 909 | /* |
3eb65aea TG |
910 | * [12] check_exit_conditions_4() protected by task->pi_lock |
911 | * and lock->wait_lock. The actual decisions are made after we | |
912 | * dropped the locks. | |
913 | * | |
82084984 TG |
914 | * Check whether the task which owns the current lock is pi |
915 | * blocked itself. If yes we store a pointer to the lock for | |
916 | * the lock chain change detection above. After we dropped | |
917 | * task->pi_lock next_lock cannot be dereferenced anymore. | |
918 | */ | |
919 | next_lock = task_blocked_on_lock(task); | |
a57594a1 TG |
920 | /* |
921 | * Store the top waiter of @lock for the end of chain walk | |
922 | * decision below. | |
923 | */ | |
23f78d4a | 924 | top_waiter = rt_mutex_top_waiter(lock); |
3eb65aea TG |
925 | |
926 | /* [13] Drop the locks */ | |
b4abf910 TG |
927 | raw_spin_unlock(&task->pi_lock); |
928 | raw_spin_unlock_irq(&lock->wait_lock); | |
23f78d4a | 929 | |
82084984 | 930 | /* |
3eb65aea TG |
931 | * Make the actual exit decisions [12], based on the stored |
932 | * values. | |
933 | * | |
82084984 TG |
934 | * We reached the end of the lock chain. Stop right here. No |
935 | * point to go back just to figure that out. | |
936 | */ | |
937 | if (!next_lock) | |
938 | goto out_put_task; | |
939 | ||
a57594a1 TG |
940 | /* |
941 | * If the current waiter is not the top waiter on the lock, | |
942 | * then we can stop the chain walk here if we are not in full | |
943 | * deadlock detection mode. | |
944 | */ | |
23f78d4a IM |
945 | if (!detect_deadlock && waiter != top_waiter) |
946 | goto out_put_task; | |
947 | ||
948 | goto again; | |
949 | ||
950 | out_unlock_pi: | |
b4abf910 | 951 | raw_spin_unlock_irq(&task->pi_lock); |
23f78d4a IM |
952 | out_put_task: |
953 | put_task_struct(task); | |
36c8b586 | 954 | |
23f78d4a IM |
955 | return ret; |
956 | } | |
957 | ||
23f78d4a IM |
958 | /* |
959 | * Try to take an rt-mutex | |
960 | * | |
b4abf910 | 961 | * Must be called with lock->wait_lock held and interrupts disabled |
8161239a | 962 | * |
358c331f TG |
963 | * @lock: The lock to be acquired. |
964 | * @task: The task which wants to acquire the lock | |
9f40a51a | 965 | * @waiter: The waiter that is queued to the lock's wait tree if the |
358c331f | 966 | * callsite called task_blocked_on_lock(), otherwise NULL |
23f78d4a | 967 | */ |
d7a2edb8 | 968 | static int __sched |
830e6acc | 969 | try_to_take_rt_mutex(struct rt_mutex_base *lock, struct task_struct *task, |
d7a2edb8 | 970 | struct rt_mutex_waiter *waiter) |
23f78d4a | 971 | { |
e0aad5b4 PZ |
972 | lockdep_assert_held(&lock->wait_lock); |
973 | ||
23f78d4a | 974 | /* |
358c331f TG |
975 | * Before testing whether we can acquire @lock, we set the |
976 | * RT_MUTEX_HAS_WAITERS bit in @lock->owner. This forces all | |
977 | * other tasks which try to modify @lock into the slow path | |
978 | * and they serialize on @lock->wait_lock. | |
23f78d4a | 979 | * |
358c331f TG |
980 | * The RT_MUTEX_HAS_WAITERS bit can have a transitional state |
981 | * as explained at the top of this file if and only if: | |
23f78d4a | 982 | * |
358c331f TG |
983 | * - There is a lock owner. The caller must fixup the |
984 | * transient state if it does a trylock or leaves the lock | |
985 | * function due to a signal or timeout. | |
986 | * | |
987 | * - @task acquires the lock and there are no other | |
988 | * waiters. This is undone in rt_mutex_set_owner(@task) at | |
989 | * the end of this function. | |
23f78d4a IM |
990 | */ |
991 | mark_rt_mutex_waiters(lock); | |
992 | ||
358c331f TG |
993 | /* |
994 | * If @lock has an owner, give up. | |
995 | */ | |
8161239a | 996 | if (rt_mutex_owner(lock)) |
23f78d4a IM |
997 | return 0; |
998 | ||
8161239a | 999 | /* |
358c331f | 1000 | * If @waiter != NULL, @task has already enqueued the waiter |
9f40a51a | 1001 | * into @lock waiter tree. If @waiter == NULL then this is a |
358c331f | 1002 | * trylock attempt. |
8161239a | 1003 | */ |
358c331f | 1004 | if (waiter) { |
48eb3f4f | 1005 | struct rt_mutex_waiter *top_waiter = rt_mutex_top_waiter(lock); |
8161239a | 1006 | |
358c331f | 1007 | /* |
48eb3f4f GH |
1008 | * If waiter is the highest priority waiter of @lock, |
1009 | * or allowed to steal it, take it over. | |
358c331f | 1010 | */ |
48eb3f4f GH |
1011 | if (waiter == top_waiter || rt_mutex_steal(waiter, top_waiter)) { |
1012 | /* | |
1013 | * We can acquire the lock. Remove the waiter from the | |
1014 | * lock waiters tree. | |
1015 | */ | |
1016 | rt_mutex_dequeue(lock, waiter); | |
1017 | } else { | |
1018 | return 0; | |
1019 | } | |
358c331f | 1020 | } else { |
8161239a | 1021 | /* |
358c331f TG |
1022 | * If the lock has waiters already we check whether @task is |
1023 | * eligible to take over the lock. | |
1024 | * | |
1025 | * If there are no other waiters, @task can acquire | |
1026 | * the lock. @task->pi_blocked_on is NULL, so it does | |
1027 | * not need to be dequeued. | |
8161239a LJ |
1028 | */ |
1029 | if (rt_mutex_has_waiters(lock)) { | |
48eb3f4f GH |
1030 | /* Check whether the trylock can steal it. */ |
1031 | if (!rt_mutex_steal(task_to_waiter(task), | |
1032 | rt_mutex_top_waiter(lock))) | |
358c331f TG |
1033 | return 0; |
1034 | ||
1035 | /* | |
1036 | * The current top waiter stays enqueued. We | |
1037 | * don't have to change anything in the lock | |
1038 | * waiters order. | |
1039 | */ | |
1040 | } else { | |
1041 | /* | |
1042 | * No waiters. Take the lock without the | |
1043 | * pi_lock dance.@task->pi_blocked_on is NULL | |
1044 | * and we have no waiters to enqueue in @task | |
9f40a51a | 1045 | * pi waiters tree. |
358c331f TG |
1046 | */ |
1047 | goto takeit; | |
8161239a | 1048 | } |
8161239a LJ |
1049 | } |
1050 | ||
358c331f TG |
1051 | /* |
1052 | * Clear @task->pi_blocked_on. Requires protection by | |
1053 | * @task->pi_lock. Redundant operation for the @waiter == NULL | |
1054 | * case, but conditionals are more expensive than a redundant | |
1055 | * store. | |
1056 | */ | |
b4abf910 | 1057 | raw_spin_lock(&task->pi_lock); |
358c331f TG |
1058 | task->pi_blocked_on = NULL; |
1059 | /* | |
1060 | * Finish the lock acquisition. @task is the new owner. If | |
1061 | * other waiters exist we have to insert the highest priority | |
9f40a51a | 1062 | * waiter into @task->pi_waiters tree. |
358c331f TG |
1063 | */ |
1064 | if (rt_mutex_has_waiters(lock)) | |
1065 | rt_mutex_enqueue_pi(task, rt_mutex_top_waiter(lock)); | |
b4abf910 | 1066 | raw_spin_unlock(&task->pi_lock); |
358c331f TG |
1067 | |
1068 | takeit: | |
358c331f TG |
1069 | /* |
1070 | * This either preserves the RT_MUTEX_HAS_WAITERS bit if there | |
1071 | * are still waiters or clears it. | |
1072 | */ | |
8161239a | 1073 | rt_mutex_set_owner(lock, task); |
23f78d4a | 1074 | |
23f78d4a IM |
1075 | return 1; |
1076 | } | |
1077 | ||
1078 | /* | |
1079 | * Task blocks on lock. | |
1080 | * | |
1081 | * Prepare waiter and propagate pi chain | |
1082 | * | |
b4abf910 | 1083 | * This must be called with lock->wait_lock held and interrupts disabled |
23f78d4a | 1084 | */ |
830e6acc | 1085 | static int __sched task_blocks_on_rt_mutex(struct rt_mutex_base *lock, |
d7a2edb8 TG |
1086 | struct rt_mutex_waiter *waiter, |
1087 | struct task_struct *task, | |
add46132 | 1088 | struct ww_acquire_ctx *ww_ctx, |
d7a2edb8 | 1089 | enum rtmutex_chainwalk chwalk) |
23f78d4a | 1090 | { |
36c8b586 | 1091 | struct task_struct *owner = rt_mutex_owner(lock); |
23f78d4a | 1092 | struct rt_mutex_waiter *top_waiter = waiter; |
830e6acc | 1093 | struct rt_mutex_base *next_lock; |
db630637 | 1094 | int chain_walk = 0, res; |
23f78d4a | 1095 | |
e0aad5b4 PZ |
1096 | lockdep_assert_held(&lock->wait_lock); |
1097 | ||
397335f0 TG |
1098 | /* |
1099 | * Early deadlock detection. We really don't want the task to | |
1100 | * enqueue on itself just to untangle the mess later. It's not | |
1101 | * only an optimization. We drop the locks, so another waiter | |
1102 | * can come in before the chain walk detects the deadlock. So | |
1103 | * the other will detect the deadlock and return -EDEADLOCK, | |
1104 | * which is wrong, as the other waiter is not in a deadlock | |
1105 | * situation. | |
02ea9fc9 PZ |
1106 | * |
1107 | * Except for ww_mutex, in that case the chain walk must already deal | |
1108 | * with spurious cycles, see the comments at [3] and [6]. | |
397335f0 | 1109 | */ |
02ea9fc9 | 1110 | if (owner == task && !(build_ww_mutex() && ww_ctx)) |
397335f0 TG |
1111 | return -EDEADLK; |
1112 | ||
b4abf910 | 1113 | raw_spin_lock(&task->pi_lock); |
8dac456a | 1114 | waiter->task = task; |
23f78d4a | 1115 | waiter->lock = lock; |
715f7f9e | 1116 | waiter_update_prio(waiter, task); |
23f78d4a IM |
1117 | |
1118 | /* Get the top priority waiter on the lock */ | |
1119 | if (rt_mutex_has_waiters(lock)) | |
1120 | top_waiter = rt_mutex_top_waiter(lock); | |
fb00aca4 | 1121 | rt_mutex_enqueue(lock, waiter); |
23f78d4a | 1122 | |
8dac456a | 1123 | task->pi_blocked_on = waiter; |
23f78d4a | 1124 | |
b4abf910 | 1125 | raw_spin_unlock(&task->pi_lock); |
23f78d4a | 1126 | |
add46132 PZ |
1127 | if (build_ww_mutex() && ww_ctx) { |
1128 | struct rt_mutex *rtm; | |
1129 | ||
1130 | /* Check whether the waiter should back out immediately */ | |
1131 | rtm = container_of(lock, struct rt_mutex, rtmutex); | |
1132 | res = __ww_mutex_add_waiter(waiter, rtm, ww_ctx); | |
37e8abff TG |
1133 | if (res) { |
1134 | raw_spin_lock(&task->pi_lock); | |
1135 | rt_mutex_dequeue(lock, waiter); | |
1136 | task->pi_blocked_on = NULL; | |
1137 | raw_spin_unlock(&task->pi_lock); | |
add46132 | 1138 | return res; |
37e8abff | 1139 | } |
add46132 PZ |
1140 | } |
1141 | ||
8161239a LJ |
1142 | if (!owner) |
1143 | return 0; | |
1144 | ||
b4abf910 | 1145 | raw_spin_lock(&owner->pi_lock); |
23f78d4a | 1146 | if (waiter == rt_mutex_top_waiter(lock)) { |
fb00aca4 PZ |
1147 | rt_mutex_dequeue_pi(owner, top_waiter); |
1148 | rt_mutex_enqueue_pi(owner, waiter); | |
23f78d4a | 1149 | |
acd58620 | 1150 | rt_mutex_adjust_prio(owner); |
db630637 SR |
1151 | if (owner->pi_blocked_on) |
1152 | chain_walk = 1; | |
8930ed80 | 1153 | } else if (rt_mutex_cond_detect_deadlock(waiter, chwalk)) { |
db630637 | 1154 | chain_walk = 1; |
82084984 | 1155 | } |
db630637 | 1156 | |
82084984 TG |
1157 | /* Store the lock on which owner is blocked or NULL */ |
1158 | next_lock = task_blocked_on_lock(owner); | |
1159 | ||
b4abf910 | 1160 | raw_spin_unlock(&owner->pi_lock); |
82084984 TG |
1161 | /* |
1162 | * Even if full deadlock detection is on, if the owner is not | |
1163 | * blocked itself, we can avoid finding this out in the chain | |
1164 | * walk. | |
1165 | */ | |
1166 | if (!chain_walk || !next_lock) | |
23f78d4a IM |
1167 | return 0; |
1168 | ||
db630637 SR |
1169 | /* |
1170 | * The owner can't disappear while holding a lock, | |
1171 | * so the owner struct is protected by wait_lock. | |
1172 | * Gets dropped in rt_mutex_adjust_prio_chain()! | |
1173 | */ | |
1174 | get_task_struct(owner); | |
1175 | ||
b4abf910 | 1176 | raw_spin_unlock_irq(&lock->wait_lock); |
23f78d4a | 1177 | |
8930ed80 | 1178 | res = rt_mutex_adjust_prio_chain(owner, chwalk, lock, |
82084984 | 1179 | next_lock, waiter, task); |
23f78d4a | 1180 | |
b4abf910 | 1181 | raw_spin_lock_irq(&lock->wait_lock); |
23f78d4a IM |
1182 | |
1183 | return res; | |
1184 | } | |
1185 | ||
1186 | /* | |
9f40a51a | 1187 | * Remove the top waiter from the current tasks pi waiter tree and |
45ab4eff | 1188 | * queue it up. |
23f78d4a | 1189 | * |
b4abf910 | 1190 | * Called with lock->wait_lock held and interrupts disabled. |
23f78d4a | 1191 | */ |
7980aa39 | 1192 | static void __sched mark_wakeup_next_waiter(struct rt_wake_q_head *wqh, |
830e6acc | 1193 | struct rt_mutex_base *lock) |
23f78d4a IM |
1194 | { |
1195 | struct rt_mutex_waiter *waiter; | |
23f78d4a | 1196 | |
b4abf910 | 1197 | raw_spin_lock(¤t->pi_lock); |
23f78d4a IM |
1198 | |
1199 | waiter = rt_mutex_top_waiter(lock); | |
23f78d4a IM |
1200 | |
1201 | /* | |
acd58620 PZ |
1202 | * Remove it from current->pi_waiters and deboost. |
1203 | * | |
1204 | * We must in fact deboost here in order to ensure we call | |
1205 | * rt_mutex_setprio() to update p->pi_top_task before the | |
1206 | * task unblocks. | |
23f78d4a | 1207 | */ |
fb00aca4 | 1208 | rt_mutex_dequeue_pi(current, waiter); |
acd58620 | 1209 | rt_mutex_adjust_prio(current); |
23f78d4a | 1210 | |
27e35715 TG |
1211 | /* |
1212 | * As we are waking up the top waiter, and the waiter stays | |
1213 | * queued on the lock until it gets the lock, this lock | |
1214 | * obviously has waiters. Just set the bit here and this has | |
1215 | * the added benefit of forcing all new tasks into the | |
1216 | * slow path making sure no task of lower priority than | |
1217 | * the top waiter can steal this lock. | |
1218 | */ | |
1219 | lock->owner = (void *) RT_MUTEX_HAS_WAITERS; | |
23f78d4a | 1220 | |
acd58620 PZ |
1221 | /* |
1222 | * We deboosted before waking the top waiter task such that we don't | |
1223 | * run two tasks with the 'same' priority (and ensure the | |
1224 | * p->pi_top_task pointer points to a blocked task). This however can | |
1225 | * lead to priority inversion if we would get preempted after the | |
1226 | * deboost but before waking our donor task, hence the preempt_disable() | |
1227 | * before unlock. | |
1228 | * | |
7980aa39 | 1229 | * Pairs with preempt_enable() in rt_mutex_wake_up_q(); |
acd58620 PZ |
1230 | */ |
1231 | preempt_disable(); | |
7980aa39 | 1232 | rt_mutex_wake_q_add(wqh, waiter); |
acd58620 | 1233 | raw_spin_unlock(¤t->pi_lock); |
23f78d4a IM |
1234 | } |
1235 | ||
e17ba59b TG |
1236 | static int __sched __rt_mutex_slowtrylock(struct rt_mutex_base *lock) |
1237 | { | |
1238 | int ret = try_to_take_rt_mutex(lock, current, NULL); | |
1239 | ||
1240 | /* | |
1241 | * try_to_take_rt_mutex() sets the lock waiters bit | |
1242 | * unconditionally. Clean this up. | |
1243 | */ | |
1244 | fixup_rt_mutex_waiters(lock); | |
1245 | ||
1246 | return ret; | |
1247 | } | |
1248 | ||
1249 | /* | |
1250 | * Slow path try-lock function: | |
1251 | */ | |
1252 | static int __sched rt_mutex_slowtrylock(struct rt_mutex_base *lock) | |
1253 | { | |
1254 | unsigned long flags; | |
1255 | int ret; | |
1256 | ||
1257 | /* | |
1258 | * If the lock already has an owner we fail to get the lock. | |
1259 | * This can be done without taking the @lock->wait_lock as | |
1260 | * it is only being read, and this is a trylock anyway. | |
1261 | */ | |
1262 | if (rt_mutex_owner(lock)) | |
1263 | return 0; | |
1264 | ||
1265 | /* | |
1266 | * The mutex has currently no owner. Lock the wait lock and try to | |
1267 | * acquire the lock. We use irqsave here to support early boot calls. | |
1268 | */ | |
1269 | raw_spin_lock_irqsave(&lock->wait_lock, flags); | |
1270 | ||
1271 | ret = __rt_mutex_slowtrylock(lock); | |
1272 | ||
1273 | raw_spin_unlock_irqrestore(&lock->wait_lock, flags); | |
1274 | ||
1275 | return ret; | |
1276 | } | |
1277 | ||
1278 | static __always_inline int __rt_mutex_trylock(struct rt_mutex_base *lock) | |
1279 | { | |
1280 | if (likely(rt_mutex_cmpxchg_acquire(lock, NULL, current))) | |
1281 | return 1; | |
1282 | ||
1283 | return rt_mutex_slowtrylock(lock); | |
1284 | } | |
1285 | ||
1286 | /* | |
1287 | * Slow path to release a rt-mutex. | |
1288 | */ | |
1289 | static void __sched rt_mutex_slowunlock(struct rt_mutex_base *lock) | |
1290 | { | |
1291 | DEFINE_RT_WAKE_Q(wqh); | |
1292 | unsigned long flags; | |
1293 | ||
1294 | /* irqsave required to support early boot calls */ | |
1295 | raw_spin_lock_irqsave(&lock->wait_lock, flags); | |
1296 | ||
1297 | debug_rt_mutex_unlock(lock); | |
1298 | ||
1299 | /* | |
1300 | * We must be careful here if the fast path is enabled. If we | |
1301 | * have no waiters queued we cannot set owner to NULL here | |
1302 | * because of: | |
1303 | * | |
1304 | * foo->lock->owner = NULL; | |
1305 | * rtmutex_lock(foo->lock); <- fast path | |
1306 | * free = atomic_dec_and_test(foo->refcnt); | |
1307 | * rtmutex_unlock(foo->lock); <- fast path | |
1308 | * if (free) | |
1309 | * kfree(foo); | |
1310 | * raw_spin_unlock(foo->lock->wait_lock); | |
1311 | * | |
1312 | * So for the fastpath enabled kernel: | |
1313 | * | |
1314 | * Nothing can set the waiters bit as long as we hold | |
1315 | * lock->wait_lock. So we do the following sequence: | |
1316 | * | |
1317 | * owner = rt_mutex_owner(lock); | |
1318 | * clear_rt_mutex_waiters(lock); | |
1319 | * raw_spin_unlock(&lock->wait_lock); | |
1320 | * if (cmpxchg(&lock->owner, owner, 0) == owner) | |
1321 | * return; | |
1322 | * goto retry; | |
1323 | * | |
1324 | * The fastpath disabled variant is simple as all access to | |
1325 | * lock->owner is serialized by lock->wait_lock: | |
1326 | * | |
1327 | * lock->owner = NULL; | |
1328 | * raw_spin_unlock(&lock->wait_lock); | |
1329 | */ | |
1330 | while (!rt_mutex_has_waiters(lock)) { | |
1331 | /* Drops lock->wait_lock ! */ | |
1332 | if (unlock_rt_mutex_safe(lock, flags) == true) | |
1333 | return; | |
1334 | /* Relock the rtmutex and try again */ | |
1335 | raw_spin_lock_irqsave(&lock->wait_lock, flags); | |
1336 | } | |
1337 | ||
1338 | /* | |
1339 | * The wakeup next waiter path does not suffer from the above | |
1340 | * race. See the comments there. | |
1341 | * | |
1342 | * Queue the next waiter for wakeup once we release the wait_lock. | |
1343 | */ | |
1344 | mark_wakeup_next_waiter(&wqh, lock); | |
1345 | raw_spin_unlock_irqrestore(&lock->wait_lock, flags); | |
1346 | ||
1347 | rt_mutex_wake_up_q(&wqh); | |
1348 | } | |
1349 | ||
1350 | static __always_inline void __rt_mutex_unlock(struct rt_mutex_base *lock) | |
1351 | { | |
1352 | if (likely(rt_mutex_cmpxchg_release(lock, current, NULL))) | |
1353 | return; | |
1354 | ||
1355 | rt_mutex_slowunlock(lock); | |
1356 | } | |
1357 | ||
992caf7f SR |
1358 | #ifdef CONFIG_SMP |
1359 | static bool rtmutex_spin_on_owner(struct rt_mutex_base *lock, | |
1360 | struct rt_mutex_waiter *waiter, | |
1361 | struct task_struct *owner) | |
1362 | { | |
1363 | bool res = true; | |
1364 | ||
1365 | rcu_read_lock(); | |
1366 | for (;;) { | |
1367 | /* If owner changed, trylock again. */ | |
1368 | if (owner != rt_mutex_owner(lock)) | |
1369 | break; | |
1370 | /* | |
1371 | * Ensure that @owner is dereferenced after checking that | |
1372 | * the lock owner still matches @owner. If that fails, | |
1373 | * @owner might point to freed memory. If it still matches, | |
1374 | * the rcu_read_lock() ensures the memory stays valid. | |
1375 | */ | |
1376 | barrier(); | |
1377 | /* | |
1378 | * Stop spinning when: | |
1379 | * - the lock owner has been scheduled out | |
1380 | * - current is not longer the top waiter | |
1381 | * - current is requested to reschedule (redundant | |
1382 | * for CONFIG_PREEMPT_RCU=y) | |
1383 | * - the VCPU on which owner runs is preempted | |
1384 | */ | |
c0bed69d | 1385 | if (!owner_on_cpu(owner) || need_resched() || |
f16cc980 | 1386 | !rt_mutex_waiter_is_top_waiter(lock, waiter)) { |
992caf7f SR |
1387 | res = false; |
1388 | break; | |
1389 | } | |
1390 | cpu_relax(); | |
1391 | } | |
1392 | rcu_read_unlock(); | |
1393 | return res; | |
1394 | } | |
1395 | #else | |
1396 | static bool rtmutex_spin_on_owner(struct rt_mutex_base *lock, | |
1397 | struct rt_mutex_waiter *waiter, | |
1398 | struct task_struct *owner) | |
1399 | { | |
1400 | return false; | |
1401 | } | |
1402 | #endif | |
1403 | ||
e17ba59b TG |
1404 | #ifdef RT_MUTEX_BUILD_MUTEX |
1405 | /* | |
1406 | * Functions required for: | |
1407 | * - rtmutex, futex on all kernels | |
1408 | * - mutex and rwsem substitutions on RT kernels | |
1409 | */ | |
1410 | ||
23f78d4a | 1411 | /* |
8161239a | 1412 | * Remove a waiter from a lock and give up |
23f78d4a | 1413 | * |
e17ba59b | 1414 | * Must be called with lock->wait_lock held and interrupts disabled. It must |
8161239a | 1415 | * have just failed to try_to_take_rt_mutex(). |
23f78d4a | 1416 | */ |
830e6acc | 1417 | static void __sched remove_waiter(struct rt_mutex_base *lock, |
d7a2edb8 | 1418 | struct rt_mutex_waiter *waiter) |
23f78d4a | 1419 | { |
1ca7b860 | 1420 | bool is_top_waiter = (waiter == rt_mutex_top_waiter(lock)); |
36c8b586 | 1421 | struct task_struct *owner = rt_mutex_owner(lock); |
830e6acc | 1422 | struct rt_mutex_base *next_lock; |
23f78d4a | 1423 | |
e0aad5b4 PZ |
1424 | lockdep_assert_held(&lock->wait_lock); |
1425 | ||
b4abf910 | 1426 | raw_spin_lock(¤t->pi_lock); |
fb00aca4 | 1427 | rt_mutex_dequeue(lock, waiter); |
23f78d4a | 1428 | current->pi_blocked_on = NULL; |
b4abf910 | 1429 | raw_spin_unlock(¤t->pi_lock); |
23f78d4a | 1430 | |
1ca7b860 TG |
1431 | /* |
1432 | * Only update priority if the waiter was the highest priority | |
1433 | * waiter of the lock and there is an owner to update. | |
1434 | */ | |
1435 | if (!owner || !is_top_waiter) | |
8161239a LJ |
1436 | return; |
1437 | ||
b4abf910 | 1438 | raw_spin_lock(&owner->pi_lock); |
23f78d4a | 1439 | |
1ca7b860 | 1440 | rt_mutex_dequeue_pi(owner, waiter); |
23f78d4a | 1441 | |
1ca7b860 TG |
1442 | if (rt_mutex_has_waiters(lock)) |
1443 | rt_mutex_enqueue_pi(owner, rt_mutex_top_waiter(lock)); | |
23f78d4a | 1444 | |
acd58620 | 1445 | rt_mutex_adjust_prio(owner); |
23f78d4a | 1446 | |
1ca7b860 TG |
1447 | /* Store the lock on which owner is blocked or NULL */ |
1448 | next_lock = task_blocked_on_lock(owner); | |
db630637 | 1449 | |
b4abf910 | 1450 | raw_spin_unlock(&owner->pi_lock); |
23f78d4a | 1451 | |
1ca7b860 TG |
1452 | /* |
1453 | * Don't walk the chain, if the owner task is not blocked | |
1454 | * itself. | |
1455 | */ | |
82084984 | 1456 | if (!next_lock) |
23f78d4a IM |
1457 | return; |
1458 | ||
db630637 SR |
1459 | /* gets dropped in rt_mutex_adjust_prio_chain()! */ |
1460 | get_task_struct(owner); | |
1461 | ||
b4abf910 | 1462 | raw_spin_unlock_irq(&lock->wait_lock); |
23f78d4a | 1463 | |
8930ed80 TG |
1464 | rt_mutex_adjust_prio_chain(owner, RT_MUTEX_MIN_CHAINWALK, lock, |
1465 | next_lock, NULL, current); | |
23f78d4a | 1466 | |
b4abf910 | 1467 | raw_spin_lock_irq(&lock->wait_lock); |
23f78d4a IM |
1468 | } |
1469 | ||
8dac456a | 1470 | /** |
ebbdc41e | 1471 | * rt_mutex_slowlock_block() - Perform the wait-wake-try-to-take loop |
8dac456a | 1472 | * @lock: the rt_mutex to take |
add46132 | 1473 | * @ww_ctx: WW mutex context pointer |
8dac456a | 1474 | * @state: the state the task should block in (TASK_INTERRUPTIBLE |
b4abf910 | 1475 | * or TASK_UNINTERRUPTIBLE) |
8dac456a DH |
1476 | * @timeout: the pre-initialized and started timer, or NULL for none |
1477 | * @waiter: the pre-initialized rt_mutex_waiter | |
8dac456a | 1478 | * |
b4abf910 | 1479 | * Must be called with lock->wait_lock held and interrupts disabled |
23f78d4a | 1480 | */ |
ebbdc41e | 1481 | static int __sched rt_mutex_slowlock_block(struct rt_mutex_base *lock, |
add46132 | 1482 | struct ww_acquire_ctx *ww_ctx, |
ebbdc41e TG |
1483 | unsigned int state, |
1484 | struct hrtimer_sleeper *timeout, | |
1485 | struct rt_mutex_waiter *waiter) | |
23f78d4a | 1486 | { |
add46132 | 1487 | struct rt_mutex *rtm = container_of(lock, struct rt_mutex, rtmutex); |
992caf7f | 1488 | struct task_struct *owner; |
23f78d4a IM |
1489 | int ret = 0; |
1490 | ||
23f78d4a IM |
1491 | for (;;) { |
1492 | /* Try to acquire the lock: */ | |
8161239a | 1493 | if (try_to_take_rt_mutex(lock, current, waiter)) |
23f78d4a IM |
1494 | break; |
1495 | ||
a51a327f TG |
1496 | if (timeout && !timeout->task) { |
1497 | ret = -ETIMEDOUT; | |
1498 | break; | |
1499 | } | |
1500 | if (signal_pending_state(state, current)) { | |
1501 | ret = -EINTR; | |
1502 | break; | |
23f78d4a IM |
1503 | } |
1504 | ||
add46132 PZ |
1505 | if (build_ww_mutex() && ww_ctx) { |
1506 | ret = __ww_mutex_check_kill(rtm, waiter, ww_ctx); | |
1507 | if (ret) | |
1508 | break; | |
1509 | } | |
1510 | ||
992caf7f SR |
1511 | if (waiter == rt_mutex_top_waiter(lock)) |
1512 | owner = rt_mutex_owner(lock); | |
1513 | else | |
1514 | owner = NULL; | |
b4abf910 | 1515 | raw_spin_unlock_irq(&lock->wait_lock); |
23f78d4a | 1516 | |
992caf7f SR |
1517 | if (!owner || !rtmutex_spin_on_owner(lock, waiter, owner)) |
1518 | schedule(); | |
23f78d4a | 1519 | |
b4abf910 | 1520 | raw_spin_lock_irq(&lock->wait_lock); |
23f78d4a IM |
1521 | set_current_state(state); |
1522 | } | |
1523 | ||
afffc6c1 | 1524 | __set_current_state(TASK_RUNNING); |
8dac456a DH |
1525 | return ret; |
1526 | } | |
1527 | ||
d7a2edb8 TG |
1528 | static void __sched rt_mutex_handle_deadlock(int res, int detect_deadlock, |
1529 | struct rt_mutex_waiter *w) | |
3d5c9340 TG |
1530 | { |
1531 | /* | |
1532 | * If the result is not -EDEADLOCK or the caller requested | |
1533 | * deadlock detection, nothing to do here. | |
1534 | */ | |
1535 | if (res != -EDEADLOCK || detect_deadlock) | |
1536 | return; | |
1537 | ||
add46132 PZ |
1538 | if (build_ww_mutex() && w->ww_ctx) |
1539 | return; | |
1540 | ||
3d5c9340 | 1541 | /* |
e2db7592 | 1542 | * Yell loudly and stop the task right here. |
3d5c9340 | 1543 | */ |
6d41c675 | 1544 | WARN(1, "rtmutex deadlock detected\n"); |
3d5c9340 TG |
1545 | while (1) { |
1546 | set_current_state(TASK_INTERRUPTIBLE); | |
1547 | schedule(); | |
1548 | } | |
1549 | } | |
1550 | ||
ebbdc41e TG |
1551 | /** |
1552 | * __rt_mutex_slowlock - Locking slowpath invoked with lock::wait_lock held | |
1553 | * @lock: The rtmutex to block lock | |
add46132 | 1554 | * @ww_ctx: WW mutex context pointer |
ebbdc41e TG |
1555 | * @state: The task state for sleeping |
1556 | * @chwalk: Indicator whether full or partial chainwalk is requested | |
1557 | * @waiter: Initializer waiter for blocking | |
8dac456a | 1558 | */ |
ebbdc41e | 1559 | static int __sched __rt_mutex_slowlock(struct rt_mutex_base *lock, |
add46132 | 1560 | struct ww_acquire_ctx *ww_ctx, |
ebbdc41e TG |
1561 | unsigned int state, |
1562 | enum rtmutex_chainwalk chwalk, | |
1563 | struct rt_mutex_waiter *waiter) | |
8dac456a | 1564 | { |
add46132 PZ |
1565 | struct rt_mutex *rtm = container_of(lock, struct rt_mutex, rtmutex); |
1566 | struct ww_mutex *ww = ww_container_of(rtm); | |
ebbdc41e | 1567 | int ret; |
8dac456a | 1568 | |
ebbdc41e | 1569 | lockdep_assert_held(&lock->wait_lock); |
8dac456a DH |
1570 | |
1571 | /* Try to acquire the lock again: */ | |
add46132 PZ |
1572 | if (try_to_take_rt_mutex(lock, current, NULL)) { |
1573 | if (build_ww_mutex() && ww_ctx) { | |
1574 | __ww_mutex_check_waiters(rtm, ww_ctx); | |
1575 | ww_mutex_lock_acquired(ww, ww_ctx); | |
1576 | } | |
8dac456a | 1577 | return 0; |
add46132 | 1578 | } |
8dac456a DH |
1579 | |
1580 | set_current_state(state); | |
1581 | ||
add46132 | 1582 | ret = task_blocks_on_rt_mutex(lock, waiter, current, ww_ctx, chwalk); |
8161239a | 1583 | if (likely(!ret)) |
add46132 PZ |
1584 | ret = rt_mutex_slowlock_block(lock, ww_ctx, state, NULL, waiter); |
1585 | ||
1586 | if (likely(!ret)) { | |
1587 | /* acquired the lock */ | |
1588 | if (build_ww_mutex() && ww_ctx) { | |
1589 | if (!ww_ctx->is_wait_die) | |
1590 | __ww_mutex_check_waiters(rtm, ww_ctx); | |
1591 | ww_mutex_lock_acquired(ww, ww_ctx); | |
1592 | } | |
1593 | } else { | |
9d3e2d02 | 1594 | __set_current_state(TASK_RUNNING); |
ebbdc41e TG |
1595 | remove_waiter(lock, waiter); |
1596 | rt_mutex_handle_deadlock(ret, chwalk, waiter); | |
3d5c9340 | 1597 | } |
23f78d4a IM |
1598 | |
1599 | /* | |
1600 | * try_to_take_rt_mutex() sets the waiter bit | |
1601 | * unconditionally. We might have to fix that up. | |
1602 | */ | |
1603 | fixup_rt_mutex_waiters(lock); | |
ebbdc41e TG |
1604 | return ret; |
1605 | } | |
23f78d4a | 1606 | |
ebbdc41e | 1607 | static inline int __rt_mutex_slowlock_locked(struct rt_mutex_base *lock, |
add46132 | 1608 | struct ww_acquire_ctx *ww_ctx, |
ebbdc41e TG |
1609 | unsigned int state) |
1610 | { | |
1611 | struct rt_mutex_waiter waiter; | |
1612 | int ret; | |
1613 | ||
1614 | rt_mutex_init_waiter(&waiter); | |
add46132 | 1615 | waiter.ww_ctx = ww_ctx; |
23f78d4a | 1616 | |
add46132 PZ |
1617 | ret = __rt_mutex_slowlock(lock, ww_ctx, state, RT_MUTEX_MIN_CHAINWALK, |
1618 | &waiter); | |
23f78d4a | 1619 | |
23f78d4a | 1620 | debug_rt_mutex_free_waiter(&waiter); |
ebbdc41e TG |
1621 | return ret; |
1622 | } | |
1623 | ||
1624 | /* | |
1625 | * rt_mutex_slowlock - Locking slowpath invoked when fast path fails | |
1626 | * @lock: The rtmutex to block lock | |
add46132 | 1627 | * @ww_ctx: WW mutex context pointer |
ebbdc41e TG |
1628 | * @state: The task state for sleeping |
1629 | */ | |
1630 | static int __sched rt_mutex_slowlock(struct rt_mutex_base *lock, | |
add46132 | 1631 | struct ww_acquire_ctx *ww_ctx, |
ebbdc41e TG |
1632 | unsigned int state) |
1633 | { | |
1634 | unsigned long flags; | |
1635 | int ret; | |
1636 | ||
1637 | /* | |
1638 | * Technically we could use raw_spin_[un]lock_irq() here, but this can | |
1639 | * be called in early boot if the cmpxchg() fast path is disabled | |
1640 | * (debug, no architecture support). In this case we will acquire the | |
1641 | * rtmutex with lock->wait_lock held. But we cannot unconditionally | |
1642 | * enable interrupts in that early boot case. So we need to use the | |
1643 | * irqsave/restore variants. | |
1644 | */ | |
1645 | raw_spin_lock_irqsave(&lock->wait_lock, flags); | |
add46132 | 1646 | ret = __rt_mutex_slowlock_locked(lock, ww_ctx, state); |
ebbdc41e | 1647 | raw_spin_unlock_irqrestore(&lock->wait_lock, flags); |
23f78d4a IM |
1648 | |
1649 | return ret; | |
1650 | } | |
1651 | ||
830e6acc | 1652 | static __always_inline int __rt_mutex_lock(struct rt_mutex_base *lock, |
531ae4b0 TG |
1653 | unsigned int state) |
1654 | { | |
1655 | if (likely(rt_mutex_cmpxchg_acquire(lock, NULL, current))) | |
1656 | return 0; | |
1657 | ||
add46132 | 1658 | return rt_mutex_slowlock(lock, NULL, state); |
531ae4b0 | 1659 | } |
e17ba59b | 1660 | #endif /* RT_MUTEX_BUILD_MUTEX */ |
1c143c4b TG |
1661 | |
1662 | #ifdef RT_MUTEX_BUILD_SPINLOCKS | |
1663 | /* | |
1664 | * Functions required for spin/rw_lock substitution on RT kernels | |
1665 | */ | |
1666 | ||
1667 | /** | |
1668 | * rtlock_slowlock_locked - Slow path lock acquisition for RT locks | |
1669 | * @lock: The underlying RT mutex | |
1670 | */ | |
1671 | static void __sched rtlock_slowlock_locked(struct rt_mutex_base *lock) | |
1672 | { | |
1673 | struct rt_mutex_waiter waiter; | |
992caf7f | 1674 | struct task_struct *owner; |
1c143c4b TG |
1675 | |
1676 | lockdep_assert_held(&lock->wait_lock); | |
1677 | ||
1678 | if (try_to_take_rt_mutex(lock, current, NULL)) | |
1679 | return; | |
1680 | ||
1681 | rt_mutex_init_rtlock_waiter(&waiter); | |
1682 | ||
1683 | /* Save current state and set state to TASK_RTLOCK_WAIT */ | |
1684 | current_save_and_set_rtlock_wait_state(); | |
1685 | ||
add46132 | 1686 | task_blocks_on_rt_mutex(lock, &waiter, current, NULL, RT_MUTEX_MIN_CHAINWALK); |
1c143c4b TG |
1687 | |
1688 | for (;;) { | |
1689 | /* Try to acquire the lock again */ | |
1690 | if (try_to_take_rt_mutex(lock, current, &waiter)) | |
1691 | break; | |
1692 | ||
992caf7f SR |
1693 | if (&waiter == rt_mutex_top_waiter(lock)) |
1694 | owner = rt_mutex_owner(lock); | |
1695 | else | |
1696 | owner = NULL; | |
1c143c4b TG |
1697 | raw_spin_unlock_irq(&lock->wait_lock); |
1698 | ||
992caf7f SR |
1699 | if (!owner || !rtmutex_spin_on_owner(lock, &waiter, owner)) |
1700 | schedule_rtlock(); | |
1c143c4b TG |
1701 | |
1702 | raw_spin_lock_irq(&lock->wait_lock); | |
1703 | set_current_state(TASK_RTLOCK_WAIT); | |
1704 | } | |
1705 | ||
1706 | /* Restore the task state */ | |
1707 | current_restore_rtlock_saved_state(); | |
1708 | ||
1709 | /* | |
1710 | * try_to_take_rt_mutex() sets the waiter bit unconditionally. | |
1711 | * We might have to fix that up: | |
1712 | */ | |
1713 | fixup_rt_mutex_waiters(lock); | |
1714 | debug_rt_mutex_free_waiter(&waiter); | |
1715 | } | |
1716 | ||
1717 | static __always_inline void __sched rtlock_slowlock(struct rt_mutex_base *lock) | |
1718 | { | |
1719 | unsigned long flags; | |
1720 | ||
1721 | raw_spin_lock_irqsave(&lock->wait_lock, flags); | |
1722 | rtlock_slowlock_locked(lock); | |
1723 | raw_spin_unlock_irqrestore(&lock->wait_lock, flags); | |
1724 | } | |
1725 | ||
1726 | #endif /* RT_MUTEX_BUILD_SPINLOCKS */ |