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Ingo Molnar23f78d4a2006-06-27 02:54:53 -07001/*
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
Steven Rostedtd07fe822006-07-30 03:04:03 -070010 *
11 * See Documentation/rt-mutex-design.txt for details.
Ingo Molnar23f78d4a2006-06-27 02:54:53 -070012 */
13#include <linux/spinlock.h>
14#include <linux/module.h>
15#include <linux/sched.h>
16#include <linux/timer.h>
17
18#include "rtmutex_common.h"
19
Ingo Molnar23f78d4a2006-06-27 02:54:53 -070020/*
21 * lock->owner state tracking:
22 *
23 * lock->owner holds the task_struct pointer of the owner. Bit 0 and 1
24 * are used to keep track of the "owner is pending" and "lock has
25 * waiters" state.
26 *
27 * owner bit1 bit0
28 * NULL 0 0 lock is free (fast acquire possible)
29 * NULL 0 1 invalid state
30 * NULL 1 0 Transitional State*
31 * NULL 1 1 invalid state
32 * taskpointer 0 0 lock is held (fast release possible)
33 * taskpointer 0 1 task is pending owner
34 * taskpointer 1 0 lock is held and has waiters
35 * taskpointer 1 1 task is pending owner and lock has more waiters
36 *
37 * Pending ownership is assigned to the top (highest priority)
38 * waiter of the lock, when the lock is released. The thread is woken
39 * up and can now take the lock. Until the lock is taken (bit 0
40 * cleared) a competing higher priority thread can steal the lock
41 * which puts the woken up thread back on the waiters list.
42 *
43 * The fast atomic compare exchange based acquire and release is only
44 * possible when bit 0 and 1 of lock->owner are 0.
45 *
46 * (*) There's a small time where the owner can be NULL and the
47 * "lock has waiters" bit is set. This can happen when grabbing the lock.
48 * To prevent a cmpxchg of the owner releasing the lock, we need to set this
49 * bit before looking at the lock, hence the reason this is a transitional
50 * state.
51 */
52
Thomas Gleixnerbd197232007-06-17 21:11:10 +020053static void
Ingo Molnar23f78d4a2006-06-27 02:54:53 -070054rt_mutex_set_owner(struct rt_mutex *lock, struct task_struct *owner,
55 unsigned long mask)
56{
57 unsigned long val = (unsigned long)owner | mask;
58
59 if (rt_mutex_has_waiters(lock))
60 val |= RT_MUTEX_HAS_WAITERS;
61
62 lock->owner = (struct task_struct *)val;
63}
64
65static inline void clear_rt_mutex_waiters(struct rt_mutex *lock)
66{
67 lock->owner = (struct task_struct *)
68 ((unsigned long)lock->owner & ~RT_MUTEX_HAS_WAITERS);
69}
70
71static void fixup_rt_mutex_waiters(struct rt_mutex *lock)
72{
73 if (!rt_mutex_has_waiters(lock))
74 clear_rt_mutex_waiters(lock);
75}
76
77/*
Thomas Gleixnerbd197232007-06-17 21:11:10 +020078 * We can speed up the acquire/release, if the architecture
79 * supports cmpxchg and if there's no debugging state to be set up
80 */
81#if defined(__HAVE_ARCH_CMPXCHG) && !defined(CONFIG_DEBUG_RT_MUTEXES)
82# define rt_mutex_cmpxchg(l,c,n) (cmpxchg(&l->owner, c, n) == c)
83static inline void mark_rt_mutex_waiters(struct rt_mutex *lock)
84{
85 unsigned long owner, *p = (unsigned long *) &lock->owner;
86
87 do {
88 owner = *p;
89 } while (cmpxchg(p, owner, owner | RT_MUTEX_HAS_WAITERS) != owner);
90}
91#else
92# define rt_mutex_cmpxchg(l,c,n) (0)
93static inline void mark_rt_mutex_waiters(struct rt_mutex *lock)
94{
95 lock->owner = (struct task_struct *)
96 ((unsigned long)lock->owner | RT_MUTEX_HAS_WAITERS);
97}
98#endif
99
100/*
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700101 * Calculate task priority from the waiter list priority
102 *
103 * Return task->normal_prio when the waiter list is empty or when
104 * the waiter is not allowed to do priority boosting
105 */
106int rt_mutex_getprio(struct task_struct *task)
107{
108 if (likely(!task_has_pi_waiters(task)))
109 return task->normal_prio;
110
111 return min(task_top_pi_waiter(task)->pi_list_entry.prio,
112 task->normal_prio);
113}
114
115/*
116 * Adjust the priority of a task, after its pi_waiters got modified.
117 *
118 * This can be both boosting and unboosting. task->pi_lock must be held.
119 */
Thomas Gleixnerbd197232007-06-17 21:11:10 +0200120static void __rt_mutex_adjust_prio(struct task_struct *task)
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700121{
122 int prio = rt_mutex_getprio(task);
123
124 if (task->prio != prio)
125 rt_mutex_setprio(task, prio);
126}
127
128/*
129 * Adjust task priority (undo boosting). Called from the exit path of
130 * rt_mutex_slowunlock() and rt_mutex_slowlock().
131 *
132 * (Note: We do this outside of the protection of lock->wait_lock to
133 * allow the lock to be taken while or before we readjust the priority
134 * of task. We do not use the spin_xx_mutex() variants here as we are
135 * outside of the debug path.)
136 */
137static void rt_mutex_adjust_prio(struct task_struct *task)
138{
139 unsigned long flags;
140
Thomas Gleixner1d615482009-11-17 14:54:03 +0100141 raw_spin_lock_irqsave(&task->pi_lock, flags);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700142 __rt_mutex_adjust_prio(task);
Thomas Gleixner1d615482009-11-17 14:54:03 +0100143 raw_spin_unlock_irqrestore(&task->pi_lock, flags);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700144}
145
146/*
147 * Max number of times we'll walk the boosting chain:
148 */
149int max_lock_depth = 1024;
150
151/*
152 * Adjust the priority chain. Also used for deadlock detection.
153 * Decreases task's usage by one - may thus free the task.
154 * Returns 0 or -EDEADLK.
155 */
Thomas Gleixnerbd197232007-06-17 21:11:10 +0200156static int rt_mutex_adjust_prio_chain(struct task_struct *task,
157 int deadlock_detect,
158 struct rt_mutex *orig_lock,
159 struct rt_mutex_waiter *orig_waiter,
160 struct task_struct *top_task)
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700161{
162 struct rt_mutex *lock;
163 struct rt_mutex_waiter *waiter, *top_waiter = orig_waiter;
164 int detect_deadlock, ret = 0, depth = 0;
165 unsigned long flags;
166
167 detect_deadlock = debug_rt_mutex_detect_deadlock(orig_waiter,
168 deadlock_detect);
169
170 /*
171 * The (de)boosting is a step by step approach with a lot of
172 * pitfalls. We want this to be preemptible and we want hold a
173 * maximum of two locks per step. So we have to check
174 * carefully whether things change under us.
175 */
176 again:
177 if (++depth > max_lock_depth) {
178 static int prev_max;
179
180 /*
181 * Print this only once. If the admin changes the limit,
182 * print a new message when reaching the limit again.
183 */
184 if (prev_max != max_lock_depth) {
185 prev_max = max_lock_depth;
186 printk(KERN_WARNING "Maximum lock depth %d reached "
187 "task: %s (%d)\n", max_lock_depth,
Pavel Emelyanovba25f9d2007-10-18 23:40:40 -0700188 top_task->comm, task_pid_nr(top_task));
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700189 }
190 put_task_struct(task);
191
192 return deadlock_detect ? -EDEADLK : 0;
193 }
194 retry:
195 /*
196 * Task can not go away as we did a get_task() before !
197 */
Thomas Gleixner1d615482009-11-17 14:54:03 +0100198 raw_spin_lock_irqsave(&task->pi_lock, flags);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700199
200 waiter = task->pi_blocked_on;
201 /*
202 * Check whether the end of the boosting chain has been
203 * reached or the state of the chain has changed while we
204 * dropped the locks.
205 */
206 if (!waiter || !waiter->task)
207 goto out_unlock_pi;
208
Thomas Gleixner1a539a82007-06-08 13:46:58 -0700209 /*
210 * Check the orig_waiter state. After we dropped the locks,
211 * the previous owner of the lock might have released the lock
212 * and made us the pending owner:
213 */
214 if (orig_waiter && !orig_waiter->task)
215 goto out_unlock_pi;
216
217 /*
218 * Drop out, when the task has no waiters. Note,
219 * top_waiter can be NULL, when we are in the deboosting
220 * mode!
221 */
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700222 if (top_waiter && (!task_has_pi_waiters(task) ||
223 top_waiter != task_top_pi_waiter(task)))
224 goto out_unlock_pi;
225
226 /*
227 * When deadlock detection is off then we check, if further
228 * priority adjustment is necessary.
229 */
230 if (!detect_deadlock && waiter->list_entry.prio == task->prio)
231 goto out_unlock_pi;
232
233 lock = waiter->lock;
Thomas Gleixnerd209d742009-11-17 18:22:11 +0100234 if (!raw_spin_trylock(&lock->wait_lock)) {
Thomas Gleixner1d615482009-11-17 14:54:03 +0100235 raw_spin_unlock_irqrestore(&task->pi_lock, flags);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700236 cpu_relax();
237 goto retry;
238 }
239
240 /* Deadlock detection */
Thomas Gleixner95e02ca2006-06-27 02:55:02 -0700241 if (lock == orig_lock || rt_mutex_owner(lock) == top_task) {
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700242 debug_rt_mutex_deadlock(deadlock_detect, orig_waiter, lock);
Thomas Gleixnerd209d742009-11-17 18:22:11 +0100243 raw_spin_unlock(&lock->wait_lock);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700244 ret = deadlock_detect ? -EDEADLK : 0;
245 goto out_unlock_pi;
246 }
247
248 top_waiter = rt_mutex_top_waiter(lock);
249
250 /* Requeue the waiter */
251 plist_del(&waiter->list_entry, &lock->wait_list);
252 waiter->list_entry.prio = task->prio;
253 plist_add(&waiter->list_entry, &lock->wait_list);
254
255 /* Release the task */
Thomas Gleixner1d615482009-11-17 14:54:03 +0100256 raw_spin_unlock_irqrestore(&task->pi_lock, flags);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700257 put_task_struct(task);
258
259 /* Grab the next task */
260 task = rt_mutex_owner(lock);
Steven Rostedtdb630632006-09-29 01:59:44 -0700261 get_task_struct(task);
Thomas Gleixner1d615482009-11-17 14:54:03 +0100262 raw_spin_lock_irqsave(&task->pi_lock, flags);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700263
264 if (waiter == rt_mutex_top_waiter(lock)) {
265 /* Boost the owner */
266 plist_del(&top_waiter->pi_list_entry, &task->pi_waiters);
267 waiter->pi_list_entry.prio = waiter->list_entry.prio;
268 plist_add(&waiter->pi_list_entry, &task->pi_waiters);
269 __rt_mutex_adjust_prio(task);
270
271 } else if (top_waiter == waiter) {
272 /* Deboost the owner */
273 plist_del(&waiter->pi_list_entry, &task->pi_waiters);
274 waiter = rt_mutex_top_waiter(lock);
275 waiter->pi_list_entry.prio = waiter->list_entry.prio;
276 plist_add(&waiter->pi_list_entry, &task->pi_waiters);
277 __rt_mutex_adjust_prio(task);
278 }
279
Thomas Gleixner1d615482009-11-17 14:54:03 +0100280 raw_spin_unlock_irqrestore(&task->pi_lock, flags);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700281
282 top_waiter = rt_mutex_top_waiter(lock);
Thomas Gleixnerd209d742009-11-17 18:22:11 +0100283 raw_spin_unlock(&lock->wait_lock);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700284
285 if (!detect_deadlock && waiter != top_waiter)
286 goto out_put_task;
287
288 goto again;
289
290 out_unlock_pi:
Thomas Gleixner1d615482009-11-17 14:54:03 +0100291 raw_spin_unlock_irqrestore(&task->pi_lock, flags);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700292 out_put_task:
293 put_task_struct(task);
Ingo Molnar36c8b582006-07-03 00:25:41 -0700294
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700295 return ret;
296}
297
298/*
299 * Optimization: check if we can steal the lock from the
300 * assigned pending owner [which might not have taken the
301 * lock yet]:
302 */
Darren Hart8dac4562009-04-03 13:40:12 -0700303static inline int try_to_steal_lock(struct rt_mutex *lock,
304 struct task_struct *task)
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700305{
306 struct task_struct *pendowner = rt_mutex_owner(lock);
307 struct rt_mutex_waiter *next;
308 unsigned long flags;
309
310 if (!rt_mutex_owner_pending(lock))
311 return 0;
312
Darren Hart8dac4562009-04-03 13:40:12 -0700313 if (pendowner == task)
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700314 return 1;
315
Thomas Gleixner1d615482009-11-17 14:54:03 +0100316 raw_spin_lock_irqsave(&pendowner->pi_lock, flags);
Darren Hart8dac4562009-04-03 13:40:12 -0700317 if (task->prio >= pendowner->prio) {
Thomas Gleixner1d615482009-11-17 14:54:03 +0100318 raw_spin_unlock_irqrestore(&pendowner->pi_lock, flags);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700319 return 0;
320 }
321
322 /*
323 * Check if a waiter is enqueued on the pending owners
324 * pi_waiters list. Remove it and readjust pending owners
325 * priority.
326 */
327 if (likely(!rt_mutex_has_waiters(lock))) {
Thomas Gleixner1d615482009-11-17 14:54:03 +0100328 raw_spin_unlock_irqrestore(&pendowner->pi_lock, flags);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700329 return 1;
330 }
331
332 /* No chain handling, pending owner is not blocked on anything: */
333 next = rt_mutex_top_waiter(lock);
334 plist_del(&next->pi_list_entry, &pendowner->pi_waiters);
335 __rt_mutex_adjust_prio(pendowner);
Thomas Gleixner1d615482009-11-17 14:54:03 +0100336 raw_spin_unlock_irqrestore(&pendowner->pi_lock, flags);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700337
338 /*
339 * We are going to steal the lock and a waiter was
340 * enqueued on the pending owners pi_waiters queue. So
341 * we have to enqueue this waiter into
Darren Hart8dac4562009-04-03 13:40:12 -0700342 * task->pi_waiters list. This covers the case,
343 * where task is boosted because it holds another
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700344 * lock and gets unboosted because the booster is
345 * interrupted, so we would delay a waiter with higher
Darren Hart8dac4562009-04-03 13:40:12 -0700346 * priority as task->normal_prio.
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700347 *
348 * Note: in the rare case of a SCHED_OTHER task changing
349 * its priority and thus stealing the lock, next->task
Darren Hart8dac4562009-04-03 13:40:12 -0700350 * might be task:
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700351 */
Darren Hart8dac4562009-04-03 13:40:12 -0700352 if (likely(next->task != task)) {
Thomas Gleixner1d615482009-11-17 14:54:03 +0100353 raw_spin_lock_irqsave(&task->pi_lock, flags);
Darren Hart8dac4562009-04-03 13:40:12 -0700354 plist_add(&next->pi_list_entry, &task->pi_waiters);
355 __rt_mutex_adjust_prio(task);
Thomas Gleixner1d615482009-11-17 14:54:03 +0100356 raw_spin_unlock_irqrestore(&task->pi_lock, flags);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700357 }
358 return 1;
359}
360
361/*
362 * Try to take an rt-mutex
363 *
364 * This fails
365 * - when the lock has a real owner
366 * - when a different pending owner exists and has higher priority than current
367 *
368 * Must be called with lock->wait_lock held.
369 */
Ingo Molnar9a11b49a2006-07-03 00:24:33 -0700370static int try_to_take_rt_mutex(struct rt_mutex *lock)
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700371{
372 /*
373 * We have to be careful here if the atomic speedups are
374 * enabled, such that, when
375 * - no other waiter is on the lock
376 * - the lock has been released since we did the cmpxchg
377 * the lock can be released or taken while we are doing the
378 * checks and marking the lock with RT_MUTEX_HAS_WAITERS.
379 *
380 * The atomic acquire/release aware variant of
381 * mark_rt_mutex_waiters uses a cmpxchg loop. After setting
382 * the WAITERS bit, the atomic release / acquire can not
383 * happen anymore and lock->wait_lock protects us from the
384 * non-atomic case.
385 *
386 * Note, that this might set lock->owner =
387 * RT_MUTEX_HAS_WAITERS in the case the lock is not contended
388 * any more. This is fixed up when we take the ownership.
389 * This is the transitional state explained at the top of this file.
390 */
391 mark_rt_mutex_waiters(lock);
392
Darren Hart8dac4562009-04-03 13:40:12 -0700393 if (rt_mutex_owner(lock) && !try_to_steal_lock(lock, current))
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700394 return 0;
395
396 /* We got the lock. */
Ingo Molnar9a11b49a2006-07-03 00:24:33 -0700397 debug_rt_mutex_lock(lock);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700398
399 rt_mutex_set_owner(lock, current, 0);
400
401 rt_mutex_deadlock_account_lock(lock, current);
402
403 return 1;
404}
405
406/*
407 * Task blocks on lock.
408 *
409 * Prepare waiter and propagate pi chain
410 *
411 * This must be called with lock->wait_lock held.
412 */
413static int task_blocks_on_rt_mutex(struct rt_mutex *lock,
414 struct rt_mutex_waiter *waiter,
Darren Hart8dac4562009-04-03 13:40:12 -0700415 struct task_struct *task,
Ingo Molnar9a11b49a2006-07-03 00:24:33 -0700416 int detect_deadlock)
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700417{
Ingo Molnar36c8b582006-07-03 00:25:41 -0700418 struct task_struct *owner = rt_mutex_owner(lock);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700419 struct rt_mutex_waiter *top_waiter = waiter;
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700420 unsigned long flags;
Steven Rostedtdb630632006-09-29 01:59:44 -0700421 int chain_walk = 0, res;
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700422
Thomas Gleixner1d615482009-11-17 14:54:03 +0100423 raw_spin_lock_irqsave(&task->pi_lock, flags);
Darren Hart8dac4562009-04-03 13:40:12 -0700424 __rt_mutex_adjust_prio(task);
425 waiter->task = task;
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700426 waiter->lock = lock;
Darren Hart8dac4562009-04-03 13:40:12 -0700427 plist_node_init(&waiter->list_entry, task->prio);
428 plist_node_init(&waiter->pi_list_entry, task->prio);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700429
430 /* Get the top priority waiter on the lock */
431 if (rt_mutex_has_waiters(lock))
432 top_waiter = rt_mutex_top_waiter(lock);
433 plist_add(&waiter->list_entry, &lock->wait_list);
434
Darren Hart8dac4562009-04-03 13:40:12 -0700435 task->pi_blocked_on = waiter;
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700436
Thomas Gleixner1d615482009-11-17 14:54:03 +0100437 raw_spin_unlock_irqrestore(&task->pi_lock, flags);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700438
439 if (waiter == rt_mutex_top_waiter(lock)) {
Thomas Gleixner1d615482009-11-17 14:54:03 +0100440 raw_spin_lock_irqsave(&owner->pi_lock, flags);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700441 plist_del(&top_waiter->pi_list_entry, &owner->pi_waiters);
442 plist_add(&waiter->pi_list_entry, &owner->pi_waiters);
443
444 __rt_mutex_adjust_prio(owner);
Steven Rostedtdb630632006-09-29 01:59:44 -0700445 if (owner->pi_blocked_on)
446 chain_walk = 1;
Thomas Gleixner1d615482009-11-17 14:54:03 +0100447 raw_spin_unlock_irqrestore(&owner->pi_lock, flags);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700448 }
Steven Rostedtdb630632006-09-29 01:59:44 -0700449 else if (debug_rt_mutex_detect_deadlock(waiter, detect_deadlock))
450 chain_walk = 1;
451
452 if (!chain_walk)
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700453 return 0;
454
Steven Rostedtdb630632006-09-29 01:59:44 -0700455 /*
456 * The owner can't disappear while holding a lock,
457 * so the owner struct is protected by wait_lock.
458 * Gets dropped in rt_mutex_adjust_prio_chain()!
459 */
460 get_task_struct(owner);
461
Thomas Gleixnerd209d742009-11-17 18:22:11 +0100462 raw_spin_unlock(&lock->wait_lock);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700463
Thomas Gleixner95e02ca2006-06-27 02:55:02 -0700464 res = rt_mutex_adjust_prio_chain(owner, detect_deadlock, lock, waiter,
Darren Hart8dac4562009-04-03 13:40:12 -0700465 task);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700466
Thomas Gleixnerd209d742009-11-17 18:22:11 +0100467 raw_spin_lock(&lock->wait_lock);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700468
469 return res;
470}
471
472/*
473 * Wake up the next waiter on the lock.
474 *
475 * Remove the top waiter from the current tasks waiter list and from
476 * the lock waiter list. Set it as pending owner. Then wake it up.
477 *
478 * Called with lock->wait_lock held.
479 */
480static void wakeup_next_waiter(struct rt_mutex *lock)
481{
482 struct rt_mutex_waiter *waiter;
483 struct task_struct *pendowner;
484 unsigned long flags;
485
Thomas Gleixner1d615482009-11-17 14:54:03 +0100486 raw_spin_lock_irqsave(&current->pi_lock, flags);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700487
488 waiter = rt_mutex_top_waiter(lock);
489 plist_del(&waiter->list_entry, &lock->wait_list);
490
491 /*
492 * Remove it from current->pi_waiters. We do not adjust a
493 * possible priority boost right now. We execute wakeup in the
494 * boosted mode and go back to normal after releasing
495 * lock->wait_lock.
496 */
497 plist_del(&waiter->pi_list_entry, &current->pi_waiters);
498 pendowner = waiter->task;
499 waiter->task = NULL;
500
501 rt_mutex_set_owner(lock, pendowner, RT_MUTEX_OWNER_PENDING);
502
Thomas Gleixner1d615482009-11-17 14:54:03 +0100503 raw_spin_unlock_irqrestore(&current->pi_lock, flags);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700504
505 /*
506 * Clear the pi_blocked_on variable and enqueue a possible
507 * waiter into the pi_waiters list of the pending owner. This
508 * prevents that in case the pending owner gets unboosted a
509 * waiter with higher priority than pending-owner->normal_prio
510 * is blocked on the unboosted (pending) owner.
511 */
Thomas Gleixner1d615482009-11-17 14:54:03 +0100512 raw_spin_lock_irqsave(&pendowner->pi_lock, flags);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700513
514 WARN_ON(!pendowner->pi_blocked_on);
515 WARN_ON(pendowner->pi_blocked_on != waiter);
516 WARN_ON(pendowner->pi_blocked_on->lock != lock);
517
518 pendowner->pi_blocked_on = NULL;
519
520 if (rt_mutex_has_waiters(lock)) {
521 struct rt_mutex_waiter *next;
522
523 next = rt_mutex_top_waiter(lock);
524 plist_add(&next->pi_list_entry, &pendowner->pi_waiters);
525 }
Thomas Gleixner1d615482009-11-17 14:54:03 +0100526 raw_spin_unlock_irqrestore(&pendowner->pi_lock, flags);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700527
528 wake_up_process(pendowner);
529}
530
531/*
532 * Remove a waiter from a lock
533 *
534 * Must be called with lock->wait_lock held
535 */
Thomas Gleixnerbd197232007-06-17 21:11:10 +0200536static void remove_waiter(struct rt_mutex *lock,
537 struct rt_mutex_waiter *waiter)
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700538{
539 int first = (waiter == rt_mutex_top_waiter(lock));
Ingo Molnar36c8b582006-07-03 00:25:41 -0700540 struct task_struct *owner = rt_mutex_owner(lock);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700541 unsigned long flags;
Steven Rostedtdb630632006-09-29 01:59:44 -0700542 int chain_walk = 0;
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700543
Thomas Gleixner1d615482009-11-17 14:54:03 +0100544 raw_spin_lock_irqsave(&current->pi_lock, flags);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700545 plist_del(&waiter->list_entry, &lock->wait_list);
546 waiter->task = NULL;
547 current->pi_blocked_on = NULL;
Thomas Gleixner1d615482009-11-17 14:54:03 +0100548 raw_spin_unlock_irqrestore(&current->pi_lock, flags);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700549
550 if (first && owner != current) {
551
Thomas Gleixner1d615482009-11-17 14:54:03 +0100552 raw_spin_lock_irqsave(&owner->pi_lock, flags);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700553
554 plist_del(&waiter->pi_list_entry, &owner->pi_waiters);
555
556 if (rt_mutex_has_waiters(lock)) {
557 struct rt_mutex_waiter *next;
558
559 next = rt_mutex_top_waiter(lock);
560 plist_add(&next->pi_list_entry, &owner->pi_waiters);
561 }
562 __rt_mutex_adjust_prio(owner);
563
Steven Rostedtdb630632006-09-29 01:59:44 -0700564 if (owner->pi_blocked_on)
565 chain_walk = 1;
566
Thomas Gleixner1d615482009-11-17 14:54:03 +0100567 raw_spin_unlock_irqrestore(&owner->pi_lock, flags);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700568 }
569
570 WARN_ON(!plist_node_empty(&waiter->pi_list_entry));
571
Steven Rostedtdb630632006-09-29 01:59:44 -0700572 if (!chain_walk)
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700573 return;
574
Steven Rostedtdb630632006-09-29 01:59:44 -0700575 /* gets dropped in rt_mutex_adjust_prio_chain()! */
576 get_task_struct(owner);
577
Thomas Gleixnerd209d742009-11-17 18:22:11 +0100578 raw_spin_unlock(&lock->wait_lock);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700579
Ingo Molnar9a11b49a2006-07-03 00:24:33 -0700580 rt_mutex_adjust_prio_chain(owner, 0, lock, NULL, current);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700581
Thomas Gleixnerd209d742009-11-17 18:22:11 +0100582 raw_spin_lock(&lock->wait_lock);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700583}
584
585/*
Thomas Gleixner95e02ca2006-06-27 02:55:02 -0700586 * Recheck the pi chain, in case we got a priority setting
587 *
588 * Called from sched_setscheduler
589 */
590void rt_mutex_adjust_pi(struct task_struct *task)
591{
592 struct rt_mutex_waiter *waiter;
593 unsigned long flags;
594
Thomas Gleixner1d615482009-11-17 14:54:03 +0100595 raw_spin_lock_irqsave(&task->pi_lock, flags);
Thomas Gleixner95e02ca2006-06-27 02:55:02 -0700596
597 waiter = task->pi_blocked_on;
598 if (!waiter || waiter->list_entry.prio == task->prio) {
Thomas Gleixner1d615482009-11-17 14:54:03 +0100599 raw_spin_unlock_irqrestore(&task->pi_lock, flags);
Thomas Gleixner95e02ca2006-06-27 02:55:02 -0700600 return;
601 }
602
Thomas Gleixner1d615482009-11-17 14:54:03 +0100603 raw_spin_unlock_irqrestore(&task->pi_lock, flags);
Thomas Gleixner95e02ca2006-06-27 02:55:02 -0700604
Steven Rostedtdb630632006-09-29 01:59:44 -0700605 /* gets dropped in rt_mutex_adjust_prio_chain()! */
606 get_task_struct(task);
Ingo Molnar9a11b49a2006-07-03 00:24:33 -0700607 rt_mutex_adjust_prio_chain(task, 0, NULL, NULL, task);
Thomas Gleixner95e02ca2006-06-27 02:55:02 -0700608}
609
Darren Hart8dac4562009-04-03 13:40:12 -0700610/**
611 * __rt_mutex_slowlock() - Perform the wait-wake-try-to-take loop
612 * @lock: the rt_mutex to take
613 * @state: the state the task should block in (TASK_INTERRUPTIBLE
614 * or TASK_UNINTERRUPTIBLE)
615 * @timeout: the pre-initialized and started timer, or NULL for none
616 * @waiter: the pre-initialized rt_mutex_waiter
617 * @detect_deadlock: passed to task_blocks_on_rt_mutex
618 *
619 * lock->wait_lock must be held by the caller.
620 */
621static int __sched
622__rt_mutex_slowlock(struct rt_mutex *lock, int state,
623 struct hrtimer_sleeper *timeout,
624 struct rt_mutex_waiter *waiter,
625 int detect_deadlock)
626{
627 int ret = 0;
628
629 for (;;) {
630 /* Try to acquire the lock: */
631 if (try_to_take_rt_mutex(lock))
632 break;
633
634 /*
635 * TASK_INTERRUPTIBLE checks for signals and
636 * timeout. Ignored otherwise.
637 */
638 if (unlikely(state == TASK_INTERRUPTIBLE)) {
639 /* Signal pending? */
640 if (signal_pending(current))
641 ret = -EINTR;
642 if (timeout && !timeout->task)
643 ret = -ETIMEDOUT;
644 if (ret)
645 break;
646 }
647
648 /*
649 * waiter->task is NULL the first time we come here and
650 * when we have been woken up by the previous owner
651 * but the lock got stolen by a higher prio task.
652 */
653 if (!waiter->task) {
654 ret = task_blocks_on_rt_mutex(lock, waiter, current,
655 detect_deadlock);
656 /*
657 * If we got woken up by the owner then start loop
658 * all over without going into schedule to try
659 * to get the lock now:
660 */
661 if (unlikely(!waiter->task)) {
662 /*
663 * Reset the return value. We might
664 * have returned with -EDEADLK and the
665 * owner released the lock while we
666 * were walking the pi chain.
667 */
668 ret = 0;
669 continue;
670 }
671 if (unlikely(ret))
672 break;
673 }
674
Thomas Gleixnerd209d742009-11-17 18:22:11 +0100675 raw_spin_unlock(&lock->wait_lock);
Darren Hart8dac4562009-04-03 13:40:12 -0700676
677 debug_rt_mutex_print_deadlock(waiter);
678
679 if (waiter->task)
680 schedule_rt_mutex(lock);
681
Thomas Gleixnerd209d742009-11-17 18:22:11 +0100682 raw_spin_lock(&lock->wait_lock);
Darren Hart8dac4562009-04-03 13:40:12 -0700683 set_current_state(state);
684 }
685
686 return ret;
687}
688
Thomas Gleixner95e02ca2006-06-27 02:55:02 -0700689/*
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700690 * Slow path lock function:
691 */
692static int __sched
693rt_mutex_slowlock(struct rt_mutex *lock, int state,
694 struct hrtimer_sleeper *timeout,
Ingo Molnar9a11b49a2006-07-03 00:24:33 -0700695 int detect_deadlock)
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700696{
697 struct rt_mutex_waiter waiter;
698 int ret = 0;
699
700 debug_rt_mutex_init_waiter(&waiter);
701 waiter.task = NULL;
702
Thomas Gleixnerd209d742009-11-17 18:22:11 +0100703 raw_spin_lock(&lock->wait_lock);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700704
705 /* Try to acquire the lock again: */
Ingo Molnar9a11b49a2006-07-03 00:24:33 -0700706 if (try_to_take_rt_mutex(lock)) {
Thomas Gleixnerd209d742009-11-17 18:22:11 +0100707 raw_spin_unlock(&lock->wait_lock);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700708 return 0;
709 }
710
711 set_current_state(state);
712
713 /* Setup the timer, when timeout != NULL */
Peter Zijlstra720a2592008-02-13 15:45:36 +0100714 if (unlikely(timeout)) {
Arjan van de Vencc584b22008-09-01 15:02:30 -0700715 hrtimer_start_expires(&timeout->timer, HRTIMER_MODE_ABS);
Peter Zijlstra720a2592008-02-13 15:45:36 +0100716 if (!hrtimer_active(&timeout->timer))
717 timeout->task = NULL;
718 }
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700719
Darren Hart8dac4562009-04-03 13:40:12 -0700720 ret = __rt_mutex_slowlock(lock, state, timeout, &waiter,
721 detect_deadlock);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700722
723 set_current_state(TASK_RUNNING);
724
725 if (unlikely(waiter.task))
Ingo Molnar9a11b49a2006-07-03 00:24:33 -0700726 remove_waiter(lock, &waiter);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700727
728 /*
729 * try_to_take_rt_mutex() sets the waiter bit
730 * unconditionally. We might have to fix that up.
731 */
732 fixup_rt_mutex_waiters(lock);
733
Thomas Gleixnerd209d742009-11-17 18:22:11 +0100734 raw_spin_unlock(&lock->wait_lock);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700735
736 /* Remove pending timer: */
737 if (unlikely(timeout))
738 hrtimer_cancel(&timeout->timer);
739
740 /*
741 * Readjust priority, when we did not get the lock. We might
742 * have been the pending owner and boosted. Since we did not
743 * take the lock, the PI boost has to go.
744 */
745 if (unlikely(ret))
746 rt_mutex_adjust_prio(current);
747
748 debug_rt_mutex_free_waiter(&waiter);
749
750 return ret;
751}
752
753/*
754 * Slow path try-lock function:
755 */
756static inline int
Ingo Molnar9a11b49a2006-07-03 00:24:33 -0700757rt_mutex_slowtrylock(struct rt_mutex *lock)
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700758{
759 int ret = 0;
760
Thomas Gleixnerd209d742009-11-17 18:22:11 +0100761 raw_spin_lock(&lock->wait_lock);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700762
763 if (likely(rt_mutex_owner(lock) != current)) {
764
Ingo Molnar9a11b49a2006-07-03 00:24:33 -0700765 ret = try_to_take_rt_mutex(lock);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700766 /*
767 * try_to_take_rt_mutex() sets the lock waiters
768 * bit unconditionally. Clean this up.
769 */
770 fixup_rt_mutex_waiters(lock);
771 }
772
Thomas Gleixnerd209d742009-11-17 18:22:11 +0100773 raw_spin_unlock(&lock->wait_lock);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700774
775 return ret;
776}
777
778/*
779 * Slow path to release a rt-mutex:
780 */
781static void __sched
782rt_mutex_slowunlock(struct rt_mutex *lock)
783{
Thomas Gleixnerd209d742009-11-17 18:22:11 +0100784 raw_spin_lock(&lock->wait_lock);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700785
786 debug_rt_mutex_unlock(lock);
787
788 rt_mutex_deadlock_account_unlock(current);
789
790 if (!rt_mutex_has_waiters(lock)) {
791 lock->owner = NULL;
Thomas Gleixnerd209d742009-11-17 18:22:11 +0100792 raw_spin_unlock(&lock->wait_lock);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700793 return;
794 }
795
796 wakeup_next_waiter(lock);
797
Thomas Gleixnerd209d742009-11-17 18:22:11 +0100798 raw_spin_unlock(&lock->wait_lock);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700799
800 /* Undo pi boosting if necessary: */
801 rt_mutex_adjust_prio(current);
802}
803
804/*
805 * debug aware fast / slowpath lock,trylock,unlock
806 *
807 * The atomic acquire/release ops are compiled away, when either the
808 * architecture does not support cmpxchg or when debugging is enabled.
809 */
810static inline int
811rt_mutex_fastlock(struct rt_mutex *lock, int state,
812 int detect_deadlock,
813 int (*slowfn)(struct rt_mutex *lock, int state,
814 struct hrtimer_sleeper *timeout,
Ingo Molnar9a11b49a2006-07-03 00:24:33 -0700815 int detect_deadlock))
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700816{
817 if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) {
818 rt_mutex_deadlock_account_lock(lock, current);
819 return 0;
820 } else
Ingo Molnar9a11b49a2006-07-03 00:24:33 -0700821 return slowfn(lock, state, NULL, detect_deadlock);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700822}
823
824static inline int
825rt_mutex_timed_fastlock(struct rt_mutex *lock, int state,
826 struct hrtimer_sleeper *timeout, int detect_deadlock,
827 int (*slowfn)(struct rt_mutex *lock, int state,
828 struct hrtimer_sleeper *timeout,
Ingo Molnar9a11b49a2006-07-03 00:24:33 -0700829 int detect_deadlock))
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700830{
831 if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) {
832 rt_mutex_deadlock_account_lock(lock, current);
833 return 0;
834 } else
Ingo Molnar9a11b49a2006-07-03 00:24:33 -0700835 return slowfn(lock, state, timeout, detect_deadlock);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700836}
837
838static inline int
839rt_mutex_fasttrylock(struct rt_mutex *lock,
Ingo Molnar9a11b49a2006-07-03 00:24:33 -0700840 int (*slowfn)(struct rt_mutex *lock))
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700841{
842 if (likely(rt_mutex_cmpxchg(lock, NULL, current))) {
843 rt_mutex_deadlock_account_lock(lock, current);
844 return 1;
845 }
Ingo Molnar9a11b49a2006-07-03 00:24:33 -0700846 return slowfn(lock);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700847}
848
849static inline void
850rt_mutex_fastunlock(struct rt_mutex *lock,
851 void (*slowfn)(struct rt_mutex *lock))
852{
853 if (likely(rt_mutex_cmpxchg(lock, current, NULL)))
854 rt_mutex_deadlock_account_unlock(current);
855 else
856 slowfn(lock);
857}
858
859/**
860 * rt_mutex_lock - lock a rt_mutex
861 *
862 * @lock: the rt_mutex to be locked
863 */
864void __sched rt_mutex_lock(struct rt_mutex *lock)
865{
866 might_sleep();
867
868 rt_mutex_fastlock(lock, TASK_UNINTERRUPTIBLE, 0, rt_mutex_slowlock);
869}
870EXPORT_SYMBOL_GPL(rt_mutex_lock);
871
872/**
873 * rt_mutex_lock_interruptible - lock a rt_mutex interruptible
874 *
875 * @lock: the rt_mutex to be locked
876 * @detect_deadlock: deadlock detection on/off
877 *
878 * Returns:
879 * 0 on success
880 * -EINTR when interrupted by a signal
881 * -EDEADLK when the lock would deadlock (when deadlock detection is on)
882 */
883int __sched rt_mutex_lock_interruptible(struct rt_mutex *lock,
884 int detect_deadlock)
885{
886 might_sleep();
887
888 return rt_mutex_fastlock(lock, TASK_INTERRUPTIBLE,
889 detect_deadlock, rt_mutex_slowlock);
890}
891EXPORT_SYMBOL_GPL(rt_mutex_lock_interruptible);
892
893/**
Luis Henriques23b94b92009-04-29 21:54:51 +0100894 * rt_mutex_timed_lock - lock a rt_mutex interruptible
895 * the timeout structure is provided
896 * by the caller
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700897 *
898 * @lock: the rt_mutex to be locked
899 * @timeout: timeout structure or NULL (no timeout)
900 * @detect_deadlock: deadlock detection on/off
901 *
902 * Returns:
903 * 0 on success
904 * -EINTR when interrupted by a signal
Jean Delvare3ac49a12009-06-04 16:20:28 +0200905 * -ETIMEDOUT when the timeout expired
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700906 * -EDEADLK when the lock would deadlock (when deadlock detection is on)
907 */
908int
909rt_mutex_timed_lock(struct rt_mutex *lock, struct hrtimer_sleeper *timeout,
910 int detect_deadlock)
911{
912 might_sleep();
913
914 return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout,
915 detect_deadlock, rt_mutex_slowlock);
916}
917EXPORT_SYMBOL_GPL(rt_mutex_timed_lock);
918
919/**
920 * rt_mutex_trylock - try to lock a rt_mutex
921 *
922 * @lock: the rt_mutex to be locked
923 *
924 * Returns 1 on success and 0 on contention
925 */
926int __sched rt_mutex_trylock(struct rt_mutex *lock)
927{
928 return rt_mutex_fasttrylock(lock, rt_mutex_slowtrylock);
929}
930EXPORT_SYMBOL_GPL(rt_mutex_trylock);
931
932/**
933 * rt_mutex_unlock - unlock a rt_mutex
934 *
935 * @lock: the rt_mutex to be unlocked
936 */
937void __sched rt_mutex_unlock(struct rt_mutex *lock)
938{
939 rt_mutex_fastunlock(lock, rt_mutex_slowunlock);
940}
941EXPORT_SYMBOL_GPL(rt_mutex_unlock);
942
Luis Henriques23b94b92009-04-29 21:54:51 +0100943/**
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700944 * rt_mutex_destroy - mark a mutex unusable
945 * @lock: the mutex to be destroyed
946 *
947 * This function marks the mutex uninitialized, and any subsequent
948 * use of the mutex is forbidden. The mutex must not be locked when
949 * this function is called.
950 */
951void rt_mutex_destroy(struct rt_mutex *lock)
952{
953 WARN_ON(rt_mutex_is_locked(lock));
954#ifdef CONFIG_DEBUG_RT_MUTEXES
955 lock->magic = NULL;
956#endif
957}
958
959EXPORT_SYMBOL_GPL(rt_mutex_destroy);
960
961/**
962 * __rt_mutex_init - initialize the rt lock
963 *
964 * @lock: the rt lock to be initialized
965 *
966 * Initialize the rt lock to unlocked state.
967 *
968 * Initializing of a locked rt lock is not allowed
969 */
970void __rt_mutex_init(struct rt_mutex *lock, const char *name)
971{
972 lock->owner = NULL;
Thomas Gleixnerd209d742009-11-17 18:22:11 +0100973 raw_spin_lock_init(&lock->wait_lock);
974 plist_head_init_raw(&lock->wait_list, &lock->wait_lock);
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700975
976 debug_rt_mutex_init(lock, name);
977}
978EXPORT_SYMBOL_GPL(__rt_mutex_init);
Ingo Molnar0cdbee92006-06-27 02:54:57 -0700979
980/**
981 * rt_mutex_init_proxy_locked - initialize and lock a rt_mutex on behalf of a
982 * proxy owner
983 *
984 * @lock: the rt_mutex to be locked
985 * @proxy_owner:the task to set as owner
986 *
987 * No locking. Caller has to do serializing itself
988 * Special API call for PI-futex support
989 */
990void rt_mutex_init_proxy_locked(struct rt_mutex *lock,
991 struct task_struct *proxy_owner)
992{
993 __rt_mutex_init(lock, NULL);
Ingo Molnar9a11b49a2006-07-03 00:24:33 -0700994 debug_rt_mutex_proxy_lock(lock, proxy_owner);
Ingo Molnar0cdbee92006-06-27 02:54:57 -0700995 rt_mutex_set_owner(lock, proxy_owner, 0);
996 rt_mutex_deadlock_account_lock(lock, proxy_owner);
997}
998
999/**
1000 * rt_mutex_proxy_unlock - release a lock on behalf of owner
1001 *
1002 * @lock: the rt_mutex to be locked
1003 *
1004 * No locking. Caller has to do serializing itself
1005 * Special API call for PI-futex support
1006 */
1007void rt_mutex_proxy_unlock(struct rt_mutex *lock,
1008 struct task_struct *proxy_owner)
1009{
1010 debug_rt_mutex_proxy_unlock(lock);
1011 rt_mutex_set_owner(lock, NULL, 0);
1012 rt_mutex_deadlock_account_unlock(proxy_owner);
1013}
1014
1015/**
Darren Hart8dac4562009-04-03 13:40:12 -07001016 * rt_mutex_start_proxy_lock() - Start lock acquisition for another task
1017 * @lock: the rt_mutex to take
1018 * @waiter: the pre-initialized rt_mutex_waiter
1019 * @task: the task to prepare
1020 * @detect_deadlock: perform deadlock detection (1) or not (0)
1021 *
1022 * Returns:
1023 * 0 - task blocked on lock
1024 * 1 - acquired the lock for task, caller should wake it up
1025 * <0 - error
1026 *
1027 * Special API call for FUTEX_REQUEUE_PI support.
1028 */
1029int rt_mutex_start_proxy_lock(struct rt_mutex *lock,
1030 struct rt_mutex_waiter *waiter,
1031 struct task_struct *task, int detect_deadlock)
1032{
1033 int ret;
1034
Thomas Gleixnerd209d742009-11-17 18:22:11 +01001035 raw_spin_lock(&lock->wait_lock);
Darren Hart8dac4562009-04-03 13:40:12 -07001036
1037 mark_rt_mutex_waiters(lock);
1038
1039 if (!rt_mutex_owner(lock) || try_to_steal_lock(lock, task)) {
1040 /* We got the lock for task. */
1041 debug_rt_mutex_lock(lock);
Darren Hart8dac4562009-04-03 13:40:12 -07001042 rt_mutex_set_owner(lock, task, 0);
Thomas Gleixnerd209d742009-11-17 18:22:11 +01001043 raw_spin_unlock(&lock->wait_lock);
Darren Hart8dac4562009-04-03 13:40:12 -07001044 rt_mutex_deadlock_account_lock(lock, task);
1045 return 1;
1046 }
1047
1048 ret = task_blocks_on_rt_mutex(lock, waiter, task, detect_deadlock);
1049
Darren Hart8dac4562009-04-03 13:40:12 -07001050 if (ret && !waiter->task) {
1051 /*
1052 * Reset the return value. We might have
1053 * returned with -EDEADLK and the owner
1054 * released the lock while we were walking the
1055 * pi chain. Let the waiter sort it out.
1056 */
1057 ret = 0;
1058 }
Thomas Gleixnerd209d742009-11-17 18:22:11 +01001059 raw_spin_unlock(&lock->wait_lock);
Darren Hart8dac4562009-04-03 13:40:12 -07001060
1061 debug_rt_mutex_print_deadlock(waiter);
1062
1063 return ret;
1064}
1065
1066/**
Ingo Molnar0cdbee92006-06-27 02:54:57 -07001067 * rt_mutex_next_owner - return the next owner of the lock
1068 *
1069 * @lock: the rt lock query
1070 *
1071 * Returns the next owner of the lock or NULL
1072 *
1073 * Caller has to serialize against other accessors to the lock
1074 * itself.
1075 *
1076 * Special API call for PI-futex support
1077 */
1078struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock)
1079{
1080 if (!rt_mutex_has_waiters(lock))
1081 return NULL;
1082
1083 return rt_mutex_top_waiter(lock)->task;
1084}
Darren Hart8dac4562009-04-03 13:40:12 -07001085
1086/**
1087 * rt_mutex_finish_proxy_lock() - Complete lock acquisition
1088 * @lock: the rt_mutex we were woken on
1089 * @to: the timeout, null if none. hrtimer should already have
1090 * been started.
1091 * @waiter: the pre-initialized rt_mutex_waiter
1092 * @detect_deadlock: perform deadlock detection (1) or not (0)
1093 *
1094 * Complete the lock acquisition started our behalf by another thread.
1095 *
1096 * Returns:
1097 * 0 - success
1098 * <0 - error, one of -EINTR, -ETIMEDOUT, or -EDEADLK
1099 *
1100 * Special API call for PI-futex requeue support
1101 */
1102int rt_mutex_finish_proxy_lock(struct rt_mutex *lock,
1103 struct hrtimer_sleeper *to,
1104 struct rt_mutex_waiter *waiter,
1105 int detect_deadlock)
1106{
1107 int ret;
1108
Thomas Gleixnerd209d742009-11-17 18:22:11 +01001109 raw_spin_lock(&lock->wait_lock);
Darren Hart8dac4562009-04-03 13:40:12 -07001110
1111 set_current_state(TASK_INTERRUPTIBLE);
1112
1113 ret = __rt_mutex_slowlock(lock, TASK_INTERRUPTIBLE, to, waiter,
1114 detect_deadlock);
1115
1116 set_current_state(TASK_RUNNING);
1117
1118 if (unlikely(waiter->task))
1119 remove_waiter(lock, waiter);
1120
1121 /*
1122 * try_to_take_rt_mutex() sets the waiter bit unconditionally. We might
1123 * have to fix that up.
1124 */
1125 fixup_rt_mutex_waiters(lock);
1126
Thomas Gleixnerd209d742009-11-17 18:22:11 +01001127 raw_spin_unlock(&lock->wait_lock);
Darren Hart8dac4562009-04-03 13:40:12 -07001128
1129 /*
1130 * Readjust priority, when we did not get the lock. We might have been
1131 * the pending owner and boosted. Since we did not take the lock, the
1132 * PI boost has to go.
1133 */
1134 if (unlikely(ret))
1135 rt_mutex_adjust_prio(current);
1136
1137 return ret;
1138}