Commit | Line | Data |
---|---|---|
6053ee3b IM |
1 | /* |
2 | * kernel/mutex.c | |
3 | * | |
4 | * Mutexes: blocking mutual exclusion locks | |
5 | * | |
6 | * Started by Ingo Molnar: | |
7 | * | |
8 | * Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com> | |
9 | * | |
10 | * Many thanks to Arjan van de Ven, Thomas Gleixner, Steven Rostedt and | |
11 | * David Howells for suggestions and improvements. | |
12 | * | |
13 | * Also see Documentation/mutex-design.txt. | |
14 | */ | |
15 | #include <linux/mutex.h> | |
16 | #include <linux/sched.h> | |
17 | #include <linux/module.h> | |
18 | #include <linux/spinlock.h> | |
19 | #include <linux/interrupt.h> | |
9a11b49a | 20 | #include <linux/debug_locks.h> |
6053ee3b IM |
21 | |
22 | /* | |
23 | * In the DEBUG case we are using the "NULL fastpath" for mutexes, | |
24 | * which forces all calls into the slowpath: | |
25 | */ | |
26 | #ifdef CONFIG_DEBUG_MUTEXES | |
27 | # include "mutex-debug.h" | |
28 | # include <asm-generic/mutex-null.h> | |
29 | #else | |
30 | # include "mutex.h" | |
31 | # include <asm/mutex.h> | |
32 | #endif | |
33 | ||
34 | /*** | |
35 | * mutex_init - initialize the mutex | |
36 | * @lock: the mutex to be initialized | |
37 | * | |
38 | * Initialize the mutex to unlocked state. | |
39 | * | |
40 | * It is not allowed to initialize an already locked mutex. | |
41 | */ | |
ef5d4707 IM |
42 | void |
43 | __mutex_init(struct mutex *lock, const char *name, struct lock_class_key *key) | |
6053ee3b IM |
44 | { |
45 | atomic_set(&lock->count, 1); | |
46 | spin_lock_init(&lock->wait_lock); | |
47 | INIT_LIST_HEAD(&lock->wait_list); | |
48 | ||
ef5d4707 | 49 | debug_mutex_init(lock, name, key); |
6053ee3b IM |
50 | } |
51 | ||
52 | EXPORT_SYMBOL(__mutex_init); | |
53 | ||
e4564f79 | 54 | #ifndef CONFIG_DEBUG_LOCK_ALLOC |
6053ee3b IM |
55 | /* |
56 | * We split the mutex lock/unlock logic into separate fastpath and | |
57 | * slowpath functions, to reduce the register pressure on the fastpath. | |
58 | * We also put the fastpath first in the kernel image, to make sure the | |
59 | * branch is predicted by the CPU as default-untaken. | |
60 | */ | |
61 | static void fastcall noinline __sched | |
9a11b49a | 62 | __mutex_lock_slowpath(atomic_t *lock_count); |
6053ee3b IM |
63 | |
64 | /*** | |
65 | * mutex_lock - acquire the mutex | |
66 | * @lock: the mutex to be acquired | |
67 | * | |
68 | * Lock the mutex exclusively for this task. If the mutex is not | |
69 | * available right now, it will sleep until it can get it. | |
70 | * | |
71 | * The mutex must later on be released by the same task that | |
72 | * acquired it. Recursive locking is not allowed. The task | |
73 | * may not exit without first unlocking the mutex. Also, kernel | |
74 | * memory where the mutex resides mutex must not be freed with | |
75 | * the mutex still locked. The mutex must first be initialized | |
76 | * (or statically defined) before it can be locked. memset()-ing | |
77 | * the mutex to 0 is not allowed. | |
78 | * | |
79 | * ( The CONFIG_DEBUG_MUTEXES .config option turns on debugging | |
80 | * checks that will enforce the restrictions and will also do | |
81 | * deadlock debugging. ) | |
82 | * | |
83 | * This function is similar to (but not equivalent to) down(). | |
84 | */ | |
9a11b49a | 85 | void inline fastcall __sched mutex_lock(struct mutex *lock) |
6053ee3b | 86 | { |
c544bdb1 | 87 | might_sleep(); |
6053ee3b IM |
88 | /* |
89 | * The locking fastpath is the 1->0 transition from | |
90 | * 'unlocked' into 'locked' state. | |
6053ee3b IM |
91 | */ |
92 | __mutex_fastpath_lock(&lock->count, __mutex_lock_slowpath); | |
93 | } | |
94 | ||
95 | EXPORT_SYMBOL(mutex_lock); | |
e4564f79 | 96 | #endif |
6053ee3b IM |
97 | |
98 | static void fastcall noinline __sched | |
9a11b49a | 99 | __mutex_unlock_slowpath(atomic_t *lock_count); |
6053ee3b IM |
100 | |
101 | /*** | |
102 | * mutex_unlock - release the mutex | |
103 | * @lock: the mutex to be released | |
104 | * | |
105 | * Unlock a mutex that has been locked by this task previously. | |
106 | * | |
107 | * This function must not be used in interrupt context. Unlocking | |
108 | * of a not locked mutex is not allowed. | |
109 | * | |
110 | * This function is similar to (but not equivalent to) up(). | |
111 | */ | |
112 | void fastcall __sched mutex_unlock(struct mutex *lock) | |
113 | { | |
114 | /* | |
115 | * The unlocking fastpath is the 0->1 transition from 'locked' | |
116 | * into 'unlocked' state: | |
6053ee3b IM |
117 | */ |
118 | __mutex_fastpath_unlock(&lock->count, __mutex_unlock_slowpath); | |
119 | } | |
120 | ||
121 | EXPORT_SYMBOL(mutex_unlock); | |
122 | ||
123 | /* | |
124 | * Lock a mutex (possibly interruptible), slowpath: | |
125 | */ | |
126 | static inline int __sched | |
e4564f79 PZ |
127 | __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass, |
128 | unsigned long ip) | |
6053ee3b IM |
129 | { |
130 | struct task_struct *task = current; | |
131 | struct mutex_waiter waiter; | |
132 | unsigned int old_val; | |
1fb00c6c | 133 | unsigned long flags; |
6053ee3b | 134 | |
1fb00c6c | 135 | spin_lock_mutex(&lock->wait_lock, flags); |
6053ee3b | 136 | |
9a11b49a | 137 | debug_mutex_lock_common(lock, &waiter); |
e4564f79 | 138 | mutex_acquire(&lock->dep_map, subclass, 0, ip); |
c9f4f06d | 139 | debug_mutex_add_waiter(lock, &waiter, task_thread_info(task)); |
6053ee3b IM |
140 | |
141 | /* add waiting tasks to the end of the waitqueue (FIFO): */ | |
142 | list_add_tail(&waiter.list, &lock->wait_list); | |
143 | waiter.task = task; | |
144 | ||
4fe87745 PZ |
145 | old_val = atomic_xchg(&lock->count, -1); |
146 | if (old_val == 1) | |
147 | goto done; | |
148 | ||
e4564f79 | 149 | lock_contended(&lock->dep_map, ip); |
4fe87745 | 150 | |
6053ee3b IM |
151 | for (;;) { |
152 | /* | |
153 | * Lets try to take the lock again - this is needed even if | |
154 | * we get here for the first time (shortly after failing to | |
155 | * acquire the lock), to make sure that we get a wakeup once | |
156 | * it's unlocked. Later on, if we sleep, this is the | |
157 | * operation that gives us the lock. We xchg it to -1, so | |
158 | * that when we release the lock, we properly wake up the | |
159 | * other waiters: | |
160 | */ | |
161 | old_val = atomic_xchg(&lock->count, -1); | |
162 | if (old_val == 1) | |
163 | break; | |
164 | ||
165 | /* | |
166 | * got a signal? (This code gets eliminated in the | |
167 | * TASK_UNINTERRUPTIBLE case.) | |
168 | */ | |
ad776537 LH |
169 | if (unlikely((state == TASK_INTERRUPTIBLE && |
170 | signal_pending(task)) || | |
171 | (state == TASK_KILLABLE && | |
172 | fatal_signal_pending(task)))) { | |
173 | mutex_remove_waiter(lock, &waiter, | |
174 | task_thread_info(task)); | |
e4564f79 | 175 | mutex_release(&lock->dep_map, 1, ip); |
1fb00c6c | 176 | spin_unlock_mutex(&lock->wait_lock, flags); |
6053ee3b IM |
177 | |
178 | debug_mutex_free_waiter(&waiter); | |
179 | return -EINTR; | |
180 | } | |
181 | __set_task_state(task, state); | |
182 | ||
183 | /* didnt get the lock, go to sleep: */ | |
1fb00c6c | 184 | spin_unlock_mutex(&lock->wait_lock, flags); |
6053ee3b | 185 | schedule(); |
1fb00c6c | 186 | spin_lock_mutex(&lock->wait_lock, flags); |
6053ee3b IM |
187 | } |
188 | ||
4fe87745 | 189 | done: |
96645678 | 190 | lock_acquired(&lock->dep_map); |
6053ee3b | 191 | /* got the lock - rejoice! */ |
c9f4f06d RZ |
192 | mutex_remove_waiter(lock, &waiter, task_thread_info(task)); |
193 | debug_mutex_set_owner(lock, task_thread_info(task)); | |
6053ee3b IM |
194 | |
195 | /* set it to 0 if there are no waiters left: */ | |
196 | if (likely(list_empty(&lock->wait_list))) | |
197 | atomic_set(&lock->count, 0); | |
198 | ||
1fb00c6c | 199 | spin_unlock_mutex(&lock->wait_lock, flags); |
6053ee3b IM |
200 | |
201 | debug_mutex_free_waiter(&waiter); | |
202 | ||
6053ee3b IM |
203 | return 0; |
204 | } | |
205 | ||
ef5d4707 IM |
206 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
207 | void __sched | |
208 | mutex_lock_nested(struct mutex *lock, unsigned int subclass) | |
209 | { | |
210 | might_sleep(); | |
e4564f79 | 211 | __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, subclass, _RET_IP_); |
ef5d4707 IM |
212 | } |
213 | ||
214 | EXPORT_SYMBOL_GPL(mutex_lock_nested); | |
d63a5a74 | 215 | |
ad776537 LH |
216 | int __sched |
217 | mutex_lock_killable_nested(struct mutex *lock, unsigned int subclass) | |
218 | { | |
219 | might_sleep(); | |
220 | return __mutex_lock_common(lock, TASK_KILLABLE, subclass, _RET_IP_); | |
221 | } | |
222 | EXPORT_SYMBOL_GPL(mutex_lock_killable_nested); | |
223 | ||
d63a5a74 N |
224 | int __sched |
225 | mutex_lock_interruptible_nested(struct mutex *lock, unsigned int subclass) | |
226 | { | |
227 | might_sleep(); | |
e4564f79 | 228 | return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, subclass, _RET_IP_); |
d63a5a74 N |
229 | } |
230 | ||
231 | EXPORT_SYMBOL_GPL(mutex_lock_interruptible_nested); | |
ef5d4707 IM |
232 | #endif |
233 | ||
6053ee3b IM |
234 | /* |
235 | * Release the lock, slowpath: | |
236 | */ | |
9a11b49a | 237 | static fastcall inline void |
ef5d4707 | 238 | __mutex_unlock_common_slowpath(atomic_t *lock_count, int nested) |
6053ee3b | 239 | { |
02706647 | 240 | struct mutex *lock = container_of(lock_count, struct mutex, count); |
1fb00c6c | 241 | unsigned long flags; |
6053ee3b | 242 | |
1fb00c6c | 243 | spin_lock_mutex(&lock->wait_lock, flags); |
ef5d4707 | 244 | mutex_release(&lock->dep_map, nested, _RET_IP_); |
9a11b49a | 245 | debug_mutex_unlock(lock); |
6053ee3b IM |
246 | |
247 | /* | |
248 | * some architectures leave the lock unlocked in the fastpath failure | |
249 | * case, others need to leave it locked. In the later case we have to | |
250 | * unlock it here | |
251 | */ | |
252 | if (__mutex_slowpath_needs_to_unlock()) | |
253 | atomic_set(&lock->count, 1); | |
254 | ||
6053ee3b IM |
255 | if (!list_empty(&lock->wait_list)) { |
256 | /* get the first entry from the wait-list: */ | |
257 | struct mutex_waiter *waiter = | |
258 | list_entry(lock->wait_list.next, | |
259 | struct mutex_waiter, list); | |
260 | ||
261 | debug_mutex_wake_waiter(lock, waiter); | |
262 | ||
263 | wake_up_process(waiter->task); | |
264 | } | |
265 | ||
266 | debug_mutex_clear_owner(lock); | |
267 | ||
1fb00c6c | 268 | spin_unlock_mutex(&lock->wait_lock, flags); |
6053ee3b IM |
269 | } |
270 | ||
9a11b49a IM |
271 | /* |
272 | * Release the lock, slowpath: | |
273 | */ | |
274 | static fastcall noinline void | |
275 | __mutex_unlock_slowpath(atomic_t *lock_count) | |
276 | { | |
ef5d4707 | 277 | __mutex_unlock_common_slowpath(lock_count, 1); |
9a11b49a IM |
278 | } |
279 | ||
e4564f79 | 280 | #ifndef CONFIG_DEBUG_LOCK_ALLOC |
6053ee3b IM |
281 | /* |
282 | * Here come the less common (and hence less performance-critical) APIs: | |
283 | * mutex_lock_interruptible() and mutex_trylock(). | |
284 | */ | |
285 | static int fastcall noinline __sched | |
ad776537 LH |
286 | __mutex_lock_killable_slowpath(atomic_t *lock_count); |
287 | ||
288 | static noinline int fastcall __sched | |
9a11b49a | 289 | __mutex_lock_interruptible_slowpath(atomic_t *lock_count); |
6053ee3b IM |
290 | |
291 | /*** | |
292 | * mutex_lock_interruptible - acquire the mutex, interruptable | |
293 | * @lock: the mutex to be acquired | |
294 | * | |
295 | * Lock the mutex like mutex_lock(), and return 0 if the mutex has | |
296 | * been acquired or sleep until the mutex becomes available. If a | |
297 | * signal arrives while waiting for the lock then this function | |
298 | * returns -EINTR. | |
299 | * | |
300 | * This function is similar to (but not equivalent to) down_interruptible(). | |
301 | */ | |
302 | int fastcall __sched mutex_lock_interruptible(struct mutex *lock) | |
303 | { | |
c544bdb1 | 304 | might_sleep(); |
6053ee3b IM |
305 | return __mutex_fastpath_lock_retval |
306 | (&lock->count, __mutex_lock_interruptible_slowpath); | |
307 | } | |
308 | ||
309 | EXPORT_SYMBOL(mutex_lock_interruptible); | |
310 | ||
ad776537 LH |
311 | int fastcall __sched mutex_lock_killable(struct mutex *lock) |
312 | { | |
313 | might_sleep(); | |
314 | return __mutex_fastpath_lock_retval | |
315 | (&lock->count, __mutex_lock_killable_slowpath); | |
316 | } | |
317 | EXPORT_SYMBOL(mutex_lock_killable); | |
318 | ||
e4564f79 PZ |
319 | static void fastcall noinline __sched |
320 | __mutex_lock_slowpath(atomic_t *lock_count) | |
321 | { | |
322 | struct mutex *lock = container_of(lock_count, struct mutex, count); | |
323 | ||
324 | __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, 0, _RET_IP_); | |
325 | } | |
326 | ||
6053ee3b | 327 | static int fastcall noinline __sched |
ad776537 LH |
328 | __mutex_lock_killable_slowpath(atomic_t *lock_count) |
329 | { | |
330 | struct mutex *lock = container_of(lock_count, struct mutex, count); | |
331 | ||
332 | return __mutex_lock_common(lock, TASK_KILLABLE, 0, _RET_IP_); | |
333 | } | |
334 | ||
335 | static noinline int fastcall __sched | |
9a11b49a | 336 | __mutex_lock_interruptible_slowpath(atomic_t *lock_count) |
6053ee3b IM |
337 | { |
338 | struct mutex *lock = container_of(lock_count, struct mutex, count); | |
339 | ||
e4564f79 | 340 | return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, 0, _RET_IP_); |
6053ee3b | 341 | } |
e4564f79 | 342 | #endif |
6053ee3b IM |
343 | |
344 | /* | |
345 | * Spinlock based trylock, we take the spinlock and check whether we | |
346 | * can get the lock: | |
347 | */ | |
348 | static inline int __mutex_trylock_slowpath(atomic_t *lock_count) | |
349 | { | |
350 | struct mutex *lock = container_of(lock_count, struct mutex, count); | |
1fb00c6c | 351 | unsigned long flags; |
6053ee3b IM |
352 | int prev; |
353 | ||
1fb00c6c | 354 | spin_lock_mutex(&lock->wait_lock, flags); |
6053ee3b IM |
355 | |
356 | prev = atomic_xchg(&lock->count, -1); | |
ef5d4707 | 357 | if (likely(prev == 1)) { |
9a11b49a | 358 | debug_mutex_set_owner(lock, current_thread_info()); |
ef5d4707 IM |
359 | mutex_acquire(&lock->dep_map, 0, 1, _RET_IP_); |
360 | } | |
6053ee3b IM |
361 | /* Set it back to 0 if there are no waiters: */ |
362 | if (likely(list_empty(&lock->wait_list))) | |
363 | atomic_set(&lock->count, 0); | |
364 | ||
1fb00c6c | 365 | spin_unlock_mutex(&lock->wait_lock, flags); |
6053ee3b IM |
366 | |
367 | return prev == 1; | |
368 | } | |
369 | ||
370 | /*** | |
371 | * mutex_trylock - try acquire the mutex, without waiting | |
372 | * @lock: the mutex to be acquired | |
373 | * | |
374 | * Try to acquire the mutex atomically. Returns 1 if the mutex | |
375 | * has been acquired successfully, and 0 on contention. | |
376 | * | |
377 | * NOTE: this function follows the spin_trylock() convention, so | |
378 | * it is negated to the down_trylock() return values! Be careful | |
379 | * about this when converting semaphore users to mutexes. | |
380 | * | |
381 | * This function must not be used in interrupt context. The | |
382 | * mutex must be released by the same task that acquired it. | |
383 | */ | |
9cebb552 | 384 | int fastcall __sched mutex_trylock(struct mutex *lock) |
6053ee3b IM |
385 | { |
386 | return __mutex_fastpath_trylock(&lock->count, | |
387 | __mutex_trylock_slowpath); | |
388 | } | |
389 | ||
390 | EXPORT_SYMBOL(mutex_trylock); |