1 | /* Copyright (C) 2002-2017 Free Software Foundation, Inc. |
2 | This file is part of the GNU C Library. |
3 | Contributed by Ulrich Drepper <drepper@redhat.com>, 2002. |
4 | |
5 | The GNU C Library is free software; you can redistribute it and/or |
6 | modify it under the terms of the GNU Lesser General Public |
7 | License as published by the Free Software Foundation; either |
8 | version 2.1 of the License, or (at your option) any later version. |
9 | |
10 | The GNU C Library is distributed in the hope that it will be useful, |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
13 | Lesser General Public License for more details. |
14 | |
15 | You should have received a copy of the GNU Lesser General Public |
16 | License along with the GNU C Library; if not, see |
17 | <http://www.gnu.org/licenses/>. */ |
18 | |
19 | #include <assert.h> |
20 | #include <errno.h> |
21 | #include <stdlib.h> |
22 | #include "pthreadP.h" |
23 | #include <lowlevellock.h> |
24 | #include <stap-probe.h> |
25 | |
26 | #ifndef lll_unlock_elision |
27 | #define lll_unlock_elision(a,b,c) ({ lll_unlock (a,c); 0; }) |
28 | #endif |
29 | |
30 | static int |
31 | internal_function |
32 | __pthread_mutex_unlock_full (pthread_mutex_t *mutex, int decr) |
33 | __attribute_noinline__; |
34 | |
35 | int |
36 | internal_function attribute_hidden |
37 | __pthread_mutex_unlock_usercnt (pthread_mutex_t *mutex, int decr) |
38 | { |
39 | int type = PTHREAD_MUTEX_TYPE_ELISION (mutex); |
40 | if (__builtin_expect (type & |
41 | ~(PTHREAD_MUTEX_KIND_MASK_NP|PTHREAD_MUTEX_ELISION_FLAGS_NP), 0)) |
42 | return __pthread_mutex_unlock_full (mutex, decr); |
43 | |
44 | if (__builtin_expect (type, PTHREAD_MUTEX_TIMED_NP) |
45 | == PTHREAD_MUTEX_TIMED_NP) |
46 | { |
47 | /* Always reset the owner field. */ |
48 | normal: |
49 | mutex->__data.__owner = 0; |
50 | if (decr) |
51 | /* One less user. */ |
52 | --mutex->__data.__nusers; |
53 | |
54 | /* Unlock. */ |
55 | lll_unlock (mutex->__data.__lock, PTHREAD_MUTEX_PSHARED (mutex)); |
56 | |
57 | LIBC_PROBE (mutex_release, 1, mutex); |
58 | |
59 | return 0; |
60 | } |
61 | else if (__glibc_likely (type == PTHREAD_MUTEX_TIMED_ELISION_NP)) |
62 | { |
63 | /* Don't reset the owner/users fields for elision. */ |
64 | return lll_unlock_elision (mutex->__data.__lock, mutex->__data.__elision, |
65 | PTHREAD_MUTEX_PSHARED (mutex)); |
66 | } |
67 | else if (__builtin_expect (PTHREAD_MUTEX_TYPE (mutex) |
68 | == PTHREAD_MUTEX_RECURSIVE_NP, 1)) |
69 | { |
70 | /* Recursive mutex. */ |
71 | if (mutex->__data.__owner != THREAD_GETMEM (THREAD_SELF, tid)) |
72 | return EPERM; |
73 | |
74 | if (--mutex->__data.__count != 0) |
75 | /* We still hold the mutex. */ |
76 | return 0; |
77 | goto normal; |
78 | } |
79 | else if (__builtin_expect (PTHREAD_MUTEX_TYPE (mutex) |
80 | == PTHREAD_MUTEX_ADAPTIVE_NP, 1)) |
81 | goto normal; |
82 | else |
83 | { |
84 | /* Error checking mutex. */ |
85 | assert (type == PTHREAD_MUTEX_ERRORCHECK_NP); |
86 | if (mutex->__data.__owner != THREAD_GETMEM (THREAD_SELF, tid) |
87 | || ! lll_islocked (mutex->__data.__lock)) |
88 | return EPERM; |
89 | goto normal; |
90 | } |
91 | } |
92 | |
93 | |
94 | static int |
95 | internal_function |
96 | __pthread_mutex_unlock_full (pthread_mutex_t *mutex, int decr) |
97 | { |
98 | int newowner = 0; |
99 | int private; |
100 | |
101 | switch (PTHREAD_MUTEX_TYPE (mutex)) |
102 | { |
103 | case PTHREAD_MUTEX_ROBUST_RECURSIVE_NP: |
104 | /* Recursive mutex. */ |
105 | if ((mutex->__data.__lock & FUTEX_TID_MASK) |
106 | == THREAD_GETMEM (THREAD_SELF, tid) |
107 | && __builtin_expect (mutex->__data.__owner |
108 | == PTHREAD_MUTEX_INCONSISTENT, 0)) |
109 | { |
110 | if (--mutex->__data.__count != 0) |
111 | /* We still hold the mutex. */ |
112 | return ENOTRECOVERABLE; |
113 | |
114 | goto notrecoverable; |
115 | } |
116 | |
117 | if (mutex->__data.__owner != THREAD_GETMEM (THREAD_SELF, tid)) |
118 | return EPERM; |
119 | |
120 | if (--mutex->__data.__count != 0) |
121 | /* We still hold the mutex. */ |
122 | return 0; |
123 | |
124 | goto robust; |
125 | |
126 | case PTHREAD_MUTEX_ROBUST_ERRORCHECK_NP: |
127 | case PTHREAD_MUTEX_ROBUST_NORMAL_NP: |
128 | case PTHREAD_MUTEX_ROBUST_ADAPTIVE_NP: |
129 | if ((mutex->__data.__lock & FUTEX_TID_MASK) |
130 | != THREAD_GETMEM (THREAD_SELF, tid) |
131 | || ! lll_islocked (mutex->__data.__lock)) |
132 | return EPERM; |
133 | |
134 | /* If the previous owner died and the caller did not succeed in |
135 | making the state consistent, mark the mutex as unrecoverable |
136 | and make all waiters. */ |
137 | if (__builtin_expect (mutex->__data.__owner |
138 | == PTHREAD_MUTEX_INCONSISTENT, 0)) |
139 | notrecoverable: |
140 | newowner = PTHREAD_MUTEX_NOTRECOVERABLE; |
141 | |
142 | robust: |
143 | /* Remove mutex from the list. */ |
144 | THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, |
145 | &mutex->__data.__list.__next); |
146 | /* We must set op_pending before we dequeue the mutex. Also see |
147 | comments at ENQUEUE_MUTEX. */ |
148 | __asm ("" ::: "memory" ); |
149 | DEQUEUE_MUTEX (mutex); |
150 | |
151 | mutex->__data.__owner = newowner; |
152 | if (decr) |
153 | /* One less user. */ |
154 | --mutex->__data.__nusers; |
155 | |
156 | /* Unlock by setting the lock to 0 (not acquired); if the lock had |
157 | FUTEX_WAITERS set previously, then wake any waiters. |
158 | The unlock operation must be the last access to the mutex to not |
159 | violate the mutex destruction requirements (see __lll_unlock). */ |
160 | private = PTHREAD_ROBUST_MUTEX_PSHARED (mutex); |
161 | if (__glibc_unlikely ((atomic_exchange_rel (&mutex->__data.__lock, 0) |
162 | & FUTEX_WAITERS) != 0)) |
163 | lll_futex_wake (&mutex->__data.__lock, 1, private); |
164 | |
165 | /* We must clear op_pending after we release the mutex. |
166 | FIXME However, this violates the mutex destruction requirements |
167 | because another thread could acquire the mutex, destroy it, and |
168 | reuse the memory for something else; then, if this thread crashes, |
169 | and the memory happens to have a value equal to the TID, the kernel |
170 | will believe it is still related to the mutex (which has been |
171 | destroyed already) and will modify some other random object. */ |
172 | __asm ("" ::: "memory" ); |
173 | THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL); |
174 | break; |
175 | |
176 | /* The PI support requires the Linux futex system call. If that's not |
177 | available, pthread_mutex_init should never have allowed the type to |
178 | be set. So it will get the default case for an invalid type. */ |
179 | #ifdef __NR_futex |
180 | case PTHREAD_MUTEX_PI_RECURSIVE_NP: |
181 | /* Recursive mutex. */ |
182 | if (mutex->__data.__owner != THREAD_GETMEM (THREAD_SELF, tid)) |
183 | return EPERM; |
184 | |
185 | if (--mutex->__data.__count != 0) |
186 | /* We still hold the mutex. */ |
187 | return 0; |
188 | goto continue_pi_non_robust; |
189 | |
190 | case PTHREAD_MUTEX_PI_ROBUST_RECURSIVE_NP: |
191 | /* Recursive mutex. */ |
192 | if ((mutex->__data.__lock & FUTEX_TID_MASK) |
193 | == THREAD_GETMEM (THREAD_SELF, tid) |
194 | && __builtin_expect (mutex->__data.__owner |
195 | == PTHREAD_MUTEX_INCONSISTENT, 0)) |
196 | { |
197 | if (--mutex->__data.__count != 0) |
198 | /* We still hold the mutex. */ |
199 | return ENOTRECOVERABLE; |
200 | |
201 | goto pi_notrecoverable; |
202 | } |
203 | |
204 | if (mutex->__data.__owner != THREAD_GETMEM (THREAD_SELF, tid)) |
205 | return EPERM; |
206 | |
207 | if (--mutex->__data.__count != 0) |
208 | /* We still hold the mutex. */ |
209 | return 0; |
210 | |
211 | goto continue_pi_robust; |
212 | |
213 | case PTHREAD_MUTEX_PI_ERRORCHECK_NP: |
214 | case PTHREAD_MUTEX_PI_NORMAL_NP: |
215 | case PTHREAD_MUTEX_PI_ADAPTIVE_NP: |
216 | case PTHREAD_MUTEX_PI_ROBUST_ERRORCHECK_NP: |
217 | case PTHREAD_MUTEX_PI_ROBUST_NORMAL_NP: |
218 | case PTHREAD_MUTEX_PI_ROBUST_ADAPTIVE_NP: |
219 | if ((mutex->__data.__lock & FUTEX_TID_MASK) |
220 | != THREAD_GETMEM (THREAD_SELF, tid) |
221 | || ! lll_islocked (mutex->__data.__lock)) |
222 | return EPERM; |
223 | |
224 | /* If the previous owner died and the caller did not succeed in |
225 | making the state consistent, mark the mutex as unrecoverable |
226 | and make all waiters. */ |
227 | if ((mutex->__data.__kind & PTHREAD_MUTEX_ROBUST_NORMAL_NP) != 0 |
228 | && __builtin_expect (mutex->__data.__owner |
229 | == PTHREAD_MUTEX_INCONSISTENT, 0)) |
230 | pi_notrecoverable: |
231 | newowner = PTHREAD_MUTEX_NOTRECOVERABLE; |
232 | |
233 | if ((mutex->__data.__kind & PTHREAD_MUTEX_ROBUST_NORMAL_NP) != 0) |
234 | { |
235 | continue_pi_robust: |
236 | /* Remove mutex from the list. |
237 | Note: robust PI futexes are signaled by setting bit 0. */ |
238 | THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, |
239 | (void *) (((uintptr_t) &mutex->__data.__list.__next) |
240 | | 1)); |
241 | /* We must set op_pending before we dequeue the mutex. Also see |
242 | comments at ENQUEUE_MUTEX. */ |
243 | __asm ("" ::: "memory" ); |
244 | DEQUEUE_MUTEX (mutex); |
245 | } |
246 | |
247 | continue_pi_non_robust: |
248 | mutex->__data.__owner = newowner; |
249 | if (decr) |
250 | /* One less user. */ |
251 | --mutex->__data.__nusers; |
252 | |
253 | /* Unlock. Load all necessary mutex data before releasing the mutex |
254 | to not violate the mutex destruction requirements (see |
255 | lll_unlock). */ |
256 | int robust = mutex->__data.__kind & PTHREAD_MUTEX_ROBUST_NORMAL_NP; |
257 | private = (robust |
258 | ? PTHREAD_ROBUST_MUTEX_PSHARED (mutex) |
259 | : PTHREAD_MUTEX_PSHARED (mutex)); |
260 | /* Unlock the mutex using a CAS unless there are futex waiters or our |
261 | TID is not the value of __lock anymore, in which case we let the |
262 | kernel take care of the situation. Use release MO in the CAS to |
263 | synchronize with acquire MO in lock acquisitions. */ |
264 | int l = atomic_load_relaxed (&mutex->__data.__lock); |
265 | do |
266 | { |
267 | if (((l & FUTEX_WAITERS) != 0) |
268 | || (l != THREAD_GETMEM (THREAD_SELF, tid))) |
269 | { |
270 | INTERNAL_SYSCALL_DECL (__err); |
271 | INTERNAL_SYSCALL (futex, __err, 2, &mutex->__data.__lock, |
272 | __lll_private_flag (FUTEX_UNLOCK_PI, private)); |
273 | break; |
274 | } |
275 | } |
276 | while (!atomic_compare_exchange_weak_release (&mutex->__data.__lock, |
277 | &l, 0)); |
278 | |
279 | /* This happens after the kernel releases the mutex but violates the |
280 | mutex destruction requirements; see comments in the code handling |
281 | PTHREAD_MUTEX_ROBUST_NORMAL_NP. */ |
282 | THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL); |
283 | break; |
284 | #endif /* __NR_futex. */ |
285 | |
286 | case PTHREAD_MUTEX_PP_RECURSIVE_NP: |
287 | /* Recursive mutex. */ |
288 | if (mutex->__data.__owner != THREAD_GETMEM (THREAD_SELF, tid)) |
289 | return EPERM; |
290 | |
291 | if (--mutex->__data.__count != 0) |
292 | /* We still hold the mutex. */ |
293 | return 0; |
294 | goto pp; |
295 | |
296 | case PTHREAD_MUTEX_PP_ERRORCHECK_NP: |
297 | /* Error checking mutex. */ |
298 | if (mutex->__data.__owner != THREAD_GETMEM (THREAD_SELF, tid) |
299 | || (mutex->__data.__lock & ~ PTHREAD_MUTEX_PRIO_CEILING_MASK) == 0) |
300 | return EPERM; |
301 | /* FALLTHROUGH */ |
302 | |
303 | case PTHREAD_MUTEX_PP_NORMAL_NP: |
304 | case PTHREAD_MUTEX_PP_ADAPTIVE_NP: |
305 | /* Always reset the owner field. */ |
306 | pp: |
307 | mutex->__data.__owner = 0; |
308 | |
309 | if (decr) |
310 | /* One less user. */ |
311 | --mutex->__data.__nusers; |
312 | |
313 | /* Unlock. Use release MO in the CAS to synchronize with acquire MO in |
314 | lock acquisitions. */ |
315 | int newval; |
316 | int oldval = atomic_load_relaxed (&mutex->__data.__lock); |
317 | do |
318 | { |
319 | newval = oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK; |
320 | } |
321 | while (!atomic_compare_exchange_weak_release (&mutex->__data.__lock, |
322 | &oldval, newval)); |
323 | |
324 | if ((oldval & ~PTHREAD_MUTEX_PRIO_CEILING_MASK) > 1) |
325 | lll_futex_wake (&mutex->__data.__lock, 1, |
326 | PTHREAD_MUTEX_PSHARED (mutex)); |
327 | |
328 | int oldprio = newval >> PTHREAD_MUTEX_PRIO_CEILING_SHIFT; |
329 | |
330 | LIBC_PROBE (mutex_release, 1, mutex); |
331 | |
332 | return __pthread_tpp_change_priority (oldprio, -1); |
333 | |
334 | default: |
335 | /* Correct code cannot set any other type. */ |
336 | return EINVAL; |
337 | } |
338 | |
339 | LIBC_PROBE (mutex_release, 1, mutex); |
340 | return 0; |
341 | } |
342 | |
343 | |
344 | int |
345 | __pthread_mutex_unlock (pthread_mutex_t *mutex) |
346 | { |
347 | return __pthread_mutex_unlock_usercnt (mutex, 1); |
348 | } |
349 | weak_alias (__pthread_mutex_unlock, pthread_mutex_unlock) |
350 | hidden_def (__pthread_mutex_unlock) |
351 | |