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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 | /* Linuxthreads - a simple clone()-based implementation of Posix */ /* threads for Linux. */ /* Copyright (C) 1996 Xavier Leroy (Xavier.Leroy@inria.fr) */ /* and Pavel Krauz (krauz@fsid.cvut.cz). */ /* */ /* This program is free software; you can redistribute it and/or */ /* modify it under the terms of the GNU Library General Public License */ /* as published by the Free Software Foundation; either version 2 */ /* of the License, or (at your option) any later version. */ /* */ /* This program is distributed in the hope that it will be useful, */ /* but WITHOUT ANY WARRANTY; without even the implied warranty of */ /* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the */ /* GNU Library General Public License for more details. */ /* Condition variables */ #include <errno.h> #include <sched.h> #include <stddef.h> #include <sys/time.h> #include "pthread.h" #include "internals.h" #include "spinlock.h" #include "queue.h" #include "restart.h" int pthread_cond_init(pthread_cond_t *cond, const pthread_condattr_t *cond_attr attribute_unused) { __pthread_init_lock(&cond->__c_lock); cond->__c_waiting = NULL; return 0; } libpthread_hidden_def(pthread_cond_init) int pthread_cond_destroy(pthread_cond_t *cond) { if (cond->__c_waiting != NULL) return EBUSY; return 0; } libpthread_hidden_def(pthread_cond_destroy) /* Function called by pthread_cancel to remove the thread from waiting on a condition variable queue. */ static int cond_extricate_func(void *obj, pthread_descr th) { volatile pthread_descr self = thread_self(); pthread_cond_t *cond = obj; int did_remove = 0; __pthread_lock(&cond->__c_lock, self); did_remove = remove_from_queue(&cond->__c_waiting, th); __pthread_unlock(&cond->__c_lock); return did_remove; } int pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex) { volatile pthread_descr self = thread_self(); pthread_extricate_if extr; int already_canceled = 0; int spurious_wakeup_count; /* Check whether the mutex is locked and owned by this thread. */ if (mutex->__m_kind != PTHREAD_MUTEX_TIMED_NP && mutex->__m_kind != PTHREAD_MUTEX_ADAPTIVE_NP && mutex->__m_owner != self) return EINVAL; /* Set up extrication interface */ extr.pu_object = cond; extr.pu_extricate_func = cond_extricate_func; /* Register extrication interface */ THREAD_SETMEM(self, p_condvar_avail, 0); __pthread_set_own_extricate_if(self, &extr); /* Atomically enqueue thread for waiting, but only if it is not canceled. If the thread is canceled, then it will fall through the suspend call below, and then call pthread_exit without having to worry about whether it is still on the condition variable queue. This depends on pthread_cancel setting p_canceled before calling the extricate function. */ __pthread_lock(&cond->__c_lock, self); if (!(THREAD_GETMEM(self, p_canceled) && THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE)) enqueue(&cond->__c_waiting, self); else already_canceled = 1; __pthread_unlock(&cond->__c_lock); if (already_canceled) { __pthread_set_own_extricate_if(self, 0); __pthread_do_exit(PTHREAD_CANCELED, CURRENT_STACK_FRAME); } __pthread_mutex_unlock(mutex); spurious_wakeup_count = 0; while (1) { suspend(self); if (THREAD_GETMEM(self, p_condvar_avail) == 0 && (THREAD_GETMEM(self, p_woken_by_cancel) == 0 || THREAD_GETMEM(self, p_cancelstate) != PTHREAD_CANCEL_ENABLE)) { /* Count resumes that don't belong to us. */ spurious_wakeup_count++; continue; } break; } __pthread_set_own_extricate_if(self, 0); /* Check for cancellation again, to provide correct cancellation point behavior */ if (THREAD_GETMEM(self, p_woken_by_cancel) && THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE) { THREAD_SETMEM(self, p_woken_by_cancel, 0); __pthread_mutex_lock(mutex); __pthread_do_exit(PTHREAD_CANCELED, CURRENT_STACK_FRAME); } /* Put back any resumes we caught that don't belong to us. */ while (spurious_wakeup_count--) restart(self); __pthread_mutex_lock(mutex); return 0; } libpthread_hidden_def(pthread_cond_wait) static int pthread_cond_timedwait_relative(pthread_cond_t *cond, pthread_mutex_t *mutex, const struct timespec * abstime) { volatile pthread_descr self = thread_self(); int already_canceled = 0; pthread_extricate_if extr; int spurious_wakeup_count; /* Check whether the mutex is locked and owned by this thread. */ if (mutex->__m_kind != PTHREAD_MUTEX_TIMED_NP && mutex->__m_kind != PTHREAD_MUTEX_ADAPTIVE_NP && mutex->__m_owner != self) return EINVAL; /* Set up extrication interface */ extr.pu_object = cond; extr.pu_extricate_func = cond_extricate_func; /* Register extrication interface */ THREAD_SETMEM(self, p_condvar_avail, 0); __pthread_set_own_extricate_if(self, &extr); /* Enqueue to wait on the condition and check for cancellation. */ __pthread_lock(&cond->__c_lock, self); if (!(THREAD_GETMEM(self, p_canceled) && THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE)) enqueue(&cond->__c_waiting, self); else already_canceled = 1; __pthread_unlock(&cond->__c_lock); if (already_canceled) { __pthread_set_own_extricate_if(self, 0); __pthread_do_exit(PTHREAD_CANCELED, CURRENT_STACK_FRAME); } __pthread_mutex_unlock(mutex); spurious_wakeup_count = 0; while (1) { if (!timedsuspend(self, abstime)) { int was_on_queue; /* __pthread_lock will queue back any spurious restarts that may happen to it. */ __pthread_lock(&cond->__c_lock, self); was_on_queue = remove_from_queue(&cond->__c_waiting, self); __pthread_unlock(&cond->__c_lock); if (was_on_queue) { __pthread_set_own_extricate_if(self, 0); __pthread_mutex_lock(mutex); return ETIMEDOUT; } /* Eat the outstanding restart() from the signaller */ suspend(self); } if (THREAD_GETMEM(self, p_condvar_avail) == 0 && (THREAD_GETMEM(self, p_woken_by_cancel) == 0 || THREAD_GETMEM(self, p_cancelstate) != PTHREAD_CANCEL_ENABLE)) { /* Count resumes that don't belong to us. */ spurious_wakeup_count++; continue; } break; } __pthread_set_own_extricate_if(self, 0); /* The remaining logic is the same as in other cancellable waits, such as pthread_join sem_wait or pthread_cond wait. */ if (THREAD_GETMEM(self, p_woken_by_cancel) && THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE) { THREAD_SETMEM(self, p_woken_by_cancel, 0); __pthread_mutex_lock(mutex); __pthread_do_exit(PTHREAD_CANCELED, CURRENT_STACK_FRAME); } /* Put back any resumes we caught that don't belong to us. */ while (spurious_wakeup_count--) restart(self); __pthread_mutex_lock(mutex); return 0; } int pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex, const struct timespec * abstime) { /* Indirect call through pointer! */ return pthread_cond_timedwait_relative(cond, mutex, abstime); } libpthread_hidden_def(pthread_cond_timedwait) int pthread_cond_signal(pthread_cond_t *cond) { pthread_descr th; __pthread_lock(&cond->__c_lock, NULL); th = dequeue(&cond->__c_waiting); __pthread_unlock(&cond->__c_lock); if (th != NULL) { th->p_condvar_avail = 1; WRITE_MEMORY_BARRIER(); restart(th); } return 0; } libpthread_hidden_def(pthread_cond_signal) int pthread_cond_broadcast(pthread_cond_t *cond) { pthread_descr tosignal, th; __pthread_lock(&cond->__c_lock, NULL); /* Copy the current state of the waiting queue and empty it */ tosignal = cond->__c_waiting; cond->__c_waiting = NULL; __pthread_unlock(&cond->__c_lock); /* Now signal each process in the queue */ while ((th = dequeue(&tosignal)) != NULL) { th->p_condvar_avail = 1; WRITE_MEMORY_BARRIER(); restart(th); } return 0; } libpthread_hidden_def(pthread_cond_broadcast) int pthread_condattr_init(pthread_condattr_t *attr attribute_unused) { return 0; } libpthread_hidden_def(pthread_condattr_init) int pthread_condattr_destroy(pthread_condattr_t *attr attribute_unused) { return 0; } libpthread_hidden_def(pthread_condattr_destroy) int pthread_condattr_getpshared (const pthread_condattr_t *attr attribute_unused, int *pshared) { *pshared = PTHREAD_PROCESS_PRIVATE; return 0; } int pthread_condattr_setpshared (pthread_condattr_t *attr attribute_unused, int pshared) { if (pshared != PTHREAD_PROCESS_PRIVATE && pshared != PTHREAD_PROCESS_SHARED) return EINVAL; /* For now it is not possible to shared a conditional variable. */ if (pshared != PTHREAD_PROCESS_PRIVATE) return ENOSYS; return 0; } |