1 /* $NetBSD: pthread_cond.c,v 1.77 2022/02/12 14:59:32 riastradh Exp $ */ 2 3 /*- 4 * Copyright (c) 2001, 2006, 2007, 2008, 2020 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by Nathan J. Williams and Andrew Doran. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 29 * POSSIBILITY OF SUCH DAMAGE. 30 */ 31 32 #include <sys/cdefs.h> 33 __RCSID("$NetBSD: pthread_cond.c,v 1.77 2022/02/12 14:59:32 riastradh Exp $"); 34 35 /* Need to use libc-private names for atomic operations. */ 36 #include "../../common/lib/libc/atomic/atomic_op_namespace.h" 37 38 #include <stdlib.h> 39 #include <errno.h> 40 #include <sys/time.h> 41 #include <sys/types.h> 42 43 #include "pthread.h" 44 #include "pthread_int.h" 45 #include "reentrant.h" 46 47 int _sys___nanosleep50(const struct timespec *, struct timespec *); 48 49 int _pthread_cond_has_waiters_np(pthread_cond_t *); 50 51 __weak_alias(pthread_cond_has_waiters_np,_pthread_cond_has_waiters_np) 52 53 __strong_alias(__libc_cond_init,pthread_cond_init) 54 __strong_alias(__libc_cond_signal,pthread_cond_signal) 55 __strong_alias(__libc_cond_broadcast,pthread_cond_broadcast) 56 __strong_alias(__libc_cond_wait,pthread_cond_wait) 57 __strong_alias(__libc_cond_timedwait,pthread_cond_timedwait) 58 __strong_alias(__libc_cond_destroy,pthread_cond_destroy) 59 60 /* 61 * A dummy waiter that's used to flag that pthread_cond_signal() is in 62 * progress and nobody else should try to modify the waiter list until 63 * it completes. 64 */ 65 static struct pthread__waiter pthread__cond_dummy; 66 67 static clockid_t 68 pthread_cond_getclock(const pthread_cond_t *cond) 69 { 70 71 pthread__error(EINVAL, "Invalid condition variable", 72 cond->ptc_magic == _PT_COND_MAGIC); 73 74 return cond->ptc_private ? 75 *(clockid_t *)cond->ptc_private : CLOCK_REALTIME; 76 } 77 78 int 79 pthread_cond_init(pthread_cond_t *cond, const pthread_condattr_t *attr) 80 { 81 if (__predict_false(__uselibcstub)) 82 return __libc_cond_init_stub(cond, attr); 83 84 pthread__error(EINVAL, "Invalid condition variable attribute", 85 (attr == NULL) || (attr->ptca_magic == _PT_CONDATTR_MAGIC)); 86 87 cond->ptc_magic = _PT_COND_MAGIC; 88 cond->ptc_waiters = NULL; 89 cond->ptc_mutex = NULL; 90 if (attr && attr->ptca_private) { 91 cond->ptc_private = malloc(sizeof(clockid_t)); 92 if (cond->ptc_private == NULL) 93 return errno; 94 *(clockid_t *)cond->ptc_private = 95 *(clockid_t *)attr->ptca_private; 96 } else 97 cond->ptc_private = NULL; 98 99 return 0; 100 } 101 102 103 int 104 pthread_cond_destroy(pthread_cond_t *cond) 105 { 106 if (__predict_false(__uselibcstub)) 107 return __libc_cond_destroy_stub(cond); 108 109 pthread__error(EINVAL, "Invalid condition variable", 110 cond->ptc_magic == _PT_COND_MAGIC); 111 pthread__error(EBUSY, "Destroying condition variable in use", 112 cond->ptc_waiters == NULL); 113 114 cond->ptc_magic = _PT_COND_DEAD; 115 free(cond->ptc_private); 116 117 return 0; 118 } 119 120 int 121 pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex, 122 const struct timespec *abstime) 123 { 124 struct pthread__waiter waiter, *next, *head; 125 pthread_t self; 126 int error, cancel; 127 clockid_t clkid = pthread_cond_getclock(cond); 128 129 if (__predict_false(__uselibcstub)) 130 return __libc_cond_timedwait_stub(cond, mutex, abstime); 131 132 pthread__error(EINVAL, "Invalid condition variable", 133 cond->ptc_magic == _PT_COND_MAGIC); 134 pthread__error(EINVAL, "Invalid mutex", 135 mutex->ptm_magic == _PT_MUTEX_MAGIC); 136 pthread__error(EPERM, "Mutex not locked in condition wait", 137 mutex->ptm_owner != NULL); 138 139 self = pthread__self(); 140 pthread__assert(self->pt_lid != 0); 141 142 if (__predict_false(self->pt_cancel)) { 143 pthread__cancelled(); 144 } 145 146 /* Note this thread as waiting on the CV. */ 147 cond->ptc_mutex = mutex; 148 for (head = cond->ptc_waiters;; head = next) { 149 /* Wait while pthread_cond_signal() in progress. */ 150 if (__predict_false(head == &pthread__cond_dummy)) { 151 sched_yield(); 152 next = cond->ptc_waiters; 153 continue; 154 } 155 waiter.lid = self->pt_lid; 156 waiter.next = head; 157 #ifndef PTHREAD__ATOMIC_IS_MEMBAR 158 membar_producer(); 159 #endif 160 next = atomic_cas_ptr(&cond->ptc_waiters, head, &waiter); 161 if (__predict_true(next == head)) { 162 break; 163 } 164 } 165 166 /* Drop the interlock and wait. */ 167 error = 0; 168 pthread_mutex_unlock(mutex); 169 while (waiter.lid && !(cancel = self->pt_cancel)) { 170 int rv = _lwp_park(clkid, TIMER_ABSTIME, __UNCONST(abstime), 171 0, NULL, NULL); 172 if (rv == 0) { 173 continue; 174 } 175 if (errno != EINTR && errno != EALREADY) { 176 error = errno; 177 break; 178 } 179 } 180 pthread_mutex_lock(mutex); 181 182 /* 183 * If this thread absorbed a wakeup from pthread_cond_signal() and 184 * cannot take the wakeup, we should ensure that another thread does. 185 * 186 * And if awoken early, we may still be on the waiter list and must 187 * remove self. 188 */ 189 if (__predict_false(cancel | error)) { 190 pthread_cond_broadcast(cond); 191 192 /* 193 * Might have raced with another thread to do the wakeup. 194 * Wait until released, otherwise "waiter" is still globally 195 * visible. 196 */ 197 pthread_mutex_unlock(mutex); 198 while (__predict_false(waiter.lid)) { 199 (void)_lwp_park(CLOCK_MONOTONIC, 0, NULL, 0, NULL, 200 NULL); 201 } 202 pthread_mutex_lock(mutex); 203 } else { 204 pthread__assert(!waiter.lid); 205 } 206 207 /* 208 * If cancelled then exit. POSIX dictates that the mutex must be 209 * held if this happens. 210 */ 211 if (cancel) { 212 pthread__cancelled(); 213 } 214 215 return error; 216 } 217 218 int 219 pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex) 220 { 221 if (__predict_false(__uselibcstub)) 222 return __libc_cond_wait_stub(cond, mutex); 223 224 return pthread_cond_timedwait(cond, mutex, NULL); 225 } 226 227 int 228 pthread_cond_signal(pthread_cond_t *cond) 229 { 230 struct pthread__waiter *head, *next; 231 pthread_mutex_t *mutex; 232 pthread_t self; 233 234 if (__predict_false(__uselibcstub)) 235 return __libc_cond_signal_stub(cond); 236 237 pthread__error(EINVAL, "Invalid condition variable", 238 cond->ptc_magic == _PT_COND_MAGIC); 239 240 /* Take ownership of one waiter. */ 241 self = pthread_self(); 242 mutex = cond->ptc_mutex; 243 for (head = cond->ptc_waiters;; head = next) { 244 /* Wait while pthread_cond_signal() in progress. */ 245 if (__predict_false(head == &pthread__cond_dummy)) { 246 sched_yield(); 247 next = cond->ptc_waiters; 248 continue; 249 } 250 if (head == NULL) { 251 return 0; 252 } 253 /* Block concurrent access to the waiter list. */ 254 next = atomic_cas_ptr(&cond->ptc_waiters, head, 255 &pthread__cond_dummy); 256 if (__predict_true(next == head)) { 257 break; 258 } 259 } 260 261 /* Now that list is locked, read pointer to next and then unlock. */ 262 membar_enter(); 263 cond->ptc_waiters = head->next; 264 membar_producer(); 265 head->next = NULL; 266 267 /* Now transfer waiter to the mutex. */ 268 pthread__mutex_deferwake(self, mutex, head); 269 return 0; 270 } 271 272 int 273 pthread_cond_broadcast(pthread_cond_t *cond) 274 { 275 struct pthread__waiter *head, *next; 276 pthread_mutex_t *mutex; 277 pthread_t self; 278 279 if (__predict_false(__uselibcstub)) 280 return __libc_cond_broadcast_stub(cond); 281 282 pthread__error(EINVAL, "Invalid condition variable", 283 cond->ptc_magic == _PT_COND_MAGIC); 284 285 if (cond->ptc_waiters == NULL) 286 return 0; 287 288 /* Take ownership of current set of waiters. */ 289 self = pthread_self(); 290 mutex = cond->ptc_mutex; 291 for (head = cond->ptc_waiters;; head = next) { 292 /* Wait while pthread_cond_signal() in progress. */ 293 if (__predict_false(head == &pthread__cond_dummy)) { 294 sched_yield(); 295 next = cond->ptc_waiters; 296 continue; 297 } 298 if (head == NULL) { 299 return 0; 300 } 301 next = atomic_cas_ptr(&cond->ptc_waiters, head, NULL); 302 if (__predict_true(next == head)) { 303 break; 304 } 305 } 306 membar_enter(); 307 308 /* Now transfer waiters to the mutex. */ 309 pthread__mutex_deferwake(self, mutex, head); 310 return 0; 311 } 312 313 int 314 _pthread_cond_has_waiters_np(pthread_cond_t *cond) 315 { 316 317 return cond->ptc_waiters != NULL; 318 } 319 320 int 321 pthread_condattr_init(pthread_condattr_t *attr) 322 { 323 324 attr->ptca_magic = _PT_CONDATTR_MAGIC; 325 attr->ptca_private = NULL; 326 327 return 0; 328 } 329 330 int 331 pthread_condattr_setclock(pthread_condattr_t *attr, clockid_t clck) 332 { 333 334 pthread__error(EINVAL, "Invalid condition variable attribute", 335 attr->ptca_magic == _PT_CONDATTR_MAGIC); 336 337 switch (clck) { 338 case CLOCK_MONOTONIC: 339 case CLOCK_REALTIME: 340 if (attr->ptca_private == NULL) 341 attr->ptca_private = malloc(sizeof(clockid_t)); 342 if (attr->ptca_private == NULL) 343 return errno; 344 *(clockid_t *)attr->ptca_private = clck; 345 return 0; 346 default: 347 return EINVAL; 348 } 349 } 350 351 int 352 pthread_condattr_getclock(const pthread_condattr_t *__restrict attr, 353 clockid_t *__restrict clock_id) 354 { 355 356 pthread__error(EINVAL, "Invalid condition variable attribute", 357 attr->ptca_magic == _PT_CONDATTR_MAGIC); 358 359 if (attr == NULL || attr->ptca_private == NULL) 360 return EINVAL; 361 *clock_id = *(clockid_t *)attr->ptca_private; 362 return 0; 363 } 364 365 int 366 pthread_condattr_destroy(pthread_condattr_t *attr) 367 { 368 369 pthread__error(EINVAL, "Invalid condition variable attribute", 370 attr->ptca_magic == _PT_CONDATTR_MAGIC); 371 372 attr->ptca_magic = _PT_CONDATTR_DEAD; 373 free(attr->ptca_private); 374 375 return 0; 376 } 377 378 #ifdef _PTHREAD_PSHARED 379 int 380 pthread_condattr_getpshared(const pthread_condattr_t * __restrict attr, 381 int * __restrict pshared) 382 { 383 384 pthread__error(EINVAL, "Invalid condition variable attribute", 385 attr->ptca_magic == _PT_CONDATTR_MAGIC); 386 387 *pshared = PTHREAD_PROCESS_PRIVATE; 388 return 0; 389 } 390 391 int 392 pthread_condattr_setpshared(pthread_condattr_t *attr, int pshared) 393 { 394 395 pthread__error(EINVAL, "Invalid condition variable attribute", 396 attr->ptca_magic == _PT_CONDATTR_MAGIC); 397 398 switch(pshared) { 399 case PTHREAD_PROCESS_PRIVATE: 400 return 0; 401 case PTHREAD_PROCESS_SHARED: 402 return ENOSYS; 403 } 404 return EINVAL; 405 } 406 #endif 407