1/* 2 * Copyright (c) 2005 David Xu <davidxu@freebsd.org> 3 * Copyright (c) 2015 The FreeBSD Foundation 4 * All rights reserved. 5 * 6 * Portions of this software were developed by Konstantin Belousov 7 * under sponsorship from the FreeBSD Foundation. 8 * 9 * Redistribution and use in source and binary forms, with or without 10 * modification, are permitted provided that the following conditions 11 * are met: 12 * 1. Redistributions of source code must retain the above copyright 13 * notice unmodified, this list of conditions, and the following 14 * 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 AUTHOR ``AS IS'' AND ANY EXPRESS OR 20 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 21 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 22 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 23 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 24 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 25 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 26 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 27 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 28 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 29 */ 30 31#include <sys/cdefs.h> 32__FBSDID("$FreeBSD: stable/11/lib/libthr/thread/thr_cond.c 338707 2018-09-17 02:51:08Z pfg $"); 33 34#include "namespace.h" 35#include <stdlib.h> 36#include <errno.h> 37#include <string.h> 38#include <pthread.h> 39#include <limits.h> 40#include "un-namespace.h" 41 42#include "thr_private.h" 43 44_Static_assert(sizeof(struct pthread_cond) <= PAGE_SIZE, 45 "pthread_cond too large"); 46 47/* 48 * Prototypes 49 */ 50int __pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex); 51int __pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex, 52 const struct timespec * abstime); 53static int cond_init(pthread_cond_t *cond, const pthread_condattr_t *attr); 54static int cond_wait_common(pthread_cond_t *cond, pthread_mutex_t *mutex, 55 const struct timespec *abstime, int cancel); 56static int cond_signal_common(pthread_cond_t *cond); 57static int cond_broadcast_common(pthread_cond_t *cond); 58 59/* 60 * Double underscore versions are cancellation points. Single underscore 61 * versions are not and are provided for libc internal usage (which 62 * shouldn't introduce cancellation points). 63 */ 64__weak_reference(__pthread_cond_wait, pthread_cond_wait); 65__weak_reference(__pthread_cond_timedwait, pthread_cond_timedwait); 66 67__weak_reference(_pthread_cond_init, pthread_cond_init); 68__weak_reference(_pthread_cond_destroy, pthread_cond_destroy); 69__weak_reference(_pthread_cond_signal, pthread_cond_signal); 70__weak_reference(_pthread_cond_broadcast, pthread_cond_broadcast); 71 72#define CV_PSHARED(cvp) (((cvp)->kcond.c_flags & USYNC_PROCESS_SHARED) != 0) 73 74static void 75cond_init_body(struct pthread_cond *cvp, const struct pthread_cond_attr *cattr) 76{ 77 78 if (cattr == NULL) { 79 cvp->kcond.c_clockid = CLOCK_REALTIME; 80 } else { 81 if (cattr->c_pshared) 82 cvp->kcond.c_flags |= USYNC_PROCESS_SHARED; 83 cvp->kcond.c_clockid = cattr->c_clockid; 84 } 85} 86 87static int 88cond_init(pthread_cond_t *cond, const pthread_condattr_t *cond_attr) 89{ 90 struct pthread_cond *cvp; 91 const struct pthread_cond_attr *cattr; 92 int pshared; 93 94 cattr = cond_attr != NULL ? *cond_attr : NULL; 95 if (cattr == NULL || cattr->c_pshared == PTHREAD_PROCESS_PRIVATE) { 96 pshared = 0; 97 cvp = calloc(1, sizeof(struct pthread_cond)); 98 if (cvp == NULL) 99 return (ENOMEM); 100 } else { 101 pshared = 1; 102 cvp = __thr_pshared_offpage(cond, 1); 103 if (cvp == NULL) 104 return (EFAULT); 105 } 106 107 /* 108 * Initialise the condition variable structure: 109 */ 110 cond_init_body(cvp, cattr); 111 *cond = pshared ? THR_PSHARED_PTR : cvp; 112 return (0); 113} 114 115static int 116init_static(struct pthread *thread, pthread_cond_t *cond) 117{ 118 int ret; 119 120 THR_LOCK_ACQUIRE(thread, &_cond_static_lock); 121 122 if (*cond == NULL) 123 ret = cond_init(cond, NULL); 124 else 125 ret = 0; 126 127 THR_LOCK_RELEASE(thread, &_cond_static_lock); 128 129 return (ret); 130} 131 132#define CHECK_AND_INIT_COND \ 133 if (*cond == THR_PSHARED_PTR) { \ 134 cvp = __thr_pshared_offpage(cond, 0); \ 135 if (cvp == NULL) \ 136 return (EINVAL); \ 137 } else if (__predict_false((cvp = (*cond)) <= THR_COND_DESTROYED)) { \ 138 if (cvp == THR_COND_INITIALIZER) { \ 139 int ret; \ 140 ret = init_static(_get_curthread(), cond); \ 141 if (ret) \ 142 return (ret); \ 143 } else if (cvp == THR_COND_DESTROYED) { \ 144 return (EINVAL); \ 145 } \ 146 cvp = *cond; \ 147 } 148 149int 150_pthread_cond_init(pthread_cond_t * __restrict cond, 151 const pthread_condattr_t * __restrict cond_attr) 152{ 153 154 *cond = NULL; 155 return (cond_init(cond, cond_attr)); 156} 157 158int 159_pthread_cond_destroy(pthread_cond_t *cond) 160{ 161 struct pthread_cond *cvp; 162 int error; 163 164 error = 0; 165 if (*cond == THR_PSHARED_PTR) { 166 cvp = __thr_pshared_offpage(cond, 0); 167 if (cvp != NULL) 168 __thr_pshared_destroy(cond); 169 *cond = THR_COND_DESTROYED; 170 } else if ((cvp = *cond) == THR_COND_INITIALIZER) { 171 /* nothing */ 172 } else if (cvp == THR_COND_DESTROYED) { 173 error = EINVAL; 174 } else { 175 cvp = *cond; 176 *cond = THR_COND_DESTROYED; 177 free(cvp); 178 } 179 return (error); 180} 181 182/* 183 * Cancellation behavior: 184 * Thread may be canceled at start, if thread is canceled, it means it 185 * did not get a wakeup from pthread_cond_signal(), otherwise, it is 186 * not canceled. 187 * Thread cancellation never cause wakeup from pthread_cond_signal() 188 * to be lost. 189 */ 190static int 191cond_wait_kernel(struct pthread_cond *cvp, struct pthread_mutex *mp, 192 const struct timespec *abstime, int cancel) 193{ 194 struct pthread *curthread; 195 int error, error2, recurse, robust; 196 197 curthread = _get_curthread(); 198 robust = _mutex_enter_robust(curthread, mp); 199 200 error = _mutex_cv_detach(mp, &recurse); 201 if (error != 0) { 202 if (robust) 203 _mutex_leave_robust(curthread, mp); 204 return (error); 205 } 206 207 if (cancel) 208 _thr_cancel_enter2(curthread, 0); 209 error = _thr_ucond_wait(&cvp->kcond, &mp->m_lock, abstime, 210 CVWAIT_ABSTIME | CVWAIT_CLOCKID); 211 if (cancel) 212 _thr_cancel_leave(curthread, 0); 213 214 /* 215 * Note that PP mutex and ROBUST mutex may return 216 * interesting error codes. 217 */ 218 if (error == 0) { 219 error2 = _mutex_cv_lock(mp, recurse, true); 220 } else if (error == EINTR || error == ETIMEDOUT) { 221 error2 = _mutex_cv_lock(mp, recurse, true); 222 /* 223 * Do not do cancellation on EOWNERDEAD there. The 224 * cancellation cleanup handler will use the protected 225 * state and unlock the mutex without making the state 226 * consistent and the state will be unrecoverable. 227 */ 228 if (error2 == 0 && cancel) { 229 if (robust) { 230 _mutex_leave_robust(curthread, mp); 231 robust = false; 232 } 233 _thr_testcancel(curthread); 234 } 235 236 if (error == EINTR) 237 error = 0; 238 } else { 239 /* We know that it didn't unlock the mutex. */ 240 _mutex_cv_attach(mp, recurse); 241 if (cancel) { 242 if (robust) { 243 _mutex_leave_robust(curthread, mp); 244 robust = false; 245 } 246 _thr_testcancel(curthread); 247 } 248 error2 = 0; 249 } 250 if (robust) 251 _mutex_leave_robust(curthread, mp); 252 return (error2 != 0 ? error2 : error); 253} 254 255/* 256 * Thread waits in userland queue whenever possible, when thread 257 * is signaled or broadcasted, it is removed from the queue, and 258 * is saved in curthread's defer_waiters[] buffer, but won't be 259 * woken up until mutex is unlocked. 260 */ 261 262static int 263cond_wait_user(struct pthread_cond *cvp, struct pthread_mutex *mp, 264 const struct timespec *abstime, int cancel) 265{ 266 struct pthread *curthread; 267 struct sleepqueue *sq; 268 int deferred, error, error2, recurse; 269 270 curthread = _get_curthread(); 271 if (curthread->wchan != NULL) 272 PANIC("thread %p was already on queue.", curthread); 273 274 if (cancel) 275 _thr_testcancel(curthread); 276 277 _sleepq_lock(cvp); 278 /* 279 * set __has_user_waiters before unlocking mutex, this allows 280 * us to check it without locking in pthread_cond_signal(). 281 */ 282 cvp->__has_user_waiters = 1; 283 deferred = 0; 284 (void)_mutex_cv_unlock(mp, &recurse, &deferred); 285 curthread->mutex_obj = mp; 286 _sleepq_add(cvp, curthread); 287 for(;;) { 288 _thr_clear_wake(curthread); 289 _sleepq_unlock(cvp); 290 if (deferred) { 291 deferred = 0; 292 if ((mp->m_lock.m_owner & UMUTEX_CONTESTED) == 0) 293 (void)_umtx_op_err(&mp->m_lock, 294 UMTX_OP_MUTEX_WAKE2, mp->m_lock.m_flags, 295 0, 0); 296 } 297 if (curthread->nwaiter_defer > 0) { 298 _thr_wake_all(curthread->defer_waiters, 299 curthread->nwaiter_defer); 300 curthread->nwaiter_defer = 0; 301 } 302 303 if (cancel) 304 _thr_cancel_enter2(curthread, 0); 305 error = _thr_sleep(curthread, cvp->kcond.c_clockid, abstime); 306 if (cancel) 307 _thr_cancel_leave(curthread, 0); 308 309 _sleepq_lock(cvp); 310 if (curthread->wchan == NULL) { 311 error = 0; 312 break; 313 } else if (cancel && SHOULD_CANCEL(curthread)) { 314 sq = _sleepq_lookup(cvp); 315 cvp->__has_user_waiters = _sleepq_remove(sq, curthread); 316 _sleepq_unlock(cvp); 317 curthread->mutex_obj = NULL; 318 error2 = _mutex_cv_lock(mp, recurse, false); 319 if (!THR_IN_CRITICAL(curthread)) 320 _pthread_exit(PTHREAD_CANCELED); 321 else /* this should not happen */ 322 return (error2); 323 } else if (error == ETIMEDOUT) { 324 sq = _sleepq_lookup(cvp); 325 cvp->__has_user_waiters = 326 _sleepq_remove(sq, curthread); 327 break; 328 } 329 } 330 _sleepq_unlock(cvp); 331 curthread->mutex_obj = NULL; 332 error2 = _mutex_cv_lock(mp, recurse, false); 333 if (error == 0) 334 error = error2; 335 return (error); 336} 337 338static int 339cond_wait_common(pthread_cond_t *cond, pthread_mutex_t *mutex, 340 const struct timespec *abstime, int cancel) 341{ 342 struct pthread *curthread = _get_curthread(); 343 struct pthread_cond *cvp; 344 struct pthread_mutex *mp; 345 int error; 346 347 CHECK_AND_INIT_COND 348 349 if (*mutex == THR_PSHARED_PTR) { 350 mp = __thr_pshared_offpage(mutex, 0); 351 if (mp == NULL) 352 return (EINVAL); 353 } else { 354 mp = *mutex; 355 } 356 357 if ((error = _mutex_owned(curthread, mp)) != 0) 358 return (error); 359 360 if (curthread->attr.sched_policy != SCHED_OTHER || 361 (mp->m_lock.m_flags & (UMUTEX_PRIO_PROTECT | UMUTEX_PRIO_INHERIT | 362 USYNC_PROCESS_SHARED)) != 0 || CV_PSHARED(cvp)) 363 return (cond_wait_kernel(cvp, mp, abstime, cancel)); 364 else 365 return (cond_wait_user(cvp, mp, abstime, cancel)); 366} 367 368int 369_pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex) 370{ 371 372 return (cond_wait_common(cond, mutex, NULL, 0)); 373} 374 375int 376__pthread_cond_wait(pthread_cond_t * __restrict cond, 377 pthread_mutex_t * __restrict mutex) 378{ 379 380 return (cond_wait_common(cond, mutex, NULL, 1)); 381} 382 383int 384_pthread_cond_timedwait(pthread_cond_t * __restrict cond, 385 pthread_mutex_t * __restrict mutex, 386 const struct timespec * __restrict abstime) 387{ 388 389 if (abstime == NULL || abstime->tv_sec < 0 || abstime->tv_nsec < 0 || 390 abstime->tv_nsec >= 1000000000) 391 return (EINVAL); 392 393 return (cond_wait_common(cond, mutex, abstime, 0)); 394} 395 396int 397__pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex, 398 const struct timespec *abstime) 399{ 400 401 if (abstime == NULL || abstime->tv_sec < 0 || abstime->tv_nsec < 0 || 402 abstime->tv_nsec >= 1000000000) 403 return (EINVAL); 404 405 return (cond_wait_common(cond, mutex, abstime, 1)); 406} 407 408static int 409cond_signal_common(pthread_cond_t *cond) 410{ 411 struct pthread *curthread = _get_curthread(); 412 struct pthread *td; 413 struct pthread_cond *cvp; 414 struct pthread_mutex *mp; 415 struct sleepqueue *sq; 416 int *waddr; 417 int pshared; 418 419 /* 420 * If the condition variable is statically initialized, perform dynamic 421 * initialization. 422 */ 423 CHECK_AND_INIT_COND 424 425 pshared = CV_PSHARED(cvp); 426 427 _thr_ucond_signal(&cvp->kcond); 428 429 if (pshared || cvp->__has_user_waiters == 0) 430 return (0); 431 432 curthread = _get_curthread(); 433 waddr = NULL; 434 _sleepq_lock(cvp); 435 sq = _sleepq_lookup(cvp); 436 if (sq == NULL) { 437 _sleepq_unlock(cvp); 438 return (0); 439 } 440 441 td = _sleepq_first(sq); 442 mp = td->mutex_obj; 443 cvp->__has_user_waiters = _sleepq_remove(sq, td); 444 if (PMUTEX_OWNER_ID(mp) == TID(curthread)) { 445 if (curthread->nwaiter_defer >= MAX_DEFER_WAITERS) { 446 _thr_wake_all(curthread->defer_waiters, 447 curthread->nwaiter_defer); 448 curthread->nwaiter_defer = 0; 449 } 450 curthread->defer_waiters[curthread->nwaiter_defer++] = 451 &td->wake_addr->value; 452 mp->m_flags |= PMUTEX_FLAG_DEFERRED; 453 } else { 454 waddr = &td->wake_addr->value; 455 } 456 _sleepq_unlock(cvp); 457 if (waddr != NULL) 458 _thr_set_wake(waddr); 459 return (0); 460} 461 462struct broadcast_arg { 463 struct pthread *curthread; 464 unsigned int *waddrs[MAX_DEFER_WAITERS]; 465 int count; 466}; 467 468static void 469drop_cb(struct pthread *td, void *arg) 470{ 471 struct broadcast_arg *ba = arg; 472 struct pthread_mutex *mp; 473 struct pthread *curthread = ba->curthread; 474 475 mp = td->mutex_obj; 476 if (PMUTEX_OWNER_ID(mp) == TID(curthread)) { 477 if (curthread->nwaiter_defer >= MAX_DEFER_WAITERS) { 478 _thr_wake_all(curthread->defer_waiters, 479 curthread->nwaiter_defer); 480 curthread->nwaiter_defer = 0; 481 } 482 curthread->defer_waiters[curthread->nwaiter_defer++] = 483 &td->wake_addr->value; 484 mp->m_flags |= PMUTEX_FLAG_DEFERRED; 485 } else { 486 if (ba->count >= MAX_DEFER_WAITERS) { 487 _thr_wake_all(ba->waddrs, ba->count); 488 ba->count = 0; 489 } 490 ba->waddrs[ba->count++] = &td->wake_addr->value; 491 } 492} 493 494static int 495cond_broadcast_common(pthread_cond_t *cond) 496{ 497 int pshared; 498 struct pthread_cond *cvp; 499 struct sleepqueue *sq; 500 struct broadcast_arg ba; 501 502 /* 503 * If the condition variable is statically initialized, perform dynamic 504 * initialization. 505 */ 506 CHECK_AND_INIT_COND 507 508 pshared = CV_PSHARED(cvp); 509 510 _thr_ucond_broadcast(&cvp->kcond); 511 512 if (pshared || cvp->__has_user_waiters == 0) 513 return (0); 514 515 ba.curthread = _get_curthread(); 516 ba.count = 0; 517 518 _sleepq_lock(cvp); 519 sq = _sleepq_lookup(cvp); 520 if (sq == NULL) { 521 _sleepq_unlock(cvp); 522 return (0); 523 } 524 _sleepq_drop(sq, drop_cb, &ba); 525 cvp->__has_user_waiters = 0; 526 _sleepq_unlock(cvp); 527 if (ba.count > 0) 528 _thr_wake_all(ba.waddrs, ba.count); 529 return (0); 530} 531 532int 533_pthread_cond_signal(pthread_cond_t * cond) 534{ 535 536 return (cond_signal_common(cond)); 537} 538 539int 540_pthread_cond_broadcast(pthread_cond_t * cond) 541{ 542 543 return (cond_broadcast_common(cond)); 544} 545