lib/libthr/thread/thr_cond.c

   1 /*-
   2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
   3  *
   4  * Copyright (c) 2005 David Xu <davidxu@freebsd.org>
   5  * Copyright (c) 2015 The FreeBSD Foundation
   6  * All rights reserved.
   7  *
   8  * Portions of this software were developed by Konstantin Belousov
   9  * under sponsorship from the FreeBSD Foundation.
  10  *
  11  * Redistribution and use in source and binary forms, with or without
  12  * modification, are permitted provided that the following conditions
  13  * are met:
  14  * 1. Redistributions of source code must retain the above copyright
  15  *    notice unmodified, this list of conditions, and the following
  16  *    disclaimer.
  17  * 2. Redistributions in binary form must reproduce the above copyright
  18  *    notice, this list of conditions and the following disclaimer in the
  19  *    documentation and/or other materials provided with the distribution.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  22  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  23  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  24  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  25  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  26  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  27  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  28  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  29  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  30  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  31  */
  32
  33 #include <sys/cdefs.h>
  34 __FBSDID("$FreeBSD$");
  35
  36 #include "namespace.h"
  37 #include <stdlib.h>
  38 #include <errno.h>
  39 #include <string.h>
  40 #include <pthread.h>
  41 #include <limits.h>
  42 #include "un-namespace.h"
  43
  44 #include "thr_private.h"
  45
  46 _Static_assert(sizeof(struct pthread_cond) <= PAGE_SIZE,
  47     "pthread_cond too large");
  48
  49 /*
  50  * Prototypes
  51  */
  52 int     __pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex);
  53 int     __pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
  54                        const struct timespec * abstime);
  55 static int cond_init(pthread_cond_t *cond, const pthread_condattr_t *attr);
  56 static int cond_wait_common(pthread_cond_t *cond, pthread_mutex_t *mutex,
  57                     const struct timespec *abstime, int cancel);
  58 static int cond_signal_common(pthread_cond_t *cond);
  59 static int cond_broadcast_common(pthread_cond_t *cond);
  60
  61 /*
  62  * Double underscore versions are cancellation points.  Single underscore
  63  * versions are not and are provided for libc internal usage (which
  64  * shouldn't introduce cancellation points).
  65  */
  66 __weak_reference(__pthread_cond_wait, pthread_cond_wait);
  67 __weak_reference(__pthread_cond_timedwait, pthread_cond_timedwait);
  68
  69 __weak_reference(_pthread_cond_init, pthread_cond_init);
  70 __weak_reference(_pthread_cond_destroy, pthread_cond_destroy);
  71 __weak_reference(_pthread_cond_signal, pthread_cond_signal);
  72 __weak_reference(_pthread_cond_broadcast, pthread_cond_broadcast);
  73
  74 #define CV_PSHARED(cvp) (((cvp)->kcond.c_flags & USYNC_PROCESS_SHARED) != 0)
  75
  76 static void
  77 cond_init_body(struct pthread_cond *cvp, const struct pthread_cond_attr *cattr)
  78 {
  79
  80         if (cattr == NULL) {
  81                 cvp->kcond.c_clockid = CLOCK_REALTIME;
  82         } else {
  83                 if (cattr->c_pshared)
  84                         cvp->kcond.c_flags |= USYNC_PROCESS_SHARED;
  85                 cvp->kcond.c_clockid = cattr->c_clockid;
  86         }
  87 }
  88
  89 static int
  90 cond_init(pthread_cond_t *cond, const pthread_condattr_t *cond_attr)
  91 {
  92         struct pthread_cond *cvp;
  93         const struct pthread_cond_attr *cattr;
  94         int pshared;
  95
  96         cattr = cond_attr != NULL ? *cond_attr : NULL;
  97         if (cattr == NULL || cattr->c_pshared == PTHREAD_PROCESS_PRIVATE) {
  98                 pshared = 0;
  99                 cvp = calloc(1, sizeof(struct pthread_cond));
 100                 if (cvp == NULL)
 101                         return (ENOMEM);
 102         } else {
 103                 pshared = 1;
 104                 cvp = __thr_pshared_offpage(cond, 1);
 105                 if (cvp == NULL)
 106                         return (EFAULT);
 107         }
 108
 109         /*
 110          * Initialise the condition variable structure:
 111          */
 112         cond_init_body(cvp, cattr);
 113         *cond = pshared ? THR_PSHARED_PTR : cvp;
 114         return (0);
 115 }
 116
 117 static int
 118 init_static(struct pthread *thread, pthread_cond_t *cond)
 119 {
 120         int ret;
 121
 122         THR_LOCK_ACQUIRE(thread, &_cond_static_lock);
 123
 124         if (*cond == NULL)
 125                 ret = cond_init(cond, NULL);
 126         else
 127                 ret = 0;
 128
 129         THR_LOCK_RELEASE(thread, &_cond_static_lock);
 130
 131         return (ret);
 132 }
 133
 134 #define CHECK_AND_INIT_COND                                                     \
 135         if (*cond == THR_PSHARED_PTR) {                                         \
 136                 cvp = __thr_pshared_offpage(cond, 0);                           \
 137                 if (cvp == NULL)                                                \
 138                         return (EINVAL);                                        \
 139         } else if (__predict_false((cvp = (*cond)) <= THR_COND_DESTROYED)) {    \
 140                 if (cvp == THR_COND_INITIALIZER) {                              \
 141                         int ret;                                                \
 142                         ret = init_static(_get_curthread(), cond);              \
 143                         if (ret)                                                \
 144                                 return (ret);                                   \
 145                 } else if (cvp == THR_COND_DESTROYED) {                         \
 146                         return (EINVAL);                                        \
 147                 }                                                               \
 148                 cvp = *cond;                                                    \
 149         }
 150
 151 int
 152 _pthread_cond_init(pthread_cond_t * __restrict cond,
 153     const pthread_condattr_t * __restrict cond_attr)
 154 {
 155
 156         *cond = NULL;
 157         return (cond_init(cond, cond_attr));
 158 }
 159
 160 int
 161 _pthread_cond_destroy(pthread_cond_t *cond)
 162 {
 163         struct pthread_cond *cvp;
 164         int error;
 165
 166         error = 0;
 167         if (*cond == THR_PSHARED_PTR) {
 168                 cvp = __thr_pshared_offpage(cond, 0);
 169                 if (cvp != NULL) {
 170                         if (cvp->kcond.c_has_waiters)
 171                                 error = EBUSY;
 172                         else
 173                                 __thr_pshared_destroy(cond);
 174                 }
 175                 if (error == 0)
 176                         *cond = THR_COND_DESTROYED;
 177         } else if ((cvp = *cond) == THR_COND_INITIALIZER) {
 178                 /* nothing */
 179         } else if (cvp == THR_COND_DESTROYED) {
 180                 error = EINVAL;
 181         } else {
 182                 cvp = *cond;
 183                 if (cvp->__has_user_waiters || cvp->kcond.c_has_waiters)
 184                         error = EBUSY;
 185                 else {
 186                         *cond = THR_COND_DESTROYED;
 187                         free(cvp);
 188                 }
 189         }
 190         return (error);
 191 }
 192
 193 /*
 194  * Cancellation behavior:
 195  *   Thread may be canceled at start, if thread is canceled, it means it
 196  *   did not get a wakeup from pthread_cond_signal(), otherwise, it is
 197  *   not canceled.
 198  *   Thread cancellation never cause wakeup from pthread_cond_signal()
 199  *   to be lost.
 200  */
 201 static int
 202 cond_wait_kernel(struct pthread_cond *cvp, struct pthread_mutex *mp,
 203     const struct timespec *abstime, int cancel)
 204 {
 205         struct pthread *curthread;
 206         int error, error2, recurse, robust;
 207
 208         curthread = _get_curthread();
 209         robust = _mutex_enter_robust(curthread, mp);
 210
 211         error = _mutex_cv_detach(mp, &recurse);
 212         if (error != 0) {
 213                 if (robust)
 214                         _mutex_leave_robust(curthread, mp);
 215                 return (error);
 216         }
 217
 218         if (cancel)
 219                 _thr_cancel_enter2(curthread, 0);
 220         error = _thr_ucond_wait(&cvp->kcond, &mp->m_lock, abstime,
 221             CVWAIT_ABSTIME | CVWAIT_CLOCKID);
 222         if (cancel)
 223                 _thr_cancel_leave(curthread, 0);
 224
 225         /*
 226          * Note that PP mutex and ROBUST mutex may return
 227          * interesting error codes.
 228          */
 229         if (error == 0) {
 230                 error2 = _mutex_cv_lock(mp, recurse, true);
 231         } else if (error == EINTR || error == ETIMEDOUT) {
 232                 error2 = _mutex_cv_lock(mp, recurse, true);
 233                 /*
 234                  * Do not do cancellation on EOWNERDEAD there.  The
 235                  * cancellation cleanup handler will use the protected
 236                  * state and unlock the mutex without making the state
 237                  * consistent and the state will be unrecoverable.
 238                  */
 239                 if (error2 == 0 && cancel) {
 240                         if (robust) {
 241                                 _mutex_leave_robust(curthread, mp);
 242                                 robust = false;
 243                         }
 244                         _thr_testcancel(curthread);
 245                 }
 246
 247                 if (error == EINTR)
 248                         error = 0;
 249         } else {
 250                 /* We know that it didn't unlock the mutex. */
 251                 _mutex_cv_attach(mp, recurse);
 252                 if (cancel) {
 253                         if (robust) {
 254                                 _mutex_leave_robust(curthread, mp);
 255                                 robust = false;
 256                         }
 257                         _thr_testcancel(curthread);
 258                 }
 259                 error2 = 0;
 260         }
 261         if (robust)
 262                 _mutex_leave_robust(curthread, mp);
 263         return (error2 != 0 ? error2 : error);
 264 }
 265
 266 /*
 267  * Thread waits in userland queue whenever possible, when thread
 268  * is signaled or broadcasted, it is removed from the queue, and
 269  * is saved in curthread's defer_waiters[] buffer, but won't be
 270  * woken up until mutex is unlocked.
 271  */
 272
 273 static int
 274 cond_wait_user(struct pthread_cond *cvp, struct pthread_mutex *mp,
 275     const struct timespec *abstime, int cancel)
 276 {
 277         struct pthread *curthread;
 278         struct sleepqueue *sq;
 279         int deferred, error, error2, recurse;
 280
 281         curthread = _get_curthread();
 282         if (curthread->wchan != NULL)
 283                 PANIC("thread %p was already on queue.", curthread);
 284
 285         if (cancel)
 286                 _thr_testcancel(curthread);
 287
 288         _sleepq_lock(cvp);
 289         /*
 290          * set __has_user_waiters before unlocking mutex, this allows
 291          * us to check it without locking in pthread_cond_signal().
 292          */
 293         cvp->__has_user_waiters = 1;
 294         deferred = 0;
 295         (void)_mutex_cv_unlock(mp, &recurse, &deferred);
 296         curthread->mutex_obj = mp;
 297         _sleepq_add(cvp, curthread);
 298         for(;;) {
 299                 _thr_clear_wake(curthread);
 300                 _sleepq_unlock(cvp);
 301                 if (deferred) {
 302                         deferred = 0;
 303                         if ((mp->m_lock.m_owner & UMUTEX_CONTESTED) == 0)
 304                                 (void)_umtx_op_err(&mp->m_lock,
 305                                     UMTX_OP_MUTEX_WAKE2, mp->m_lock.m_flags,
 306                                     0, 0);
 307                 }
 308                 if (curthread->nwaiter_defer > 0) {
 309                         _thr_wake_all(curthread->defer_waiters,
 310                             curthread->nwaiter_defer);
 311                         curthread->nwaiter_defer = 0;
 312                 }
 313
 314                 if (cancel)
 315                         _thr_cancel_enter2(curthread, 0);
 316                 error = _thr_sleep(curthread, cvp->kcond.c_clockid, abstime);
 317                 if (cancel)
 318                         _thr_cancel_leave(curthread, 0);
 319
 320                 _sleepq_lock(cvp);
 321                 if (curthread->wchan == NULL) {
 322                         error = 0;
 323                         break;
 324                 } else if (cancel && SHOULD_CANCEL(curthread)) {
 325                         sq = _sleepq_lookup(cvp);
 326                         cvp->__has_user_waiters = _sleepq_remove(sq, curthread);
 327                         _sleepq_unlock(cvp);
 328                         curthread->mutex_obj = NULL;
 329                         error2 = _mutex_cv_lock(mp, recurse, false);
 330                         if (!THR_IN_CRITICAL(curthread))
 331                                 _pthread_exit(PTHREAD_CANCELED);
 332                         else /* this should not happen */
 333                                 return (error2);
 334                 } else if (error == ETIMEDOUT) {
 335                         sq = _sleepq_lookup(cvp);
 336                         cvp->__has_user_waiters =
 337                             _sleepq_remove(sq, curthread);
 338                         break;
 339                 }
 340         }
 341         _sleepq_unlock(cvp);
 342         curthread->mutex_obj = NULL;
 343         error2 = _mutex_cv_lock(mp, recurse, false);
 344         if (error == 0)
 345                 error = error2;
 346         return (error);
 347 }
 348
 349 static int
 350 cond_wait_common(pthread_cond_t *cond, pthread_mutex_t *mutex,
 351         const struct timespec *abstime, int cancel)
 352 {
 353         struct pthread  *curthread = _get_curthread();
 354         struct pthread_cond *cvp;
 355         struct pthread_mutex *mp;
 356         int     error;
 357
 358         CHECK_AND_INIT_COND
 359
 360         if (*mutex == THR_PSHARED_PTR) {
 361                 mp = __thr_pshared_offpage(mutex, 0);
 362                 if (mp == NULL)
 363                         return (EINVAL);
 364         } else {
 365                 mp = *mutex;
 366         }
 367
 368         if ((error = _mutex_owned(curthread, mp)) != 0)
 369                 return (error);
 370
 371         if (curthread->attr.sched_policy != SCHED_OTHER ||
 372             (mp->m_lock.m_flags & (UMUTEX_PRIO_PROTECT | UMUTEX_PRIO_INHERIT |
 373             USYNC_PROCESS_SHARED)) != 0 || CV_PSHARED(cvp))
 374                 return (cond_wait_kernel(cvp, mp, abstime, cancel));
 375         else
 376                 return (cond_wait_user(cvp, mp, abstime, cancel));
 377 }
 378
 379 int
 380 _pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
 381 {
 382
 383         return (cond_wait_common(cond, mutex, NULL, 0));
 384 }
 385
 386 int
 387 __pthread_cond_wait(pthread_cond_t * __restrict cond,
 388     pthread_mutex_t * __restrict mutex)
 389 {
 390
 391         return (cond_wait_common(cond, mutex, NULL, 1));
 392 }
 393
 394 int
 395 _pthread_cond_timedwait(pthread_cond_t * __restrict cond,
 396     pthread_mutex_t * __restrict mutex,
 397     const struct timespec * __restrict abstime)
 398 {
 399
 400         if (abstime == NULL || abstime->tv_sec < 0 || abstime->tv_nsec < 0 ||
 401             abstime->tv_nsec >= 1000000000)
 402                 return (EINVAL);
 403
 404         return (cond_wait_common(cond, mutex, abstime, 0));
 405 }
 406
 407 int
 408 __pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
 409                        const struct timespec *abstime)
 410 {
 411
 412         if (abstime == NULL || abstime->tv_sec < 0 || abstime->tv_nsec < 0 ||
 413             abstime->tv_nsec >= 1000000000)
 414                 return (EINVAL);
 415
 416         return (cond_wait_common(cond, mutex, abstime, 1));
 417 }
 418
 419 static int
 420 cond_signal_common(pthread_cond_t *cond)
 421 {
 422         struct pthread  *curthread = _get_curthread();
 423         struct pthread *td;
 424         struct pthread_cond *cvp;
 425         struct pthread_mutex *mp;
 426         struct sleepqueue *sq;
 427         int     *waddr;
 428         int     pshared;
 429
 430         /*
 431          * If the condition variable is statically initialized, perform dynamic
 432          * initialization.
 433          */
 434         CHECK_AND_INIT_COND
 435
 436         pshared = CV_PSHARED(cvp);
 437
 438         _thr_ucond_signal(&cvp->kcond);
 439
 440         if (pshared || cvp->__has_user_waiters == 0)
 441                 return (0);
 442
 443         curthread = _get_curthread();
 444         waddr = NULL;
 445         _sleepq_lock(cvp);
 446         sq = _sleepq_lookup(cvp);
 447         if (sq == NULL) {
 448                 _sleepq_unlock(cvp);
 449                 return (0);
 450         }
 451
 452         td = _sleepq_first(sq);
 453         mp = td->mutex_obj;
 454         cvp->__has_user_waiters = _sleepq_remove(sq, td);
 455         if (PMUTEX_OWNER_ID(mp) == TID(curthread)) {
 456                 if (curthread->nwaiter_defer >= MAX_DEFER_WAITERS) {
 457                         _thr_wake_all(curthread->defer_waiters,
 458                             curthread->nwaiter_defer);
 459                         curthread->nwaiter_defer = 0;
 460                 }
 461                 curthread->defer_waiters[curthread->nwaiter_defer++] =
 462                     &td->wake_addr->value;
 463                 mp->m_flags |= PMUTEX_FLAG_DEFERRED;
 464         } else {
 465                 waddr = &td->wake_addr->value;
 466         }
 467         _sleepq_unlock(cvp);
 468         if (waddr != NULL)
 469                 _thr_set_wake(waddr);
 470         return (0);
 471 }
 472
 473 struct broadcast_arg {
 474         struct pthread *curthread;
 475         unsigned int *waddrs[MAX_DEFER_WAITERS];
 476         int count;
 477 };
 478
 479 static void
 480 drop_cb(struct pthread *td, void *arg)
 481 {
 482         struct broadcast_arg *ba = arg;
 483         struct pthread_mutex *mp;
 484         struct pthread *curthread = ba->curthread;
 485
 486         mp = td->mutex_obj;
 487         if (PMUTEX_OWNER_ID(mp) == TID(curthread)) {
 488                 if (curthread->nwaiter_defer >= MAX_DEFER_WAITERS) {
 489                         _thr_wake_all(curthread->defer_waiters,
 490                             curthread->nwaiter_defer);
 491                         curthread->nwaiter_defer = 0;
 492                 }
 493                 curthread->defer_waiters[curthread->nwaiter_defer++] =
 494                     &td->wake_addr->value;
 495                 mp->m_flags |= PMUTEX_FLAG_DEFERRED;
 496         } else {
 497                 if (ba->count >= MAX_DEFER_WAITERS) {
 498                         _thr_wake_all(ba->waddrs, ba->count);
 499                         ba->count = 0;
 500                 }
 501                 ba->waddrs[ba->count++] = &td->wake_addr->value;
 502         }
 503 }
 504
 505 static int
 506 cond_broadcast_common(pthread_cond_t *cond)
 507 {
 508         int    pshared;
 509         struct pthread_cond *cvp;
 510         struct sleepqueue *sq;
 511         struct broadcast_arg ba;
 512
 513         /*
 514          * If the condition variable is statically initialized, perform dynamic
 515          * initialization.
 516          */
 517         CHECK_AND_INIT_COND
 518
 519         pshared = CV_PSHARED(cvp);
 520
 521         _thr_ucond_broadcast(&cvp->kcond);
 522
 523         if (pshared || cvp->__has_user_waiters == 0)
 524                 return (0);
 525
 526         ba.curthread = _get_curthread();
 527         ba.count = 0;
 528
 529         _sleepq_lock(cvp);
 530         sq = _sleepq_lookup(cvp);
 531         if (sq == NULL) {
 532                 _sleepq_unlock(cvp);
 533                 return (0);
 534         }
 535         _sleepq_drop(sq, drop_cb, &ba);
 536         cvp->__has_user_waiters = 0;
 537         _sleepq_unlock(cvp);
 538         if (ba.count > 0)
 539                 _thr_wake_all(ba.waddrs, ba.count);
 540         return (0);
 541 }
 542
 543 int
 544 _pthread_cond_signal(pthread_cond_t * cond)
 545 {
 546
 547         return (cond_signal_common(cond));
 548 }
 549
 550 int
 551 _pthread_cond_broadcast(pthread_cond_t * cond)
 552 {
 553
 554         return (cond_broadcast_common(cond));
 555 }