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 *cond, const pthread_condattr_t *cond_attr)
 153 {
 154
 155         *cond = NULL;
 156         return (cond_init(cond, cond_attr));
 157 }
 158
 159 int
 160 _pthread_cond_destroy(pthread_cond_t *cond)
 161 {
 162         struct pthread_cond *cvp;
 163         int error;
 164
 165         error = 0;
 166         if (*cond == THR_PSHARED_PTR) {
 167                 cvp = __thr_pshared_offpage(cond, 0);
 168                 if (cvp != NULL)
 169                         __thr_pshared_destroy(cond);
 170                 *cond = THR_COND_DESTROYED;
 171         } else if ((cvp = *cond) == THR_COND_INITIALIZER) {
 172                 /* nothing */
 173         } else if (cvp == THR_COND_DESTROYED) {
 174                 error = EINVAL;
 175         } else {
 176                 cvp = *cond;
 177                 *cond = THR_COND_DESTROYED;
 178                 free(cvp);
 179         }
 180         return (error);
 181 }
 182
 183 /*
 184  * Cancellation behavior:
 185  *   Thread may be canceled at start, if thread is canceled, it means it
 186  *   did not get a wakeup from pthread_cond_signal(), otherwise, it is
 187  *   not canceled.
 188  *   Thread cancellation never cause wakeup from pthread_cond_signal()
 189  *   to be lost.
 190  */
 191 static int
 192 cond_wait_kernel(struct pthread_cond *cvp, struct pthread_mutex *mp,
 193     const struct timespec *abstime, int cancel)
 194 {
 195         struct pthread *curthread;
 196         int error, error2, recurse, robust;
 197
 198         curthread = _get_curthread();
 199         robust = _mutex_enter_robust(curthread, mp);
 200
 201         error = _mutex_cv_detach(mp, &recurse);
 202         if (error != 0) {
 203                 if (robust)
 204                         _mutex_leave_robust(curthread, mp);
 205                 return (error);
 206         }
 207
 208         if (cancel)
 209                 _thr_cancel_enter2(curthread, 0);
 210         error = _thr_ucond_wait(&cvp->kcond, &mp->m_lock, abstime,
 211             CVWAIT_ABSTIME | CVWAIT_CLOCKID);
 212         if (cancel)
 213                 _thr_cancel_leave(curthread, 0);
 214
 215         /*
 216          * Note that PP mutex and ROBUST mutex may return
 217          * interesting error codes.
 218          */
 219         if (error == 0) {
 220                 error2 = _mutex_cv_lock(mp, recurse, true);
 221         } else if (error == EINTR || error == ETIMEDOUT) {
 222                 error2 = _mutex_cv_lock(mp, recurse, true);
 223                 /*
 224                  * Do not do cancellation on EOWNERDEAD there.  The
 225                  * cancellation cleanup handler will use the protected
 226                  * state and unlock the mutex without making the state
 227                  * consistent and the state will be unrecoverable.
 228                  */
 229                 if (error2 == 0 && cancel) {
 230                         if (robust) {
 231                                 _mutex_leave_robust(curthread, mp);
 232                                 robust = false;
 233                         }
 234                         _thr_testcancel(curthread);
 235                 }
 236
 237                 if (error == EINTR)
 238                         error = 0;
 239         } else {
 240                 /* We know that it didn't unlock the mutex. */
 241                 _mutex_cv_attach(mp, recurse);
 242                 if (cancel) {
 243                         if (robust) {
 244                                 _mutex_leave_robust(curthread, mp);
 245                                 robust = false;
 246                         }
 247                         _thr_testcancel(curthread);
 248                 }
 249                 error2 = 0;
 250         }
 251         if (robust)
 252                 _mutex_leave_robust(curthread, mp);
 253         return (error2 != 0 ? error2 : error);
 254 }
 255
 256 /*
 257  * Thread waits in userland queue whenever possible, when thread
 258  * is signaled or broadcasted, it is removed from the queue, and
 259  * is saved in curthread's defer_waiters[] buffer, but won't be
 260  * woken up until mutex is unlocked.
 261  */
 262
 263 static int
 264 cond_wait_user(struct pthread_cond *cvp, struct pthread_mutex *mp,
 265     const struct timespec *abstime, int cancel)
 266 {
 267         struct pthread *curthread;
 268         struct sleepqueue *sq;
 269         int deferred, error, error2, recurse;
 270
 271         curthread = _get_curthread();
 272         if (curthread->wchan != NULL)
 273                 PANIC("thread %p was already on queue.", curthread);
 274
 275         if (cancel)
 276                 _thr_testcancel(curthread);
 277
 278         _sleepq_lock(cvp);
 279         /*
 280          * set __has_user_waiters before unlocking mutex, this allows
 281          * us to check it without locking in pthread_cond_signal().
 282          */
 283         cvp->__has_user_waiters = 1;
 284         deferred = 0;
 285         (void)_mutex_cv_unlock(mp, &recurse, &deferred);
 286         curthread->mutex_obj = mp;
 287         _sleepq_add(cvp, curthread);
 288         for(;;) {
 289                 _thr_clear_wake(curthread);
 290                 _sleepq_unlock(cvp);
 291                 if (deferred) {
 292                         deferred = 0;
 293                         if ((mp->m_lock.m_owner & UMUTEX_CONTESTED) == 0)
 294                                 (void)_umtx_op_err(&mp->m_lock,
 295                                     UMTX_OP_MUTEX_WAKE2, mp->m_lock.m_flags,
 296                                     0, 0);
 297                 }
 298                 if (curthread->nwaiter_defer > 0) {
 299                         _thr_wake_all(curthread->defer_waiters,
 300                             curthread->nwaiter_defer);
 301                         curthread->nwaiter_defer = 0;
 302                 }
 303
 304                 if (cancel)
 305                         _thr_cancel_enter2(curthread, 0);
 306                 error = _thr_sleep(curthread, cvp->kcond.c_clockid, abstime);
 307                 if (cancel)
 308                         _thr_cancel_leave(curthread, 0);
 309
 310                 _sleepq_lock(cvp);
 311                 if (curthread->wchan == NULL) {
 312                         error = 0;
 313                         break;
 314                 } else if (cancel && SHOULD_CANCEL(curthread)) {
 315                         sq = _sleepq_lookup(cvp);
 316                         cvp->__has_user_waiters = _sleepq_remove(sq, curthread);
 317                         _sleepq_unlock(cvp);
 318                         curthread->mutex_obj = NULL;
 319                         error2 = _mutex_cv_lock(mp, recurse, false);
 320                         if (!THR_IN_CRITICAL(curthread))
 321                                 _pthread_exit(PTHREAD_CANCELED);
 322                         else /* this should not happen */
 323                                 return (error2);
 324                 } else if (error == ETIMEDOUT) {
 325                         sq = _sleepq_lookup(cvp);
 326                         cvp->__has_user_waiters =
 327                             _sleepq_remove(sq, curthread);
 328                         break;
 329                 }
 330         }
 331         _sleepq_unlock(cvp);
 332         curthread->mutex_obj = NULL;
 333         error2 = _mutex_cv_lock(mp, recurse, false);
 334         if (error == 0)
 335                 error = error2;
 336         return (error);
 337 }
 338
 339 static int
 340 cond_wait_common(pthread_cond_t *cond, pthread_mutex_t *mutex,
 341         const struct timespec *abstime, int cancel)
 342 {
 343         struct pthread  *curthread = _get_curthread();
 344         struct pthread_cond *cvp;
 345         struct pthread_mutex *mp;
 346         int     error;
 347
 348         CHECK_AND_INIT_COND
 349
 350         if (*mutex == THR_PSHARED_PTR) {
 351                 mp = __thr_pshared_offpage(mutex, 0);
 352                 if (mp == NULL)
 353                         return (EINVAL);
 354         } else {
 355                 mp = *mutex;
 356         }
 357
 358         if ((error = _mutex_owned(curthread, mp)) != 0)
 359                 return (error);
 360
 361         if (curthread->attr.sched_policy != SCHED_OTHER ||
 362             (mp->m_lock.m_flags & (UMUTEX_PRIO_PROTECT | UMUTEX_PRIO_INHERIT |
 363             USYNC_PROCESS_SHARED)) != 0 || CV_PSHARED(cvp))
 364                 return (cond_wait_kernel(cvp, mp, abstime, cancel));
 365         else
 366                 return (cond_wait_user(cvp, mp, abstime, cancel));
 367 }
 368
 369 int
 370 _pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
 371 {
 372
 373         return (cond_wait_common(cond, mutex, NULL, 0));
 374 }
 375
 376 int
 377 __pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
 378 {
 379
 380         return (cond_wait_common(cond, mutex, NULL, 1));
 381 }
 382
 383 int
 384 _pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
 385                        const struct timespec * abstime)
 386 {
 387
 388         if (abstime == NULL || abstime->tv_sec < 0 || abstime->tv_nsec < 0 ||
 389             abstime->tv_nsec >= 1000000000)
 390                 return (EINVAL);
 391
 392         return (cond_wait_common(cond, mutex, abstime, 0));
 393 }
 394
 395 int
 396 __pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
 397                        const struct timespec *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, 1));
 405 }
 406
 407 static int
 408 cond_signal_common(pthread_cond_t *cond)
 409 {
 410         struct pthread  *curthread = _get_curthread();
 411         struct pthread *td;
 412         struct pthread_cond *cvp;
 413         struct pthread_mutex *mp;
 414         struct sleepqueue *sq;
 415         int     *waddr;
 416         int     pshared;
 417
 418         /*
 419          * If the condition variable is statically initialized, perform dynamic
 420          * initialization.
 421          */
 422         CHECK_AND_INIT_COND
 423
 424         pshared = CV_PSHARED(cvp);
 425
 426         _thr_ucond_signal(&cvp->kcond);
 427
 428         if (pshared || cvp->__has_user_waiters == 0)
 429                 return (0);
 430
 431         curthread = _get_curthread();
 432         waddr = NULL;
 433         _sleepq_lock(cvp);
 434         sq = _sleepq_lookup(cvp);
 435         if (sq == NULL) {
 436                 _sleepq_unlock(cvp);
 437                 return (0);
 438         }
 439
 440         td = _sleepq_first(sq);
 441         mp = td->mutex_obj;
 442         cvp->__has_user_waiters = _sleepq_remove(sq, td);
 443         if (PMUTEX_OWNER_ID(mp) == TID(curthread)) {
 444                 if (curthread->nwaiter_defer >= MAX_DEFER_WAITERS) {
 445                         _thr_wake_all(curthread->defer_waiters,
 446                             curthread->nwaiter_defer);
 447                         curthread->nwaiter_defer = 0;
 448                 }
 449                 curthread->defer_waiters[curthread->nwaiter_defer++] =
 450                     &td->wake_addr->value;
 451                 mp->m_flags |= PMUTEX_FLAG_DEFERRED;
 452         } else {
 453                 waddr = &td->wake_addr->value;
 454         }
 455         _sleepq_unlock(cvp);
 456         if (waddr != NULL)
 457                 _thr_set_wake(waddr);
 458         return (0);
 459 }
 460
 461 struct broadcast_arg {
 462         struct pthread *curthread;
 463         unsigned int *waddrs[MAX_DEFER_WAITERS];
 464         int count;
 465 };
 466
 467 static void
 468 drop_cb(struct pthread *td, void *arg)
 469 {
 470         struct broadcast_arg *ba = arg;
 471         struct pthread_mutex *mp;
 472         struct pthread *curthread = ba->curthread;
 473
 474         mp = td->mutex_obj;
 475         if (PMUTEX_OWNER_ID(mp) == TID(curthread)) {
 476                 if (curthread->nwaiter_defer >= MAX_DEFER_WAITERS) {
 477                         _thr_wake_all(curthread->defer_waiters,
 478                             curthread->nwaiter_defer);
 479                         curthread->nwaiter_defer = 0;
 480                 }
 481                 curthread->defer_waiters[curthread->nwaiter_defer++] =
 482                     &td->wake_addr->value;
 483                 mp->m_flags |= PMUTEX_FLAG_DEFERRED;
 484         } else {
 485                 if (ba->count >= MAX_DEFER_WAITERS) {
 486                         _thr_wake_all(ba->waddrs, ba->count);
 487                         ba->count = 0;
 488                 }
 489                 ba->waddrs[ba->count++] = &td->wake_addr->value;
 490         }
 491 }
 492
 493 static int
 494 cond_broadcast_common(pthread_cond_t *cond)
 495 {
 496         int    pshared;
 497         struct pthread_cond *cvp;
 498         struct sleepqueue *sq;
 499         struct broadcast_arg ba;
 500
 501         /*
 502          * If the condition variable is statically initialized, perform dynamic
 503          * initialization.
 504          */
 505         CHECK_AND_INIT_COND
 506
 507         pshared = CV_PSHARED(cvp);
 508
 509         _thr_ucond_broadcast(&cvp->kcond);
 510
 511         if (pshared || cvp->__has_user_waiters == 0)
 512                 return (0);
 513
 514         ba.curthread = _get_curthread();
 515         ba.count = 0;
 516
 517         _sleepq_lock(cvp);
 518         sq = _sleepq_lookup(cvp);
 519         if (sq == NULL) {
 520                 _sleepq_unlock(cvp);
 521                 return (0);
 522         }
 523         _sleepq_drop(sq, drop_cb, &ba);
 524         cvp->__has_user_waiters = 0;
 525         _sleepq_unlock(cvp);
 526         if (ba.count > 0)
 527                 _thr_wake_all(ba.waddrs, ba.count);
 528         return (0);
 529 }
 530
 531 int
 532 _pthread_cond_signal(pthread_cond_t * cond)
 533 {
 534
 535         return (cond_signal_common(cond));
 536 }
 537
 538 int
 539 _pthread_cond_broadcast(pthread_cond_t * cond)
 540 {
 541
 542         return (cond_broadcast_common(cond));
 543 }