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_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
  53                        const struct timespec * abstime);
  54 static int cond_init(pthread_cond_t *cond, const pthread_condattr_t *attr);
  55 static int cond_wait_common(pthread_cond_t *cond, pthread_mutex_t *mutex,
  56                     const struct timespec *abstime, int cancel);
  57 static int cond_signal_common(pthread_cond_t *cond);
  58 static int cond_broadcast_common(pthread_cond_t *cond);
  59
  60 /*
  61  * Double underscore versions are cancellation points.  Single underscore
  62  * versions are not and are provided for libc internal usage (which
  63  * shouldn't introduce cancellation points).
  64  */
  65 __weak_reference(__thr_cond_wait, pthread_cond_wait);
  66 __weak_reference(__thr_cond_wait, __pthread_cond_wait);
  67 __weak_reference(_thr_cond_wait, _pthread_cond_wait);
  68 __weak_reference(__pthread_cond_timedwait, pthread_cond_timedwait);
  69 __weak_reference(_thr_cond_init, pthread_cond_init);
  70 __weak_reference(_thr_cond_init, _pthread_cond_init);
  71 __weak_reference(_thr_cond_destroy, pthread_cond_destroy);
  72 __weak_reference(_thr_cond_destroy, _pthread_cond_destroy);
  73 __weak_reference(_thr_cond_signal, pthread_cond_signal);
  74 __weak_reference(_thr_cond_signal, _pthread_cond_signal);
  75 __weak_reference(_thr_cond_broadcast, pthread_cond_broadcast);
  76 __weak_reference(_thr_cond_broadcast, _pthread_cond_broadcast);
  77
  78 #define CV_PSHARED(cvp) (((cvp)->kcond.c_flags & USYNC_PROCESS_SHARED) != 0)
  79
  80 static void
  81 cond_init_body(struct pthread_cond *cvp, const struct pthread_cond_attr *cattr)
  82 {
  83
  84         if (cattr == NULL) {
  85                 cvp->kcond.c_clockid = CLOCK_REALTIME;
  86         } else {
  87                 if (cattr->c_pshared)
  88                         cvp->kcond.c_flags |= USYNC_PROCESS_SHARED;
  89                 cvp->kcond.c_clockid = cattr->c_clockid;
  90         }
  91 }
  92
  93 static int
  94 cond_init(pthread_cond_t *cond, const pthread_condattr_t *cond_attr)
  95 {
  96         struct pthread_cond *cvp;
  97         const struct pthread_cond_attr *cattr;
  98         int pshared;
  99
 100         cattr = cond_attr != NULL ? *cond_attr : NULL;
 101         if (cattr == NULL || cattr->c_pshared == PTHREAD_PROCESS_PRIVATE) {
 102                 pshared = 0;
 103                 cvp = calloc(1, sizeof(struct pthread_cond));
 104                 if (cvp == NULL)
 105                         return (ENOMEM);
 106         } else {
 107                 pshared = 1;
 108                 cvp = __thr_pshared_offpage(cond, 1);
 109                 if (cvp == NULL)
 110                         return (EFAULT);
 111         }
 112
 113         /*
 114          * Initialise the condition variable structure:
 115          */
 116         cond_init_body(cvp, cattr);
 117         *cond = pshared ? THR_PSHARED_PTR : cvp;
 118         return (0);
 119 }
 120
 121 static int
 122 init_static(struct pthread *thread, pthread_cond_t *cond)
 123 {
 124         int ret;
 125
 126         THR_LOCK_ACQUIRE(thread, &_cond_static_lock);
 127
 128         if (*cond == NULL)
 129                 ret = cond_init(cond, NULL);
 130         else
 131                 ret = 0;
 132
 133         THR_LOCK_RELEASE(thread, &_cond_static_lock);
 134
 135         return (ret);
 136 }
 137
 138 #define CHECK_AND_INIT_COND                                                     \
 139         if (*cond == THR_PSHARED_PTR) {                                         \
 140                 cvp = __thr_pshared_offpage(cond, 0);                           \
 141                 if (cvp == NULL)                                                \
 142                         return (EINVAL);                                        \
 143         } else if (__predict_false((cvp = (*cond)) <= THR_COND_DESTROYED)) {    \
 144                 if (cvp == THR_COND_INITIALIZER) {                              \
 145                         int ret;                                                \
 146                         ret = init_static(_get_curthread(), cond);              \
 147                         if (ret)                                                \
 148                                 return (ret);                                   \
 149                 } else if (cvp == THR_COND_DESTROYED) {                         \
 150                         return (EINVAL);                                        \
 151                 }                                                               \
 152                 cvp = *cond;                                                    \
 153         }
 154
 155 int
 156 _thr_cond_init(pthread_cond_t * __restrict cond,
 157     const pthread_condattr_t * __restrict cond_attr)
 158 {
 159
 160         *cond = NULL;
 161         return (cond_init(cond, cond_attr));
 162 }
 163
 164 int
 165 _thr_cond_destroy(pthread_cond_t *cond)
 166 {
 167         struct pthread_cond *cvp;
 168         int error;
 169
 170         error = 0;
 171         if (*cond == THR_PSHARED_PTR) {
 172                 cvp = __thr_pshared_offpage(cond, 0);
 173                 if (cvp != NULL) {
 174                         if (cvp->kcond.c_has_waiters)
 175                                 error = EBUSY;
 176                         else
 177                                 __thr_pshared_destroy(cond);
 178                 }
 179                 if (error == 0)
 180                         *cond = THR_COND_DESTROYED;
 181         } else if ((cvp = *cond) == THR_COND_INITIALIZER) {
 182                 /* nothing */
 183         } else if (cvp == THR_COND_DESTROYED) {
 184                 error = EINVAL;
 185         } else {
 186                 cvp = *cond;
 187                 if (cvp->__has_user_waiters || cvp->kcond.c_has_waiters)
 188                         error = EBUSY;
 189                 else {
 190                         *cond = THR_COND_DESTROYED;
 191                         free(cvp);
 192                 }
 193         }
 194         return (error);
 195 }
 196
 197 /*
 198  * Cancellation behavior:
 199  *   Thread may be canceled at start, if thread is canceled, it means it
 200  *   did not get a wakeup from pthread_cond_signal(), otherwise, it is
 201  *   not canceled.
 202  *   Thread cancellation never cause wakeup from pthread_cond_signal()
 203  *   to be lost.
 204  */
 205 static int
 206 cond_wait_kernel(struct pthread_cond *cvp, struct pthread_mutex *mp,
 207     const struct timespec *abstime, int cancel)
 208 {
 209         struct pthread *curthread;
 210         int error, error2, recurse, robust;
 211
 212         curthread = _get_curthread();
 213         robust = _mutex_enter_robust(curthread, mp);
 214
 215         error = _mutex_cv_detach(mp, &recurse);
 216         if (error != 0) {
 217                 if (robust)
 218                         _mutex_leave_robust(curthread, mp);
 219                 return (error);
 220         }
 221
 222         if (cancel)
 223                 _thr_cancel_enter2(curthread, 0);
 224         error = _thr_ucond_wait(&cvp->kcond, &mp->m_lock, abstime,
 225             CVWAIT_ABSTIME | CVWAIT_CLOCKID);
 226         if (cancel)
 227                 _thr_cancel_leave(curthread, 0);
 228
 229         /*
 230          * Note that PP mutex and ROBUST mutex may return
 231          * interesting error codes.
 232          */
 233         if (error == 0) {
 234                 error2 = _mutex_cv_lock(mp, recurse, true);
 235         } else if (error == EINTR || error == ETIMEDOUT) {
 236                 error2 = _mutex_cv_lock(mp, recurse, true);
 237                 /*
 238                  * Do not do cancellation on EOWNERDEAD there.  The
 239                  * cancellation cleanup handler will use the protected
 240                  * state and unlock the mutex without making the state
 241                  * consistent and the state will be unrecoverable.
 242                  */
 243                 if (error2 == 0 && cancel) {
 244                         if (robust) {
 245                                 _mutex_leave_robust(curthread, mp);
 246                                 robust = false;
 247                         }
 248                         _thr_testcancel(curthread);
 249                 }
 250
 251                 if (error == EINTR)
 252                         error = 0;
 253         } else {
 254                 /* We know that it didn't unlock the mutex. */
 255                 _mutex_cv_attach(mp, recurse);
 256                 if (cancel) {
 257                         if (robust) {
 258                                 _mutex_leave_robust(curthread, mp);
 259                                 robust = false;
 260                         }
 261                         _thr_testcancel(curthread);
 262                 }
 263                 error2 = 0;
 264         }
 265         if (robust)
 266                 _mutex_leave_robust(curthread, mp);
 267         return (error2 != 0 ? error2 : error);
 268 }
 269
 270 /*
 271  * Thread waits in userland queue whenever possible, when thread
 272  * is signaled or broadcasted, it is removed from the queue, and
 273  * is saved in curthread's defer_waiters[] buffer, but won't be
 274  * woken up until mutex is unlocked.
 275  */
 276
 277 static int
 278 cond_wait_user(struct pthread_cond *cvp, struct pthread_mutex *mp,
 279     const struct timespec *abstime, int cancel)
 280 {
 281         struct pthread *curthread;
 282         struct sleepqueue *sq;
 283         int deferred, error, error2, recurse;
 284
 285         curthread = _get_curthread();
 286         if (curthread->wchan != NULL)
 287                 PANIC("thread %p was already on queue.", curthread);
 288
 289         if (cancel)
 290                 _thr_testcancel(curthread);
 291
 292         _sleepq_lock(cvp);
 293         /*
 294          * set __has_user_waiters before unlocking mutex, this allows
 295          * us to check it without locking in pthread_cond_signal().
 296          */
 297         cvp->__has_user_waiters = 1;
 298         deferred = 0;
 299         (void)_mutex_cv_unlock(mp, &recurse, &deferred);
 300         curthread->mutex_obj = mp;
 301         _sleepq_add(cvp, curthread);
 302         for(;;) {
 303                 _thr_clear_wake(curthread);
 304                 _sleepq_unlock(cvp);
 305                 if (deferred) {
 306                         deferred = 0;
 307                         if ((mp->m_lock.m_owner & UMUTEX_CONTESTED) == 0)
 308                                 (void)_umtx_op_err(&mp->m_lock,
 309                                     UMTX_OP_MUTEX_WAKE2, mp->m_lock.m_flags,
 310                                     0, 0);
 311                 }
 312                 if (curthread->nwaiter_defer > 0) {
 313                         _thr_wake_all(curthread->defer_waiters,
 314                             curthread->nwaiter_defer);
 315                         curthread->nwaiter_defer = 0;
 316                 }
 317
 318                 if (cancel)
 319                         _thr_cancel_enter2(curthread, 0);
 320                 error = _thr_sleep(curthread, cvp->kcond.c_clockid, abstime);
 321                 if (cancel)
 322                         _thr_cancel_leave(curthread, 0);
 323
 324                 _sleepq_lock(cvp);
 325                 if (curthread->wchan == NULL) {
 326                         error = 0;
 327                         break;
 328                 } else if (cancel && SHOULD_CANCEL(curthread)) {
 329                         sq = _sleepq_lookup(cvp);
 330                         cvp->__has_user_waiters = _sleepq_remove(sq, curthread);
 331                         _sleepq_unlock(cvp);
 332                         curthread->mutex_obj = NULL;
 333                         error2 = _mutex_cv_lock(mp, recurse, false);
 334                         if (!THR_IN_CRITICAL(curthread))
 335                                 _pthread_exit(PTHREAD_CANCELED);
 336                         else /* this should not happen */
 337                                 return (error2);
 338                 } else if (error == ETIMEDOUT) {
 339                         sq = _sleepq_lookup(cvp);
 340                         cvp->__has_user_waiters =
 341                             _sleepq_remove(sq, curthread);
 342                         break;
 343                 }
 344         }
 345         _sleepq_unlock(cvp);
 346         curthread->mutex_obj = NULL;
 347         error2 = _mutex_cv_lock(mp, recurse, false);
 348         if (error == 0)
 349                 error = error2;
 350         return (error);
 351 }
 352
 353 static int
 354 cond_wait_common(pthread_cond_t *cond, pthread_mutex_t *mutex,
 355         const struct timespec *abstime, int cancel)
 356 {
 357         struct pthread  *curthread = _get_curthread();
 358         struct pthread_cond *cvp;
 359         struct pthread_mutex *mp;
 360         int     error;
 361
 362         CHECK_AND_INIT_COND
 363
 364         if (*mutex == THR_PSHARED_PTR) {
 365                 mp = __thr_pshared_offpage(mutex, 0);
 366                 if (mp == NULL)
 367                         return (EINVAL);
 368         } else {
 369                 mp = *mutex;
 370         }
 371
 372         if ((error = _mutex_owned(curthread, mp)) != 0)
 373                 return (error);
 374
 375         if (curthread->attr.sched_policy != SCHED_OTHER ||
 376             (mp->m_lock.m_flags & (UMUTEX_PRIO_PROTECT | UMUTEX_PRIO_INHERIT |
 377             USYNC_PROCESS_SHARED)) != 0 || CV_PSHARED(cvp))
 378                 return (cond_wait_kernel(cvp, mp, abstime, cancel));
 379         else
 380                 return (cond_wait_user(cvp, mp, abstime, cancel));
 381 }
 382
 383 int
 384 _thr_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
 385 {
 386
 387         return (cond_wait_common(cond, mutex, NULL, 0));
 388 }
 389
 390 int
 391 __thr_cond_wait(pthread_cond_t * __restrict cond,
 392     pthread_mutex_t * __restrict mutex)
 393 {
 394
 395         return (cond_wait_common(cond, mutex, NULL, 1));
 396 }
 397
 398 int
 399 _thr_cond_timedwait(pthread_cond_t * __restrict cond,
 400     pthread_mutex_t * __restrict mutex,
 401     const struct timespec * __restrict abstime)
 402 {
 403
 404         if (abstime == NULL || abstime->tv_sec < 0 || abstime->tv_nsec < 0 ||
 405             abstime->tv_nsec >= 1000000000)
 406                 return (EINVAL);
 407
 408         return (cond_wait_common(cond, mutex, abstime, 0));
 409 }
 410
 411 int
 412 __pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
 413                        const struct timespec *abstime)
 414 {
 415
 416         if (abstime == NULL || abstime->tv_sec < 0 || abstime->tv_nsec < 0 ||
 417             abstime->tv_nsec >= 1000000000)
 418                 return (EINVAL);
 419
 420         return (cond_wait_common(cond, mutex, abstime, 1));
 421 }
 422
 423 static int
 424 cond_signal_common(pthread_cond_t *cond)
 425 {
 426         struct pthread  *curthread = _get_curthread();
 427         struct pthread *td;
 428         struct pthread_cond *cvp;
 429         struct pthread_mutex *mp;
 430         struct sleepqueue *sq;
 431         int     *waddr;
 432         int     pshared;
 433
 434         /*
 435          * If the condition variable is statically initialized, perform dynamic
 436          * initialization.
 437          */
 438         CHECK_AND_INIT_COND
 439
 440         pshared = CV_PSHARED(cvp);
 441
 442         _thr_ucond_signal(&cvp->kcond);
 443
 444         if (pshared || cvp->__has_user_waiters == 0)
 445                 return (0);
 446
 447         curthread = _get_curthread();
 448         waddr = NULL;
 449         _sleepq_lock(cvp);
 450         sq = _sleepq_lookup(cvp);
 451         if (sq == NULL) {
 452                 _sleepq_unlock(cvp);
 453                 return (0);
 454         }
 455
 456         td = _sleepq_first(sq);
 457         mp = td->mutex_obj;
 458         cvp->__has_user_waiters = _sleepq_remove(sq, td);
 459         if (PMUTEX_OWNER_ID(mp) == TID(curthread)) {
 460                 if (curthread->nwaiter_defer >= MAX_DEFER_WAITERS) {
 461                         _thr_wake_all(curthread->defer_waiters,
 462                             curthread->nwaiter_defer);
 463                         curthread->nwaiter_defer = 0;
 464                 }
 465                 curthread->defer_waiters[curthread->nwaiter_defer++] =
 466                     &td->wake_addr->value;
 467                 mp->m_flags |= PMUTEX_FLAG_DEFERRED;
 468         } else {
 469                 waddr = &td->wake_addr->value;
 470         }
 471         _sleepq_unlock(cvp);
 472         if (waddr != NULL)
 473                 _thr_set_wake(waddr);
 474         return (0);
 475 }
 476
 477 struct broadcast_arg {
 478         struct pthread *curthread;
 479         unsigned int *waddrs[MAX_DEFER_WAITERS];
 480         int count;
 481 };
 482
 483 static void
 484 drop_cb(struct pthread *td, void *arg)
 485 {
 486         struct broadcast_arg *ba = arg;
 487         struct pthread_mutex *mp;
 488         struct pthread *curthread = ba->curthread;
 489
 490         mp = td->mutex_obj;
 491         if (PMUTEX_OWNER_ID(mp) == TID(curthread)) {
 492                 if (curthread->nwaiter_defer >= MAX_DEFER_WAITERS) {
 493                         _thr_wake_all(curthread->defer_waiters,
 494                             curthread->nwaiter_defer);
 495                         curthread->nwaiter_defer = 0;
 496                 }
 497                 curthread->defer_waiters[curthread->nwaiter_defer++] =
 498                     &td->wake_addr->value;
 499                 mp->m_flags |= PMUTEX_FLAG_DEFERRED;
 500         } else {
 501                 if (ba->count >= MAX_DEFER_WAITERS) {
 502                         _thr_wake_all(ba->waddrs, ba->count);
 503                         ba->count = 0;
 504                 }
 505                 ba->waddrs[ba->count++] = &td->wake_addr->value;
 506         }
 507 }
 508
 509 static int
 510 cond_broadcast_common(pthread_cond_t *cond)
 511 {
 512         int    pshared;
 513         struct pthread_cond *cvp;
 514         struct sleepqueue *sq;
 515         struct broadcast_arg ba;
 516
 517         /*
 518          * If the condition variable is statically initialized, perform dynamic
 519          * initialization.
 520          */
 521         CHECK_AND_INIT_COND
 522
 523         pshared = CV_PSHARED(cvp);
 524
 525         _thr_ucond_broadcast(&cvp->kcond);
 526
 527         if (pshared || cvp->__has_user_waiters == 0)
 528                 return (0);
 529
 530         ba.curthread = _get_curthread();
 531         ba.count = 0;
 532
 533         _sleepq_lock(cvp);
 534         sq = _sleepq_lookup(cvp);
 535         if (sq == NULL) {
 536                 _sleepq_unlock(cvp);
 537                 return (0);
 538         }
 539         _sleepq_drop(sq, drop_cb, &ba);
 540         cvp->__has_user_waiters = 0;
 541         _sleepq_unlock(cvp);
 542         if (ba.count > 0)
 543                 _thr_wake_all(ba.waddrs, ba.count);
 544         return (0);
 545 }
 546
 547 int
 548 _thr_cond_signal(pthread_cond_t * cond)
 549 {
 550
 551         return (cond_signal_common(cond));
 552 }
 553
 554 int
 555 _thr_cond_broadcast(pthread_cond_t * cond)
 556 {
 557
 558         return (cond_broadcast_common(cond));
 559 }