lib/libthr/thread/thr_cond.c

   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("$FreeBSD$");
  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  */
  50 int     __pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex);
  51 int     __pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
  52                        const struct timespec * abstime);
  53 static int cond_init(pthread_cond_t *cond, const pthread_condattr_t *attr);
  54 static int cond_wait_common(pthread_cond_t *cond, pthread_mutex_t *mutex,
  55                     const struct timespec *abstime, int cancel);
  56 static int cond_signal_common(pthread_cond_t *cond);
  57 static 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
  74 static void
  75 cond_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
  87 static int
  88 cond_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
 115 static int
 116 init_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
 149 int
 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
 158 int
 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  */
 190 static int
 191 cond_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
 262 static int
 263 cond_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
 338 static int
 339 cond_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
 368 int
 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
 375 int
 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
 383 int
 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
 396 int
 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
 408 static int
 409 cond_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
 462 struct broadcast_arg {
 463         struct pthread *curthread;
 464         unsigned int *waddrs[MAX_DEFER_WAITERS];
 465         int count;
 466 };
 467
 468 static void
 469 drop_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
 494 static int
 495 cond_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
 532 int
 533 _pthread_cond_signal(pthread_cond_t * cond)
 534 {
 535
 536         return (cond_signal_common(cond));
 537 }
 538
 539 int
 540 _pthread_cond_broadcast(pthread_cond_t * cond)
 541 {
 542
 543         return (cond_broadcast_common(cond));
 544 }