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 *cond, const pthread_condattr_t *cond_attr)
 151 {
 152
 153         *cond = NULL;
 154         return (cond_init(cond, cond_attr));
 155 }
 156
 157 int
 158 _pthread_cond_destroy(pthread_cond_t *cond)
 159 {
 160         struct pthread_cond *cvp;
 161         int error;
 162
 163         error = 0;
 164         if (*cond == THR_PSHARED_PTR) {
 165                 cvp = __thr_pshared_offpage(cond, 0);
 166                 if (cvp != NULL)
 167                         __thr_pshared_destroy(cond);
 168                 *cond = THR_COND_DESTROYED;
 169         } else if ((cvp = *cond) == THR_COND_INITIALIZER) {
 170                 /* nothing */
 171         } else if (cvp == THR_COND_DESTROYED) {
 172                 error = EINVAL;
 173         } else {
 174                 cvp = *cond;
 175                 *cond = THR_COND_DESTROYED;
 176                 free(cvp);
 177         }
 178         return (error);
 179 }
 180
 181 /*
 182  * Cancellation behavior:
 183  *   Thread may be canceled at start, if thread is canceled, it means it
 184  *   did not get a wakeup from pthread_cond_signal(), otherwise, it is
 185  *   not canceled.
 186  *   Thread cancellation never cause wakeup from pthread_cond_signal()
 187  *   to be lost.
 188  */
 189 static int
 190 cond_wait_kernel(struct pthread_cond *cvp, struct pthread_mutex *mp,
 191     const struct timespec *abstime, int cancel)
 192 {
 193         struct pthread *curthread;
 194         int error, error2, recurse, robust;
 195
 196         curthread = _get_curthread();
 197         robust = _mutex_enter_robust(curthread, mp);
 198
 199         error = _mutex_cv_detach(mp, &recurse);
 200         if (error != 0) {
 201                 if (robust)
 202                         _mutex_leave_robust(curthread, mp);
 203                 return (error);
 204         }
 205
 206         if (cancel)
 207                 _thr_cancel_enter2(curthread, 0);
 208         error = _thr_ucond_wait(&cvp->kcond, &mp->m_lock, abstime,
 209             CVWAIT_ABSTIME | CVWAIT_CLOCKID);
 210         if (cancel)
 211                 _thr_cancel_leave(curthread, 0);
 212
 213         /*
 214          * Note that PP mutex and ROBUST mutex may return
 215          * interesting error codes.
 216          */
 217         if (error == 0) {
 218                 error2 = _mutex_cv_lock(mp, recurse, true);
 219         } else if (error == EINTR || error == ETIMEDOUT) {
 220                 error2 = _mutex_cv_lock(mp, recurse, true);
 221                 /*
 222                  * Do not do cancellation on EOWNERDEAD there.  The
 223                  * cancellation cleanup handler will use the protected
 224                  * state and unlock the mutex without making the state
 225                  * consistent and the state will be unrecoverable.
 226                  */
 227                 if (error2 == 0 && cancel) {
 228                         if (robust) {
 229                                 _mutex_leave_robust(curthread, mp);
 230                                 robust = false;
 231                         }
 232                         _thr_testcancel(curthread);
 233                 }
 234
 235                 if (error == EINTR)
 236                         error = 0;
 237         } else {
 238                 /* We know that it didn't unlock the mutex. */
 239                 _mutex_cv_attach(mp, recurse);
 240                 if (cancel) {
 241                         if (robust) {
 242                                 _mutex_leave_robust(curthread, mp);
 243                                 robust = false;
 244                         }
 245                         _thr_testcancel(curthread);
 246                 }
 247                 error2 = 0;
 248         }
 249         if (robust)
 250                 _mutex_leave_robust(curthread, mp);
 251         return (error2 != 0 ? error2 : error);
 252 }
 253
 254 /*
 255  * Thread waits in userland queue whenever possible, when thread
 256  * is signaled or broadcasted, it is removed from the queue, and
 257  * is saved in curthread's defer_waiters[] buffer, but won't be
 258  * woken up until mutex is unlocked.
 259  */
 260
 261 static int
 262 cond_wait_user(struct pthread_cond *cvp, struct pthread_mutex *mp,
 263     const struct timespec *abstime, int cancel)
 264 {
 265         struct pthread *curthread;
 266         struct sleepqueue *sq;
 267         int deferred, error, error2, recurse;
 268
 269         curthread = _get_curthread();
 270         if (curthread->wchan != NULL)
 271                 PANIC("thread %p was already on queue.", curthread);
 272
 273         if (cancel)
 274                 _thr_testcancel(curthread);
 275
 276         _sleepq_lock(cvp);
 277         /*
 278          * set __has_user_waiters before unlocking mutex, this allows
 279          * us to check it without locking in pthread_cond_signal().
 280          */
 281         cvp->__has_user_waiters = 1;
 282         deferred = 0;
 283         (void)_mutex_cv_unlock(mp, &recurse, &deferred);
 284         curthread->mutex_obj = mp;
 285         _sleepq_add(cvp, curthread);
 286         for(;;) {
 287                 _thr_clear_wake(curthread);
 288                 _sleepq_unlock(cvp);
 289                 if (deferred) {
 290                         deferred = 0;
 291                         if ((mp->m_lock.m_owner & UMUTEX_CONTESTED) == 0)
 292                                 (void)_umtx_op_err(&mp->m_lock,
 293                                     UMTX_OP_MUTEX_WAKE2, mp->m_lock.m_flags,
 294                                     0, 0);
 295                 }
 296                 if (curthread->nwaiter_defer > 0) {
 297                         _thr_wake_all(curthread->defer_waiters,
 298                             curthread->nwaiter_defer);
 299                         curthread->nwaiter_defer = 0;
 300                 }
 301
 302                 if (cancel)
 303                         _thr_cancel_enter2(curthread, 0);
 304                 error = _thr_sleep(curthread, cvp->kcond.c_clockid, abstime);
 305                 if (cancel)
 306                         _thr_cancel_leave(curthread, 0);
 307
 308                 _sleepq_lock(cvp);
 309                 if (curthread->wchan == NULL) {
 310                         error = 0;
 311                         break;
 312                 } else if (cancel && SHOULD_CANCEL(curthread)) {
 313                         sq = _sleepq_lookup(cvp);
 314                         cvp->__has_user_waiters = _sleepq_remove(sq, curthread);
 315                         _sleepq_unlock(cvp);
 316                         curthread->mutex_obj = NULL;
 317                         error2 = _mutex_cv_lock(mp, recurse, false);
 318                         if (!THR_IN_CRITICAL(curthread))
 319                                 _pthread_exit(PTHREAD_CANCELED);
 320                         else /* this should not happen */
 321                                 return (error2);
 322                 } else if (error == ETIMEDOUT) {
 323                         sq = _sleepq_lookup(cvp);
 324                         cvp->__has_user_waiters =
 325                             _sleepq_remove(sq, curthread);
 326                         break;
 327                 }
 328         }
 329         _sleepq_unlock(cvp);
 330         curthread->mutex_obj = NULL;
 331         error2 = _mutex_cv_lock(mp, recurse, false);
 332         if (error == 0)
 333                 error = error2;
 334         return (error);
 335 }
 336
 337 static int
 338 cond_wait_common(pthread_cond_t *cond, pthread_mutex_t *mutex,
 339         const struct timespec *abstime, int cancel)
 340 {
 341         struct pthread  *curthread = _get_curthread();
 342         struct pthread_cond *cvp;
 343         struct pthread_mutex *mp;
 344         int     error;
 345
 346         CHECK_AND_INIT_COND
 347
 348         if (*mutex == THR_PSHARED_PTR) {
 349                 mp = __thr_pshared_offpage(mutex, 0);
 350                 if (mp == NULL)
 351                         return (EINVAL);
 352         } else {
 353                 mp = *mutex;
 354         }
 355
 356         if ((error = _mutex_owned(curthread, mp)) != 0)
 357                 return (error);
 358
 359         if (curthread->attr.sched_policy != SCHED_OTHER ||
 360             (mp->m_lock.m_flags & (UMUTEX_PRIO_PROTECT | UMUTEX_PRIO_INHERIT |
 361             USYNC_PROCESS_SHARED)) != 0 || CV_PSHARED(cvp))
 362                 return (cond_wait_kernel(cvp, mp, abstime, cancel));
 363         else
 364                 return (cond_wait_user(cvp, mp, abstime, cancel));
 365 }
 366
 367 int
 368 _pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
 369 {
 370
 371         return (cond_wait_common(cond, mutex, NULL, 0));
 372 }
 373
 374 int
 375 __pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
 376 {
 377
 378         return (cond_wait_common(cond, mutex, NULL, 1));
 379 }
 380
 381 int
 382 _pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
 383                        const struct timespec * abstime)
 384 {
 385
 386         if (abstime == NULL || abstime->tv_sec < 0 || abstime->tv_nsec < 0 ||
 387             abstime->tv_nsec >= 1000000000)
 388                 return (EINVAL);
 389
 390         return (cond_wait_common(cond, mutex, abstime, 0));
 391 }
 392
 393 int
 394 __pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
 395                        const struct timespec *abstime)
 396 {
 397
 398         if (abstime == NULL || abstime->tv_sec < 0 || abstime->tv_nsec < 0 ||
 399             abstime->tv_nsec >= 1000000000)
 400                 return (EINVAL);
 401
 402         return (cond_wait_common(cond, mutex, abstime, 1));
 403 }
 404
 405 static int
 406 cond_signal_common(pthread_cond_t *cond)
 407 {
 408         struct pthread  *curthread = _get_curthread();
 409         struct pthread *td;
 410         struct pthread_cond *cvp;
 411         struct pthread_mutex *mp;
 412         struct sleepqueue *sq;
 413         int     *waddr;
 414         int     pshared;
 415
 416         /*
 417          * If the condition variable is statically initialized, perform dynamic
 418          * initialization.
 419          */
 420         CHECK_AND_INIT_COND
 421
 422         pshared = CV_PSHARED(cvp);
 423
 424         _thr_ucond_signal(&cvp->kcond);
 425
 426         if (pshared || cvp->__has_user_waiters == 0)
 427                 return (0);
 428
 429         curthread = _get_curthread();
 430         waddr = NULL;
 431         _sleepq_lock(cvp);
 432         sq = _sleepq_lookup(cvp);
 433         if (sq == NULL) {
 434                 _sleepq_unlock(cvp);
 435                 return (0);
 436         }
 437
 438         td = _sleepq_first(sq);
 439         mp = td->mutex_obj;
 440         cvp->__has_user_waiters = _sleepq_remove(sq, td);
 441         if (PMUTEX_OWNER_ID(mp) == TID(curthread)) {
 442                 if (curthread->nwaiter_defer >= MAX_DEFER_WAITERS) {
 443                         _thr_wake_all(curthread->defer_waiters,
 444                             curthread->nwaiter_defer);
 445                         curthread->nwaiter_defer = 0;
 446                 }
 447                 curthread->defer_waiters[curthread->nwaiter_defer++] =
 448                     &td->wake_addr->value;
 449                 mp->m_flags |= PMUTEX_FLAG_DEFERRED;
 450         } else {
 451                 waddr = &td->wake_addr->value;
 452         }
 453         _sleepq_unlock(cvp);
 454         if (waddr != NULL)
 455                 _thr_set_wake(waddr);
 456         return (0);
 457 }
 458
 459 struct broadcast_arg {
 460         struct pthread *curthread;
 461         unsigned int *waddrs[MAX_DEFER_WAITERS];
 462         int count;
 463 };
 464
 465 static void
 466 drop_cb(struct pthread *td, void *arg)
 467 {
 468         struct broadcast_arg *ba = arg;
 469         struct pthread_mutex *mp;
 470         struct pthread *curthread = ba->curthread;
 471
 472         mp = td->mutex_obj;
 473         if (PMUTEX_OWNER_ID(mp) == TID(curthread)) {
 474                 if (curthread->nwaiter_defer >= MAX_DEFER_WAITERS) {
 475                         _thr_wake_all(curthread->defer_waiters,
 476                             curthread->nwaiter_defer);
 477                         curthread->nwaiter_defer = 0;
 478                 }
 479                 curthread->defer_waiters[curthread->nwaiter_defer++] =
 480                     &td->wake_addr->value;
 481                 mp->m_flags |= PMUTEX_FLAG_DEFERRED;
 482         } else {
 483                 if (ba->count >= MAX_DEFER_WAITERS) {
 484                         _thr_wake_all(ba->waddrs, ba->count);
 485                         ba->count = 0;
 486                 }
 487                 ba->waddrs[ba->count++] = &td->wake_addr->value;
 488         }
 489 }
 490
 491 static int
 492 cond_broadcast_common(pthread_cond_t *cond)
 493 {
 494         int    pshared;
 495         struct pthread_cond *cvp;
 496         struct sleepqueue *sq;
 497         struct broadcast_arg ba;
 498
 499         /*
 500          * If the condition variable is statically initialized, perform dynamic
 501          * initialization.
 502          */
 503         CHECK_AND_INIT_COND
 504
 505         pshared = CV_PSHARED(cvp);
 506
 507         _thr_ucond_broadcast(&cvp->kcond);
 508
 509         if (pshared || cvp->__has_user_waiters == 0)
 510                 return (0);
 511
 512         ba.curthread = _get_curthread();
 513         ba.count = 0;
 514
 515         _sleepq_lock(cvp);
 516         sq = _sleepq_lookup(cvp);
 517         if (sq == NULL) {
 518                 _sleepq_unlock(cvp);
 519                 return (0);
 520         }
 521         _sleepq_drop(sq, drop_cb, &ba);
 522         cvp->__has_user_waiters = 0;
 523         _sleepq_unlock(cvp);
 524         if (ba.count > 0)
 525                 _thr_wake_all(ba.waddrs, ba.count);
 526         return (0);
 527 }
 528
 529 int
 530 _pthread_cond_signal(pthread_cond_t * cond)
 531 {
 532
 533         return (cond_signal_common(cond));
 534 }
 535
 536 int
 537 _pthread_cond_broadcast(pthread_cond_t * cond)
 538 {
 539
 540         return (cond_broadcast_common(cond));
 541 }