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pthread_cond.c revision 1.58
      1  1.58  christos /*	$NetBSD: pthread_cond.c,v 1.58 2012/11/03 03:10:50 christos Exp $	*/
      2   1.2   thorpej 
      3   1.2   thorpej /*-
      4  1.43        ad  * Copyright (c) 2001, 2006, 2007, 2008 The NetBSD Foundation, Inc.
      5   1.2   thorpej  * All rights reserved.
      6   1.2   thorpej  *
      7   1.2   thorpej  * This code is derived from software contributed to The NetBSD Foundation
      8  1.26        ad  * by Nathan J. Williams and Andrew Doran.
      9   1.2   thorpej  *
     10   1.2   thorpej  * Redistribution and use in source and binary forms, with or without
     11   1.2   thorpej  * modification, are permitted provided that the following conditions
     12   1.2   thorpej  * are met:
     13   1.2   thorpej  * 1. Redistributions of source code must retain the above copyright
     14   1.2   thorpej  *    notice, this list of conditions and the following disclaimer.
     15   1.2   thorpej  * 2. Redistributions in binary form must reproduce the above copyright
     16   1.2   thorpej  *    notice, this list of conditions and the following disclaimer in the
     17   1.2   thorpej  *    documentation and/or other materials provided with the distribution.
     18   1.2   thorpej  *
     19   1.2   thorpej  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     20   1.2   thorpej  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     21   1.2   thorpej  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     22   1.2   thorpej  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     23   1.2   thorpej  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     24   1.2   thorpej  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     25   1.2   thorpej  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     26   1.2   thorpej  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     27   1.2   thorpej  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     28   1.2   thorpej  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     29   1.2   thorpej  * POSSIBILITY OF SUCH DAMAGE.
     30   1.2   thorpej  */
     31   1.2   thorpej 
     32  1.47        ad /*
     33  1.47        ad  * We assume that there will be no contention on pthread_cond_t::ptc_lock
     34  1.47        ad  * because functioning applications must call both the wait and wakeup
     35  1.47        ad  * functions while holding the same application provided mutex.  The
     36  1.47        ad  * spinlock is present only to prevent libpthread causing the application
     37  1.47        ad  * to crash or malfunction as a result of corrupted data structures, in
     38  1.47        ad  * the event that the application is buggy.
     39  1.47        ad  *
     40  1.47        ad  * If there is contention on spinlock when real-time threads are in use,
     41  1.47        ad  * it could cause a deadlock due to priority inversion: the thread holding
     42  1.47        ad  * the spinlock may not get CPU time to make forward progress and release
     43  1.47        ad  * the spinlock to a higher priority thread that is waiting for it.
     44  1.47        ad  * Contention on the spinlock will only occur with buggy applications,
     45  1.47        ad  * so at the time of writing it's not considered a major bug in libpthread.
     46  1.47        ad  */
     47  1.47        ad 
     48   1.8     lukem #include <sys/cdefs.h>
     49  1.58  christos __RCSID("$NetBSD: pthread_cond.c,v 1.58 2012/11/03 03:10:50 christos Exp $");
     50   1.8     lukem 
     51   1.2   thorpej #include <errno.h>
     52   1.6   nathanw #include <sys/time.h>
     53   1.6   nathanw #include <sys/types.h>
     54  1.58  christos #include <stdlib.h>
     55   1.2   thorpej 
     56   1.2   thorpej #include "pthread.h"
     57   1.2   thorpej #include "pthread_int.h"
     58   1.2   thorpej 
     59  1.55  drochner int	_sys___nanosleep50(const struct timespec *, struct timespec *);
     60   1.6   nathanw 
     61   1.6   nathanw extern int pthread__started;
     62   1.6   nathanw 
     63   1.6   nathanw static int pthread_cond_wait_nothread(pthread_t, pthread_mutex_t *,
     64  1.58  christos     pthread_cond_t *, const struct timespec *);
     65   1.2   thorpej 
     66  1.51     pooka int	_pthread_cond_has_waiters_np(pthread_cond_t *);
     67  1.51     pooka 
     68  1.53      yamt __weak_alias(pthread_cond_has_waiters_np,_pthread_cond_has_waiters_np)
     69  1.51     pooka 
     70   1.2   thorpej __strong_alias(__libc_cond_init,pthread_cond_init)
     71   1.2   thorpej __strong_alias(__libc_cond_signal,pthread_cond_signal)
     72   1.2   thorpej __strong_alias(__libc_cond_broadcast,pthread_cond_broadcast)
     73   1.2   thorpej __strong_alias(__libc_cond_wait,pthread_cond_wait)
     74   1.2   thorpej __strong_alias(__libc_cond_timedwait,pthread_cond_timedwait)
     75   1.2   thorpej __strong_alias(__libc_cond_destroy,pthread_cond_destroy)
     76   1.2   thorpej 
     77   1.2   thorpej int
     78   1.2   thorpej pthread_cond_init(pthread_cond_t *cond, const pthread_condattr_t *attr)
     79   1.2   thorpej {
     80   1.2   thorpej 
     81  1.11   nathanw 	pthread__error(EINVAL, "Invalid condition variable attribute",
     82  1.11   nathanw 	    (attr == NULL) || (attr->ptca_magic == _PT_CONDATTR_MAGIC));
     83   1.2   thorpej 
     84   1.2   thorpej 	cond->ptc_magic = _PT_COND_MAGIC;
     85   1.2   thorpej 	pthread_lockinit(&cond->ptc_lock);
     86   1.2   thorpej 	PTQ_INIT(&cond->ptc_waiters);
     87   1.2   thorpej 	cond->ptc_mutex = NULL;
     88  1.58  christos 	if (attr && attr->ptca_private) {
     89  1.58  christos 		cond->ptc_private = malloc(sizeof(clockid_t));
     90  1.58  christos 		if (cond->ptc_private == NULL)
     91  1.58  christos 			return errno;
     92  1.58  christos 		*(clockid_t *)cond->ptc_private =
     93  1.58  christos 		    *(clockid_t *)attr->ptca_private;
     94  1.58  christos 	} else
     95  1.58  christos 		cond->ptc_private = NULL;
     96   1.2   thorpej 
     97   1.2   thorpej 	return 0;
     98   1.2   thorpej }
     99   1.2   thorpej 
    100   1.2   thorpej 
    101   1.2   thorpej int
    102   1.2   thorpej pthread_cond_destroy(pthread_cond_t *cond)
    103   1.2   thorpej {
    104   1.2   thorpej 
    105  1.11   nathanw 	pthread__error(EINVAL, "Invalid condition variable",
    106  1.11   nathanw 	    cond->ptc_magic == _PT_COND_MAGIC);
    107  1.11   nathanw 	pthread__error(EBUSY, "Destroying condition variable in use",
    108  1.11   nathanw 	    cond->ptc_mutex == NULL);
    109   1.2   thorpej 
    110   1.2   thorpej 	cond->ptc_magic = _PT_COND_DEAD;
    111  1.58  christos 	free(cond->ptc_private);
    112   1.2   thorpej 
    113   1.2   thorpej 	return 0;
    114   1.2   thorpej }
    115   1.2   thorpej 
    116  1.57     joerg int
    117  1.43        ad pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
    118  1.43        ad 		       const struct timespec *abstime)
    119   1.2   thorpej {
    120   1.2   thorpej 	pthread_t self;
    121  1.43        ad 	int retval;
    122  1.10   nathanw 
    123  1.11   nathanw 	pthread__error(EINVAL, "Invalid condition variable",
    124  1.11   nathanw 	    cond->ptc_magic == _PT_COND_MAGIC);
    125  1.11   nathanw 	pthread__error(EINVAL, "Invalid mutex",
    126  1.11   nathanw 	    mutex->ptm_magic == _PT_MUTEX_MAGIC);
    127  1.11   nathanw 	pthread__error(EPERM, "Mutex not locked in condition wait",
    128  1.35        ad 	    mutex->ptm_owner != NULL);
    129  1.43        ad 	if (abstime != NULL) {
    130  1.43        ad 		pthread__error(EINVAL, "Invalid wait time",
    131  1.43        ad 		    (abstime->tv_sec >= 0) &&
    132  1.43        ad 		    (abstime->tv_nsec >= 0) &&
    133  1.43        ad 		    (abstime->tv_nsec < 1000000000));
    134  1.43        ad 	}
    135  1.10   nathanw 
    136   1.2   thorpej 	self = pthread__self();
    137   1.6   nathanw 
    138   1.6   nathanw 	/* Just hang out for a while if threads aren't running yet. */
    139  1.43        ad 	if (__predict_false(pthread__started == 0)) {
    140  1.58  christos 		return pthread_cond_wait_nothread(self, mutex, cond, abstime);
    141  1.43        ad 	}
    142  1.43        ad 	if (__predict_false(self->pt_cancel)) {
    143  1.40        ad 		pthread__cancelled();
    144  1.43        ad 	}
    145  1.32        ad 
    146  1.43        ad 	/* Note this thread as waiting on the CV. */
    147  1.38        ad 	pthread__spinlock(self, &cond->ptc_lock);
    148  1.36        ad 	cond->ptc_mutex = mutex;
    149  1.23        ad 	PTQ_INSERT_HEAD(&cond->ptc_waiters, self, pt_sleep);
    150  1.43        ad 	self->pt_sleepobj = cond;
    151  1.38        ad 	pthread__spinunlock(self, &cond->ptc_lock);
    152  1.32        ad 
    153  1.43        ad 	do {
    154  1.44        ad 		self->pt_willpark = 1;
    155  1.43        ad 		pthread_mutex_unlock(mutex);
    156  1.44        ad 		self->pt_willpark = 0;
    157  1.43        ad 		self->pt_blocking++;
    158  1.43        ad 		retval = _lwp_park(abstime, self->pt_unpark,
    159  1.43        ad 		    __UNVOLATILE(&mutex->ptm_waiters),
    160  1.43        ad 		    __UNVOLATILE(&mutex->ptm_waiters));
    161  1.43        ad 		self->pt_unpark = 0;
    162  1.43        ad 		self->pt_blocking--;
    163  1.43        ad 		membar_sync();
    164  1.43        ad 		pthread_mutex_lock(mutex);
    165  1.32        ad 
    166  1.43        ad 		/*
    167  1.43        ad 		 * If we have cancelled then exit.  POSIX dictates that
    168  1.43        ad 		 * the mutex must be held when we action the cancellation.
    169  1.43        ad 		 *
    170  1.43        ad 		 * If we absorbed a pthread_cond_signal() and cannot take
    171  1.43        ad 		 * the wakeup, we must ensure that another thread does.
    172  1.43        ad 		 *
    173  1.46        ad 		 * If awoke early, we may still be on the sleep queue and
    174  1.46        ad 		 * must remove ourself.
    175  1.43        ad 		 */
    176  1.46        ad 		if (__predict_false(retval != 0)) {
    177  1.46        ad 			switch (errno) {
    178  1.46        ad 			case EINTR:
    179  1.46        ad 			case EALREADY:
    180  1.46        ad 				retval = 0;
    181  1.46        ad 				break;
    182  1.46        ad 			default:
    183  1.46        ad 				retval = errno;
    184  1.46        ad 				break;
    185  1.46        ad 			}
    186  1.45        ad 		}
    187  1.45        ad 		if (__predict_false(self->pt_cancel | retval)) {
    188  1.48        ad 			pthread_cond_signal(cond);
    189  1.43        ad 			if (self->pt_cancel) {
    190  1.43        ad 				pthread__cancelled();
    191  1.43        ad 			}
    192  1.43        ad 			break;
    193  1.43        ad 		}
    194  1.43        ad 	} while (self->pt_sleepobj != NULL);
    195  1.32        ad 
    196  1.43        ad 	return retval;
    197   1.2   thorpej }
    198   1.2   thorpej 
    199   1.2   thorpej int
    200  1.43        ad pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
    201   1.2   thorpej {
    202  1.32        ad 
    203  1.43        ad 	return pthread_cond_timedwait(cond, mutex, NULL);
    204   1.2   thorpej }
    205   1.2   thorpej 
    206  1.49        ad static int __noinline
    207  1.49        ad pthread__cond_wake_one(pthread_cond_t *cond)
    208   1.2   thorpej {
    209   1.2   thorpej 	pthread_t self, signaled;
    210  1.28        ad 	pthread_mutex_t *mutex;
    211  1.43        ad 	lwpid_t lid;
    212  1.43        ad 
    213  1.11   nathanw 	pthread__error(EINVAL, "Invalid condition variable",
    214  1.11   nathanw 	    cond->ptc_magic == _PT_COND_MAGIC);
    215   1.2   thorpej 
    216  1.48        ad 	/*
    217  1.48        ad 	 * Pull the first thread off the queue.  If the current thread
    218  1.48        ad 	 * is associated with the condition variable, remove it without
    219  1.48        ad 	 * awakening (error case in pthread_cond_timedwait()).
    220  1.48        ad 	 */
    221  1.27        ad 	self = pthread__self();
    222  1.38        ad 	pthread__spinlock(self, &cond->ptc_lock);
    223  1.48        ad 	if (self->pt_sleepobj == cond) {
    224  1.48        ad 		PTQ_REMOVE(&cond->ptc_waiters, self, pt_sleep);
    225  1.48        ad 		self->pt_sleepobj = NULL;
    226  1.48        ad 	}
    227  1.43        ad 	signaled = PTQ_FIRST(&cond->ptc_waiters);
    228  1.28        ad 	if (__predict_false(signaled == NULL)) {
    229  1.50        ad 		cond->ptc_mutex = NULL;
    230  1.46        ad 		pthread__spinunlock(self, &cond->ptc_lock);
    231  1.28        ad 		return 0;
    232  1.28        ad 	}
    233  1.28        ad 	mutex = cond->ptc_mutex;
    234  1.43        ad 	if (PTQ_NEXT(signaled, pt_sleep) == NULL) {
    235  1.28        ad 		cond->ptc_mutex = NULL;
    236  1.43        ad 		PTQ_INIT(&cond->ptc_waiters);
    237  1.43        ad 	} else {
    238  1.43        ad 		PTQ_REMOVE(&cond->ptc_waiters, signaled, pt_sleep);
    239  1.43        ad 	}
    240  1.43        ad 	signaled->pt_sleepobj = NULL;
    241  1.43        ad 	lid = signaled->pt_lid;
    242  1.43        ad 	pthread__spinunlock(self, &cond->ptc_lock);
    243  1.28        ad 
    244  1.28        ad 	/*
    245  1.28        ad 	 * For all valid uses of pthread_cond_signal(), the caller will
    246  1.28        ad 	 * hold the mutex that the target is using to synchronize with.
    247  1.56     skrll 	 * To avoid the target awakening and immediately blocking on the
    248  1.35        ad 	 * mutex, transfer the thread to be awoken to the current thread's
    249  1.35        ad 	 * deferred wakeup list.  The waiter will be set running when the
    250  1.35        ad 	 * caller (this thread) releases the mutex.
    251  1.28        ad 	 */
    252  1.54     lukem 	if (__predict_false(self->pt_nwaiters == (size_t)pthread__unpark_max)) {
    253  1.43        ad 		(void)_lwp_unpark_all(self->pt_waiters, self->pt_nwaiters,
    254  1.43        ad 		    __UNVOLATILE(&mutex->ptm_waiters));
    255  1.43        ad 		self->pt_nwaiters = 0;
    256   1.4   nathanw 	}
    257  1.43        ad 	self->pt_waiters[self->pt_nwaiters++] = lid;
    258  1.43        ad 	pthread__mutex_deferwake(self, mutex);
    259   1.2   thorpej 	return 0;
    260   1.2   thorpej }
    261   1.2   thorpej 
    262   1.2   thorpej int
    263  1.49        ad pthread_cond_signal(pthread_cond_t *cond)
    264  1.49        ad {
    265  1.49        ad 
    266  1.49        ad 	if (__predict_true(PTQ_EMPTY(&cond->ptc_waiters)))
    267  1.49        ad 		return 0;
    268  1.49        ad 	return pthread__cond_wake_one(cond);
    269  1.49        ad }
    270  1.49        ad 
    271  1.49        ad static int __noinline
    272  1.49        ad pthread__cond_wake_all(pthread_cond_t *cond)
    273   1.2   thorpej {
    274  1.43        ad 	pthread_t self, signaled;
    275  1.28        ad 	pthread_mutex_t *mutex;
    276  1.52      matt 	u_int max;
    277  1.52      matt 	size_t nwaiters;
    278   1.2   thorpej 
    279  1.43        ad 	pthread__error(EINVAL, "Invalid condition variable",
    280  1.43        ad 	    cond->ptc_magic == _PT_COND_MAGIC);
    281  1.28        ad 
    282  1.28        ad 	/*
    283  1.35        ad 	 * Try to defer waking threads (see pthread_cond_signal()).
    284  1.35        ad 	 * Only transfer waiters for which there is no pending wakeup.
    285  1.28        ad 	 */
    286  1.43        ad 	self = pthread__self();
    287  1.43        ad 	pthread__spinlock(self, &cond->ptc_lock);
    288  1.43        ad 	max = pthread__unpark_max;
    289  1.43        ad 	mutex = cond->ptc_mutex;
    290  1.43        ad 	nwaiters = self->pt_nwaiters;
    291  1.43        ad 	PTQ_FOREACH(signaled, &cond->ptc_waiters, pt_sleep) {
    292  1.48        ad 		if (__predict_false(nwaiters == max)) {
    293  1.43        ad 			/* Overflow. */
    294  1.43        ad 			(void)_lwp_unpark_all(self->pt_waiters,
    295  1.43        ad 			    nwaiters, __UNVOLATILE(&mutex->ptm_waiters));
    296  1.43        ad 			nwaiters = 0;
    297  1.28        ad 		}
    298  1.43        ad 		signaled->pt_sleepobj = NULL;
    299  1.43        ad 		self->pt_waiters[nwaiters++] = signaled->pt_lid;
    300  1.35        ad 	}
    301  1.43        ad 	PTQ_INIT(&cond->ptc_waiters);
    302  1.43        ad 	self->pt_nwaiters = nwaiters;
    303  1.43        ad 	cond->ptc_mutex = NULL;
    304  1.43        ad 	pthread__spinunlock(self, &cond->ptc_lock);
    305  1.43        ad 	pthread__mutex_deferwake(self, mutex);
    306  1.43        ad 
    307   1.2   thorpej 	return 0;
    308   1.2   thorpej }
    309   1.2   thorpej 
    310  1.49        ad int
    311  1.49        ad pthread_cond_broadcast(pthread_cond_t *cond)
    312  1.49        ad {
    313  1.49        ad 
    314  1.49        ad 	if (__predict_true(PTQ_EMPTY(&cond->ptc_waiters)))
    315  1.49        ad 		return 0;
    316  1.49        ad 	return pthread__cond_wake_all(cond);
    317  1.49        ad }
    318   1.2   thorpej 
    319   1.2   thorpej int
    320  1.51     pooka _pthread_cond_has_waiters_np(pthread_cond_t *cond)
    321  1.51     pooka {
    322  1.51     pooka 
    323  1.51     pooka 	return !PTQ_EMPTY(&cond->ptc_waiters);
    324  1.51     pooka }
    325  1.51     pooka 
    326  1.51     pooka int
    327   1.2   thorpej pthread_condattr_init(pthread_condattr_t *attr)
    328   1.2   thorpej {
    329   1.2   thorpej 
    330   1.2   thorpej 	attr->ptca_magic = _PT_CONDATTR_MAGIC;
    331  1.58  christos 	attr->ptca_private = NULL;
    332   1.2   thorpej 
    333   1.2   thorpej 	return 0;
    334   1.2   thorpej }
    335   1.2   thorpej 
    336   1.2   thorpej int
    337  1.58  christos pthread_condattr_setclock(pthread_condattr_t *attr, clockid_t clck)
    338  1.58  christos {
    339  1.58  christos 	switch (clck) {
    340  1.58  christos 	case CLOCK_MONOTONIC:
    341  1.58  christos 	case CLOCK_REALTIME:
    342  1.58  christos 		if (attr->ptca_private == NULL)
    343  1.58  christos 			attr->ptca_private = malloc(sizeof(clockid_t));
    344  1.58  christos 		if (attr->ptca_private == NULL)
    345  1.58  christos 			return errno;
    346  1.58  christos 		*(clockid_t *)attr->ptca_private = clck;
    347  1.58  christos 		return 0;
    348  1.58  christos 	default:
    349  1.58  christos 		return EINVAL;
    350  1.58  christos 	}
    351  1.58  christos }
    352  1.58  christos 
    353  1.58  christos int
    354   1.2   thorpej pthread_condattr_destroy(pthread_condattr_t *attr)
    355   1.2   thorpej {
    356   1.2   thorpej 
    357  1.11   nathanw 	pthread__error(EINVAL, "Invalid condition variable attribute",
    358  1.11   nathanw 	    attr->ptca_magic == _PT_CONDATTR_MAGIC);
    359   1.2   thorpej 
    360   1.2   thorpej 	attr->ptca_magic = _PT_CONDATTR_DEAD;
    361  1.58  christos 	free(attr->ptca_private);
    362   1.2   thorpej 
    363   1.2   thorpej 	return 0;
    364   1.6   nathanw }
    365   1.6   nathanw 
    366   1.6   nathanw /* Utility routine to hang out for a while if threads haven't started yet. */
    367   1.6   nathanw static int
    368   1.6   nathanw pthread_cond_wait_nothread(pthread_t self, pthread_mutex_t *mutex,
    369  1.58  christos     pthread_cond_t *cond, const struct timespec *abstime)
    370   1.6   nathanw {
    371  1.18   mycroft 	struct timespec now, diff;
    372   1.6   nathanw 	int retval;
    373   1.6   nathanw 
    374  1.18   mycroft 	if (abstime == NULL) {
    375  1.18   mycroft 		diff.tv_sec = 99999999;
    376  1.18   mycroft 		diff.tv_nsec = 0;
    377  1.18   mycroft 	} else {
    378  1.58  christos 		clockid_t clck = cond->ptc_private ?
    379  1.58  christos 		    *(clockid_t *)cond->ptc_private : CLOCK_REALTIME;
    380  1.58  christos 		clock_gettime(clck, &now);
    381  1.18   mycroft 		if  (timespeccmp(abstime, &now, <))
    382  1.18   mycroft 			timespecclear(&diff);
    383  1.17   nathanw 		else
    384  1.18   mycroft 			timespecsub(abstime, &now, &diff);
    385   1.6   nathanw 	}
    386   1.6   nathanw 
    387  1.18   mycroft 	do {
    388  1.18   mycroft 		pthread__testcancel(self);
    389  1.18   mycroft 		pthread_mutex_unlock(mutex);
    390  1.55  drochner 		retval = _sys___nanosleep50(&diff, NULL);
    391  1.18   mycroft 		pthread_mutex_lock(mutex);
    392  1.18   mycroft 	} while (abstime == NULL && retval == 0);
    393   1.6   nathanw 	pthread__testcancel(self);
    394   1.6   nathanw 
    395   1.6   nathanw 	if (retval == 0)
    396   1.6   nathanw 		return ETIMEDOUT;
    397   1.6   nathanw 	else
    398  1.15    kleink 		/* spurious wakeup */
    399  1.15    kleink 		return 0;
    400   1.2   thorpej }
    401