443 lines
13 KiB
C
443 lines
13 KiB
C
/* $NetBSD: pthread_cond.c,v 1.41 2008/02/14 21:40:51 ad Exp $ */
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/*-
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* Copyright (c) 2001, 2006, 2007 The NetBSD Foundation, Inc.
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* All rights reserved.
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*
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* This code is derived from software contributed to The NetBSD Foundation
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* by Nathan J. Williams and Andrew Doran.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the NetBSD
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* Foundation, Inc. and its contributors.
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* 4. Neither the name of The NetBSD Foundation nor the names of its
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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__RCSID("$NetBSD: pthread_cond.c,v 1.41 2008/02/14 21:40:51 ad Exp $");
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#include <errno.h>
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#include <sys/time.h>
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#include <sys/types.h>
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#include "pthread.h"
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#include "pthread_int.h"
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int _sys_nanosleep(const struct timespec *, struct timespec *);
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extern int pthread__started;
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static int pthread_cond_wait_nothread(pthread_t, pthread_mutex_t *,
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const struct timespec *);
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__strong_alias(__libc_cond_init,pthread_cond_init)
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__strong_alias(__libc_cond_signal,pthread_cond_signal)
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__strong_alias(__libc_cond_broadcast,pthread_cond_broadcast)
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__strong_alias(__libc_cond_wait,pthread_cond_wait)
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__strong_alias(__libc_cond_timedwait,pthread_cond_timedwait)
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__strong_alias(__libc_cond_destroy,pthread_cond_destroy)
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int
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pthread_cond_init(pthread_cond_t *cond, const pthread_condattr_t *attr)
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{
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pthread__error(EINVAL, "Invalid condition variable attribute",
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(attr == NULL) || (attr->ptca_magic == _PT_CONDATTR_MAGIC));
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cond->ptc_magic = _PT_COND_MAGIC;
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pthread_lockinit(&cond->ptc_lock);
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PTQ_INIT(&cond->ptc_waiters);
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cond->ptc_mutex = NULL;
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return 0;
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}
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int
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pthread_cond_destroy(pthread_cond_t *cond)
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{
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pthread__error(EINVAL, "Invalid condition variable",
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cond->ptc_magic == _PT_COND_MAGIC);
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pthread__error(EBUSY, "Destroying condition variable in use",
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cond->ptc_mutex == NULL);
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cond->ptc_magic = _PT_COND_DEAD;
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return 0;
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}
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int
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pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
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{
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pthread_t self;
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pthread__error(EINVAL, "Invalid condition variable",
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cond->ptc_magic == _PT_COND_MAGIC);
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pthread__error(EINVAL, "Invalid mutex",
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mutex->ptm_magic == _PT_MUTEX_MAGIC);
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pthread__error(EPERM, "Mutex not locked in condition wait",
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mutex->ptm_owner != NULL);
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self = pthread__self();
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/* Just hang out for a while if threads aren't running yet. */
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if (__predict_false(pthread__started == 0))
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return pthread_cond_wait_nothread(self, mutex, NULL);
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if (__predict_false(self->pt_cancel))
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pthread__cancelled();
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/*
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* Note this thread as waiting on the CV. To ensure good
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* performance it's critical that the spinlock is held for
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* as short a time as possible - that means no system calls.
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*/
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pthread__spinlock(self, &cond->ptc_lock);
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#ifdef ERRORCHECK
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if (cond->ptc_mutex == NULL)
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cond->ptc_mutex = mutex;
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else {
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pthread__error(EINVAL,
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"Multiple mutexes used for condition wait",
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cond->ptc_mutex == mutex);
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}
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#else
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cond->ptc_mutex = mutex;
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#endif
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PTQ_INSERT_HEAD(&cond->ptc_waiters, self, pt_sleep);
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self->pt_signalled = 0;
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self->pt_sleeponq = 1;
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self->pt_sleepobj = &cond->ptc_waiters;
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pthread__spinunlock(self, &cond->ptc_lock);
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/*
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* Before releasing the mutex, note that this thread is
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* about to block by setting the willpark flag. If there
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* is a single waiter on the mutex, setting the flag will
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* defer restarting it until calling into the kernel to
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* park, saving a syscall & involuntary context switch.
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*/
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self->pt_willpark = 1;
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pthread_mutex_unlock(mutex);
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(void)pthread__park(self, &cond->ptc_lock, &cond->ptc_waiters,
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NULL, 1, __UNVOLATILE(&mutex->ptm_waiters));
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pthread_mutex_lock(mutex);
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/*
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* If we awoke abnormally the waiters list will have been
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* made empty by the current thread (in pthread__park()),
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* so we can check the value safely without locking.
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*
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* Otherwise, it will have been updated by whichever thread
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* last issued a wakeup.
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*/
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if (PTQ_EMPTY(&cond->ptc_waiters) && cond->ptc_mutex != NULL) {
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pthread__spinlock(self, &cond->ptc_lock);
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if (PTQ_EMPTY(&cond->ptc_waiters))
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cond->ptc_mutex = NULL;
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pthread__spinunlock(self, &cond->ptc_lock);
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}
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/*
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* If we have cancelled then exit. POSIX dictates that the
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* mutex must be held when we action the cancellation.
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*/
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if (__predict_false(self->pt_cancel)) {
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if (self->pt_signalled)
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pthread_cond_signal(cond);
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pthread__cancelled();
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}
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return 0;
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}
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int
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pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
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const struct timespec *abstime)
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{
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pthread_t self;
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int retval;
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pthread__error(EINVAL, "Invalid condition variable",
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cond->ptc_magic == _PT_COND_MAGIC);
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pthread__error(EINVAL, "Invalid mutex",
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mutex->ptm_magic == _PT_MUTEX_MAGIC);
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pthread__error(EPERM, "Mutex not locked in condition wait",
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mutex->ptm_owner != NULL);
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pthread__error(EINVAL, "Invalid wait time",
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(abstime->tv_sec >= 0) &&
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(abstime->tv_nsec >= 0) && (abstime->tv_nsec < 1000000000));
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self = pthread__self();
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/* Just hang out for a while if threads aren't running yet. */
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if (__predict_false(pthread__started == 0))
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return pthread_cond_wait_nothread(self, mutex, abstime);
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if (__predict_false(self->pt_cancel))
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pthread__cancelled();
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/*
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* Note this thread as waiting on the CV. To ensure good
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* performance it's critical that the spinlock is held for
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* as short a time as possible - that means no system calls.
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*/
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pthread__spinlock(self, &cond->ptc_lock);
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#ifdef ERRORCHECK
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if (cond->ptc_mutex == NULL)
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cond->ptc_mutex = mutex;
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else {
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pthread__error(EINVAL,
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"Multiple mutexes used for condition wait",
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cond->ptc_mutex == mutex);
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}
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#else
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cond->ptc_mutex = mutex;
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#endif
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PTQ_INSERT_HEAD(&cond->ptc_waiters, self, pt_sleep);
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self->pt_signalled = 0;
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self->pt_sleeponq = 1;
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self->pt_sleepobj = &cond->ptc_waiters;
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pthread__spinunlock(self, &cond->ptc_lock);
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/*
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* Before releasing the mutex, note that this thread is
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* about to block by setting the willpark flag. If there
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* is a single waiter on the mutex, setting the flag will
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* defer restarting it until calling into the kernel to
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* park, saving a syscall & involuntary context switch.
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*/
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self->pt_willpark = 1;
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pthread_mutex_unlock(mutex);
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retval = pthread__park(self, &cond->ptc_lock, &cond->ptc_waiters,
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abstime, 1, __UNVOLATILE(&mutex->ptm_waiters));
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pthread_mutex_lock(mutex);
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/*
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* If we awoke abnormally the waiters list will have been
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* made empty by the current thread (in pthread__park()),
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* so we can check the value safely without locking.
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*
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* Otherwise, it will have been updated by whichever thread
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* last issued a wakeup.
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*/
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if (PTQ_EMPTY(&cond->ptc_waiters) && cond->ptc_mutex != NULL) {
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pthread__spinlock(self, &cond->ptc_lock);
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if (PTQ_EMPTY(&cond->ptc_waiters))
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cond->ptc_mutex = NULL;
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pthread__spinunlock(self, &cond->ptc_lock);
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}
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/*
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* If we have cancelled then exit. POSIX dictates that the
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* mutex must be held when we action the cancellation.
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*/
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if (__predict_false(self->pt_cancel | retval)) {
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if (self->pt_signalled)
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pthread_cond_signal(cond);
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if (self->pt_cancel)
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pthread__cancelled();
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}
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return retval;
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}
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int
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pthread_cond_signal(pthread_cond_t *cond)
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{
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pthread_t self, signaled;
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pthread_mutex_t *mutex;
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pthread__error(EINVAL, "Invalid condition variable",
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cond->ptc_magic == _PT_COND_MAGIC);
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if (PTQ_EMPTY(&cond->ptc_waiters))
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return 0;
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self = pthread__self();
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pthread__spinlock(self, &cond->ptc_lock);
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/*
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* Find a thread that is still blocked (no pending wakeup).
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* A wakeup can be pending if we have interrupted unpark_all
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* as it releases the interlock.
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*/
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PTQ_FOREACH(signaled, &cond->ptc_waiters, pt_sleep) {
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if (signaled->pt_sleepobj != NULL)
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break;
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}
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if (__predict_false(signaled == NULL)) {
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cond->ptc_mutex = NULL;
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pthread__spinunlock(self, &cond->ptc_lock);
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return 0;
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}
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/*
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* Pull the thread off the queue, and set pt_signalled.
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*
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* After resuming execution, the thread must check to see if it
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* has been restarted as a result of pthread_cond_signal(). If it
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* has, but cannot take the wakeup (because of eg a timeout) then
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* try to ensure that another thread sees it. This is necessary
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* because there may be multiple waiters, and at least one should
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* take the wakeup if possible.
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*/
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PTQ_REMOVE(&cond->ptc_waiters, signaled, pt_sleep);
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mutex = cond->ptc_mutex;
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if (PTQ_EMPTY(&cond->ptc_waiters))
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cond->ptc_mutex = NULL;
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signaled->pt_signalled = 1;
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/*
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* For all valid uses of pthread_cond_signal(), the caller will
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* hold the mutex that the target is using to synchronize with.
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* To avoid the target awakening and immediatley blocking on the
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* mutex, transfer the thread to be awoken to the current thread's
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* deferred wakeup list. The waiter will be set running when the
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* caller (this thread) releases the mutex.
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*/
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if (mutex != NULL && self->pt_nwaiters < pthread__unpark_max &&
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pthread__mutex_deferwake(self, mutex)) {
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signaled->pt_sleepobj = NULL;
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signaled->pt_sleeponq = 0;
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pthread__spinunlock(self, &cond->ptc_lock);
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self->pt_waiters[self->pt_nwaiters++] = signaled->pt_lid;
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} else {
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pthread__unpark(self, &cond->ptc_lock,
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&cond->ptc_waiters, signaled);
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}
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return 0;
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}
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int
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pthread_cond_broadcast(pthread_cond_t *cond)
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{
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pthread_t self, signaled, next;
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pthread_mutex_t *mutex;
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pthread__error(EINVAL, "Invalid condition variable",
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cond->ptc_magic == _PT_COND_MAGIC);
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if (PTQ_EMPTY(&cond->ptc_waiters))
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return 0;
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self = pthread__self();
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pthread__spinlock(self, &cond->ptc_lock);
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mutex = cond->ptc_mutex;
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cond->ptc_mutex = NULL;
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/*
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* Try to defer waking threads (see pthread_cond_signal()).
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* Only transfer waiters for which there is no pending wakeup.
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*/
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if (mutex != NULL && pthread__mutex_deferwake(self, mutex)) {
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for (signaled = PTQ_FIRST(&cond->ptc_waiters);
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signaled != NULL;
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signaled = next) {
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next = PTQ_NEXT(signaled, pt_sleep);
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if (__predict_false(signaled->pt_sleepobj == NULL))
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continue;
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if (self->pt_nwaiters == pthread__unpark_max) {
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/* Overflow, take the slow path. */
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break;
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}
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PTQ_REMOVE(&cond->ptc_waiters, signaled, pt_sleep);
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signaled->pt_sleepobj = NULL;
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signaled->pt_sleeponq = 0;
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self->pt_waiters[self->pt_nwaiters++] =
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signaled->pt_lid;
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}
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if (signaled == NULL) {
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/* Anything more to do? */
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pthread__spinunlock(self, &cond->ptc_lock);
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return 0;
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}
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}
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pthread__unpark_all(self, &cond->ptc_lock, &cond->ptc_waiters);
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return 0;
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}
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int
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pthread_condattr_init(pthread_condattr_t *attr)
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{
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attr->ptca_magic = _PT_CONDATTR_MAGIC;
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return 0;
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}
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int
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pthread_condattr_destroy(pthread_condattr_t *attr)
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{
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pthread__error(EINVAL, "Invalid condition variable attribute",
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attr->ptca_magic == _PT_CONDATTR_MAGIC);
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attr->ptca_magic = _PT_CONDATTR_DEAD;
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return 0;
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}
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/* Utility routine to hang out for a while if threads haven't started yet. */
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static int
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pthread_cond_wait_nothread(pthread_t self, pthread_mutex_t *mutex,
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const struct timespec *abstime)
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{
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struct timespec now, diff;
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int retval;
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if (abstime == NULL) {
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diff.tv_sec = 99999999;
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diff.tv_nsec = 0;
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} else {
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clock_gettime(CLOCK_REALTIME, &now);
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if (timespeccmp(abstime, &now, <))
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timespecclear(&diff);
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else
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timespecsub(abstime, &now, &diff);
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}
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do {
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pthread__testcancel(self);
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pthread_mutex_unlock(mutex);
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retval = _sys_nanosleep(&diff, NULL);
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pthread_mutex_lock(mutex);
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} while (abstime == NULL && retval == 0);
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pthread__testcancel(self);
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if (retval == 0)
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return ETIMEDOUT;
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else
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/* spurious wakeup */
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return 0;
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}
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