202 lines
6.4 KiB
Groff
202 lines
6.4 KiB
Groff
.\" $NetBSD: pthread_cond_wait.3,v 1.13 2009/07/02 19:43:06 rumble Exp $
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.\"
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.\" Copyright (c) 2002, 2008 The NetBSD Foundation, Inc.
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.\" All rights reserved.
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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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.\" 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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.\" Copyright (c) 1997 Brian Cully <shmit@kublai.com>
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.\" All rights reserved.
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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. Neither the name of the author nor the names of any co-contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD: src/lib/libpthread/man/pthread_cond_wait.3,v 1.16 2002/09/16 19:29:28 mini Exp $
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.\"
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.Dd December 31, 2008
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.Dt PTHREAD_COND_WAIT 3
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.Os
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.Sh NAME
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.Nm pthread_cond_wait ,
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.Nm pthread_cond_timedwait
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.Nd wait on a condition variable
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.Sh LIBRARY
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.Lb libpthread
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.Sh SYNOPSIS
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.In pthread.h
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.Ft int
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.Fn pthread_cond_wait "pthread_cond_t * restrict cond" "pthread_mutex_t * restrict mutex"
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.Ft int
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.Fn pthread_cond_timedwait "pthread_cond_t * restrict cond" "pthread_mutex_t * restrict mutex" "const struct timespec * restrict abstime"
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.Sh DESCRIPTION
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The
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.Fn pthread_cond_wait
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function atomically blocks the current thread waiting on the condition
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variable specified by
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.Fa cond ,
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and unlocks the mutex specified by
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.Fa mutex .
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The waiting thread unblocks after another thread calls
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.Xr pthread_cond_signal 3 ,
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or
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.Xr pthread_cond_broadcast 3
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with the same condition variable.
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The current thread holds the lock on
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.Fa mutex
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upon return from the
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.Fa pthread_cond_wait
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call.
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.Pp
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The
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.Fn pthread_cond_timedwait
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function atomically blocks the current thread waiting on the condition
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variable specified by
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.Fa cond ,
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and unlocks the mutex specified by
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.Fa mutex .
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The waiting thread unblocks after another thread calls
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.Xr pthread_cond_signal 3 ,
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or
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.Xr pthread_cond_broadcast 3
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with the same condition variable, or if the system time reaches the
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time specified in
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.Fa abstime .
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.Pp
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Note that a call to
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.Fn pthread_cond_wait
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or
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.Fn pthread_cond_timedwait
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may wake up spontaneously, without a call to
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.Xr pthread_cond_signal 3
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or
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.Xr pthread_cond_broadcast 3 .
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The caller should prepare for this by invoking
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.Fn pthread_cond_wait
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or
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.Fn pthread_cond_timedwait
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within a predicate loop that tests whether the thread should proceed.
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.Pp
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When calling
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.Fn pthread_cond_wait
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or
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.Fn pthread_cond_timedwait ,
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a temporary binding is established between the condition variable
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.Fa cond
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and the mutex
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.Fa mutex .
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.Pp
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The same mutex must be held while calling
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.Fn pthread_cond_broadcast
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and
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.Fn pthread_cond_signal
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on
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.Fa cond .
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Additionally, the same mutex must be used for concurrent calls to
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.Fn pthread_cond_wait
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and
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.Fn pthread_cond_timedwait .
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Only when a condition variable is known to be quiescent may an application
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change the mutex associated with it.
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In this implementation, none of the functions enforce this requirement, but
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if the mutex is not held or independent mutexes are used the resulting
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behaviour is undefined.
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.Sh RETURN VALUES
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If successful, the
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.Fn pthread_cond_wait
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and
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.Fn pthread_cond_timedwait
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functions will return zero.
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Otherwise an error number will be returned to
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indicate the error.
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.Sh ERRORS
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.Fn pthread_cond_wait
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may fail if:
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.Bl -tag -width Er
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.It Bq Er EINVAL
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The value specified by
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.Fa cond
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or the value specified by
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.Fa mutex
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is invalid.
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.El
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.Pp
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.Fn pthread_cond_timedwait
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shall fail if:
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.Bl -tag -width Er
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.It Bq Er ETIMEDOUT
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The system time has reached or exceeded the time specified in
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.Fa abstime .
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.El
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.Pp
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.Fn pthread_cond_timedwait
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may fail if:
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.Bl -tag -width Er
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.It Bq Er EINVAL
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The value specified by
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.Fa cond ,
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.Fa mutex ,
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or
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.Fa abstime
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is invalid.
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.El
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.Pp
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.Fn pthread_cond_wait
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and
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.Fn pthread_cond_timedwait
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may fail if:
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.Bl -tag -width Er
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.It Bq Er EPERM
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The value specified by
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.Fa mutex
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is not locked in condition wait.
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.El
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.Sh SEE ALSO
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.Xr pthread_cond_broadcast 3 ,
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.Xr pthread_cond_destroy 3 ,
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.Xr pthread_cond_init 3 ,
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.Xr pthread_cond_signal 3
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.Sh STANDARDS
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.Fn pthread_cond_wait
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and
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.Fn pthread_cond_timedwait
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conform to
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.St -p1003.1-96 .
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