219 lines
6.9 KiB
Groff
219 lines
6.9 KiB
Groff
.\" $NetBSD: pthread_mutex.3,v 1.5 2010/07/09 10:55:11 wiz Exp $
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.\"
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.\" Copyright (c) 2002, 2010 The NetBSD Foundation, Inc.
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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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.\"
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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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.\" ----------------------------------------------------------------------------
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.Dd July 8, 2010
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.Dt PTHREAD_MUTEX 3
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.Os
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.Sh NAME
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.Nm pthread_mutex
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.Nd mutual exclusion primitives
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.Sh LIBRARY
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.Lb libpthread
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.\" ----------------------------------------------------------------------------
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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_mutex_init "pthread_mutex_t * restrict mutex" \
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"const pthread_mutexattr_t * restrict attr"
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.Ft int
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.Fn pthread_mutex_destroy "pthread_mutex_t *mutex"
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.Ft int
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.Fn pthread_mutex_lock "pthread_mutex_t *mutex"
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.Ft int
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.Fn pthread_mutex_trylock "pthread_mutex_t *mutex"
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.Ft int
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.Fn pthread_mutex_unlock "pthread_mutex_t *mutex"
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.Pp
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.Va pthread_mutex_t mutex = Dv PTHREAD_MUTEX_INITIALIZER;
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.\" ----------------------------------------------------------------------------
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.Sh DESCRIPTION
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The
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.Fn pthread_mutex_init
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function creates a new mutex, with attributes specified with
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.Fa attr .
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If
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.Fa attr
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is
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.Dv NULL ,
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the default attributes are used.
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.Pp
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The macro
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.Dv PTHREAD_MUTEX_INITIALIZER
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can be used to initialize a mutex when the default attributes are
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appropriate and the mutex can be statically allocated.
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The behavior is similar to
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.Fn pthread_mutex_init
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with
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.Fa attr
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specified as
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.Dv NULL ,
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except that no error checking is done.
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.Pp
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.\" -----
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The
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.Fn pthread_mutex_destroy
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function frees the resources allocated for
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.Fa mutex .
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It is possible to reinitialize a destroyed mutex, but undefined
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behavior may follow if the destroyed object is otherwise referenced.
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.Pp
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.\" -----
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The
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.Fn pthread_mutex_lock
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function locks
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.Fa mutex .
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If the mutex is already locked, the calling thread will block until the
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mutex becomes available.
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The error conditions may vary depending on the type of the mutex; see
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.Xr pthread_mutexattr 3
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for additional details.
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.Pp
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The
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.Fn pthread_mutex_trylock
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function locks
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.Fa mutex .
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If the mutex is already locked,
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.Fn pthread_mutex_trylock
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will not block waiting for the mutex, but will return an error condition.
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.Pp
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.\" -----
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The
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.Fn pthread_mutex_unlock
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function unlocks an acquired
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.Fa mutex .
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When operating with the default mutex type,
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undefined behavior follows if a thread tries to unlock a mutex
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that has not been locked by it, or if a thread tries to release
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a mutex that is already unlocked.
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.\" ----------------------------------------------------------------------------
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.Sh RETURN VALUES
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Upon success all described functions return zero.
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Otherwise, an error number will be returned to indicate the error.
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.Sh ERRORS
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.Fn pthread_mutex_init
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may fail if:
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.Bl -tag -width Er
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.It Bq Er EAGAIN
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The system lacks the resources to initialize another mutex.
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.It Bq Er EINVAL
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The value specified by
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.Fa attr
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is invalid.
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.It Bq Er ENOMEM
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The process cannot allocate enough memory to initialize another mutex.
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.El
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.Pp
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.\" -----
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.Fn pthread_mutex_destroy
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may fail if:
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.Bl -tag -width Er
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.It Bq Er EBUSY
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.Fa Mutex
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is locked by another thread.
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.It Bq Er EINVAL
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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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.\" -----
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.Fn pthread_mutex_lock
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may fail if:
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.Bl -tag -width Er
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.It Bq Er EDEADLK
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A deadlock would occur if the thread blocked waiting for
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.Fa mutex .
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.It Bq Er EINVAL
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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_mutex_trylock
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may fail if:
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.Bl -tag -width Er
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.It Bq Er EBUSY
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.Fa Mutex
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is already locked.
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.It Bq Er EINVAL
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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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.\" -----
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.Fn pthread_mutex_unlock
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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 mutex
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is invalid.
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.It Bq Er EPERM
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The current thread does not hold a lock on
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.Fa mutex .
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.El
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.\" ----------------------------------------------------------------------------
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.Sh SEE ALSO
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.Xr pthread 3 ,
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.Xr pthread_barrier 3 ,
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.Xr pthread_cond 3 ,
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.Xr pthread_mutexattr 3 ,
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.Xr pthread_rwlock 3 ,
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.Xr pthread_spin 3
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.\" ----------------------------------------------------------------------------
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.Sh STANDARDS
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These functions conform to
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.St -p1003.1-2001 .
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