167 lines
4.6 KiB
Groff
167 lines
4.6 KiB
Groff
.\" $OpenBSD: pthread_mutex_lock.3,v 1.11 2013/06/05 03:44:50 tedu Exp $
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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: pthread_mutex_lock.3,v 1.5 1999/08/28 00:03:07 peter Exp $
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.\"
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.Dd $Mdocdate: June 5 2013 $
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.Dt PTHREAD_MUTEX_LOCK 3
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.Os
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.Sh NAME
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.Nm pthread_mutex_lock ,
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.Nm pthread_mutex_timedlock ,
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.Nm pthread_mutex_trylock
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.Nd lock a mutex
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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_lock "pthread_mutex_t *mutex"
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.Ft int
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.Fn pthread_mutex_timedlock "pthread_mutex_t *mutex" "const struct timespec *abstime"
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.Ft int
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.Fn pthread_mutex_trylock "pthread_mutex_t *mutex"
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.Sh DESCRIPTION
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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 currently locked by another thread,
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the calling thread will block until the
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mutex becomes available.
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.Pp
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If the mutex is currently locked by the calling thread,
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then the behavior depends on the type of the mutex.
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If
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.Fa mutex
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is of type
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.Dv PTHREAD_MUTEX_NORMAL ,
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then the calling thread will deadlock and never return from
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.Fn pthread_mutex_lock .
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If
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.Fa mutex
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is of type
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.Dv PTHREAD_MUTEX_ERRORCHECK ,
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then
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.Er EDEADLK
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is immediately returned.
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If
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.Fa mutex
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is of type
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.Dv PTHREAD_MUTEX_RECURSIVE ,
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then the recursion count on the mutex is incremented.
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.Pp
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The
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.Fn pthread_mutex_timedlock
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function locks
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.Fa mutex
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like
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.Fn pthread_mutex_lock
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except that it will not block or deadlock past the system time
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specified in
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.Fa abstime .
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If that time is reached without being able to lock
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.Fa mutex ,
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then it returns
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.Er ETIMEDOUT .
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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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like
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.Fn pthread_mutex_lock
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except that if
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.Fa mutex
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is locked by another thread,
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or is locked by the calling thread and is not of type
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.Dv PTHREAD_MUTEX_RECURSIVE ,
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then it will immediately return
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.Er EBUSY .
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.Sh RETURN VALUES
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If successful,
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.Fn pthread_mutex_lock ,
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.Fn pthread_mutex_timedlock ,
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and
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.Fn pthread_mutex_trylock
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will return zero, 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_mutex_lock ,
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.Fn pthread_mutex_timedlock ,
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and
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.Fn pthread_mutex_trylock
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will 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 EAGAIN
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The mutex is of type
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.Dv PTHREAD_MUTEX_RECURSIVE
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and the maximum recursion count has been reached.
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.El
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.Pp
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In addition,
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.Fn pthread_mutex_lock
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and
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.Fn pthread_mutex_timedlock
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may return the following error:
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.Bl -tag -width Er
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.It Bq Er EDEADLK
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The mutex is of type
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.Dv PTHREAD_MUTEX_ERRORCHECK
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and is already locked by the calling thread.
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.El
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.Pp
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.Fn pthread_mutex_timedlock
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may return the following error:
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.Bl -tag -width Er
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.It Bq Er ETIMEDOUT
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The mutex could not be locked and the specified time was reached.
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.El
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.Pp
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.Fn pthread_mutex_trylock
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may return the following error:
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.Bl -tag -width Er
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.It Bq Er EBUSY
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The mutex could not be locked because it was already locked.
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.El
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.Sh SEE ALSO
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.Xr pthread_mutex_destroy 3 ,
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.Xr pthread_mutex_init 3 ,
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.Xr pthread_mutex_unlock 3 ,
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.Xr pthread_mutexattr_settype 3
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.Sh STANDARDS
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.Fn pthread_mutex_lock ,
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.Fn pthread_mutex_timedlock ,
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and
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.Fn pthread_mutex_trylock
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conform to
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.St -p1003.1-2008 .
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