c0e366326f
UNIX Specification. As with our standard mutexes, process shared locks are not supported at this time.
103 lines
3.1 KiB
Groff
103 lines
3.1 KiB
Groff
.\" Copyright (c) 1998 Alex Nash
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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 AUTHOR 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 AUTHOR 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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.\" $Id$
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.\"
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.Dd August 4, 1998
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.Dt PTHREAD_RWLOCK_WRLOCK 3
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.Os
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.Sh NAME
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.Nm pthread_rwlock_wrlock ,
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.Nm pthread_rwlock_trywrlock
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.Nd acquire a read/write lock for writing
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.Sh SYNOPSIS
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.Fd #include <pthread.h>
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.Ft int
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.Fn pthread_rwlock_wrlock "pthread_rwlock_t *lock"
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.Ft int
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.Fn pthread_rwlock_trywrlock "pthread_rwlock_t *lock"
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.Sh DESCRIPTION
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The
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.Fn pthread_rwlock_wrlock
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function blocks until a write lock can be acquired against
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.Fa lock .
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The
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.Fn pthread_rwlock_trywrlock
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function performs the same action, but does not block if the lock
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cannot be immediately obtained.
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.Pp
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The results are undefined if the calling thread already holds the
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lock at the time the call is made.
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.Sh IMPLEMENTATION NOTES
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To prevent writer starvation, writers are favored over readers.
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.Sh RETURN VALUES
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If successful, the
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.Fn pthread_rwlock_wrlock
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and
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.Fn pthread_rwlock_trywrlock
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functions will return zero. Otherwise an error number will be returned
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to indicate the error.
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.Sh SEE ALSO
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.Xr pthread_rwlock_trywrlock 3 ,
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.Xr pthread_rwlock_unlock 3 ,
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.Xr pthread_rwlock_wrlock 3
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.Sh STANDARDS
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The
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.Fn pthread_rwlock_wrlock
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and
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.Fn pthread_rwlock_trywrlock
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functions are expected to conform to
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.St -susv2 .
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.Sh ERRORS
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The
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.Fn pthread_rwlock_trywrlock
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function will fail if:
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.Bl -tag -width Er
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.It Bq Er EBUSY
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The calling thread is not able to acquire the lock without blocking.
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.El
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.Pp
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The
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.Fn pthread_rwlock_wrlock
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and
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.Fn pthread_rwlock_trywrlock
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functions may fail if:
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.Bl -tag -width Er
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.It Bq Er EDEADLK
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The calling thread already owns the read/write lock (for reading
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or writing).
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.It Bq Er EINVAL
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The value specified by
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.Fa lock
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is invalid.
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.It Bq Er ENOMEM
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Insufficient memory exists to initialize the lock (applies to
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statically initialized locks only).
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.El
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.Sh HISTORY
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The
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.Fn pthread_rwlock_wrlock
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function first appeared in
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.Fx 3.0 .
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