.\" $NetBSD: pthread_rwlock_wrlock.3,v 1.5 2003/07/04 11:59:34 wiz Exp $
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.\" Copyright (c) 1998 Alex Nash
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.\" modification, are permitted provided that the following conditions
.\" are met:
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.\" $FreeBSD: src/lib/libpthread/man/pthread_rwlock_wrlock.3,v 1.5 2002/09/16 19:29:29 mini Exp $
.\"
.Dd January 30, 2003
.Dt PTHREAD_RWLOCK_WRLOCK 3
.Os
.Sh NAME
.Nm pthread_rwlock_wrlock ,
.Nm pthread_rwlock_timedwrlock ,
.Nm pthread_rwlock_trywrlock
.Nd acquire a read/write lock for writing
.Sh LIBRARY
.Lb libpthread
.Sh SYNOPSIS
.In pthread.h
.Ft int
.Fn pthread_rwlock_wrlock "pthread_rwlock_t *lock"
.Ft int
.Fn pthread_rwlock_timedwrlock "pthread_rwlock_t *lock" "const struct timespec *abstime"
.Ft int
.Fn pthread_rwlock_trywrlock "pthread_rwlock_t *lock"
.Sh DESCRIPTION
The
.Fn pthread_rwlock_wrlock
function blocks until a write lock can be acquired against
.Fa lock .
.Pp
The
.Fn pthread_rwlock_timedwrlock
performs the same action, but will not wait beyond
.Fa abstime
to obtain the lock before returning.
.Pp
The
.Fn pthread_rwlock_trywrlock
function performs the same action as
.Fn pthread_rwlock_wrlock ,
but does not block if the lock cannot be immediately obtained.
.Pp
The results are undefined if the calling thread already holds the
lock at the time the call is made.
.Sh RETURN VALUES
If successful, the
.Fn pthread_rwlock_wrlock ,
.Fn pthread_rwlock_timedwrlock ,
and
.Fn pthread_rwlock_trywrlock
functions will return zero.  Otherwise an error number will be returned
to indicate the error.
.Sh ERRORS
The
.Fn pthread_rwlock_trywrlock
function shall fail if:
.Bl -tag -width Er
.It Bq Er EBUSY
The calling thread is not able to acquire the lock without blocking.
.El
.Pp
The
.Fn pthread_rwlock_timedrdlock
function shall fail if:
.Bl -tag -width Er
.It Bq Er ETIMEDOUT
The time specified by
.Fa abstime
was reached before the lock could be obtained.
.El
.Pp
The
.Fn pthread_rwlock_wrlock ,
.Fn pthread_rwlock_timedwrlock ,
and
.Fn pthread_rwlock_trywrlock
functions may fail if:
.Bl -tag -width Er
.It Bq Er EDEADLK
The calling thread already owns the read/write lock (for reading
or writing).
.It Bq Er EINVAL
The value specified by
.Fa lock
is invalid.
.El
.Sh SEE ALSO
.Xr pthread_rwlock_destroy 3 ,
.Xr pthread_rwlock_init 3 ,
.Xr pthread_rwlock_rdlock 3 ,
.Xr pthread_rwlock_unlock 3
.Sh STANDARDS
.Fn pthread_rwlock_wrlock ,
.Fn pthread_rwlock_timedwrlock ,
 and
.Fn pthread_rwlock_trywrlock
conform to
.St -p1003.1-96 .