1.\" $OpenBSD: pthread_rwlock_wrlock.3,v 1.7 2007/05/31 19:19:37 jmc Exp $ 2.\" Copyright (c) 1998 Alex Nash 3.\" All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice, this list of conditions and the following disclaimer. 10.\" 2. Redistributions in binary form must reproduce the above copyright 11.\" notice, this list of conditions and the following disclaimer in the 12.\" documentation and/or other materials provided with the distribution. 13.\" 14.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24.\" SUCH DAMAGE. 25.\" 26.\" $FreeBSD: pthread_rwlock_wrlock.3,v 1.2 1999/08/28 00:03:10 peter Exp $ 27.\" 28.Dd $Mdocdate: May 31 2007 $ 29.Dt PTHREAD_RWLOCK_WRLOCK 3 30.Os 31.Sh NAME 32.Nm pthread_rwlock_wrlock , 33.Nm pthread_rwlock_trywrlock 34.Nd acquire a read/write lock for writing 35.Sh SYNOPSIS 36.Fd #include <pthread.h> 37.Ft int 38.Fn pthread_rwlock_wrlock "pthread_rwlock_t *lock" 39.Ft int 40.Fn pthread_rwlock_trywrlock "pthread_rwlock_t *lock" 41.Sh DESCRIPTION 42The 43.Fn pthread_rwlock_wrlock 44function blocks until a write lock can be acquired against 45.Fa lock . 46The 47.Fn pthread_rwlock_trywrlock 48function performs the same action, but does not block if the lock 49cannot be immediately obtained. 50.Pp 51The results are undefined if the calling thread already holds the 52lock at the time the call is made. 53.Sh IMPLEMENTATION NOTES 54To prevent writer starvation, writers are favored over readers. 55.Sh RETURN VALUES 56If successful, the 57.Fn pthread_rwlock_wrlock 58and 59.Fn pthread_rwlock_trywrlock 60functions will return zero. 61Otherwise an error number will be returned to indicate the error. 62.Sh ERRORS 63The 64.Fn pthread_rwlock_trywrlock 65function will fail if: 66.Bl -tag -width Er 67.It Bq Er EBUSY 68The calling thread is not able to acquire the lock without blocking. 69.El 70.Pp 71The 72.Fn pthread_rwlock_wrlock 73and 74.Fn pthread_rwlock_trywrlock 75functions may fail if: 76.Bl -tag -width Er 77.It Bq Er EDEADLK 78The calling thread already owns the read/write lock (for reading 79or writing). 80.It Bq Er EINVAL 81The value specified by 82.Fa lock 83is invalid. 84.It Bq Er ENOMEM 85Insufficient memory exists to initialize the lock (applies to 86statically initialized locks only). 87.El 88.Sh SEE ALSO 89.Xr pthread_rwlock_unlock 3 90.Sh STANDARDS 91The 92.Fn pthread_rwlock_wrlock 93and 94.Fn pthread_rwlock_trywrlock 95functions are expected to conform to 96.St -susv2 . 97.Sh HISTORY 98The 99.Fn pthread_rwlock_wrlock 100function first appeared in 101.Fx 3.0 102and 103.Ox 2.5 . 104