1.\" $OpenBSD: pthread_rwlock_wrlock.3,v 1.4 2000/04/12 21:48:02 aaron 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 August 4, 1998 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. Otherwise an error number will be returned 61to indicate the error. 62.Sh SEE ALSO 63.Xr pthread_rwlock_trywrlock 3 , 64.Xr pthread_rwlock_unlock 3 , 65.Xr pthread_rwlock_wrlock 3 66.Sh STANDARDS 67The 68.Fn pthread_rwlock_wrlock 69and 70.Fn pthread_rwlock_trywrlock 71functions are expected to conform to 72.St -susv2 . 73.Sh ERRORS 74The 75.Fn pthread_rwlock_trywrlock 76function will fail if: 77.Bl -tag -width Er 78.It Bq Er EBUSY 79The calling thread is not able to acquire the lock without blocking. 80.El 81.Pp 82The 83.Fn pthread_rwlock_wrlock 84and 85.Fn pthread_rwlock_trywrlock 86functions may fail if: 87.Bl -tag -width Er 88.It Bq Er EDEADLK 89The calling thread already owns the read/write lock (for reading 90or writing). 91.It Bq Er EINVAL 92The value specified by 93.Fa lock 94is invalid. 95.It Bq Er ENOMEM 96Insufficient memory exists to initialize the lock (applies to 97statically initialized locks only). 98.El 99.Sh HISTORY 100The 101.Fn pthread_rwlock_wrlock 102function first appeared in 103.Fx 3.0 104and 105.Ox 2.5 . 106