1.\" Copyright (c) 1998 Alex Nash 2.\" All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 13.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 14.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 15.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 16.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 17.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 18.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 19.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 20.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 21.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 22.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 23.\" SUCH DAMAGE. 24.\" 25.\" $FreeBSD$ 26.\" 27.Dd August 4, 1998 28.Dt PTHREAD_RWLOCK_WRLOCK 3 29.Os 30.Sh NAME 31.Nm pthread_rwlock_wrlock , 32.Nm pthread_rwlock_trywrlock 33.Nd acquire a read/write lock for writing 34.Sh LIBRARY 35.Lb libc_r 36.Lb libpthread 37.Lb libthr 38.Sh SYNOPSIS 39.In pthread.h 40.Ft int 41.Fn pthread_rwlock_wrlock "pthread_rwlock_t *lock" 42.Ft int 43.Fn pthread_rwlock_trywrlock "pthread_rwlock_t *lock" 44.Sh DESCRIPTION 45The 46.Fn pthread_rwlock_wrlock 47function blocks until a write lock can be acquired against 48.Fa lock . 49The 50.Fn pthread_rwlock_trywrlock 51function performs the same action, but does not block if the lock 52cannot be immediately obtained. 53.Pp 54The results are undefined if the calling thread already holds the 55lock at the time the call is made. 56.Sh IMPLEMENTATION NOTES 57To prevent writer starvation, writers are favored over readers. 58.Sh RETURN VALUES 59If successful, the 60.Fn pthread_rwlock_wrlock 61and 62.Fn pthread_rwlock_trywrlock 63functions will return zero. Otherwise an error number will be returned 64to indicate the error. 65.Sh SEE ALSO 66.Xr pthread_rwlock_init 3 , 67.Xr pthread_rwlock_rdlock 3 , 68.Xr pthread_rwlock_tryrdlock 3 , 69.Xr pthread_rwlock_unlock 3 70.Sh STANDARDS 71The 72.Fn pthread_rwlock_wrlock 73and 74.Fn pthread_rwlock_trywrlock 75functions are expected to conform to 76.St -susv2 . 77.Sh ERRORS 78The 79.Fn pthread_rwlock_trywrlock 80function will fail if: 81.Bl -tag -width Er 82.It Bq Er EBUSY 83The calling thread is not able to acquire the lock without blocking. 84.El 85.Pp 86The 87.Fn pthread_rwlock_wrlock 88and 89.Fn pthread_rwlock_trywrlock 90functions may fail if: 91.Bl -tag -width Er 92.It Bq Er EDEADLK 93The calling thread already owns the read/write lock (for reading 94or writing). 95.It Bq Er EINVAL 96The value specified by 97.Fa lock 98is invalid. 99.It Bq Er ENOMEM 100Insufficient memory exists to initialize the lock (applies to 101statically initialized locks only). 102.El 103.Sh HISTORY 104The 105.Fn pthread_rwlock_wrlock 106function first appeared in 107.Fx 3.0 . 108