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 libpthread 36.Lb libthr 37.Sh SYNOPSIS 38.In pthread.h 39.Ft int 40.Fn pthread_rwlock_wrlock "pthread_rwlock_t *lock" 41.Ft int 42.Fn pthread_rwlock_trywrlock "pthread_rwlock_t *lock" 43.Sh DESCRIPTION 44The 45.Fn pthread_rwlock_wrlock 46function blocks until a write lock can be acquired against 47.Fa lock . 48The 49.Fn pthread_rwlock_trywrlock 50function performs the same action, but does not block if the lock 51cannot be immediately obtained. 52.Pp 53The results are undefined if the calling thread already holds the 54lock at the time the call is made. 55.Sh IMPLEMENTATION NOTES 56To prevent writer starvation, writers are favored over readers. 57.Sh RETURN VALUES 58If successful, the 59.Fn pthread_rwlock_wrlock 60and 61.Fn pthread_rwlock_trywrlock 62functions will return zero. 63Otherwise an error number will be returned 64to indicate the error. 65.Sh ERRORS 66The 67.Fn pthread_rwlock_trywrlock 68function will fail if: 69.Bl -tag -width Er 70.It Bq Er EBUSY 71The calling thread is not able to acquire the lock without blocking. 72.El 73.Pp 74The 75.Fn pthread_rwlock_wrlock 76and 77.Fn pthread_rwlock_trywrlock 78functions may fail if: 79.Bl -tag -width Er 80.It Bq Er EDEADLK 81The calling thread already owns the read/write lock (for reading 82or writing). 83.It Bq Er EINVAL 84The value specified by 85.Fa lock 86is invalid. 87.It Bq Er ENOMEM 88Insufficient memory exists to initialize the lock (applies to 89statically initialized locks only). 90.El 91.Sh SEE ALSO 92.Xr pthread_rwlock_init 3 , 93.Xr pthread_rwlock_rdlock 3 , 94.Xr pthread_rwlock_tryrdlock 3 , 95.Xr pthread_rwlock_unlock 3 96.Sh STANDARDS 97The 98.Fn pthread_rwlock_wrlock 99and 100.Fn pthread_rwlock_trywrlock 101functions are expected to conform to 102.St -susv2 . 103.Sh HISTORY 104The 105.Fn pthread_rwlock_wrlock 106function first appeared in 107.Fx 3.0 . 108