[apple/libc.git] / pthreads / pthread_rwlock_wrlock.3

.\" Copyright (c) 1998 Alex Nash
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $FreeBSD: src/lib/libc_r/man/pthread_rwlock_wrlock.3,v 1.4 2001/10/01 16:09:09 ru Exp $
.\"
.Dd August 4, 1998
.Dt PTHREAD_RWLOCK_WRLOCK 3
.Os
.Sh NAME
.Nm pthread_rwlock_wrlock ,
.Nm pthread_rwlock_trywrlock
.Nd acquire a read/write lock for writing
.Sh SYNOPSIS
.In pthread.h
.Ft int
.Fn pthread_rwlock_wrlock "pthread_rwlock_t *lock"
.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 .
The
.Fn pthread_rwlock_trywrlock
function performs the same action, 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 IMPLEMENTATION NOTES
To prevent writer starvation, writers are favored over readers.
.Sh RETURN VALUES
If successful, the
.Fn pthread_rwlock_wrlock
and
.Fn pthread_rwlock_trywrlock
functions will return zero.  Otherwise an error number will be returned
to indicate the error.
.Sh SEE ALSO
.Xr pthread_rwlock_trywrlock 3 ,
.Xr pthread_rwlock_unlock 3 ,
.Xr pthread_rwlock_wrlock 3
.Sh STANDARDS
The
.Fn pthread_rwlock_wrlock
and
.Fn pthread_rwlock_trywrlock
functions are expected to conform to
.St -susv2 .
.Sh ERRORS
The
.Fn pthread_rwlock_trywrlock
function will 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_wrlock
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.
.It Bq Er ENOMEM
Insufficient memory exists to initialize the lock (applies to
statically initialized locks only).
.El
.Sh HISTORY
The
.Fn pthread_rwlock_wrlock
function first appeared in
.Fx 3.0 .
Commit	Line	Data
5b2abdfb A	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: src/lib/libc_r/man/pthread_rwlock_wrlock.3,v 1.4 2001/10/01 16:09:09 ru Exp $
	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 SYNOPSIS
	35	.In pthread.h
	36	.Ft int
	37	.Fn pthread_rwlock_wrlock "pthread_rwlock_t *lock"
	38	.Ft int
	39	.Fn pthread_rwlock_trywrlock "pthread_rwlock_t *lock"
	40	.Sh DESCRIPTION
	41	The
	42	.Fn pthread_rwlock_wrlock
	43	function blocks until a write lock can be acquired against
	44	.Fa lock .
	45	The
	46	.Fn pthread_rwlock_trywrlock
	47	function performs the same action, but does not block if the lock
	48	cannot be immediately obtained.
	49	.Pp
	50	The results are undefined if the calling thread already holds the
	51	lock at the time the call is made.
	52	.Sh IMPLEMENTATION NOTES
	53	To prevent writer starvation, writers are favored over readers.
	54	.Sh RETURN VALUES
	55	If successful, the
	56	.Fn pthread_rwlock_wrlock
	57	and
	58	.Fn pthread_rwlock_trywrlock
	59	functions will return zero. Otherwise an error number will be returned
	60	to indicate the error.
	61	.Sh SEE ALSO
	62	.Xr pthread_rwlock_trywrlock 3 ,
	63	.Xr pthread_rwlock_unlock 3 ,
	64	.Xr pthread_rwlock_wrlock 3
65	.Sh STANDARDS
66	The
67	.Fn pthread_rwlock_wrlock
68	and
69	.Fn pthread_rwlock_trywrlock
70	functions are expected to conform to
71	.St -susv2 .
72	.Sh ERRORS
73	The
74	.Fn pthread_rwlock_trywrlock
75	function will fail if:
76	.Bl -tag -width Er
77	.It Bq Er EBUSY
78	The calling thread is not able to acquire the lock without blocking.
79	.El
80	.Pp
81	The
82	.Fn pthread_rwlock_wrlock
83	and
84	.Fn pthread_rwlock_trywrlock
85	functions may fail if:
86	.Bl -tag -width Er
87	.It Bq Er EDEADLK
88	The calling thread already owns the read/write lock (for reading
89	or writing).
90	.It Bq Er EINVAL
91	The value specified by
92	.Fa lock
93	is invalid.
94	.It Bq Er ENOMEM
95	Insufficient memory exists to initialize the lock (applies to
96	statically initialized locks only).
97	.El
98	.Sh HISTORY
99	The
100	.Fn pthread_rwlock_wrlock
101	function first appeared in
102	.Fx 3.0 .