NetBSD/lib/libpthread/pthread_cond_wait.3

169 lines
5.7 KiB
Groff
Raw Normal View History

2003-07-04 14:19:42 +04:00
.\" $NetBSD: pthread_cond_wait.3,v 1.5 2003/07/04 10:19:42 wiz Exp $
.\"
.\" Copyright (c) 2002 The NetBSD Foundation, Inc.
.\" 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.
.\" 3. Neither the name of The NetBSD Foundation nor the names of its
.\" contributors may be used to endorse or promote products derived
.\" from this software without specific prior written permission.
.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. 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 FOUNDATION 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.
.\"
.\" Copyright (c) 1997 Brian Cully <shmit@kublai.com>
.\" 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.
.\" 3. Neither the name of the author nor the names of any co-contributors
.\" may be used to endorse or promote products derived from this software
.\" without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL 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 REGENTS 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/libpthread/man/pthread_cond_wait.3,v 1.16 2002/09/16 19:29:28 mini Exp $
.\"
.Dd January 30, 2003
.Dt PTHREAD_COND_WAIT 3
.Os
.Sh NAME
.Nm pthread_cond_wait ,
.Nm pthread_cond_timedwait
.Nd wait on a condition variable
.Sh LIBRARY
.Lb libpthread
.Sh SYNOPSIS
.In pthread.h
.Ft int
.Fn pthread_cond_wait "pthread_cond_t *cond" "pthread_mutex_t *mutex"
.Ft int
.Fn pthread_cond_timedwait "pthread_cond_t *cond" "pthread_mutex_t *mutex" "const struct timespec *abstime"
.Sh DESCRIPTION
The
.Fn pthread_cond_wait
function atomically blocks the current thread waiting on the condition
variable specified by
.Fa cond ,
and unblocks the mutex specified by
.Fa mutex .
The waiting thread unblocks after another thread calls
.Xr pthread_cond_signal 3 ,
or
.Xr pthread_cond_broadcast 3
2003-07-04 14:19:42 +04:00
with the same condition variable.
The current thread holds the lock on
2003-07-04 12:36:06 +04:00
.Fa mutex
upon return from the
.Fa pthread_cond_wait
call.
.Pp
The
.Fn pthread_cond_timedwait
function atomically blocks the current thread waiting on the condition
variable specified by
.Fa cond ,
and unblocks the mutex specified by
.Fa mutex .
The waiting thread unblocks after another thread calls
.Xr pthread_cond_signal 3 ,
or
.Xr pthread_cond_broadcast 3
with the same condition variable, or if the system time reaches the
time specified in
.Fa abstime .
.Pp
Note that a call to
.Fn pthread_cond_wait
or
.Fn pthread_cond_timedwait
may wake up spontaneously, without a call to
.Xr pthread_cond_signal 3
or
.Xr pthread_cond_broadcast 3 .
The caller should prepare for this by invoking
.Fn pthread_cond_wait
or
.Fn pthread_cond_timedwait
within a predicate loop that tests whether the thread should proceed.
.Sh RETURN VALUES
If successful, the
.Fn pthread_cond_wait
and
.Fn pthread_cond_timedwait
functions will return zero.
Otherwise an error number will be returned to
indicate the error.
.Sh ERRORS
.Fn pthread_cond_wait
may fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
The value specified by
.Fa cond
or the value specified by
.Fa mutex
is invalid.
.El
.Pp
.Fn pthread_cond_timedwait
shall fail if:
.Bl -tag -width Er
.It Bq Er ETIMEDOUT
The system time has reached or exceeded the time specified in
.Fa abstime .
.El
.Pp
.Fn pthread_cond_timedwait
may fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
The value specified by
.Fa cond ,
.Fa mutex ,
or
.Fa abstime
is invalid.
.El
.Sh SEE ALSO
.Xr pthread_cond_broadcast 3 ,
.Xr pthread_cond_destroy 3 ,
.Xr pthread_cond_init 3 ,
2003-07-04 12:41:25 +04:00
.Xr pthread_cond_signal 3
.Sh STANDARDS
.Fn pthread_cond_wait
and
.Fn pthread_cond_timedwait
conform to
.St -p1003.1-96 .