128 lines
4.2 KiB
Groff
128 lines
4.2 KiB
Groff
.\" $NetBSD: pthread_atfork.3,v 1.4 2005/06/17 18:08:00 peter Exp $
|
|
.\"
|
|
.\" Copyright (c) 2003 The NetBSD Foundation, Inc.
|
|
.\" All rights reserved.
|
|
.\"
|
|
.\" This code is derived from software contributed to The NetBSD Foundation
|
|
.\" by Nathan J. Williams.
|
|
.\"
|
|
.\" 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. All advertising materials mentioning features or use of this software
|
|
.\" must display the following acknowledgement:
|
|
.\" This product includes software developed by the NetBSD
|
|
.\" Foundation, Inc. and its contributors.
|
|
.\" 4. 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.
|
|
.\"
|
|
.Dd February 12, 2003
|
|
.Dt PTHREAD_ATFORK 3
|
|
.Os
|
|
.Sh NAME
|
|
.Nm pthread_atfork
|
|
.Nd register handlers to be called when process forks
|
|
.Sh LIBRARY
|
|
.Lb libc
|
|
.Sh SYNOPSIS
|
|
.In pthread.h
|
|
.Ft int
|
|
.Fn pthread_atfork "void (*prepare)(void)" "void (*parent)(void)" "void (*child)(void)"
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Fn pthread_atfork
|
|
function registers the provided handler functions to be called when the
|
|
.Xr fork 2
|
|
function is called.
|
|
Each of the three handlers is called at a different place in the
|
|
.Xr fork 2
|
|
sequence.
|
|
The
|
|
.Ar prepare
|
|
handler is called in the parent process before the fork happens, the
|
|
.Ar parent
|
|
handler is called in the parent process after the fork has happened, and the
|
|
.Ar child
|
|
handler is called in the child process after the fork has happened.
|
|
The
|
|
.Ar parent
|
|
and
|
|
.Ar child
|
|
handlers are called in the order in which they were registered, while the
|
|
.Ar prepare
|
|
handlers are called in reverse of the order in which they were registered.
|
|
.Pp
|
|
Any of the handlers given may be
|
|
.Dv NULL .
|
|
.Pp
|
|
The intended use of
|
|
.Fn pthread_atfork
|
|
is to provide a consistent state to a child process from a multithreaded parent
|
|
process where locks may be acquired and released asynchronously with respect to the
|
|
.Xr fork 2
|
|
call.
|
|
Each subsystem with locks that are used in a child process should register
|
|
handlers with
|
|
.Fn pthread_atfork
|
|
that acquires those locks in the
|
|
.Ar prepare
|
|
handler and releases them in the
|
|
.Ar parent
|
|
handler.
|
|
.Sh RETURN VALUES
|
|
The
|
|
.Fn pthread_atfork
|
|
function returns 0 on success and an error number on failure.
|
|
.Sh ERRORS
|
|
The following error code may be returned:
|
|
.Bl -tag -width Er
|
|
.It Bq Er ENOMEM
|
|
Insufficient memory exists to register the fork handlers.
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr fork 2
|
|
.Sh STANDARDS
|
|
The
|
|
.Fn pthread_atfork
|
|
function conforms to
|
|
.St -p1003.1c-95 .
|
|
.Sh HISTORY
|
|
The
|
|
.Fn pthread_atfork
|
|
function first appeared in
|
|
.Nx 2.0 .
|
|
.Sh CAVEATS
|
|
After calling
|
|
.Xr fork 2
|
|
from a multithreaded process, it is only safe to call
|
|
async-signal-safe functions until calling one of the
|
|
.Xr exec 3
|
|
functions.
|
|
The
|
|
.Fn pthread_*
|
|
functions are not async-signal-safe, so it is not safe to use such functions
|
|
in the
|
|
.Ar child
|
|
handler.
|
|
.Sh BUGS
|
|
There is no way to unregister a handler registered with
|
|
.Fn pthread_atfork .
|