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Revision 1.5, Wed Apr 30 13:10:50 2008 UTC (5 years, 1 month ago) by martin
Convert TNF licenses to new 2 clause variant
.\" $NetBSD: pthread_atfork.3,v 1.5 2008/04/30 13:10:50 martin 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. .\" .\" 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 .