.TH PTHREAD_ATFORK 3 LinuxThreads

.SH NAME
pthread_atfork \- register handlers to be called at fork(2) time

.SH SYNOPSIS
#include <pthread.h>

int pthread_atfork(void (*prepare)(void), void (*parent)(void), void (*child)(void));

.SH DESCRIPTION

!pthread_atfork! registers handler functions to be called just before
and just after a new process is created with !fork!(2). The |prepare|
handler will be called from the parent process, just before the new
process is created. The |parent| handler will be called from the parent
process, just before !fork!(2) returns. The |child| handler will be
called from the child process, just before !fork!(2) returns.

One or several of the three handlers |prepare|, |parent| and |child|
can be given as !NULL!, meaning that no handler needs to be called at
the corresponding point.

!pthread_atfork! can be called several times to install several sets
of handlers. At !fork!(2) time, the |prepare| handlers are called in
LIFO order (last added with !pthread_atfork!, first called before !fork!),
while the |parent| and |child| handlers are called in FIFO order
(first added, first called).

To understand the purpose of !pthread_atfork!, recall that !fork!(2)
duplicates the whole memory space, including mutexes in their current
locking state, but only the calling thread: other threads are not
running in the child process.  The mutexes are not usable after the
!fork! and must be initialized with |pthread_mutex_init| in the child
process.  This is a limitation of the current implementation and might
or might not be present in future versions.

.SH "RETURN VALUE"

!pthread_atfork! returns 0 on success and a non-zero error code on error.

.SH ERRORS
.TP
!ENOMEM!
insufficient memory available to register the handlers.

.SH AUTHOR
Xavier Leroy <Xavier.Leroy@inria.fr>

.SH "SEE ALSO"
!fork!(2),
!pthread_mutex_lock!(3),
!pthread_mutex_unlock!(3).