Provided by: glibc-doc_2.9-4ubuntu6_all
pthread_atfork - register handlers to be called at fork(2) time
int pthread_atfork(void (*prepare)(void), void (*parent)(void), void
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
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,
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.
pthread_atfork returns 0 on success and a non-zero error code on error.
ENOMEM insufficient memory available to register the handlers.
Xavier Leroy <Xavier.Leroy@inria.fr>
fork(2), pthread_mutex_lock(3), pthread_mutex_unlock(3).