pthread_atfork(3) [netbsd man page]

PTHREAD_ATFORK(3)					   BSD Library Functions Manual 					 PTHREAD_ATFORK(3)

NAME

     pthread_atfork -- register handlers to be called when process forks

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <pthread.h>

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

DESCRIPTION

     The pthread_atfork() function registers the provided handler functions to be called when the fork(2) function is called.  Each of the three
     handlers is called at a different place in the fork(2) sequence.  The prepare handler is called in the parent process before the fork hap-
     pens, the parent handler is called in the parent process after the fork has happened, and the child handler is called in the child process
     after the fork has happened.  The parent and child handlers are called in the order in which they were registered, while the prepare handlers
     are called in reverse of the order in which they were registered.

     Any of the handlers given may be NULL.

     The intended use of 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 fork(2) call.	Each subsystem with locks that are used in a child process should
     register handlers with pthread_atfork() that acquires those locks in the prepare handler and releases them in the parent handler.

RETURN VALUES

     The pthread_atfork() function returns 0 on success and an error number on failure.

ERRORS

     The following error code may be returned:

     [ENOMEM]		Insufficient memory exists to register the fork handlers.

SEE ALSO

     fork(2)

STANDARDS

     The pthread_atfork() function conforms to IEEE Std 1003.1c-1995 (``POSIX.1'').

HISTORY

     The pthread_atfork() function first appeared in NetBSD 2.0.

CAVEATS

     After calling fork(2) from a multithreaded process, it is only safe to call async-signal-safe functions until calling one of the exec(3)
     functions.  The pthread_*() functions are not async-signal-safe, so it is not safe to use such functions in the child handler.

BUGS

     There is no way to unregister a handler registered with pthread_atfork().

BSD
								 February 12, 2003							       BSD

Check Out this Related Man Page

PTHREAD_ATFORK(3)					     Library Functions Manual						 PTHREAD_ATFORK(3)

NAME

       pthread_atfork - register handlers to be called at fork(2) time

SYNOPSIS

       #include <pthread.h>

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

DESCRIPTION

       pthread_atfork  registers handler functions to be called just before and just after a new process is created with fork(2). The prepare han-
       dler 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 cor-
       responding 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.

RETURN VALUE

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

ERRORS

       ENOMEM insufficient memory available to register the handlers.

AUTHOR

       Xavier Leroy <Xavier.Leroy@inria.fr>

SEE ALSO

       fork(2), pthread_mutex_lock(3), pthread_mutex_unlock(3).

								   LinuxThreads 						 PTHREAD_ATFORK(3)

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pthread_atfork(3) [netbsd man page]

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