netbsd man page for pthread_atfork

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