pthread_atfork —
specify handler functions to call when the process
forks
#include
<pthread.h>
int
pthread_atfork(
void
(*prepare)(void),
void
(*parent)(void),
void
(*child)(void));
The
pthread_atfork() function declares fork
handlers to be called before and after
fork(2), in the context of the
thread that called
fork(2). The
prepare fork handler will be called before
fork(2) processing commences. The
parent fork handler will be called after
fork(2) processing completes in
the parent process. The
child fork handler
will be called after
fork(2)
processing completes in the child process. If no handling is desired at one or
more of these three points, the corresponding fork handler address(es) may be
set to
NULL.
The order of calls to
pthread_atfork() is
significant. The
parent and
child fork handlers will be called in the
order in which they were established by calls to
pthread_atfork(). The
prepare fork handlers will be called in the
opposite order.
If a shared object is unloaded from process memory using
dlclose(3), then any functions
registered by calling
pthread_atfork() from
that shared object will be unregistered without being invoked. Note that it is
the source of the call to
pthread_atfork()
that matters, not the source of the functions that were registered.
Upon successful completion,
pthread_atfork()
will return a value of zero. Otherwise, an error number will be returned to
indicate the error.
pthread_atfork() will fail if:
-
-
- [
ENOMEM]
- Insufficient table space exists to record the fork handler addresses. None
of the handler lists are modified.
fork(2),
atexit(3),
dlclose(3)
pthread_atfork() conforms to
IEEE Std 1003.1-2004
(“POSIX.1”).
The behavior when a shared object is unloaded is an extension to that
standard.
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