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/*
* fork.c
*
* Description:
* Implementation of fork() for POSIX threads.
*/
#include "pthread.h"
#include "implement.h"
int
pthread_atfork(void (*prepare)(void),
void (*parent)(void),
void (*child)(void))
{
/* Push handlers (unless NULL) onto their respective stacks.
Local implementation semantics:
If we get an ENOMEM at any time in here then ALL handlers
(including those from previous pthread_atfork() calls) will be
popped off each of the three atfork stacks before we return. */
int ret = 0;
if (prepare != NULL)
{
/* Push prepare. */
if (_pthread_handler_push(_PTHREAD_FORKPREPARE_STACK,
_PTHREAD_HANDLER_POP_FIFO,
(void (*prepare)(void *)), NULL) == ENOMEM)
{
ret = ENOMEM;
}
}
if (parent != NULL &&
ret != ENOMEM)
{
/* Push parent. */
if (_pthread_handler_push(_PTHREAD_FORKPARENT_STACK,
_PTHREAD_HANDLER_POP_LIFO,
(void (*parent)(void *)), NULL) == ENOMEM)
{
ret = ENOMEM;
}
}
if (child != NULL &&
ret != ENOMEM)
{
/* Push child. */
if (_pthread_handler_push(_PTHREAD_FORKCHILD_STACK,
_PTHREAD_HANDLER_POP_LIFO,
(void (*child)(void *)), arg) == ENOMEM)
{
ret = ENOMEM;
}
}
if (ret == ENOMEM)
{
/* Pop all handlers without executing them before we return
the error. */
_pthread_handler_pop_all(_PTHREAD_FORKPREPARE_STACK,
_PTHREAD_HANDLER_NOEXECUTE);
_pthread_handler_pop_all(_PTHREAD_FORKPARENT_STACK,
_PTHREAD_HANDLER_NOEXECUTE);
_pthread_handler_pop_all(_PTHREAD_FORKCHILD_STACK,
_PTHREAD_HANDLER_NOEXECUTE);
}
return ret;
}
/* It looks like the GNU linker is capable of selecting this version of
fork() over a version provided in more primitive libraries further down
the linker command line. */
#if HAVE_PID_T && HAVE_FORK
pid_t
fork()
{
pid_t pid;
/* Pop prepare handlers here. */
_pthread_handler_pop_all(_PTHREAD_FORKPREPARE_STACK,
_PTHREAD_HANDLER_EXECUTE);
/* Now call the real fork(). */
if ((pid = _fork()) > 0)
{
/* PARENT */
/* Clear the child handler stack. */
_pthread_handler_pop_all(_PTHREAD_FORKCHILD_STACK,
_PTHREAD_HANDLER_NOEXECUTE);
/* Pop parent handlers and execute them. */
_pthread_handler_pop_all(_PTHREAD_FORKPARENT_STACK,
_PTHREAD_HANDLER_EXECUTE);
/* At this point all three atfork stacks are empty. */
return pid;
}
else
{
/* CHILD */
/* Clear the parent handler stack. */
_pthread_handler_pop_all(_PTHREAD_FORKPARENT_STACK,
_PTHREAD_HANDLER_NOEXECUTE);
/* Pop child handlers and execute them. */
_pthread_handler_pop_all(_PTHREAD_FORKCHILD_STACK,
_PTHREAD_HANDLER_EXECUTE);
/* At this point all three atfork stacks are empty. */
/* Terminate all threads except pthread_self() using
pthread_cancel(). */
_pthread_cancel_all_not_self();
/* Wait for them to finish before we continue. */
_pthread_join_all_not_self();
return 0;
}
/* Not reached. */
}
#endif /* HAVE_PID_T && HAVE_FORK */
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