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/* Copyright (C) 2002-2020 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <assert.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sysdep.h>
#include <libio/libioP.h>
#include <tls.h>
#include <hp-timing.h>
#include <ldsodefs.h>
#include <stdio-lock.h>
#include <atomic.h>
#include <nptl/pthreadP.h>
#include <fork.h>
#include <arch-fork.h>
#include <futex-internal.h>
#include <malloc/malloc-internal.h>
static void
fresetlockfiles (void)
{
_IO_ITER i;
for (i = _IO_iter_begin(); i != _IO_iter_end(); i = _IO_iter_next(i))
if ((_IO_iter_file (i)->_flags & _IO_USER_LOCK) == 0)
_IO_lock_init (*((_IO_lock_t *) _IO_iter_file(i)->_lock));
}
pid_t
__libc_fork (void)
{
pid_t pid;
/* Determine if we are running multiple threads. We skip some fork
handlers in the single-thread case, to make fork safer to use in
signal handlers. POSIX requires that fork is async-signal-safe,
but our current fork implementation is not. */
bool multiple_threads = THREAD_GETMEM (THREAD_SELF, header.multiple_threads);
__run_fork_handlers (atfork_run_prepare, multiple_threads);
/* If we are not running multiple threads, we do not have to
preserve lock state. If fork runs from a signal handler, only
async-signal-safe functions can be used in the child. These data
structures are only used by unsafe functions, so their state does
not matter if fork was called from a signal handler. */
if (multiple_threads)
{
_IO_list_lock ();
/* Acquire malloc locks. This needs to come last because fork
handlers may use malloc, and the libio list lock has an
indirect malloc dependency as well (via the getdelim
function). */
call_function_static_weak (__malloc_fork_lock_parent);
}
pid = arch_fork (&THREAD_SELF->tid);
if (pid == 0)
{
struct pthread *self = THREAD_SELF;
/* See __pthread_once. */
if (__fork_generation_pointer != NULL)
*__fork_generation_pointer += __PTHREAD_ONCE_FORK_GEN_INCR;
#ifdef __NR_set_robust_list
/* Initialize the robust mutex list setting in the kernel which has
been reset during the fork. We do not check for errors because if
it fails here, it must have failed at process startup as well and
nobody could have used robust mutexes.
Before we do that, we have to clear the list of robust mutexes
because we do not inherit ownership of mutexes from the parent.
We do not have to set self->robust_head.futex_offset since we do
inherit the correct value from the parent. We do not need to clear
the pending operation because it must have been zero when fork was
called. */
# if __PTHREAD_MUTEX_HAVE_PREV
self->robust_prev = &self->robust_head;
# endif
self->robust_head.list = &self->robust_head;
# ifdef SHARED
if (__builtin_expect (__libc_pthread_functions_init, 0))
PTHFCT_CALL (ptr_set_robust, (self));
# else
extern __typeof (__nptl_set_robust) __nptl_set_robust
__attribute__((weak));
if (__builtin_expect (__nptl_set_robust != NULL, 0))
__nptl_set_robust (self);
# endif
#endif
/* Reset the lock state in the multi-threaded case. */
if (multiple_threads)
{
/* Release malloc locks. */
call_function_static_weak (__malloc_fork_unlock_child);
/* Reset the file list. These are recursive mutexes. */
fresetlockfiles ();
/* Reset locks in the I/O code. */
_IO_list_resetlock ();
}
/* Reset the lock the dynamic loader uses to protect its data. */
__rtld_lock_initialize (GL(dl_load_lock));
/* Run the handlers registered for the child. */
__run_fork_handlers (atfork_run_child, multiple_threads);
}
else
{
/* Release acquired locks in the multi-threaded case. */
if (multiple_threads)
{
/* Release malloc locks, parent process variant. */
call_function_static_weak (__malloc_fork_unlock_parent);
/* We execute this even if the 'fork' call failed. */
_IO_list_unlock ();
}
/* Run the handlers registered for the parent. */
__run_fork_handlers (atfork_run_parent, multiple_threads);
}
return pid;
}
weak_alias (__libc_fork, __fork)
libc_hidden_def (__fork)
weak_alias (__libc_fork, fork)
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