freebsd-dev/lib/libthr/thread/thr_fork.c
Konstantin Belousov 53fd961f05 Lock pshared_lock shared around fork, to ensure that the COW snapshot
of the pshared hash in child is consistent and can be safely used.

Reported and tested by:	"Oleg V. Nauman" <oleg@opentransfer.com>
Sponsored by:	The FreeBSD Foundation
2016-03-21 06:52:35 +00:00

265 lines
7.7 KiB
C

/*
* Copyright (c) 2005 David Xu <davidxu@freebsd.org>
* Copyright (c) 2003 Daniel Eischen <deischen@freebsd.org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Neither the name of the author nor the names of any co-contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* $FreeBSD$
*/
/*
* Copyright (c) 1995-1998 John Birrell <jb@cimlogic.com.au>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the author nor the names of any co-contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
*/
#include <sys/syscall.h>
#include "namespace.h"
#include <errno.h>
#include <link.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>
#include <spinlock.h>
#include "un-namespace.h"
#include "libc_private.h"
#include "rtld_lock.h"
#include "thr_private.h"
__weak_reference(_pthread_atfork, pthread_atfork);
int
_pthread_atfork(void (*prepare)(void), void (*parent)(void),
void (*child)(void))
{
struct pthread *curthread;
struct pthread_atfork *af;
_thr_check_init();
if ((af = malloc(sizeof(struct pthread_atfork))) == NULL)
return (ENOMEM);
curthread = _get_curthread();
af->prepare = prepare;
af->parent = parent;
af->child = child;
THR_CRITICAL_ENTER(curthread);
_thr_rwl_wrlock(&_thr_atfork_lock);
TAILQ_INSERT_TAIL(&_thr_atfork_list, af, qe);
_thr_rwl_unlock(&_thr_atfork_lock);
THR_CRITICAL_LEAVE(curthread);
return (0);
}
void
__pthread_cxa_finalize(struct dl_phdr_info *phdr_info)
{
atfork_head temp_list = TAILQ_HEAD_INITIALIZER(temp_list);
struct pthread *curthread;
struct pthread_atfork *af, *af1;
_thr_check_init();
curthread = _get_curthread();
THR_CRITICAL_ENTER(curthread);
_thr_rwl_wrlock(&_thr_atfork_lock);
TAILQ_FOREACH_SAFE(af, &_thr_atfork_list, qe, af1) {
if (__elf_phdr_match_addr(phdr_info, af->prepare) ||
__elf_phdr_match_addr(phdr_info, af->parent) ||
__elf_phdr_match_addr(phdr_info, af->child)) {
TAILQ_REMOVE(&_thr_atfork_list, af, qe);
TAILQ_INSERT_TAIL(&temp_list, af, qe);
}
}
_thr_rwl_unlock(&_thr_atfork_lock);
THR_CRITICAL_LEAVE(curthread);
while ((af = TAILQ_FIRST(&temp_list)) != NULL) {
TAILQ_REMOVE(&temp_list, af, qe);
free(af);
}
_thr_tsd_unload(phdr_info);
_thr_sigact_unload(phdr_info);
}
__weak_reference(__thr_fork, _fork);
pid_t
__thr_fork(void)
{
struct pthread *curthread;
struct pthread_atfork *af;
pid_t ret;
int errsave, cancelsave;
int was_threaded;
int rtld_locks[MAX_RTLD_LOCKS];
if (!_thr_is_inited())
return (__sys_fork());
curthread = _get_curthread();
cancelsave = curthread->no_cancel;
curthread->no_cancel = 1;
_thr_rwl_rdlock(&_thr_atfork_lock);
/* Run down atfork prepare handlers. */
TAILQ_FOREACH_REVERSE(af, &_thr_atfork_list, atfork_head, qe) {
if (af->prepare != NULL)
af->prepare();
}
/*
* Block all signals until we reach a safe point.
*/
_thr_signal_block(curthread);
_thr_signal_prefork();
/*
* All bets are off as to what should happen soon if the parent
* process was not so kindly as to set up pthread fork hooks to
* relinquish all running threads.
*/
if (_thr_isthreaded() != 0) {
was_threaded = 1;
_malloc_prefork();
__thr_pshared_atfork_pre();
_rtld_atfork_pre(rtld_locks);
} else {
was_threaded = 0;
}
/*
* Fork a new process.
* There is no easy way to pre-resolve the __sys_fork symbol
* without performing the fork. Use the syscall(2)
* indirection, the syscall symbol is resolved in
* _thr_rtld_init() with side-effect free call.
*/
ret = syscall(SYS_fork);
if (ret == 0) {
/* Child process */
errsave = errno;
curthread->cancel_pending = 0;
curthread->flags &= ~(THR_FLAGS_NEED_SUSPEND|THR_FLAGS_DETACHED);
/*
* Thread list will be reinitialized, and later we call
* _libpthread_init(), it will add us back to list.
*/
curthread->tlflags &= ~TLFLAGS_IN_TDLIST;
/* child is a new kernel thread. */
thr_self(&curthread->tid);
/* clear other threads locked us. */
_thr_umutex_init(&curthread->lock);
_mutex_fork(curthread);
_thr_signal_postfork_child();
if (was_threaded) {
_rtld_atfork_post(rtld_locks);
__thr_pshared_atfork_post();
}
_thr_setthreaded(0);
/* reinitalize library. */
_libpthread_init(curthread);
/* atfork is reinitialized by _libpthread_init()! */
_thr_rwl_rdlock(&_thr_atfork_lock);
if (was_threaded) {
__isthreaded = 1;
_malloc_postfork();
__isthreaded = 0;
}
/* Ready to continue, unblock signals. */
_thr_signal_unblock(curthread);
/* Run down atfork child handlers. */
TAILQ_FOREACH(af, &_thr_atfork_list, qe) {
if (af->child != NULL)
af->child();
}
_thr_rwlock_unlock(&_thr_atfork_lock);
curthread->no_cancel = cancelsave;
} else {
/* Parent process */
errsave = errno;
_thr_signal_postfork();
if (was_threaded) {
_rtld_atfork_post(rtld_locks);
__thr_pshared_atfork_post();
_malloc_postfork();
}
/* Ready to continue, unblock signals. */
_thr_signal_unblock(curthread);
/* Run down atfork parent handlers. */
TAILQ_FOREACH(af, &_thr_atfork_list, qe) {
if (af->parent != NULL)
af->parent();
}
_thr_rwlock_unlock(&_thr_atfork_lock);
curthread->no_cancel = cancelsave;
/* test async cancel */
if (curthread->cancel_async)
_thr_testcancel(curthread);
}
errno = errsave;
return (ret);
}