On Sun, Aug 12, 2012 at 08:11:29AM +0800, David Xu wrote:
On 2012/08/10 18:13, Konstantin Belousov wrote:
On Thu, Aug 09, 2012 at 02:08:50PM +0300, Konstantin Belousov wrote:
Third alternative, which seems to be even better, is to restore
single-threading of the parent for vfork().
single-threading is slow for large threaded process, don't know if it
is necessary for vfork(), POSIX says nothing about threaded process.
I agree that with both of your statements. But, being fast but allowing
silent process corruption is not good behaviour. Either we need to
actually support vfork() for threaded processes, or disable it with some
error code.
I prefer to support it. I believe that vfork() should be wrapped by
libthr in the same way as fork() is wrapped. Not sure should we call
atfork handlers, for now I decided not to call, since the handlers
assume separate address spaces for parent/child. But we could only call
parent handler in child, however weird this sounds.
The real complication with wrapping is the fact that we cannot return
from wrapper in child without destroying parent state. So I tried to
prototype the code to handle the wrapping in the same frame, thus
neccessity of using asm.
Below is WIP, only for amd64 ATM.
diff --git a/lib/libthr/arch/amd64/Makefile.inc
b/lib/libthr/arch/amd64/Makefile.inc
index e6d99ec..476d26a 100644
--- a/lib/libthr/arch/amd64/Makefile.inc
+++ b/lib/libthr/arch/amd64/Makefile.inc
@@ -1,3 +1,4 @@
#$FreeBSD$
-SRCS+= pthread_md.c _umtx_op_err.S
+CFLAGS+=-I${.CURDIR}/../libc/${MACHINE_CPUARCH}
+SRCS+= pthread_md.c _umtx_op_err.S vfork.S
diff --git a/lib/libthr/arch/amd64/amd64/vfork.S
b/lib/libthr/arch/amd64/amd64/vfork.S
new file mode 100644
index 0000000..07d813d
--- /dev/null
+++ b/lib/libthr/arch/amd64/amd64/vfork.S
@@ -0,0 +1,74 @@
+/*-
+ * Copyright (c) 2012 Konstantin Belousov <k...@freebsd.org>
+ * Copyright (c) 1990 The Regents of the University of California.
+ * All rights reserved.
+ *
+ * This code is derived from software contributed to Berkeley by
+ * William Jolitz.
+ *
+ * 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.
+ * 4. Neither the name of the University nor the names of its contributors
+ * may be used to endorse or promote products derived from this software
+ * without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
+ */
+
+#if defined(SYSLIBC_SCCS) && !defined(lint)
+ .asciz "@(#)Ovfork.s 5.1 (Berkeley) 4/23/90"
+#endif /* SYSLIBC_SCCS and not lint */
+#include <machine/asm.h>
+__FBSDID("$FreeBSD$");
+
+#include "SYS.h"
+
+ .weak _vfork
+ .set _vfork,__sys_vfork
+ .weak vfork
+ .set vfork,__sys_vfork
+ENTRY(__sys_vfork)
+ call _thr_vfork_pre
+ popq %rsi /* fetch return address (%rsi preserved) */
+ mov $SYS_vfork,%rax
+ KERNCALL
+ jb 2f
+ cmpl $0,%eax
+ jne 1f
+ pushq %rsi
+ pushq %rsi /* twice for stack alignment */
+ call _thr_vfork_post
+ popq %rsi
+ popq %rsi
+ xorl %eax,%eax
+1:
+ jmp *%rsi
+2:
+ pushq %rsi
+ pushq %rax
+ call _thr_vfork_post
+ call PIC_PLT(CNAME(__error))
+ popq %rdx
+ movq %rdx,(%rax)
+ movq $-1,%rax
+ movq $-1,%rdx
+ retq
+END(__sys_vfork)
+
+ .section .note.GNU-stack,"",%progbits
diff --git a/lib/libthr/pthread.map b/lib/libthr/pthread.map
index 355edea..40d14b4 100644
--- a/lib/libthr/pthread.map
+++ b/lib/libthr/pthread.map
@@ -157,6 +157,7 @@ FBSD_1.0 {
system;
tcdrain;
usleep;
+ vfork;
wait;
wait3;
wait4;
diff --git a/lib/libthr/thread/Makefile.inc b/lib/libthr/thread/Makefile.inc
index ddde6e9..92e82ac 100644
--- a/lib/libthr/thread/Makefile.inc
+++ b/lib/libthr/thread/Makefile.inc
@@ -55,4 +55,5 @@ SRCS+= \
thr_switch_np.c \
thr_symbols.c \
thr_umtx.c \
+ thr_vfork.c \
thr_yield.c
diff --git a/lib/libthr/thread/thr_private.h b/lib/libthr/thread/thr_private.h
index ba272fe..30f3de2 100644
--- a/lib/libthr/thread/thr_private.h
+++ b/lib/libthr/thread/thr_private.h
@@ -777,6 +777,8 @@ int _thr_setscheduler(lwpid_t, int, const struct
sched_param *) __hidden;
void _thr_signal_prefork(void) __hidden;
void _thr_signal_postfork(void) __hidden;
void _thr_signal_postfork_child(void) __hidden;
+void _thr_vfork_pre(void) __hidden;
+void _thr_vfork_post(void) __hidden;
void _thr_try_gc(struct pthread *, struct pthread *) __hidden;
int _rtp_to_schedparam(const struct rtprio *rtp, int *policy,
struct sched_param *param) __hidden;
@@ -833,6 +835,7 @@ pid_t __sys_getpid(void);
ssize_t __sys_read(int, void *, size_t);
ssize_t __sys_write(int, const void *, size_t);
void __sys_exit(int);
+pid_t __sys_vfork(void);
#endif
static inline int
diff --git a/lib/libthr/thread/thr_vfork.c b/lib/libthr/thread/thr_vfork.c
new file mode 100644
index 0000000..bed7db5
--- /dev/null
+++ b/lib/libthr/thread/thr_vfork.c
@@ -0,0 +1,112 @@
+/*
+ * Copyright (c) 2012 Konstantin Belousov <k...@freebsd.org>
+ * Copyright (c) 2005 David Xu <davi...@freebsd.org>
+ * Copyright (c) 2003 Daniel Eischen <deisc...@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 <j...@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 "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"
+
+static int rtld_locks[MAX_RTLD_LOCKS];
+static int cancelsave, was_threaded;
+
+void
+_thr_vfork_pre(void)
+{
+ struct pthread *curthread;
+
+ curthread = _get_curthread();
+ _thr_rwl_rdlock(&_thr_atfork_lock);
+ cancelsave = curthread->no_cancel;
+ curthread->no_cancel = 1;
+ _thr_signal_block(curthread);
+ _thr_signal_prefork();
+ if (_thr_isthreaded() != 0) {
+ was_threaded = 1;
+ _malloc_prefork();
+ _rtld_atfork_pre(rtld_locks);
+ } else
+ was_threaded = 0;
+}
+
+void
+_thr_vfork_post(void)
+{
+ struct pthread *curthread;
+
+ _thr_signal_postfork();
+ if (was_threaded) {
+ _rtld_atfork_post(rtld_locks);
+ _malloc_postfork();
+ }
+ curthread = _get_curthread();
+ _thr_signal_unblock(curthread);
+ curthread->no_cancel = cancelsave;
+ _thr_rwlock_unlock(&_thr_atfork_lock);
+ if (curthread->cancel_async)
+ _thr_testcancel(curthread);
+}
diff --git a/sys/kern/kern_fork.c b/sys/kern/kern_fork.c
index 6cb95cd..8735c25 100644
--- a/sys/kern/kern_fork.c
+++ b/sys/kern/kern_fork.c
@@ -150,11 +150,7 @@ sys_vfork(struct thread *td, struct vfork_args *uap)
int error, flags;
struct proc *p2;
-#ifdef XEN
- flags = RFFDG | RFPROC; /* validate that this is still an issue */
-#else
flags = RFFDG | RFPROC | RFPPWAIT | RFMEM;
-#endif
error = fork1(td, flags, 0, &p2, NULL, 0);
if (error == 0) {
td->td_retval[0] = p2->p_pid;
@@ -756,7 +752,7 @@ fork1(struct thread *td, int flags, int pages, struct proc
**procp,
struct thread *td2;
struct vmspace *vm2;
vm_ooffset_t mem_charged;
- int error;
+ int error, single_threaded;
static int curfail;
static struct timeval lastfail;
#ifdef PROCDESC
@@ -815,6 +811,19 @@ fork1(struct thread *td, int flags, int pages, struct proc
**procp,
}
#endif
+ if (((p1->p_flag & (P_HADTHREADS | P_SYSTEM)) == P_HADTHREADS) &&
+ (flags & RFPPWAIT) != 0) {
+ PROC_LOCK(p1);
+ if (thread_single(SINGLE_BOUNDARY)) {
+ PROC_UNLOCK(p1);
+ error = ERESTART;
+ goto fail2;
+ }
+ PROC_UNLOCK(p1);
+ single_threaded = 1;
+ } else
+ single_threaded = 0;
+
mem_charged = 0;
vm2 = NULL;
if (pages == 0)
@@ -945,6 +954,12 @@ fail1:
if (vm2 != NULL)
vmspace_free(vm2);
uma_zfree(proc_zone, newproc);
+ if (single_threaded) {
+ PROC_LOCK(p1);
+ thread_single_end();
+ PROC_UNLOCK(p1);
+ }
+fail2:
#ifdef PROCDESC
if (((flags & RFPROCDESC) != 0) && (fp_procdesc != NULL)) {
fdclose(td->td_proc->p_fd, fp_procdesc, *procdescp, td);
