system() using vfork() or posix_spawn() and libthr
Jilles Tjoelker
jilles at stack.nl
Sun Aug 26 22:04:44 UTC 2012
On Sun, Aug 19, 2012 at 03:26:36PM +0300, Konstantin Belousov wrote:
> On Fri, Aug 17, 2012 at 06:08:47PM +0200, Jilles Tjoelker wrote:
> > On Fri, Aug 17, 2012 at 03:43:12PM +0300, Konstantin Belousov wrote:
> > > On Fri, Aug 17, 2012 at 12:39:33AM +0200, Jilles Tjoelker wrote:
> > > > On Thu, Aug 16, 2012 at 02:44:26PM +0300, Konstantin Belousov wrote:
> > > > > BTW, returning to Jilles proposal, can we call vfork() only for
> > > > > single-threaded parent ? I think it gives good boost for single-threaded
> > > > > case, and also eliminates the concerns of non-safety.
> > > > This would probably fix the safety issues but at a price. There is a
> > > > correlation between processes so large that they benefit greatly from
> > > > vfork and threaded processes.
> > > Ok, so I will continue with my patch.
> > > > On the other hand, I think direct calls to vfork() in applications are
> > > > risky and it may not be possible to support them safely in all
> > > > circumstances. However, if libc is calling vfork() such as via popen(),
> > > > system() or posix_spawn(), it should be possible even in a
> > > > multi-threaded process. In that case, the rtld and libthr problems can
> > > > be avoided by using aliases with hidden visibility for all functions the
> > > > vforked child needs to call (or any other method that prevents
> > > > interposition and hard-codes a displacement into libc.so).
> > > I do not see how using any aliases could help there. Basically, if mt
> > > process is not single-threaded for vfork, you can have both some parent
> > > thread and child enter rtld. This is complete mess.
> > If libc calls a function with hidden visibility, this proceeds directly
> > (not via the PLT) and rtld is not involved.
> Oh, so you are only concerned with libc there ?
> If spending so much efforts on this issue, IMO it is pity to only fix
> libc and not fix vfork for all consumers.
True. If vfork can be fixed more generally without too much penalty, it
is better to do that. And it looks like that is possible, including
detecting unexpected kills, see below.
> > Several ways to do this are in section 2.2.7 Avoid Using Exported
> > Symbols of Ulrich Drepper's dsohowto. One of them is something like
> > extern __typeof(next) next_int
> > __attribute((alias("next"), visibility("hidden")));
> > in the same source as the definition of the function
> > int next(void) { ...; }
> > As Drepper notes, the visibility attribute is not strictly required if a
> > version script keeps the symbol local but it might lead to better code.
> > At least on i386, though, the optimal direct near call instruction is
> > generated even without it. For example, _nsdispatch() calls
> > libc_dlopen() (kept local by the version script) without going through
> > the PLT (from the output of objdump -dS on the libc.so.7 in /usr/obj).
> I am not confident, so this might be a hallucination, but 'optimization'
> in the recent gnu ld might rewrite the call target to avoid PLT when
> symbol visibility is hidden.
If symbol visibility is hidden, rtld does not know about the symbol's
name; therefore, the only way ld can make it work is to make the call
instruction point directly at the called function, not to a PLT entry.
Different from what I wrote earlier, on i386, there is still a penalty
in omitting the visibility attribute: the compiler will generate code to
load %ebx which may not be necessary.
> > In the assembler syscall stubs using code from lib/libc/arch/SYS.h this
> > can be done by adding another .set (we currently have foo, _foo and
> > __sys_foo for a syscall foo; some syscalls have only _foo and
> > __sys_foo) such as __syshidden_foo. The ones that are actually used
> > then need prototypes (similar to the __sys_* ones in lib/libthr/?).
> > For some reason, the symbol .cerror (HIDENAME(cerror)) is also exported.
> > Either this should be kept local or a local uninterposable alias should
> > be added and used (as with the syscalls).
I sent a patch for .cerror (i386 only) in a new mailing list thread.
> > The function __error() (to get errno's address for the current thread)
> > is and must be called via the PLT (because libthr is separate).
> > Therefore, we should ensure it is called at least once before vfork so
> > calls in the child do not involve rtld. The implementations for the
> > various architectures use the TLS register (or memory location for ARM),
> > so they seem safe.
> > This should suffice to fix posix_spawn() but the _execvpe() used by
> > posix_spawnp also uses various string functions. If not all of these
> > have already been called earlier, this will not work. Making calls to
> > them not go through the PLT seems fairly hard, even though it would make
> > sense in general, so perhaps I should instead reimplement it such that
> > the parent does almost all of the work.
> > An alternative is to write the core of posix_spawn() in assembler using
> > system calls directly but I would rather avoid that :(
> BTW, we have very gross inefficiency in our libc syscall stubs on i386.
> Namely, the PIC_PROLOGUE generates 'call 1f; 1f:' sequence, which trashes
> return stack predictor in CPU. When compiling for pentium pro and later,
> gcc calls dummy procedure that moves return address into %ebx. I think
> we ought to do this unconditionally for libc stubs in modern times.
This is indeed the case, although I don't think the inefficiency is very
gross since there will not be very many return addresses left after a
system call.
Some post-pentiumpro CPUs do know about 'call 1f; 1f:'; on these CPUs it
is slightly faster than the get_pc_thunk while it is much slower than
the get_pc_thunk on CPUs that do not treat it specially.
> > > > There may still be a problem in programs that install signal handlers
> > > > because the set of async-signal-safe functions is larger than what can
> > > > be done in a vforked child. Userland can avoid this by masking affected
> > > > signals before calling vfork() and resetting them to SIG_DFL before
> > > > unmasking them. This will add many syscalls if the code does not know
> > > > which signals are affected (such as libc). Alternatively, the kernel
> > > > could map caught signals to the default action for processes with
> > > > P_PPWAIT (just like it does not stop such processes because of signals
> > > > or TTY job control).
> > > If rtld does not work, then any library function call from a signal handler
> > > is problematic. My goal is to get a working rtld and possibly malloc.
> > > Below is the latest version of my patch for vfork, which survives (modified)
> > > tools/test/pthread_vfork_test. Patch is only for x86 right now.
> [snip single-threading]
> > If single-threading is only necessary because umtx locks are formally
> > per-process instead of per-vmspace, then I suggest avoiding the trouble
> > and depending on the fact that they are per-vmspace.
> I agree. I worried about inter-process locking to prevent simultaneous
> entry into rtld or malloc from parent other thread and child, but as
> David rightfully pointed out, still relied on single vmspace for unlock.
> So I removed the single-threading from the kernel, relying on the usermode
> locks to prevent parallel rtld entrance and to lock fork/vfork in parent.
Hmm, if the locks work properly in parent and child, is it necessary to
do prefork/postfork at all? If another thread holds an internal lock
during vfork(), the child can wait for this normally, right?
I think _thr_vfork_post_parent() can detect most of the situations where
the vforked child was killed unexpectedly. If THR_IN_CRITICAL(curthread)
at the start of _thr_vfork_post_parent(), the vforked child was in a
critical section or held an internal lock, and things are broken. In
this case, the process should be terminated because continuing is likely
to cause deadlock or other undefined behaviour.
One way to trigger such a kill is by passing an invalid struct
sched_param pointer to pthread_setschedparam(). Of course it makes no
sense to call this function in a vforked child but it provides a
deterministic way to trigger the problem.
Single-threaded processes without libthr cannot detect an unexpected
kill in this way. Then again, they are unlikely to deadlock and will
probably crash again.
> Patch below also fixes a typo in amd64/vfork.S, which also passes
> pthread_vfork_test now.
> 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..7997032
> --- /dev/null
> +++ b/lib/libthr/arch/amd64/amd64/vfork.S
> @@ -0,0 +1,77 @@
> +/*-
> + * Copyright (c) 2012 Konstantin Belousov <kib at 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.
> + */
> +
> +#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 CNAME(_thr_vfork_post_child)
> + popq %rsi
> + popq %rsi
> + xorl %eax,%eax
> + jmp *%rsi
> +1:
> + pushq %rsi
> + pushq %rax
> + call CNAME(_thr_vfork_post_parent)
> + popq %rax
> + popq %rsi
> + jmp *%rsi
> +2:
> + pushq %rsi
> + pushq %rax
> + call CNAME(_thr_vfork_post_child)
> + call PIC_PLT(CNAME(__error))
> + popq %rdx
> + movq %rdx,(%rax)
> + movq $-1,%rax
> + movq %rax,%rdx
> + retq
> +END(__sys_vfork)
> +
> + .section .note.GNU-stack,"",%progbits
> diff --git a/lib/libthr/arch/i386/Makefile.inc b/lib/libthr/arch/i386/Makefile.inc
> index 01290d5..13d55e2 100644
> --- a/lib/libthr/arch/i386/Makefile.inc
> +++ b/lib/libthr/arch/i386/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/i386/i386/vfork.S b/lib/libthr/arch/i386/i386/vfork.S
> new file mode 100644
> index 0000000..ca8896b
> --- /dev/null
> +++ b/lib/libthr/arch/i386/i386/vfork.S
> @@ -0,0 +1,82 @@
> +/*-
> + * Copyright (c) 2012 Konstantin Belousov <kib at 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.
> + */
> +
> +#include <machine/asm.h>
> +__FBSDID("$FreeBSD$");
> +
> +#include "SYS.h"
> +
> + .weak _vfork
> + .set _vfork,__sys_vfork
> + .weak vfork
> + .set vfork,__sys_vfork
> +ENTRY(__sys_vfork)
> + PIC_PROLOGUE
> + call PIC_PLT(CNAME(_thr_vfork_pre))
> + PIC_EPILOGUE
> + popl %ecx /* my rta into ecx */
> + mov $SYS_vfork,%eax
> + KERNCALL
> + jb error_ret
> + pushl %ecx
> + cmpl $0,%eax
> + jne parent_ret
> + PIC_PROLOGUE
> + call PIC_PLT(CNAME(_thr_vfork_post_child))
> + PIC_EPILOGUE
> + popl %ecx
> + xorl %eax,%eax
> + jmp *%ecx
> +parent_ret:
> + pushl %eax
> + PIC_PROLOGUE
> + call PIC_PLT(CNAME(_thr_vfork_post_parent))
> + PIC_EPILOGUE
> + popl %eax
> + popl %ecx
> + jmp *%ecx
> +error_ret:
> + pushl %ecx
> + pushl %eax
> + PIC_PROLOGUE
> + call PIC_PLT(CNAME(_thr_vfork_post_child))
> + call PIC_PLT(CNAME(__error))
> + PIC_EPILOGUE
> + popl %edx
> + movl %edx,(%eax)
> + movl $-1,%eax
> + movl %eax,%edx
> + retl
> +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..951c3b8 100644
> --- a/lib/libthr/thread/thr_private.h
> +++ b/lib/libthr/thread/thr_private.h
> @@ -757,6 +757,7 @@ void _thr_cancel_leave(struct pthread *, int) __hidden;
> void _thr_testcancel(struct pthread *) __hidden;
> void _thr_signal_block(struct pthread *) __hidden;
> void _thr_signal_unblock(struct pthread *) __hidden;
> +void _thr_signal_unblock_noref(struct pthread *) __hidden;
> void _thr_signal_init(void) __hidden;
> void _thr_signal_deinit(void) __hidden;
> int _thr_send_sig(struct pthread *, int sig) __hidden;
> @@ -777,6 +778,9 @@ 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_child(void) __hidden;
> +void _thr_vfork_post_parent(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 +837,7 @@ 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_sig.c b/lib/libthr/thread/thr_sig.c
> index 3dee8b7..3e5b25e 100644
> --- a/lib/libthr/thread/thr_sig.c
> +++ b/lib/libthr/thread/thr_sig.c
> @@ -107,6 +107,13 @@ _thr_signal_unblock(struct pthread *curthread)
> __sys_sigprocmask(SIG_SETMASK, &curthread->sigmask, NULL);
> }
>
> +void
> +_thr_signal_unblock_noref(struct pthread *curthread)
> +{
> + if (curthread->sigblock == 0)
> + __sys_sigprocmask(SIG_SETMASK, &curthread->sigmask, NULL);
> +}
> +
> int
> _thr_send_sig(struct pthread *thread, int sig)
> {
> diff --git a/lib/libthr/thread/thr_vfork.c b/lib/libthr/thread/thr_vfork.c
> new file mode 100644
> index 0000000..80c9d1e
> --- /dev/null
> +++ b/lib/libthr/thread/thr_vfork.c
> @@ -0,0 +1,123 @@
> +/*
> + * Copyright (c) 2012 Konstantin Belousov <kib at freebsd.org>
> + * Copyright (c) 2005 David Xu <davidxu at freebsd.org>
> + * Copyright (c) 2003 Daniel Eischen <deischen at 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 at 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_wrlock(&_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_child(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);
> +}
> +
> +void
> +_thr_vfork_post_parent(void)
> +{
> + struct pthread *curthread;
> +
> + curthread = _get_curthread();
> + _thr_signal_unblock_noref(curthread);
> + if (curthread->cancel_async)
> + _thr_testcancel(curthread);
> +}
> diff --git a/sys/kern/kern_fork.c b/sys/kern/kern_fork.c
> index 46cdca1..6f2cfed 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;
--
Jilles Tjoelker
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