* [Qemu-devel] qemu-kvm: sigsegv at exit
@ 2009-10-22 12:00 Michael S. Tsirkin
2009-10-22 20:57 ` [Qemu-devel] " Marcelo Tosatti
0 siblings, 1 reply; 5+ messages in thread
From: Michael S. Tsirkin @ 2009-10-22 12:00 UTC (permalink / raw)
To: kvm, qemu-devel
Hi!
I'm sometimes getting segfaults when I kill qemu.
This time I caught it when qemu was under gdb:
Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x411d0940 (LWP 14446)]
0x000000000040afb4 in qemu_mod_timer (ts=0x19f0fd0, expire_time=62275467335)
at /home/mst/scm/qemu-kvm/vl.c:1009
1009 if ((alarm_timer->flags & ALARM_FLAG_EXPIRED) == 0) {
(gdb) l
1004 ts->next = *pt;
1005 *pt = ts;
1006
1007 /* Rearm if necessary */
1008 if (pt == &active_timers[ts->clock->type]) {
1009 if ((alarm_timer->flags & ALARM_FLAG_EXPIRED) == 0) {
1010 qemu_rearm_alarm_timer(alarm_timer);
1011 }
1012 /* Interrupt execution to force deadline recalculation. */
1013 if (use_icount)
(gdb) p alarm_timer
$1 = (struct qemu_alarm_timer *) 0x0
(gdb) where
#0 0x000000000040afb4 in qemu_mod_timer (ts=0x19f0fd0, expire_time=62275467335)
at /home/mst/scm/qemu-kvm/vl.c:1009
#1 0x000000000041aadf in virtio_net_handle_tx (vdev=<value optimized out>, vq=0x19f5af0)
at /home/mst/scm/qemu-kvm/hw/virtio-net.c:696
#2 0x0000000000421669 in kvm_run (vcpu=0x19d46a0, env=0x19c2250) at /home/mst/scm/qemu-kvm/qemu-kvm.c:797
#3 0x00000000004216d6 in kvm_cpu_exec (env=0x83d0f8) at /home/mst/scm/qemu-kvm/qemu-kvm.c:1714
#4 0x0000000000422981 in ap_main_loop (_env=<value optimized out>) at /home/mst/scm/qemu-kvm/qemu-kvm.c:1969
#5 0x000000377dc06367 in start_thread () from /lib64/libpthread.so.0
#6 0x000000377d0d30ad in clone () from /lib64/libc.so.6
(gdb)
So this probably means that we have already run quit_timers:
static void quit_timers(void)
{
alarm_timer->stop(alarm_timer);
alarm_timer = NULL;
}
but kvm vcpu thread is still running.
Not sure what the right fix is here: should we stop
kvm after main loop has exited?
--
MST
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Qemu-devel] Re: qemu-kvm: sigsegv at exit
2009-10-22 12:00 [Qemu-devel] qemu-kvm: sigsegv at exit Michael S. Tsirkin
@ 2009-10-22 20:57 ` Marcelo Tosatti
2009-10-25 10:11 ` Michael S. Tsirkin
0 siblings, 1 reply; 5+ messages in thread
From: Marcelo Tosatti @ 2009-10-22 20:57 UTC (permalink / raw)
To: Michael S. Tsirkin; +Cc: qemu-devel, kvm
On Thu, Oct 22, 2009 at 02:00:15PM +0200, Michael S. Tsirkin wrote:
> Hi!
> I'm sometimes getting segfaults when I kill qemu.
> This time I caught it when qemu was under gdb:
>
>
> Program received signal SIGSEGV, Segmentation fault.
> [Switching to Thread 0x411d0940 (LWP 14446)]
> 0x000000000040afb4 in qemu_mod_timer (ts=0x19f0fd0, expire_time=62275467335)
> at /home/mst/scm/qemu-kvm/vl.c:1009
> 1009 if ((alarm_timer->flags & ALARM_FLAG_EXPIRED) == 0) {
> (gdb) l
> 1004 ts->next = *pt;
> 1005 *pt = ts;
> 1006
> 1007 /* Rearm if necessary */
> 1008 if (pt == &active_timers[ts->clock->type]) {
> 1009 if ((alarm_timer->flags & ALARM_FLAG_EXPIRED) == 0) {
> 1010 qemu_rearm_alarm_timer(alarm_timer);
> 1011 }
> 1012 /* Interrupt execution to force deadline recalculation. */
> 1013 if (use_icount)
> (gdb) p alarm_timer
> $1 = (struct qemu_alarm_timer *) 0x0
> (gdb) where
> #0 0x000000000040afb4 in qemu_mod_timer (ts=0x19f0fd0, expire_time=62275467335)
> at /home/mst/scm/qemu-kvm/vl.c:1009
> #1 0x000000000041aadf in virtio_net_handle_tx (vdev=<value optimized out>, vq=0x19f5af0)
> at /home/mst/scm/qemu-kvm/hw/virtio-net.c:696
> #2 0x0000000000421669 in kvm_run (vcpu=0x19d46a0, env=0x19c2250) at /home/mst/scm/qemu-kvm/qemu-kvm.c:797
> #3 0x00000000004216d6 in kvm_cpu_exec (env=0x83d0f8) at /home/mst/scm/qemu-kvm/qemu-kvm.c:1714
> #4 0x0000000000422981 in ap_main_loop (_env=<value optimized out>) at /home/mst/scm/qemu-kvm/qemu-kvm.c:1969
> #5 0x000000377dc06367 in start_thread () from /lib64/libpthread.so.0
> #6 0x000000377d0d30ad in clone () from /lib64/libc.so.6
> (gdb)
>
> So this probably means that we have already run quit_timers:
>
> static void quit_timers(void)
> {
> alarm_timer->stop(alarm_timer);
> alarm_timer = NULL;
> }
>
> but kvm vcpu thread is still running.
>
>
> Not sure what the right fix is here: should we stop
> kvm after main loop has exited?
kvm_main_loop_wait(env, 0) can process the stop request (signalling
iothread that vcpu is stopped, so its OK to exit) and continue to
kvm_cpu_exec.
Can you please try this:
diff --git a/qemu-kvm.c b/qemu-kvm.c
index 87ece3d..141c8b1 100644
--- a/qemu-kvm.c
+++ b/qemu-kvm.c
@@ -1931,7 +1931,8 @@ static int kvm_main_loop_cpu(CPUState *env)
}
if (run_cpu) {
kvm_main_loop_wait(env, 0);
- kvm_cpu_exec(env);
+ if (!is_cpu_stopped(env))
+ kvm_cpu_exec(env);
} else {
kvm_main_loop_wait(env, 1000);
}
^ permalink raw reply related [flat|nested] 5+ messages in thread
* [Qemu-devel] Re: qemu-kvm: sigsegv at exit
2009-10-22 20:57 ` [Qemu-devel] " Marcelo Tosatti
@ 2009-10-25 10:11 ` Michael S. Tsirkin
2009-10-26 18:43 ` Marcelo Tosatti
0 siblings, 1 reply; 5+ messages in thread
From: Michael S. Tsirkin @ 2009-10-25 10:11 UTC (permalink / raw)
To: Marcelo Tosatti; +Cc: qemu-devel, kvm
On Thu, Oct 22, 2009 at 06:57:27PM -0200, Marcelo Tosatti wrote:
> On Thu, Oct 22, 2009 at 02:00:15PM +0200, Michael S. Tsirkin wrote:
> > Hi!
> > I'm sometimes getting segfaults when I kill qemu.
> > This time I caught it when qemu was under gdb:
> >
> >
> > Program received signal SIGSEGV, Segmentation fault.
> > [Switching to Thread 0x411d0940 (LWP 14446)]
> > 0x000000000040afb4 in qemu_mod_timer (ts=0x19f0fd0, expire_time=62275467335)
> > at /home/mst/scm/qemu-kvm/vl.c:1009
> > 1009 if ((alarm_timer->flags & ALARM_FLAG_EXPIRED) == 0) {
> > (gdb) l
> > 1004 ts->next = *pt;
> > 1005 *pt = ts;
> > 1006
> > 1007 /* Rearm if necessary */
> > 1008 if (pt == &active_timers[ts->clock->type]) {
> > 1009 if ((alarm_timer->flags & ALARM_FLAG_EXPIRED) == 0) {
> > 1010 qemu_rearm_alarm_timer(alarm_timer);
> > 1011 }
> > 1012 /* Interrupt execution to force deadline recalculation. */
> > 1013 if (use_icount)
> > (gdb) p alarm_timer
> > $1 = (struct qemu_alarm_timer *) 0x0
> > (gdb) where
> > #0 0x000000000040afb4 in qemu_mod_timer (ts=0x19f0fd0, expire_time=62275467335)
> > at /home/mst/scm/qemu-kvm/vl.c:1009
> > #1 0x000000000041aadf in virtio_net_handle_tx (vdev=<value optimized out>, vq=0x19f5af0)
> > at /home/mst/scm/qemu-kvm/hw/virtio-net.c:696
> > #2 0x0000000000421669 in kvm_run (vcpu=0x19d46a0, env=0x19c2250) at /home/mst/scm/qemu-kvm/qemu-kvm.c:797
> > #3 0x00000000004216d6 in kvm_cpu_exec (env=0x83d0f8) at /home/mst/scm/qemu-kvm/qemu-kvm.c:1714
> > #4 0x0000000000422981 in ap_main_loop (_env=<value optimized out>) at /home/mst/scm/qemu-kvm/qemu-kvm.c:1969
> > #5 0x000000377dc06367 in start_thread () from /lib64/libpthread.so.0
> > #6 0x000000377d0d30ad in clone () from /lib64/libc.so.6
> > (gdb)
> >
> > So this probably means that we have already run quit_timers:
> >
> > static void quit_timers(void)
> > {
> > alarm_timer->stop(alarm_timer);
> > alarm_timer = NULL;
> > }
> >
> > but kvm vcpu thread is still running.
> >
> >
> > Not sure what the right fix is here: should we stop
> > kvm after main loop has exited?
>
> kvm_main_loop_wait(env, 0) can process the stop request (signalling
> iothread that vcpu is stopped, so its OK to exit) and continue to
> kvm_cpu_exec.
>
> Can you please try this:
I applied this, and have not yet see any segfaults at exit.
Not sure whether this is means anything as the crash is not
100% reproducable. Push it out to Anthony and we'll see, long term?
Based on the knowledge of how to fix this,
how would you go about reproducing it?
> diff --git a/qemu-kvm.c b/qemu-kvm.c
> index 87ece3d..141c8b1 100644
> --- a/qemu-kvm.c
> +++ b/qemu-kvm.c
> @@ -1931,7 +1931,8 @@ static int kvm_main_loop_cpu(CPUState *env)
> }
> if (run_cpu) {
> kvm_main_loop_wait(env, 0);
> - kvm_cpu_exec(env);
> + if (!is_cpu_stopped(env))
> + kvm_cpu_exec(env);
> } else {
> kvm_main_loop_wait(env, 1000);
> }
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Qemu-devel] Re: qemu-kvm: sigsegv at exit
2009-10-25 10:11 ` Michael S. Tsirkin
@ 2009-10-26 18:43 ` Marcelo Tosatti
2009-10-26 18:49 ` Michael S. Tsirkin
0 siblings, 1 reply; 5+ messages in thread
From: Marcelo Tosatti @ 2009-10-26 18:43 UTC (permalink / raw)
To: Michael S. Tsirkin; +Cc: qemu-devel, kvm
> On Thu, Oct 22, 2009 at 06:57:27PM -0200, Marcelo Tosatti wrote:
> > On Thu, Oct 22, 2009 at 02:00:15PM +0200, Michael S. Tsirkin wrote:
> > > Hi!
> > > I'm sometimes getting segfaults when I kill qemu.
> > > This time I caught it when qemu was under gdb:
> > >
> > >
> > > Program received signal SIGSEGV, Segmentation fault.
> > > [Switching to Thread 0x411d0940 (LWP 14446)]
> > > 0x000000000040afb4 in qemu_mod_timer (ts=0x19f0fd0, expire_time=62275467335)
> > > at /home/mst/scm/qemu-kvm/vl.c:1009
> > > 1009 if ((alarm_timer->flags & ALARM_FLAG_EXPIRED) == 0) {
> > > (gdb) l
> > > 1004 ts->next = *pt;
> > > 1005 *pt = ts;
> > > 1006
> > > 1007 /* Rearm if necessary */
> > > 1008 if (pt == &active_timers[ts->clock->type]) {
> > > 1009 if ((alarm_timer->flags & ALARM_FLAG_EXPIRED) == 0) {
> > > 1010 qemu_rearm_alarm_timer(alarm_timer);
> > > 1011 }
> > > 1012 /* Interrupt execution to force deadline recalculation. */
> > > 1013 if (use_icount)
> > > (gdb) p alarm_timer
> > > $1 = (struct qemu_alarm_timer *) 0x0
> > > (gdb) where
> > > #0 0x000000000040afb4 in qemu_mod_timer (ts=0x19f0fd0, expire_time=62275467335)
> > > at /home/mst/scm/qemu-kvm/vl.c:1009
> > > #1 0x000000000041aadf in virtio_net_handle_tx (vdev=<value optimized out>, vq=0x19f5af0)
> > > at /home/mst/scm/qemu-kvm/hw/virtio-net.c:696
> > > #2 0x0000000000421669 in kvm_run (vcpu=0x19d46a0, env=0x19c2250) at /home/mst/scm/qemu-kvm/qemu-kvm.c:797
> > > #3 0x00000000004216d6 in kvm_cpu_exec (env=0x83d0f8) at /home/mst/scm/qemu-kvm/qemu-kvm.c:1714
> > > #4 0x0000000000422981 in ap_main_loop (_env=<value optimized out>) at /home/mst/scm/qemu-kvm/qemu-kvm.c:1969
> > > #5 0x000000377dc06367 in start_thread () from /lib64/libpthread.so.0
> > > #6 0x000000377d0d30ad in clone () from /lib64/libc.so.6
> > > (gdb)
> > >
> > > So this probably means that we have already run quit_timers:
> > >
> > > static void quit_timers(void)
> > > {
> > > alarm_timer->stop(alarm_timer);
> > > alarm_timer = NULL;
> > > }
> > >
> > > but kvm vcpu thread is still running.
> > >
> > >
> > > Not sure what the right fix is here: should we stop
> > > kvm after main loop has exited?
> >
> > kvm_main_loop_wait(env, 0) can process the stop request (signalling
> > iothread that vcpu is stopped, so its OK to exit) and continue to
> > kvm_cpu_exec.
> >
> > Can you please try this:
>
> I applied this, and have not yet see any segfaults at exit.
> Not sure whether this is means anything as the crash is not
> 100% reproducable. Push it out to Anthony and we'll see, long term?
> Based on the knowledge of how to fix this,
> how would you go about reproducing it?
Add code to trigger the race manually, but i'm pretty sure thats it.
Thanks for testing.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Qemu-devel] Re: qemu-kvm: sigsegv at exit
2009-10-26 18:43 ` Marcelo Tosatti
@ 2009-10-26 18:49 ` Michael S. Tsirkin
0 siblings, 0 replies; 5+ messages in thread
From: Michael S. Tsirkin @ 2009-10-26 18:49 UTC (permalink / raw)
To: Marcelo Tosatti; +Cc: qemu-devel, kvm
On Mon, Oct 26, 2009 at 04:43:11PM -0200, Marcelo Tosatti wrote:
> > On Thu, Oct 22, 2009 at 06:57:27PM -0200, Marcelo Tosatti wrote:
> > > On Thu, Oct 22, 2009 at 02:00:15PM +0200, Michael S. Tsirkin wrote:
> > > > Hi!
> > > > I'm sometimes getting segfaults when I kill qemu.
> > > > This time I caught it when qemu was under gdb:
> > > >
> > > >
> > > > Program received signal SIGSEGV, Segmentation fault.
> > > > [Switching to Thread 0x411d0940 (LWP 14446)]
> > > > 0x000000000040afb4 in qemu_mod_timer (ts=0x19f0fd0, expire_time=62275467335)
> > > > at /home/mst/scm/qemu-kvm/vl.c:1009
> > > > 1009 if ((alarm_timer->flags & ALARM_FLAG_EXPIRED) == 0) {
> > > > (gdb) l
> > > > 1004 ts->next = *pt;
> > > > 1005 *pt = ts;
> > > > 1006
> > > > 1007 /* Rearm if necessary */
> > > > 1008 if (pt == &active_timers[ts->clock->type]) {
> > > > 1009 if ((alarm_timer->flags & ALARM_FLAG_EXPIRED) == 0) {
> > > > 1010 qemu_rearm_alarm_timer(alarm_timer);
> > > > 1011 }
> > > > 1012 /* Interrupt execution to force deadline recalculation. */
> > > > 1013 if (use_icount)
> > > > (gdb) p alarm_timer
> > > > $1 = (struct qemu_alarm_timer *) 0x0
> > > > (gdb) where
> > > > #0 0x000000000040afb4 in qemu_mod_timer (ts=0x19f0fd0, expire_time=62275467335)
> > > > at /home/mst/scm/qemu-kvm/vl.c:1009
> > > > #1 0x000000000041aadf in virtio_net_handle_tx (vdev=<value optimized out>, vq=0x19f5af0)
> > > > at /home/mst/scm/qemu-kvm/hw/virtio-net.c:696
> > > > #2 0x0000000000421669 in kvm_run (vcpu=0x19d46a0, env=0x19c2250) at /home/mst/scm/qemu-kvm/qemu-kvm.c:797
> > > > #3 0x00000000004216d6 in kvm_cpu_exec (env=0x83d0f8) at /home/mst/scm/qemu-kvm/qemu-kvm.c:1714
> > > > #4 0x0000000000422981 in ap_main_loop (_env=<value optimized out>) at /home/mst/scm/qemu-kvm/qemu-kvm.c:1969
> > > > #5 0x000000377dc06367 in start_thread () from /lib64/libpthread.so.0
> > > > #6 0x000000377d0d30ad in clone () from /lib64/libc.so.6
> > > > (gdb)
> > > >
> > > > So this probably means that we have already run quit_timers:
> > > >
> > > > static void quit_timers(void)
> > > > {
> > > > alarm_timer->stop(alarm_timer);
> > > > alarm_timer = NULL;
> > > > }
> > > >
> > > > but kvm vcpu thread is still running.
> > > >
> > > >
> > > > Not sure what the right fix is here: should we stop
> > > > kvm after main loop has exited?
> > >
> > > kvm_main_loop_wait(env, 0) can process the stop request (signalling
> > > iothread that vcpu is stopped, so its OK to exit) and continue to
> > > kvm_cpu_exec.
> > >
> > > Can you please try this:
> >
> > I applied this, and have not yet see any segfaults at exit.
> > Not sure whether this is means anything as the crash is not
> > 100% reproducable. Push it out to Anthony and we'll see, long term?
> > Based on the knowledge of how to fix this,
> > how would you go about reproducing it?
>
> Add code to trigger the race manually,
If you like, send a patch adding such code, I will test.
> but i'm pretty sure thats it.
>
> Thanks for testing.
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2009-10-26 18:51 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
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2009-10-22 12:00 [Qemu-devel] qemu-kvm: sigsegv at exit Michael S. Tsirkin
2009-10-22 20:57 ` [Qemu-devel] " Marcelo Tosatti
2009-10-25 10:11 ` Michael S. Tsirkin
2009-10-26 18:43 ` Marcelo Tosatti
2009-10-26 18:49 ` Michael S. Tsirkin
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