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);
}
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