> -----Original Message-----
> From: Paolo Bonzini [mailto:[email protected]]
> Sent: Tuesday, August 14, 2018 8:02 PM
> To: Dr. David Alan Gilbert <[email protected]>
> Cc: Zhoujian (jay) <[email protected]>; [email protected];
> [email protected]; wangxin (U) <[email protected]>
> Subject: Re: [RFC PATCH] vl: fix migration when watchdog expires
>
> On 14/08/2018 13:52, Dr. David Alan Gilbert wrote:
> > a) Should the watchdog expire when the VM is stopped; I think it
> > shouldn't - hw/acpi/tco.c uses a virtual timer as does i6300esb; so is
> > the bug here that the watchdog being used didn't use a virtual timer?
>
> All watchdogs do.
>
> > b) If the watchdog expires just before the VM gets stopped, is there
> > a race which could hit this? Possibly.
>
> Yes, I think it is a race that happens just before vm_stop, but I don't
> understand why the "qemu_clock_enable" in pause_all_vcpus does not prevent it.
Hi Paolo,
The sequence is like this I think
|
| <----- watchdog expired, which set reset_requested to
SHUTDOWN_CAUSE_GUEST_RESET
|
| <----- migration thread sets to RUN_STATE_FINISH_MIGRATE, it will
disable QEMU_CLOCK_VIRTUAL clock,
| but it is done after the setting of reset_requested
|
| <----- main loop thread sets to RUN_STATE_PRELAUNCH since it
detected a reset request
|
| <----- migration thread sets to RUN_STATE_POSTMIGRATE
Regards,
Jay Zhou
>
> It should be possible to write a deterministic testcase with qtest...
>
> Paolo
