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Re: [Xen-users] Debugging sudden hangs

On Sun, Aug 19, 2018 at 08:46:44PM +0800, Liwei wrote:
> Hi list,
>     We recently updated our system and started experiencing random
> hangs. It happens, on average, once every 1.5 days (sometimes taking 2
> days to occur, other times happening multiple times a day, somewhat
> proportional to IO load).
>     Before troubling the developers too much, I'd like to collect more
> information, however, the problem is the hangs occur without any
> symptoms/crashes/panics. I've booted xen and dom0 with:
> "loglvl=all guest_loglvl=all" and "loglevel=10 debug initcall_debug"
> respectively.

You should add iommu=debug to the command line.

>     When the hang occurs, all domUs and dom0 just stop responding to
> key presses, networking and there is no IO activity. Nothing gets
> generated in the console/logs (no symptoms either, no logs out of the
> ordinary). Even hitting ctrl+a multiple times in the console does
> nothing (indicating xen is dead too). On the video console, we just
> have a blinking cursor after the last console log (though my
> understanding is that the cursor blink might be generated by the video
> card rather than any indication that at least something is still
> running). If the hardware WDT is on, the watchdog eventually bites and
> reboots the system.

It would be interesting to get the crash trace printed by the watchdog.
And to use a debug build of the hypervisor, that might trigger some
assertions inside of Xen that could lead to the cause of the issue.


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