Re: [Xen-devel] [PATCH] Xen/timer: Disable watchdog during dumping timer queues

["Lan, Tianyu" <tianyu.lan@xxxxxxxxx>]

On 9/13/2016 11:25 PM, Jan Beulich wrote:
> Wait - what is do_invalid_op() doing on the stack? I don't think it
> belongs there, and hence I wonder whether the keypress
> happened after some already fatal event (in which case all bets
> are off anyway).
Not clear why do_invalid_op() on the stack. There is no other fatal
event. The issue disappears when set watchdog_timeout to 10s.

> > > Another solution is to schedule a tasklet to run keyhandler in timer
> > > handler and invoke process_pending_softirqs() in the dump_timerq().
> > > This also works but it requires to rework keyhandler mechanism.
> > >
> > > Disable watchdog seems to be simpler and I found dump_registers() also
> > > used the same way to deal with the issue.
> That's true. Just that on large machines it defaults to the
> alternative model, for which I'm not sure it actually needs the
> watchdog disabled (as data for a single CPU shouldn't exceed
> the threshold).
It seems not to be necessary to disable watchdog in alternative model
since dumping a single cpu's status will not last a long time.


For the issue in the dump timer info handler, disabling watchdog is ok
for you or you have other suggestions to resolve the issue?

I also found other places where dump a lot of logs disable watchdog.
(E,G run_all_keyhandlers(), debugtrace_dump() debugtrace_toggle() and so
on). This seems a common solution.






> Jan
>
> > > Here is my draft patch of reworking keyhandler.
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