Re: [PATCH 00/12] perf: more fixes

[Alexander Shishkin]

Peter Zijlstra <peterz@xxxxxxxxxxxxx> writes:

> On Wed, Feb 24, 2016 at 06:45:39PM +0100, Peter Zijlstra wrote:
>
>> With these patches syz-kaller can still trigger some fail; most notably some
>> NMI watchdog triggers and a very sporadic unthrottle bug (much like last time).
>
> So the below seems to make the sporadic unthrottle thing much less
> likely in that I haven't seen it in several hours, my machine keeps
> dying on NMI watchdog bits.
>
> Boris, who has been running syz-kaller on AMD hardware and was hitting a
> very similar bug with the AMD-IBS code, says its not fixed it for him,
> so maybe there's still more to find.
>
> ---
> Subject: perf: Fix unthrottle
>
> Its possible to IOC_PERIOD while the event is throttled, this would
> re-start the event and the next tick would then try to unthrottle it,
> and find the event wasn't actually stopped anymore.
>
> This would tickle a WARN in the x86-pmu code which isn't expecting to
> start a !stopped event.
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>

FWIW,

Reviewed-by: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>

Cheers,
--
Alex