Re: [PATCH 1/2] nohz: Disable LOCKUP_DETECTOR when NO_HZ_FULL isenabled

[Peter Zijlstra]

On Wed, May 15, 2013 at 11:27:02AM -0400, Steven Rostedt wrote:
> Right now perf requires a tick, not sure exactly why, but you can look
> at the code in perf_event_task_tick(). Thus if NO_HZ_FULL sees that a
> perf tick is pending, it won't disable ticks. Unfortunately, the
> watchdogs, both NMI and soft lockup, use the perf infrastructure to
> trigger NMIs or interrupts. This adds a perf element on the rotate list
> and keeps NO_HZ_FULL from *ever* activating.
> 

Hmm.. Stephane had a bunch of patches converting the rotation thing to
an hrtimer. I seem to have forgotten what happened to them but I can't
seem to find them merged.

I'll go look.

That leaves the frequency stuff, but the watchdog doesn't use that.

At which point we could run the watchdog without perf_event_task_tick().
> 
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/