Re: [patch-3.18.7-rt1] sched/context-tracking: fix PREEMPT_LAZY explosions

[Mike Galbraith]

On Mon, 2015-03-09 at 15:36 +0100, Mike Galbraith wrote:
> On Mon, 2015-03-09 at 14:45 +0100, Sebastian Andrzej Siewior wrote:
> > * Mike Galbraith | 2015-02-18 12:21:54 [+0100]:
> > 
> > >On Mon, 2015-02-16 at 12:18 +0100, Sebastian Andrzej Siewior wrote:
> > >
> > >> Known issues:
> > >>
> > >>       - lazy preempt on x86_64 leads to a crash with some load.
> > >
> > >The below still works for me.  (it doesn't make nohz_full actually work
> > >in rt, but at least folks who want to tinker with it can do so)
> > So your box still crashes without it?
> > 
> > The thing is I tried to reproduce it and it does not occur anymore.
> > Neither in KVM nor on real HW.
> 
> Heh, well that's interesting, I just presumed it would still explode
> because you said it would.  I'll beat on it any let you know if I'm
> carrying a placebo patch or not :)

Yup, someone made kaboom go away.  I was able to easily blow my box out
of the water by running tbench + kbuild with nohz_full active.  No more.

nohz_full doesn't work though, due to an otherwise solo task trying to
shut the tick down having just awakened ksoftirqd.. but no more kaboom.

	-Mike

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