Re: [testcase] perf: yet another fuzzer triggered crash

[Peter Zijlstra <peterz@infradead.org>]

On Fri, Jun 28, 2013 at 05:07:38PM -0400, Vince Weaver wrote:
> On Fri, 28 Jun 2013, Vince Weaver wrote:
> 
> > On Fri, 14 Jun 2013, Vince Weaver wrote:
> >  
> > > OK, I haven't managed to get a small reproducible test case for the system 
> > > crash yet
> > 
> > I wasted the last 2 days bisecting a 10000 syscall trace, but below is a 
> > 20-syscall testcase that rapidly makes a core2 machine running 3.10-rc7 
> > unusable.
> 
> and it turns out I might have bisected down too much, as though that 
> crashes my core2 system it doesn't crash newer machines.
> 
> I'm too lazy to re-bisect today, but the much longer program here:
>    http://web.eece.maine.edu/~vweaver/files/nmi_bug_snb.c
> reliably causes the same crash on a Sandybridge machine I have running 3.9

OK, so on my westmere it triggers that WARN in task_ctx_sched_out() a
_lot_ (I removed the ONCE for easier debugging earlier -- still kinda
stumped there).

Then this thing causes an RCU stall and starts triggering NMI watchdog
msgs.. so YAY! :-)

I'll see what I can find.