Re: RCU stalls -> lockup.

[Tejun Heo]

On Thu, Oct 02, 2014 at 12:36:55PM -0700, Paul E. McKenney wrote:
> On Thu, Oct 02, 2014 at 01:55:15PM -0400, Dave Jones wrote:
> > I just hit this on my box running 3.17rc7
> > It was followed by a userspace lockup. (Could still ping, and sysrq
> > from the console, but even getty wasn't responding on the console).
> > 
> > I was trying to reproduce another bug faster, and had ramped up the
> > number of processes trinity to uses to 512. This didn't take long
> > to fall out..
> 
> This might be related to an exchange I had with Tejun (CCed), where
> the work queues were running all out, preventing any quiescent states
> from happening.  One fix under consideration is to add a quiescent state,
> similar to the one in softirq handling.

Dave, can you please test whether the following patch makes a
difference if the problem is reproducible?

  http://lkml.kernel.org/r/20141003153701.7c7da030@xxxxxxxxxxxxxxxxxxxxxxxxxxxx

Thanks.

-- 
tejun
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