On Wed, Jun 18, 2014 at 04:41:09PM +0200, Jiri Kosina wrote:
> On Wed, 18 Jun 2014, Paul E. McKenney wrote:
>
> > > - both RCU stall detector and 'echo l > sysrq-trigger' can (and we've
> > > seen it happening for real) cause a complete, undebuggable, silent hang
> > > of machine (deadlock in NMI context)
> >
> > I could easily add an option to RCU to allow people to tell it not to
> > use NMIs to dump the stack. Would that help?
>
> Well, that would make unfortunately the information provided by RCU stall
> detector rather useless ... workqueue-based stack dumping is very unlikely
> to point its finger to the real offender, as it'd be coming way too late.
I would not use workqueues, but rather have the CPU detecting the
stall grovel through the other CPUs' stacks, which is what I do now for
architectures that don't support NMI-based stack dumps. Would that be
a reasonable approach?
Thanx, Paul
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