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SubjectRe: rcu: endless stalls
On Mon, Jun 11, 2012 at 04:22:23PM +0200, Mike Galbraith wrote:
> On Mon, 2012-06-11 at 06:39 -0700, Paul E. McKenney wrote:
> > On Mon, Jun 11, 2012 at 12:06:16PM +0200, Mike Galbraith wrote:
> > > Greetings,
> > >
> > > I received a report of a 48 core UV box hitting a gripe, taking longer
> > > than timeout to emit same, so box griped endlessly, forcing reboot.
> >
> > So it took minutes to print an RCU CPU stall warning? On only 48 CPUs?
> >
> > If so, yow!!!
>
> The report was a tad fuzzy on details, but serial console can take a
> while at low baud rate, and the box was apparently perma-stalled.

Which clearly demands the question "why not increase the serial-console
baud rate"... ;-)

Thanx, Paul

> > My guess is that rcu_cpu_stall_suppress must be manipulated atomically
> > for this to work reliably, for example, using xchg().
>
> Ah, thanks.
>
> -Mike
>



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