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SubjectRe: RCU detected CPU 0 stall after panic on sparc64
On Sat, Dec 12, 2009 at 01:40:02AM -0800, David Miller wrote:
> From: Meelis Roos <mroos@linux.ee>
> Date: Sat, 12 Dec 2009 10:54:19 +0200 (EET)
>
> > I tried 2.6.32 git gaad3bf0 on a SMP sparc64 machine (Ultra Enterprise
> > 250). For some reason my disks were not found (not important in this
> > bugreport) and this resulted in panic (cannnot mount root). However, the
> > machine kept going and got the below messages (RCU detected CPU 0 stall
> > (t=1000 jiffies)) from timer interrupts.
> >
> > This seems to be like a bug in RCU vs panic.
>
> It's normal actually. A panic() just loops forever and the cpu never
> goes through an RCU grace period again as a result, and this triggers
> the debugging timer that detects this condition.
>
> Probably the panic() code should disable that assertion check.

Hmmm... At first glance, it looks like RCU should put a notifier onto
the panic_notifier_list to disable this check. Or is there some global
variable that I can check?

Thanx, Paul


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