linux-kernel - Re: RCU detected CPU 0 stall after panic on sparc64

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Date:	Sat, 12 Dec 2009 01:40:02 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	mroos@...ux.ee
Cc:	linux-kernel@...r.kernel.org, sparclinux@...r.kernel.org
Subject: Re: RCU detected CPU 0 stall after panic on sparc64

From: Meelis Roos <mroos@...ux.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.
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