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Re: looking for help interpreting softlockup/stack trace

To: Chris Friesen <cfriesen@nortel.com>
Subject: Re: looking for help interpreting softlockup/stack trace
From: Ralf Baechle <ralf@linux-mips.org>
Date: Tue, 5 Aug 2008 20:16:19 +0100
Cc: linux-mips@linux-mips.org
In-reply-to: <48989AFE.5000500@nortel.com>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <48989AFE.5000500@nortel.com>
Sender: linux-mips-bounce@linux-mips.org
User-agent: Mutt/1.5.18 (2008-05-17)
On Tue, Aug 05, 2008 at 12:25:02PM -0600, Chris Friesen wrote:

> I've run into an interesting issue with an Octeon-based board, where it  
> just seems to hang.  I suspect we're hitting some kind of locking bug,  
> and I'm trying to track it down.  If it matters, the kernel is quite old  
> (heavily patched 2.6.14) and I've got no chance of upgrading it.  (The  
> usual embedded scenario.)
>
> I've added some scheduler instrumentation, as well as adding a stack  
> dump to the output of the softlockup code.
>
> In the trace below, is "epc" the program counter at the time of the  
> timer interrupt?  How does "ra" fit into this, given that the function  
> whose address it contains isn't seen in the stack trace until quite a  
> ways down?

$LBB378 is an internal symbol.  The value of RA may not be very informative
if it was overwritten by a random subroutine call.

> Any insights are greatly appreciated...

You may also try lockdep; it gives much more detailed information though
it's more heavyweight.

  Ralf

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