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Date: Tue, 9 Oct 2007 16:18:19 -0500
From: Nathan Lynch <ntl@pobox.com>
To: Linas Vepstas <linas@austin.ibm.com>
Subject: Re: Hard hang in hypervisor!?
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Linas Vepstas wrote:
> 
> I was futzing with linux-2.6.23-rc8-mm1 in a power6 lpar when,
> for whatever reason, a spinlock locked up. The bizarre thing 
> was that the rest of system locked up as well: an ssh terminal,
> and also an hvc console.
> 
> Breaking into the debugger showed 4 cpus, 1 of which was 
> deadlocked in the spinlock, and the other 3 in 
> .pseries_dedicated_idle_sleep
> 
> This was, ahhh, unexpected.  What's up with that? Can
> anyone provide any insight?

Sounds consistent with a task trying to double-acquire the lock, or an
interrupt handler attempting to acquire a lock that the current task
holds.  Or maybe even an uninitialized spinlock.  Do you know which
lock it was?