linux-kernel - Re: [PATCH] [2/2] Don't complain about disabled irqs when the system has paniced

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Message-ID: <20080902144051.GM18288@one.firstfloor.org>
Date:	Tue, 2 Sep 2008 16:40:51 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Andi Kleen <andi@...stfloor.org>, torvalds@...l.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [2/2] Don't complain about disabled irqs when the system has paniced

On Tue, Sep 02, 2008 at 04:28:03PM +0200, Peter Zijlstra wrote:
> On Tue, 2008-09-02 at 15:49 +0200, Andi Kleen wrote:
> > panic calls smp_send_stop which eventually calls smp_call_function_*.
> > smp_call_function warns about disabled interrupts. But it's legal
> > to call panic in this case. When this happens panic() prints
> > several ugly backtraces. So don't check for disabled interrupts
> > in panic state.
> 
> While it might be legal for panic to be called from such contexts, I
> understand those warnings are there to warn of deadlocks.
> 
> So with the below patch you allow panic to deadlock if I understand
> things correctly.

Please describe the deadlock exactly.  I don't think it can deadlock 
in this case. 

Besides do you prefer to not allow panic from interrupts/machine
checks etc. anymore? 

-Andi

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