Date: Fri, 2 Nov 2007 16:36:43 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Nick Piggin <npiggin@suse.de>
Cc: David Miller <davem@davemloft.net>, duaneg@dghda.com,
       linux-kernel@vger.kernel.org
Subject: Re: 2.6.23 regression: accessing invalid mmap'ed memory from gdb
	causes unkillable spinning
Message-ID: <20071102153643.GA29354@elte.hu>
References: <20071030.235600.254712083.davem@davemloft.net> <20071031074106.GE12189@wotan.suse.de> <20071031.004425.12962203.davem@davemloft.net> <20071101.220204.254984189.davem@davemloft.net> <20071102104554.GA941@wotan.suse.de>
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* Nick Piggin <npiggin@suse.de> wrote:

> > This means that even if some cpu is stuck in a spinlock loop with 
> > interrupts disabled, you'd see it with this thing.  The way it works 
> > is that cross cpu vectored interrupts are disabled independently of 
> > the processor interrupt level on sparc64.
> 
> That's really sweet. I'd better put my code where my mouth is as 
> well... this patch seems to be about the best we can do as a generic 
> fallback without getting a dedicated vector (which has to be done in 
> arch code anyway).

btw., in -rt we had something like this implemented as an NMI mechanism 
(for x86) - that way it's guaranteed that we get some output even from 
locked up CPUs.

	Ingo
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