linux-kernel - Re: 2.6.23 regression: accessing invalid mmap'ed memory from gdb causes unkillable spinning

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Message-ID: <20071102153643.GA29354@elte.hu>
Date:	Fri, 2 Nov 2007 16:36:43 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Nick Piggin <npiggin@...e.de>
Cc:	David Miller <davem@...emloft.net>, duaneg@...da.com,
	linux-kernel@...r.kernel.org
Subject: Re: 2.6.23 regression: accessing invalid mmap'ed memory from gdb
	causes unkillable spinning


* Nick Piggin <npiggin@...e.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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