Re: panic() logic

From: Andi Kleen
Date: Sat Oct 18 2008 - 03:56:33 EST

"Ani Sinha" <kernel@xxxxxxxxxxx> writes:

> I noticed an issue with the panic() firing on a back core in SMP
> lately. We are mostly working on mips architectures but it might
> effect other archs as well. Therefore, I am putting forward my
> thoughts and comments to the whole linux community. In the following,
> by front core I mean core#0 and by back core I mean other cores.

Why exactly is the "front core" special?

> smp_send_stop basically marks all the other cores as 'down' and
> updates the cpu bitmap. One implication of this is that you can not do
> an IPI later on to other cores (smp_send_function() does a
> 'for_earch_online_cpu'). This makes sense since you should not be
> allowed to do anything on a down cpu. But what if a particular
> architecture had logic to do specific things for the front core and
> other things on the back cores as a part of 'graceful reboot' process?

Is that logic in Linux or in the platform?

Normally it's best to not rely on any specific CPU for panic.
What do you do when that CPU is so broken that it cannot
process IPIs anymore?


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