Re: [PATCH 08/10] NOTIFIER: Take over TIF_MCE_NOTIFY and implement task return notifier

Avi Kivity
2011-06-15T08:51:39Z

On 06/14/2011 08:13 PM, Luck, Tony wrote:
> >Since we can't have nested #MC (due to the IST mechanism resetting %rsp
> >and clobbering the previous invocation's stack), we have to clear MCIP
> >outside the #MC handler. And that means irq_work_queue()
> >
> >(note that this changes the behaviour from memory corruption to shutdown
> >state; both suck, but one more than the other).
>
> Hmm. We currently clear MCIP inside the handler (at the very end, but
> still inside). Deferring clearing would make sense - but we'd have to
> be sure to do so a.s.a.p on all processors. It also would change how
> we look at the possibility of a process being able to run and re-execute
> an instruction that causes a machine check. If we defer clearing MCIP
> this won't just be annoying, it will be fatal (if any cpu hasn't yet
> got to the work queue to clear MCIP).

Clearly, the work queue (or thread) has to be real-time at the highest
priority.

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