linux-kernel - Re: [RFC 1/3] Unified NMI delayed call mechanism

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Date:	Mon, 14 Jun 2010 11:12:32 -0400
From:	Don Zickus <dzickus@...hat.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>,
	Ingo Molnar <mingo@...e.hu>, Huang Ying <ying.huang@...el.com>,
	Fr??d??ric Weisbecker <fweisbec@...il.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org
Subject: Re: [RFC 1/3] Unified NMI delayed call mechanism

On Mon, Jun 14, 2010 at 04:44:03PM +0200, Andi Kleen wrote:
> > I think the perf event subsytem can log events in NMI context already and
> > deliver them to userspace when the NMI is done.  This is why I think Ingo
> > wants MCE to be updated to sit on top of the perf event subsytem to avoid
> > re-invent everything again.
> 
> perf is not solving the problem this is trying to solve.
> 
> > Then again I do not know enough about the MCE stuff to understand what you
> > mean when an event comes in but you can't handle it in an NMI-safe
> > context.  An example would be helpful.
> 
> At least for MCE hwpoison recovery needs to sleep and you obviously cannot sleep in
> NMI like context. The way it's done is to first do a self interrupt, then do a work queue
> wakeup and finally the sleeping operations. 
> 
> perf does not fit into this because it has no way to process such an event
> inside the kernel.

Ah, makes sense.  Thanks for the example.

Cheers,
Don
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