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

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Date:	Fri, 18 Jun 2010 12:30:58 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Don Zickus <dzickus@...hat.com>,
	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>,
	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

* Andi Kleen <andi@...stfloor.org> 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.

That is why i requested to extend the events backend. That will unify more of 
the code than the first few steps achieved by these three patches - and offers 
the functionality to all code that uses the events framework.

> [...]
>
> perf does not fit into this because it has no way to process such an event 
> inside the kernel.

It 'does not fit' into the events backend only if you pretend that it is 
impossible or undesirable to have a delayed, in-context callback mechanism 
implemented there.

If you look at it more closely you'll notice that in reality it's not only 
possible but that it is also a pretty natural fit.

Thanks,

	Ingo
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