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

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Date:	Fri, 18 Jun 2010 16:35:32 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	huang ying <huang.ying.caritas@...il.com>
Cc:	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>,
	Huang Ying <ying.huang@...el.com>,
	Fr??d??ric Weisbecker <fweisbec@...il.com>,
	Don Zickus <dzickus@...hat.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
	Andi Kleen <andi@...stfloor.org>
Subject: Re: [RFC 1/3] Unified NMI delayed call mechanism


* huang ying <huang.ying.caritas@...il.com> wrote:

> On Fri, Jun 18, 2010 at 8:45 PM, Ingo Molnar <mingo@...e.hu> wrote:
> >> >> [...] ??At least APEI will use NMI to report some hardware events (likely
> >> >> error) to kernel. ??So I suppose we will go to have a delayed call as an
> >> >> event handler for APEI.
> >> >
> >> > Yep, that makes sense. I wasnt arguing against the functionality itself, i
> >> > was arguing against the illogical layering that limits its utility. By
> >> > making it part of perf events it becomes a generic part of that framework
> >> > and can be used by anything that deals with events and uses that
> >> > framework.
> >>
> >> I think the the 'layering' in the patchset helps instead of 'limits' its
> >> utility. It is designed to be as general as possible, so that it can be used
> >> by both perf and other NMI users. Do you think so?
> >
> > What other NMI users do you mean? EDAC/MCE is going to go utilize events 
> > as well (away from the horrible /dev/mcelog interface), the NMI watchdog 
> > already did it and the perf tool obviously does as well. There's a few 
> > leftovers like kcrash which isnt really event centric and i dont think it 
> > needs to be converted.
> 
> But why not just make it more general? It does not hurt anyone including 
> perf.

Because it's not actually more generic that way - just look at the code. It's 
x86 specific, plus it ties it to NMI delivery while the concept of delayed 
execution has nothing to do with NMIs.

	Ingo
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