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

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Date:	Sat, 12 Jun 2010 12:25:58 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	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>
Cc:	"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 <ying.huang@...el.com> wrote:

> NMI can be triggered even when IRQ is masked. So it is not safe for NMI 
> handler to call some functions. One solution is to delay the call via self 
> interrupt, so that the delayed call can be done once the interrupt is 
> enabled again. This has been implemented in MCE and perf event. This patch 
> provides a unified version and make it easier for other NMI semantic handler 
> to take use of the delayed call.
> 
> Signed-off-by: Huang Ying <ying.huang@...el.com>
> ---
>  arch/x86/include/asm/entry_arch.h  |    1 
>  arch/x86/include/asm/hw_irq.h      |    1 
>  arch/x86/include/asm/irq_vectors.h |    5 +
>  arch/x86/include/asm/nmi.h         |    7 ++
>  arch/x86/kernel/entry_64.S         |    3 +
>  arch/x86/kernel/irqinit.c          |    3 +
>  arch/x86/kernel/traps.c            |  104 +++++++++++++++++++++++++++++++++++++
>  7 files changed, 124 insertions(+)

Instead of introducing this extra intermediate facility please use the same 
approach the unified NMI watchdog is using (see latest -tip): a perf event 
callback gives all the extra functionality needed.

The MCE code needs to be updated to use that - and then it will be integrated 
into the events framework.

Thanks,

	Ingo
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