Date: Sat, 12 Jun 2010 12:25:58 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Huang Ying <ying.huang@intel.com>,
       Fr??d??ric Weisbecker <fweisbec@gmail.com>,
       Don Zickus <dzickus@redhat.com>,
       Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: "H. Peter Anvin" <hpa@zytor.com>, linux-kernel@vger.kernel.org,
       Andi Kleen <andi@firstfloor.org>
Subject: Re: [RFC 1/3] Unified NMI delayed call mechanism
Message-ID: <20100612102558.GA4000@elte.hu>
References: <1276334896-7075-1-git-send-email-ying.huang@intel.com>
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* Huang Ying <ying.huang@intel.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@intel.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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