linux-kernel - Re: [PATCH RFC] NMI Re-introduce un[set]_nmi

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Message-ID: <20080904144956.GJ28636@redhat.com>
Date:	Thu, 4 Sep 2008 10:49:56 -0400
From:	aris <arozansk@...hat.com>
To:	Prarit Bhargava <prarit@...hat.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org, dzickus@...hat.com,
	Thomas.Mingarelli@...com, ak@...ux.intel.com, mingo@...e.hu
Subject: Re: [PATCH RFC] NMI Re-introduce un[set]_nmi_callback

> Peter -- good question.  The HP systems with this HW will use the hpwdt  
> driver in place of the default nmi watchdog.  When the HW detects a  
> problem, the HW will generate a single NMI that the driver will handle.   
> The driver doesn't want the NMI to be rejected due to a reason code.   
> I'm sure that Thomas Mingarelli, who is cc'd, can provide further 
> details.
it's not the first time this is asked. I think it's needed for some kernel
debuggers as well: make sure a function is called before anything else
when a NMI happens. something that the notifier chain can't do.

> From our quick conversation as well, you raised an interesting point  
> about oprofile, kgdb, and other subsystems that use the NMI notifier  
> chains -- they may be impacted by the NMI callback.
>
> Don (dzickus) or Aris, do you have any thoughts on how to get around the  
> second issue?  We could check to see if anything is registered on the  
> notifier chain and the fail to register the callback.
or call the notifier chain in case it indentifies it's a unexpected NMI?

-- 
Aristeu

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