linux-kernel - Re: Perhaps a side effect regarding NMI returns

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Message-ID: <m2r50qlmgk.fsf@firstfloor.org>
Date:	Tue, 29 Nov 2011 12:09:47 -0800
From:	Andi Kleen <andi@...stfloor.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	Paul Turner <pjt@...gle.com>
Subject: Re: Perhaps a side effect regarding NMI returns

Linus Torvalds <torvalds@...ux-foundation.org> writes:

Not sure what problem Steven thinks is there. Once you 
switched the stack any nesting is fine.

> I would suggest that the actual NMI handler itself should probably
> never use that paranoid exit at all, and just always use a regular
> iret. Screw scheduling and TIF checks.

The reason I added them originally is to prevent the race of remote
kernel events being delayed for a long time. With Frederic's nohz work
this will be more important in the future. Today it would be eventually
picked up by the regular timer interrupts.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only
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