linux-kernel - Re: [PATCH] Revert "x86: Disable IST stacks for debug/int 3/stack fault for PREEMPT

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Message-ID: <20140105180446.GX20765@two.firstfloor.org>
Date:	Sun, 5 Jan 2014 19:04:47 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Mike Galbraith <bitbucket@...ine.de>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Ben Hutchings <ben@...adent.org.uk>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Steven Rostedt <rostedt@...tedt.homelinux.com>,
	723180@...s.debian.org, Brian Silverman <bsilver16384@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-rt-users@...r.kernel.org
Subject: Re: [PATCH] Revert "x86: Disable IST stacks for debug/int 3/stack
 fault for PREEMPT_RT"

On Sun, Jan 05, 2014 at 05:45:47AM +0100, Mike Galbraith wrote:
> On Sat, 2014-01-04 at 19:18 +0100, Andi Kleen wrote: 
> > On Fri, Jan 03, 2014 at 02:55:48PM +0100, Sebastian Andrzej Siewior wrote:
> > > where do I start. Let me explain what is going on here. The code
> > > sequence
> > 
> > Yes the IST stacks are needed for correctness, even in more cases than
> > the example below. You cannot just disable them, just because you don't
> > like them.
> 
> You had a better reason than dislike.

Ah true it was me. Good point. I forgot all about that.

Probably it needs some form of the NMI style paranoid_* switch.

-Andi
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