linux-kernel - Re: [PATCH v3 3/3] sched, x86: Check that we're on the right stack in schedule and __might

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Message-ID: <20141120074501.GA3805@gmail.com>
Date:	Thu, 20 Nov 2014 08:45:02 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andi Kleen <andi@...stfloor.org>,
	Borislav Petkov <bp@...en8.de>,
	the arch/x86 maintainers <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Tony Luck <tony.luck@...el.com>
Subject: Re: [PATCH v3 3/3] sched, x86: Check that we're on the right stack
 in schedule and __might_sleep


* Andy Lutomirski <luto@...capital.net> wrote:

> On Wed, Nov 19, 2014 at 3:59 PM, Linus Torvalds
> <torvalds@...ux-foundation.org> wrote:
> > On Wed, Nov 19, 2014 at 3:49 PM, Andy Lutomirski <luto@...capital.net> wrote:
> >>
> >> My only real objection is that it's going to be ugly and 
> >> error prone. It'll have to be something like:
> >
> > No.
> >
> >> because the whole point of this series is to make the IST 
> >> entries not be atomic when they come from userspace.
> >
> > Andy, you need to lay off the drugs.
> >
> 
> No drugs, just imprecision.  This series doesn't change NMI 
> handling at all.  It only changes machine_check int3, debug, 
> and stack_segment. (Why is #SS using IST stacks anyway?)

We made most of those preemptible in -rt and changed it away from 
the IST. I never got a good explanation from anyone for why they 
were IST in the first place - histeric accident or such.

Feel free to clean this up too!

Thanks,

	Ingo
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