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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Date:	Wed, 19 Nov 2014 15:04:00 -0800
From:	Andy Lutomirski <luto@...capital.net>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	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

On Wed, Nov 19, 2014 at 11:44 AM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
> On Wed, Nov 19, 2014 at 11:29 AM, Andi Kleen <andi@...stfloor.org> wrote:
>>
>> The exception handlers which use the IST stacks don't necessarily
>> set irq count. Maybe they should.
>
> Hmm. I think they should. Since they clearly must not schedule, as
> they use a percpu stack.
>
> Which exceptions use IST?
>
> [ grep grep ]
>
> Looks like stack, doublefault, nmi, debug and mce. And yes, I really
> think they should all raise the irq count if they don't already.
> Rather than add random arch-specific "let's check that we're on the
> right stack" code to the might-sleep stuff, just use the one we have.
>

Does that include nmi?  I'm a bit afraid of touching that code.

It's certainly easy enough to bump irq_count in the paranoid entries.

--Andy

>                     Linus



-- 
Andy Lutomirski
AMA Capital Management, LLC
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