linux-kernel - Re: Random panic in load

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Message-ID: <53D064C7.5050807@daenzer.net>
Date:	Thu, 24 Jul 2014 10:43:35 +0900
From:	Michel Dänzer <michel@...nzer.net>
To:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>
CC:	Dietmar Eggemann <dietmar.eggemann@....com>,
	Ingo Molnar <mingo@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Random panic in load_balance() with 3.16-rc

On 24.07.2014 04:20, Linus Torvalds wrote:
> On Wed, Jul 23, 2014 at 12:02 PM, Peter Zijlstra <peterz@...radead.org> wrote:
>>
>> Here goes..
> 
> Oh. So this doesn't have CPUMASK_OFFSTACK set at all, so the pointer
> has never been loaded from memory in the first place. The calculation
> has been (for me) something like
> 
>         movq    $load_balance_mask, %rax
>         add %gs:this_cpu_off, %rax
> 
> and then gcc is being stupid and saving it to the frame and reloading
> it for no good reason (at least for me it *also* saved the value in
> %rbx in order to save it into "env.cpus", and the stack spill seems to
> be just moronic).
> 
> In Michel's oops, %rbx doesn't contain the pointer any more, though,
> so he clearly does have a different compiler. His frame offsets are
> rather different too ("-136(%rbp)" vs "-168(%rbp)") so looking at
> whether possibly some stack frame got overwritten is clearly very
> compiler-specific.
> 
> Michel, mind doing
> 
>     make kernel/sched/fair.s
> 
> and sending us the resulting file?

Here it is, gzipped, hope that's okay.

Note that my tree is now based on 3.16-rc6.


-- 
Earthling Michel Dänzer            |                  http://www.amd.com
Libre software enthusiast          |                Mesa and X developer

Download attachment "fair.s.gz" of type "application/gzip" (187696 bytes)