linux-kernel - Re: frequent lockups in 3.18rc4

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Date:	Sat, 13 Dec 2014 09:15:34 -0500
From:	Sasha Levin <sasha.levin@...cle.com>
To:	Ingo Molnar <mingo@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Dave Jones <davej@...hat.com>, Chris Mason <clm@...com>,
	Mike Galbraith <umgwanakikbuti@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Dâniel Fraga <fragabr@...il.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: frequent lockups in 3.18rc4

On 12/13/2014 03:27 AM, Ingo Molnar wrote:
> 
> * Ingo Molnar <mingo@...nel.org> wrote:
> 
>>
>> * Linus Torvalds <torvalds@...ux-foundation.org> wrote:
>>
>>> On Fri, Dec 12, 2014 at 10:54 AM, Dave Jones <davej@...hat.com> wrote:
>>>
>>>>
>>>> Something that's still making me wonder if it's some kind of 
>>>> hardware problem is the non-deterministic nature of this bug.
>>>
>>> I'd expect it to be a race condition, though. Which can easily 
>>> cause these kinds of issues, and the timing will be pretty 
>>> random even if the load is very regular.
>>>
>>> And we know that the scheduler has an integer overflow under 
>>> Sasha's loads, although I didn't hear anything from Ingo and 
>>> friends about it. Ingo/Peter, you were cc'd on that report, 
>>> where at least one of the multiplcations in wake_affine() ended 
>>> up overflowing..
>>
>> Just to make sure, is there any other wake_affine report other 
>> than the one in this thread? (I tried a wake_affine full text 
>> search on my inbox and didn't find anything that appeared 
>> relevant.)
> 
> Found the report from Sasha:
> 
>     sched: odd values for effective load calculations
> 
> right?

Yup, that's the one.


Thanks,
Sasha

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