linux-kernel - Re: Odd build breakage in 4.9-rc7

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Date:   Thu, 01 Dec 2016 07:47:50 -0500
From:   Prarit Bhargava <prarit@...hat.com>
To:     Nicolas Pitre <nicolas.pitre@...aro.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
CC:     Jarod Wilson <jarod@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Tony Luck <tony.luck@...el.com>, zarniwhoop73@...glemail.com,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>
Subject: Re: Odd build breakage in 4.9-rc7



On 11/30/2016 05:41 PM, Nicolas Pitre wrote:
> On Wed, 30 Nov 2016, Linus Torvalds wrote:
> 
>> On Wed, Nov 30, 2016 at 10:50 AM, Prarit Bhargava <prarit@...hat.com> wrote:
>>>
>>> It comes back.  The steps to reproduce this are:
>>>
>>> 1.  checkout latest linux.git
>>> 2.  make -j112
>>>
>>> (IOW, it occurs 100% of the time for me on a clean tree.)
> 
> I don't have access to such hardware where -j112 could ever make sense.  :-)

:)  I could push the builds onto the -j256 but I'm doing other stuff over there. :)

> In other words, I can't reproduce regardless of the -j value I try.
> 
>> I suspect it's not new, it's just that you are able to hit the timing
>> just right (and the new include presumable makes that just be much
>> easier).
> 
> Here's the best fix I can think of. I can't convince myself any other 
> location would be 100% safe.  Obviously I can't confirm if this actually 
> fixes anything.
> 
> ----- >8
> Subject: kbuild: make sure autoksyms.h exists early
> 

I'm building with this patch on top of latest now.  I will put it in a tight
loop and clear the drop_caches between builds to see if I can make it fail.

Thanks Nicolas -- your help is very much appreciated.

P.