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

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Date:   Wed, 30 Nov 2016 17:54:26 -0500 (EST)
From:   Nicolas Pitre <nico@...xnic.net>
To:     Prarit Bhargava <prarit@...hat.com>
cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        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 Wed, 30 Nov 2016, Prarit Bhargava wrote:

> 
> 
> On 11/30/2016 01:36 PM, Linus Torvalds wrote:
> > On Wed, Nov 30, 2016 at 10:28 AM, Prarit Bhargava <prarit@...hat.com> wrote:
> > ]>
> >> In my case I tracked this to commit 3637efb00864 ("x86/mce: Add PCI quirks to
> >> identify Xeons with machine check recovery") which adds the include for
> >> generated/autoksyms.h.
> > 
> > Ok, that at least makes some sense. The other blamed commit did not
> > seem to possibly make a difference.
> > 
> >> Searching LKML and I came across a report from Ken Moffat from a month ago:
> >>
> >> http://marc.info/?l=linux-kernel&m=147794681124332&w=2
> > 
> > Does a "make clean" get rid of it forever? Or does it come back?
> 
> 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.)
> 
> To work around the bug I have to do
> 
> 1.  checkout latest linux.git
> 2.  comment out the include for generated/autoksyms.h at include/linux/export.h:81
> 3.  compile with -j112
> 
> This fails loudly, but then I do
> 
> 4.  uncomment the include for generated/autoksyms.h at include/linux/export.h:81

A simpler workaround is simply:

	touch include/generated/autoksyms.h

But hopefully the patch I just sent would fix it for good.


Nicolas