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

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Message-ID: <583F1A5A.7040708@redhat.com>
Date:   Wed, 30 Nov 2016 13:28:42 -0500
From:   Prarit Bhargava <prarit@...hat.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Jarod Wilson <jarod@...hat.com>
CC:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Tony Luck <tony.luck@...el.com>, zarniwhoop73@...glemail.com,
        linux-kbuild@...r.kernel.org
Subject: Re: Odd build breakage in 4.9-rc7



On 11/30/2016 01:18 PM, Linus Torvalds wrote:
> On Wed, Nov 30, 2016 at 9:24 AM, Jarod Wilson <jarod@...hat.com> wrote:
>>
>> Now, if I omit the -j8 and do a single-threaded build, then things work
>> fine. Prarit bisected this failure to commit
>> 9a6fb28a355d2609ace4dab4e6425442c647894d, and indeed, when reverting that
>> patch and the two that follow it from rc7, parallel make works again.
> 
> I seriously doubt that commit really makes a difference, and I think
> it was just random luck.
> 
> Do you perhaps have ccache installed?
> 
> Because ccache at some point broke dependency generation of "gcc -MM"
> that the kernel build system uses, giving those random "No such file"
> build errors.
> 
> Try uninstalling ccache and see if that helps.
> 

I reported this last week on LKML and I'm building on a freshly installed
systems that do not have ccache installed.

For example,

[root@...el-brickland-04 linux]# rpm -q ccache
package ccache is not installed
[root@...el-brickland-04 linux]# which ccache
/usr/bin/which: no ccache in
(/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/usr/libexec/git-core:/root/bin)

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.

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

Also cc'ing linux-kbuild.

P.

>               Linus
>