linux-kernel - Re: [linus:master] BUILD REGRESSION 2a26d99b251b8625d27aed14e97fc10707a3a81f

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Message-ID: <20161031045814.3j45sn6can6fzkby@wfg-t540p.sh.intel.com>
Date:   Mon, 31 Oct 2016 12:58:14 +0800
From:   Fengguang Wu <fengguang.wu@...el.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Philip Li <philip.li@...el.com>
Subject: Re: [linus:master] BUILD REGRESSION
 2a26d99b251b8625d27aed14e97fc10707a3a81f

Hi Linus,

On Sun, Oct 30, 2016 at 01:25:50PM -0700, Linus Torvalds wrote:
>On Sun, Oct 30, 2016 at 11:03 AM, kbuild test robot
><fengguang.wu@...el.com> wrote:
>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git  master
>> 2a26d99b251b8625d27aed14e97fc10707a3a81f  Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net
>
>Hmm. The build errors seem to be pretty independent of that merge,
>including internal compiler errors etc.

This "BUILD REGRESSION" report lists errors in all commits of a branch
-- ie. not only the showed HEAD commit. Sure "all commits" will be too
huge for the mainline kernel, so there will be limits applied.

>Did perhaps something change in the kbuild test robot?

Recently we lowered the threshold to 2 before sending unsolicited
reports like this. That threshold means when we find >= 3 errors in a
tree, only the first 2 will be reported in the regular way (reporting
to the first bad commit). The more errors will be send in a summary
"BUILD REGRESSION" email listing all the triggered errors.

That's a trick to avoid flooding possibly large number of duplicate
error reports to LKML while avoiding hiding possibly non-duplicate
errors. It works well for normal branches, however looks less
effective for linus/master because here we have less clue about the
origin of errors.

So sorry -- this report is a noise. The fix could be to raise the
reporting threshold significantly for linus/master. It's also possible
some bug in the 0day-bot triggered this report unexpectedly.

Regards,
Fengguang