linux-kernel - Re: Regression in "kbuild: fix if_change and friends to consider argument order"

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Date:	Tue, 7 Jun 2016 19:03:56 +0900
From:	Masahiro Yamada <yamada.masahiro@...ionext.com>
To:	Michal Marek <mmarek@...e.cz>
Cc:	"Zanoni, Paulo R" <paulo.r.zanoni@...el.com>,
	"linux-kbuild@...r.kernel.org" <linux-kbuild@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"nicolas.pitre@...aro.org" <nicolas.pitre@...aro.org>
Subject: Re: Regression in "kbuild: fix if_change and friends to consider
 argument order"

2016-06-07 18:58 GMT+09:00 Michal Marek <mmarek@...e.cz>:
> On 2016-06-07 11:38, Michal Marek wrote:
>> On 2016-06-07 03:38, Zanoni, Paulo R wrote:
>>> Hi
>>>
>>> I recently noticed that alternating between "make" and "make targz-pkg"
>>> rebuilds the whole Kernel. This was not happening before. As a Kernel
>>> developer, my build/install/test environment heavily relies on the fact
>>> that "make targz-pkg" only quickly generates the tarball if everything
>>> is already built, so this change is heavily impacting my development
>>> environment.
>>>
>>> I did some bisection and concluded that the first bad commit is:
>>>
>>> commit 9c8fa9bc08f60ac657751daba9fccf828a36cfed
>>> Author: Masahiro Yamada
>>> Date:   Sat May 7 15:48:26 2016 +0900
>>>     kbuild: fix if_change and friends to consider argument order
>>>
>>> I also verified that if I just revert this commit on top of the
>>> most recent tree it goes back to the usual behavior.
>>>
>>> I read the commit message and it seems that some unneeded rebuilds are
>>> somewhat expected, but I can't understand why such a change in the
>>> command line like the one I did triggers everything to be rebuilt.
>>> IMHO, it really shouldn't. I also wonder that maybe the regression I'm
>>> experiencing was not expected in the original change, so maybe there's
>>> a way to keep the original improvement caused by the mentioned patch
>>> without the regression I'm experiencing.
>>>
>>> How to reproduce (exact commands I used at every bisect step):
>>>
>>> $ make tinyconfig
>>> $ time make -j4 V=2 # this should build things
>>> $ time make -j4 V=2 # just to make sure nothing will be rebuilt
>>> $ time make -j4 V=2 targz-pkg
>>
>> I can reproduce it.
>
> Try the attached patch.
>
> Michal
>


Right.

I had already sent a similar patch.
https://patchwork.kernel.org/patch/9159863/

My concern is it is effectively
reverting e8f5bdb02ce0.
I hope Rik can comment on that.




-- 
Best Regards
Masahiro Yamada