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

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Date:	Tue, 7 Jun 2016 11:58:36 +0200
From:	Michal Marek <mmarek@...e.cz>
To:	"Zanoni, Paulo R" <paulo.r.zanoni@...el.com>,
	"yamada.masahiro@...ionext.com" <yamada.masahiro@...ionext.com>
Cc:	"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"

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


View attachment "0001-kbuild-Initialize-NOSTDINC_CFLAGS.patch" of type "text/x-patch" (789 bytes)