From: Russell King - ARM Linux <linux@arm.linux.org.uk>
To: Michal Marek <mmarek@suse.cz>
Cc: Jason Cooper <jason@lakedaemon.net>,
Linus Walleij <linus.walleij@linaro.org>,
Grant Likely <grant.likely@secretlab.ca>,
Rob Herring <rob.herring@linaro.org>,
linux-kernel@vger.kernel.org, devicetree@vger.kernel.org,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] ARM: kbuild: Fix forced rebuild after 'make dtbs'
Date: Tue, 25 Nov 2014 23:51:50 +0000 [thread overview]
Message-ID: <20141125235150.GH3836@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <5474F78F.2060906@suse.cz>
On Tue, Nov 25, 2014 at 10:41:35PM +0100, Michal Marek wrote:
> Dne 2.11.2014 v 21:52 Jason Cooper napsal(a):
> > After this patch:
> >
> > f4d4ffc03efc kbuild: dtbs_install: new make target
> >
> > was added the kernel tree, Linus Walleij noticed that 'make dtbs' forced
> > a following 'make zImage' to rebuild the entire tree, even though
> > nothing had changed. His report:
> >
> > After this patch a while back I have observed the following behaviour
> > of the kernel build:
> >
> > make zImage
> > make zImage
> > -> incremental build, just relink
> >
> > make zImage
> > make dtbs
> > make zImage
> > -> The whole kernel gets rebuilt
> >
> > So now if I happen to recompile my device trees, I suddenly want
> > the entire zImage to be rebuilt to? It's by definition not changes
> > that affect the kernel build :-(
> >
> > I noticed this because my build scripts calls make dtbs && make
> > zImage, and started to rebuild absolutely everything all the time.
> >
> > To fix this, we make only the dtbs_install target depend on the prepare
> > target. It's needed to make sure KERNELVERSION is calculated prior to
> > installing.
>
> If a mere 'make prepare' causes a rebuild of the whole kernel, then
> there is something fishy in the ARM Makefiles. However, if you only need
> the KERNELRELEASE variable, then you do not need to depend on prepare.
> The main Makefile makes sure that silentoldconfig is ran and therefore
> KERNELRELEASE set for all targets except make *config.
Running make prepare and then re-running a build doesn't rebuild anything
for me. However, I always build with O= Also works if I do a make
dtbs too. So, everything seems to work as expected here.
I think this needs a bit more debugging to see why the whole kernel is
being rebuilt - the kernel build system has methods to tell you why stuff
is being built, which would be a good place to start.
--
FTTC broadband for 0.8mile line: currently at 9.5Mbps down 400kbps up
according to speedtest.net.
next prev parent reply other threads:[~2014-11-25 23:51 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-01 10:15 [git pull] Devicetree changes for v3.15 Grant Likely
2014-04-01 19:42 ` Paul Bolle
2014-04-01 20:18 ` Rob Herring
[not found] ` <CAL_JsqKyLPa9PhNbzda1iPyLjfvQpsUMLR7sGRegYmLsrkY-LQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2014-04-01 20:34 ` Paul Bolle
2014-04-01 20:32 ` Grant Likely
[not found] ` <20140401203250.0B2A7C408A6-WNowdnHR2B42iJbIjFUEsiwD8/FfD2ys@public.gmane.org>
2014-04-01 20:39 ` Grant Likely
2014-04-01 20:46 ` Paul Bolle
[not found] ` <CACxGe6vCrkHPL6UNy1p8AO4+z5VFRY6w4_2grQEZQwp_3jJ7Yw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2014-09-26 12:30 ` Linus Walleij
[not found] ` <CACRpkdZoo=P7uTO1rNDD_HUPjfAk26C0=mNYPoZmTV0wcO3V-w-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2014-09-26 14:19 ` Jason Cooper
2014-09-29 8:52 ` Linus Walleij
2014-10-27 15:39 ` Linus Walleij
[not found] ` <CACRpkdYmJWy1_vs0tWRA7SvkQnvbXXKqf7pHpH5b5tZ6vR+KJg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2014-11-02 20:52 ` [PATCH] ARM: kbuild: Fix forced rebuild after 'make dtbs' Jason Cooper
2014-11-25 21:41 ` Michal Marek
2014-11-25 23:51 ` Russell King - ARM Linux [this message]
[not found] ` <20141125235150.GH3836-l+eeeJia6m9vn6HldHNs0ANdhmdF6hFW@public.gmane.org>
2014-11-26 0:57 ` Jason Cooper
2014-11-26 13:57 ` Linus Walleij
[not found] ` <CACRpkdZJoWbQeuZ4ZXGbQr0+SNG_9ZA+cQkAA0C2F9rnZDYtyQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2014-11-26 14:41 ` Russell King - ARM Linux
[not found] ` <20141126144153.GK3836-l+eeeJia6m9vn6HldHNs0ANdhmdF6hFW@public.gmane.org>
2014-11-28 14:10 ` Linus Walleij
[not found] ` <CACRpkdYwQT3+RLxP_b_kYJoHV4L7sZ7yiU=JZWVq_zHKz0EY_g-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2014-12-01 13:55 ` Michal Marek
[not found] ` <547C7364.8000009-AlSwsSmVLrQ@public.gmane.org>
2014-12-04 11:22 ` Grant Likely
2014-12-04 11:24 ` Russell King - ARM Linux
2014-11-26 9:39 ` Michal Marek
[not found] ` <20140926141943.GC23926-u4khhh1J0LxI1Ri9qeTfzeTW4wlIGRCZ@public.gmane.org>
2014-09-29 12:49 ` [git pull] Devicetree changes for v3.15 Grant Likely
[not found] ` <20140929124922.CBE9FC4150A-WNowdnHR2B42iJbIjFUEsiwD8/FfD2ys@public.gmane.org>
2014-09-29 13:52 ` Jason Cooper
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