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Date: Mon, 22 Jan 2024 11:20:50 +0100
From: Uwe =?utf-8?Q?Kleine-K=C3=B6nig?= <u.kleine-koenig@pengutronix.de>
To: Mirsad Todorovac <mirsad.todorovac@alu.unizg.hr>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, 
	Helge Deller <deller@gmx.de>, "James E.J. Bottomley" <James.Bottomley@hansenpartnership.com>, 
	Ard Biesheuvel <ardb@kernel.org>, Arnd Bergmann <arnd@arndb.de>, 
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Hans de Goede <hdegoede@redhat.com>, 
	Huacai Chen <chenhuacai@kernel.org>, Javier Martinez Canillas <javierm@redhat.com>, 
	Linus Walleij <linus.walleij@linaro.org>, Prathu Baronia <prathubaronia2011@gmail.com>, 
	Sam Ravnborg <sam@ravnborg.org>, Sui Jingfeng <suijingfeng@loongson.cn>, 
	Thomas Zimmermann <tzimmermann@suse.de>, dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org, 
	linux-parisc@vger.kernel.org
Subject: Re: [BUG][BISECTED] Freeze at loading init ramdisk
Message-ID: <2q2t7mgnpuk2t7wq2tmymxv72oki4uetojkz72xofn7wh45l64@smk3wi6zw54g>
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On Thu, Jan 18, 2024 at 09:04:05PM +0100, Mirsad Todorovac wrote:
>=20
>=20
> On 1/18/24 08:45, Uwe Kleine-K=F6nig wrote:
> > Hello Mirsad,
> >=20
> > On Wed, Jan 17, 2024 at 07:47:49PM +0100, Mirsad Todorovac wrote:
> > > On 1/16/24 01:32, Mirsad Todorovac wrote:
> > > > On the Ubuntu 22.04 LTS Jammy platform, on a mainline vanilla torva=
lds tree kernel, the boot
> > > > freezes upon first two lines and before any systemd messages.
> > > >=20
> > > > (Please find the config attached.)
> > > >=20
> > > > Bisecting the bug led to this result:
> > > >=20
> > > > marvin@defiant:~/linux/kernel/linux_torvalds$ git bisect good
> > > > d97a78423c33f68ca6543de510a409167baed6f5 is the first bad commit
> > > > commit d97a78423c33f68ca6543de510a409167baed6f5
> > > > Merge: 61da593f4458 689237ab37c5
> > > > Author: Linus Torvalds <torvalds@linux-foundation.org>
> > > > Date:=A0=A0 Fri Jan 12 14:38:08 2024 -0800
> > > >=20
> > > > [...]
> > > >=20
> > > > Hope this helps.
> > >=20
> > > P.S.
> > >=20
> > > As I see that this is a larger merge commit, with 5K+ lines changed, =
I don't think I can
> > > bisect further to determine the culprit.
> >=20
> > Actually it's not that hard. If a merge commit is the first bad commit
> > for a bisection, either the merge wasn't done correctly (less likely,
> > looking at d97a78423c33f68ca6543de510a409167baed6f5 I'd bet this isn't
> > the problem); or changes on different sides conflict or you did
> > something wrong during bisection.
> >=20
> > To rule out the third option, you can just retest d97a78423c33,
> > 61da593f4458 and 689237ab37c5. If d97a78423c33 is the only bad one, you
> > did it right.
>=20
> This was confirmed.
>=20
> > Then to further debug the second option you can find out the offending
> > commit on each side with a bisection as follows, here for the RHS (i.e.
> > 689237ab37c5):
> >=20
> > 	git bisect start 689237ab37c5 $(git merge-base 61da593f4458 689237ab37=
c5)
> >=20
> > and then in each bisection step do:
> >=20
> > 	git merge --no-commit 61da593f4458
> > 	test if the problem is present
> > 	git reset --hard
> > 	git bisect good/bad
> >=20
> > In this case you get merge conflicts in drivers/video/fbdev/amba-clcd.c
> > and drivers/video/fbdev/vermilion/vermilion.c. In the assumption that
> > you don't have these enabled in your .config, you can just ignore these.
> >=20
> > Side note: A problem during bisection can be that the .config changes
> > along the process. You should put your config into (say)
> > arch/x86/configs/lala_defconfig and do
> >=20
> > 	make lala_defconfig
> >=20
> > before building each step to prevent this.
>=20
> I must have done something wrong:
>=20
> marvin@defiant:~/linux/kernel/linux_torvalds$ git bisect log
> # bad: [689237ab37c59b9909bc9371d7fece3081683fba] fbdev/intelfb: Remove d=
river
> # good: [de927f6c0b07d9e698416c5b287c521b07694cac] Merge tag 's390-6.8-1'=
 of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux
> git bisect start '689237ab37c5' 'de927f6c0b07d9e698416c5b287c521b07694cac'
> # good: [d9f25b59ed85ae45801cf45fe17eb269b0ef3038] fbdev: Remove support =
for Carillo Ranch driver
> git bisect good d9f25b59ed85ae45801cf45fe17eb269b0ef3038
> # good: [e2e0b838a1849f92612a8305c09aaf31bf824350] video/sticore: Remove =
info field from STI struct
> git bisect good e2e0b838a1849f92612a8305c09aaf31bf824350
> # good: [778e73d2411abc8f3a2d60dbf038acaec218792e] drm/hyperv: Remove fir=
mware framebuffers with aperture helper
> git bisect good 778e73d2411abc8f3a2d60dbf038acaec218792e
> # good: [df67699c9cb0ceb70f6cc60630ca938c06773eda] firmware/sysfb: Clear =
screen_info state after consuming it
> git bisect good df67699c9cb0ceb70f6cc60630ca938c06773eda

FTR: Now that you identified df67699c9cb0ce as the culprit, calling
git bisect good on it was wrong, so something was fishy in your testing
and it's no surprise the bisection found a wrong result.

Best regards
Uwe

--=20
Pengutronix e.K.                           | Uwe Kleine-K=F6nig            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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