linux-kernel - Re: dell_rbtn - kernel panic at boot...

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Date:	Sun, 24 May 2015 21:44:32 -0700
From:	Darren Hart <dvhart@...radead.org>
To:	Pali Rohár <pali.rohar@...il.com>
Cc:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Valdis Kletnieks <Valdis.Kletnieks@...edu>,
	lkml <linux-kernel@...r.kernel.org>,
	platform-driver-x86@...r.kernel.org,
	Matthew Garrett <mjg59@...f.ucam.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: dell_rbtn - kernel panic at boot...

On Sat, May 23, 2015 at 03:05:36AM +0200, Pali Rohár wrote:
> On Saturday 23 May 2015 00:53:16 Dmitry Torokhov wrote:
> > On Thu, May 21, 2015 at 7:06 PM, Valdis Kletnieks
> > 
> > <Valdis.Kletnieks@...edu> wrote:
> > > So after I made both config variables =y, the resulting kernel
> > > built, but died a glorious death at boot.
> > 
> > I guess if both are built-in then, according to link order,
> > dell-laptop starts first, before dell-rbtn, and dies in
> > dell_rbtn_notifier_register() in call to
> > driver_for_each_device(&rbtn_driver.drv, ...) because rbtn_driver has
> > not been registered yet and thus half-initlalized.
> > 
> > Thanks.
> 
> pr_debug() messages could be useful... but no idea if we can get them.
> 
> Is there any way to fix that dependency race condition? Could 
> driver_attach() function call help?

I believe you can avoid this by moving dell-rbtn earlier in the Makefile than
dell-laptop - but this is fragile and a hack to resolve a dependency problem.

I suppose this is why thinkpad-acpi.c is huge, and why having separate drivers
talk to eachother is discouraged.

dell-laptop seems to be the base, while dell-rbtn is the more specific of the
two - which makes dell-laptop calling a dell-rbtn function which requires
dell-rbtn to have been initialized prior a poor approach.

Greg, Matthew, I'm tempted to recommend this 434 line driver be rolled into
dell-laptop.c. Any strong opinions?

-- 
Darren Hart
Intel Open Source Technology Center
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