linux-kernel - Re: [PATCH 3.11-rc1] crypto: Fix boot failure due to module dependency.

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Message-ID: <8043923.9cbosS4r2b@vostro.rjw.lan>
Date:	Sat, 20 Jul 2013 11:51:55 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Tim Chen <tim.c.chen@...ux.intel.com>
Cc:	Herbert Xu <herbert@...dor.apana.org.au>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
	linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
	ak <ak@...ux.intel.com>, "H. Peter Anvin" <hpa@...or.com>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>
Subject: Re: [PATCH 3.11-rc1] crypto: Fix boot failure due to module dependency.

On Saturday, July 20, 2013 05:06:29 AM Rafael J. Wysocki wrote:
> On Saturday, July 20, 2013 02:00:44 AM Rafael J. Wysocki wrote:
> > On Friday, July 19, 2013 04:16:30 PM Greg Kroah-Hartman wrote:
> > > On Fri, Jul 19, 2013 at 11:38:04PM +0200, Rafael J. Wysocki wrote:
> > > > Alas, this is not the one I'd like to apply.
> > > > 
> > > > With that patch applied, new device objects are created to avoid binding the
> > > > processor driver directly to the cpu system device objects, because that
> > > > apparently confuses udev and it starts to ignore the cpu modalias once the
> > > > driver has been bound to any of those objects.
> > > > 
> > > > I've verified in the meantime that this indeed is the case.
> > > > 
> > > > A link to the patch in question: https://patchwork.kernel.org/patch/2830561/
> > > > 
> > > > Greg, I asked you some time ago whether or not it was possible for udev to stop
> > > > autoloading modules that matched the cpu modalias after a driver had been bound
> > > > to the cpu system device objects and you said "no".  However, this time I can
> > > > say with certainty that that really is the case.  So, the question now is
> > > > whether or not we can do anything in the kernel to avoid that confusion in udev
> > > > instead of applying the patch linked above (which is beyond ugly in my not so
> > > > humble opinion)?
> > > 
> > > udev isn't doing any module loading, 'modprobe' is just being called for
> > > any new module alias that shows up in the system, and all of the drivers
> > > that match it then get loaded.
> > 
> > The problem is that that doesn't happen when a driver is bound to the
> > cpu system device objects.  modprobe is just not called for modules that
> > match the cpu modalias in that case.
> > 
> > If I call modprobe manually for any of the modules in question, it loads
> > and works no problem.
> 
> OK, I know what's up.  udev has no rule that would allow it to load stuff on
> the basis of MODALIAS if DRIVER is set in the event properties.
> 
> So, the following rule needs to be added to udev rules for things to work
> as before:
> 
> DRIVER=="processor", ENV{MODALIAS}=="?*", IMPORT{builtin}="kmod load $env{MODALIAS}"
> 
> To be precise, I added a file called 80-drivers.rules to /etc/udev/rules.d/

Well, that wasn't a good idea, because the original 80-drivers.rules didn't
work then, but I renamed the new file (in /etc/udev/rules.d/) to 80-cpu.rules
and put this line (alone) into it:

ACTION="add", SUBSYSTEM=="cpu", ENV{MODALIAS}=="?*", IMPORT{builtin}="kmod load $env{MODALIAS}"

After that change everything works happily again.

Thanks,
Rafael


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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