linux-kernel - Re: [PATCH] firmware loader: don't cancel _nowait requests when helper is not yet available

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Date:	Wed, 14 Mar 2012 01:10:40 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Kay Sievers <kay@...y.org>
Cc:	Greg KH <gregkh@...uxfoundation.org>,
	Christian Lamparter <chunkeey@...glemail.com>,
	linux-kernel@...r.kernel.org,
	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	alan@...rguk.ukuu.org.uk,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux PM mailing list <linux-pm@...r.kernel.org>
Subject: Re: [PATCH] firmware loader: don't cancel _nowait requests when helper is not yet available

On Wednesday, March 14, 2012, Kay Sievers wrote:
> On Tue, Mar 13, 2012 at 20:42, Rafael J. Wysocki <rjw@...k.pl> wrote:
> > On Sunday, March 11, 2012, Kay Sievers wrote:
> >> On Sat, Mar 10, 2012 at 00:36, Greg KH <gregkh@...uxfoundation.org> wrote:
> 
> >> > What does uevent have to do with things here?
> >>
> >> I don't think that the firmware loader should care about the
> >> usermodehelper at all, and that stuff fiddling should just be removed
> >> from the firmware class.
> >
> > It's there to warn people that their drivers do stupid things like
> > loading frimware during system resume, which is guaranteed not to work.
> >
> > IOW, it's there very much on purpose.
> 
> Using the /sbin/hotplug is no case that needs any warning. It' such a
> broken model these days, that firmware loading is the least problem
> that occurs with it.
> 
> >> Forking /sbin/hotplug is disabled by default, it is a broken concept,
> >> and it cannot work reliably on today's systems.
> >>
> >> Firmware is not loaded by /sbin/hotplug since many years, but by udev
> >> or whatever service handles uevents, like ueventd on android.
> >
> > Which I'm not sure why is relevant here.
> 
> It is relevant in the sense that the firmware loader should not even
> know that a uevent *can* cause a usermodehelper exec() if it runs in
> legacy mode. The firmware loader just has no business in fiddling with
> the details of driver core legacy stuff. I don't think his warning
> makes much sense.

But that warning actually triggers for drivers that attempt to use
request_firmware() during system resume, even though /sbin/hotplug isn't
used any more.

usermodehelper_is_disabled() means "we are in the middle of system power
transition" rather than anything else (I agree it should be called
suspend_in_progress() or something similar these days).

Thanks,
Rafael
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