From: Ming Lei <ming.lei@canonical.com>
To: Takashi Iwai <tiwai@suse.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
"Rafael J. Wysocki" <rjw@sisk.pl>, Kay Sievers <kay@vrfy.org>,
linux-kernel@vger.kernel.org
Subject: Re: A workaround for request_firmware() stuck in module_init
Date: Tue, 4 Sep 2012 23:52:15 +0800 [thread overview]
Message-ID: <CACVXFVP-A7M2dG9bOvAnpzR60=iTYSw=WCOEwgo9KeuioxKanQ@mail.gmail.com> (raw)
In-Reply-To: <s5hd3222azc.wl%tiwai@suse.de>
On Tue, Sep 4, 2012 at 9:06 PM, Takashi Iwai <tiwai@suse.de> wrote:
> Hi,
>
> as I've got recently a few bug reports regarding the stuck with
> request_firmware() in module_init of some sound drivers, I started
> looking at the issue. Strangely, the problem doesn't happen on
> openSUSE 12.2 although it has the same udev version with libkmod as
> Fedora. So I installed Fedora 17, and indeed I could see a problem
> there.
It should be a bug in udev, as discussed in the below link:
http://marc.info/?t=134552745100002&r=1&w=2
>
> Obviously a solution would be to rewrite the driver code to use
> request_firmware_nowait() instead. But it'd need a lot of code
> shuffling, and most of such drivers are old stuff I don't want to do a
> serious surgery.
>
> So I tried an easier workaround by using the deferred probing.
> An experimental patch is below. As you can see, from the driver side,
> it's simple: just add two lines at the head of each probe function.
In fact, the defer probe should only be applied in situations which
driver is built in kernel and request_firmware is called in .probe().
>
> Do you think this kind of hack is OK? If not, any better (IOW easier)
> solution?
Looks your solution is a bit complicated, and I have wrote a similar
patch to address the problem, but Linus thought that it may hide the
problem of drivers.
http://marc.info/?t=134278790800004&r=1&w=2
IMO, driver core needn't to be changed, and the defer probe can be
supported just by changes in request_firmware() and its caller.
Thanks,
--
Ming Lei
next prev parent reply other threads:[~2012-09-04 15:52 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-04 13:06 A workaround for request_firmware() stuck in module_init Takashi Iwai
2012-09-04 15:52 ` Ming Lei [this message]
2012-09-04 16:10 ` Takashi Iwai
2012-09-05 1:15 ` Ming Lei
2012-09-05 5:53 ` Takashi Iwai
2012-09-05 11:32 ` Ming Lei
2012-09-05 13:03 ` Alan Cox
2012-09-05 14:01 ` Takashi Iwai
2012-09-05 15:22 ` Ming Lei
2012-09-05 16:30 ` Alan Cox
2012-09-05 21:08 ` Benjamin Herrenschmidt
2012-09-05 23:18 ` Alan Cox
2012-09-06 5:06 ` Benjamin Herrenschmidt
2012-09-06 2:47 ` Linus Torvalds
2012-09-06 4:12 ` Ming Lei
2012-09-06 12:59 ` Alan Cox
2012-09-06 15:38 ` Ming Lei
2012-09-05 16:59 ` Lucas De Marchi
2012-09-05 17:09 ` Takashi Iwai
2012-09-05 16:51 ` Lucas De Marchi
2012-09-05 17:08 ` Takashi Iwai
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