linux-kernel - Re: udev 182: response timeout for request_firmware in module

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Message-ID: <CACVXFVOCXQnciE1GymwvuX2gQ4pm4wBhc2GmHN7AMDchcT8_qw@mail.gmail.com>
Date:	Fri, 24 Aug 2012 01:03:32 +0800
From:	Ming Lei <tom.leiming@...il.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Kay Sievers <kay@...y.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Johannes Berg <johannes@...solutions.net>,
	Larry Finger <Larry.Finger@...inger.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	systemd-devel@...ts.freedesktop.org
Subject: Re: udev 182: response timeout for request_firmware in module_probe path

On Fri, Aug 24, 2012 at 12:46 AM, Alan Cox <alan@...rguk.ukuu.org.uk> wrote:
>> IMO, the driver probing path is allowed to sleep, so looks request firmware
>> should be allowed inside .probe().
>
> I'm not convinced about that. It can sleep but its holding various locks
> in most cases, and it looks like that can end up in a complete heap.

Currently, only wait_for_completion() pends in the path of request_firmware
without holding other locks.

>
> By all means *request* the firmware asynchronously in the probe, but
> there needs to be a seperate method somewhere after the probe to finish
> the job once the firmware appears.

Yes, request asynchronously will work and introduce a bit complexity
(but it is not a big deal)

Looks the focus is that why request_firmware can't be used in driver
.probe().

IMO, we should consider that most of drivers call request_firmware
inside its .probe(), and maybe udev need to support the usage.


Thanks,
-- 
Ming Lei
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