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

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Message-ID: <CAPXgP13LBR6GD=VomBPim3mDPy1bJ=eFBZ=oDaKZCjEo=Xp94Q@mail.gmail.com>
Date:	Thu, 23 Aug 2012 17:31:08 +0200
From:	Kay Sievers <kay@...y.org>
To:	Ming Lei <tom.leiming@...il.com>
Cc:	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 Thu, Aug 23, 2012 at 5:16 PM, Ming Lei <tom.leiming@...il.com> wrote:
> On Tue, Aug 21, 2012 at 1:34 PM, Ming Lei <tom.leiming@...il.com> wrote:

>> I found that udev 182 doesn't response for the request_firmware in
>> module_probe path until 30sec later after the 'ADD' event of firmware
>> device, but no such problem in udev175, sounds like a regression of udev?
>
> Looks udevd is capable of handling the firmware ADD event even though
> the device ADD event is being processed( modprobe is triggered by device
> ADD event).

Calling out from inside the kernel and blocking in a firmware loading
userspace transaction during module_init() is kind of weird.

The firmware loading call should not rely on a fully functional
userspace, and modprobe should not hang and block until the firmware
request is handled.

The firmware should be requested asynchronously or from a different
context as module_init(). It depends on the type of driver/hardware
what's the best approach here.

Thanks,
Kay
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