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    SubjectRe: udev breakages - was: Re: Need of an ".async_probe()" type of callback at driver's core - Was: Re: [PATCH] [media] drxk: change it to use request_firmware_nowait()
    Em 02-10-2012 19:23, Greg KH escreveu:
    > On Tue, Oct 02, 2012 at 03:12:39PM -0700, Greg KH wrote:
    >> On Tue, Oct 02, 2012 at 09:33:03AM -0700, Linus Torvalds wrote:
    >>> I don't know where the problem started in udev, but the report I saw
    >>> was that udev175 was fine, and udev182 was broken, and would deadlock
    >>> if module_init() did a request_firmware(). That kind of nested
    >>> behavior is absolutely *required* to work, in order to not cause
    >>> idiotic problems for the kernel for no good reason.
    >>> What kind of insane udev maintainership do we have? And can we fix it?
    >>> Greg, I think you need to step up here too. You were the one who let
    >>> udev go. If the new maintainers are causing problems, they need to be
    >>> fixed some way.
    >> I've talked about this with Kay in the past (Plumbers conference I
    >> think) and I thought he said it was all fixed in the latest version of
    >> udev so there shouldn't be any problems anymore with this.
    >> Mauro, what version of udev are you using that is still showing this
    >> issue?
    >> Kay, didn't you resolve this already? If not, what was the reason why?
    > Hm, in digging through the udev tree, the only change I found was this
    > one:
    > commit 39177382a4f92a834b568d6ae5d750eb2a5a86f9
    > Author: Kay Sievers <>
    > Date: Thu Jul 19 12:32:24 2012 +0200
    > udev: firmware - do not cancel requests in the initrd
    > diff --git a/src/udev/udev-builtin-firmware.c b/src/udev/udev-builtin-firmware.c
    > index 56dc8fc..de93d7b 100644
    > --- a/src/udev/udev-builtin-firmware.c
    > +++ b/src/udev/udev-builtin-firmware.c
    > @@ -129,7 +129,13 @@ static int builtin_firmware(struct udev_device *dev, int argc, char *argv[], boo
    > err = -errno;
    > } while (err == -ENOENT);
    > rc = EXIT_FAILURE;
    > - set_loading(udev, loadpath, "-1");
    > + /*
    > + * Do not cancel the request in the initrd, the real root might have
    > + * the firmware file and the 'coldplug' run in the real root will find
    > + * this pending request and fulfill or cancel it.
    > + * */
    > + if (!in_initrd())
    > + set_loading(udev, loadpath, "-1");
    > goto exit;
    > }
    > which went into udev release 187 which I think corresponds to the place
    > when people started having problems, right Mauro?

    I'm using here udev-182.

    > If so, Mauro, is the solution just putting the firmware into the initrd?

    I don't think that putting firmware on initrd is something that we want to
    for media drivers. None of the webcam drivers currently need a firmware;
    those are required on more complex devices (typically digital TV ones).

    While there are a number of PCI devices that require firmware, in practice,
    we're seeing more people using USB devices. IMO, it doesn't make any sense
    that a hot-pluggable USB device to require a firmware at initrd/initramfs,
    with is available only at boot time.

    > No wait, it looks like this change was trying to fix the problem where
    > firmware files were not in the initrd, so it would stick around for the
    > real root to show up so that they could be loaded.
    > So this looks like it was fixing firmware loading problems for people?

    I'll run some tests with this patch applied and see what happens.

    > Kay, am I just looking at the totally wrong place here, and this file in
    > udev didn't have anything to do with the breakage?
    > thanks,
    > greg k-h

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