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    SubjectRe: hid-related 5.2-rc1 boot hang
    On Mon, Jun 3, 2019 at 4:17 PM Hans de Goede <hdegoede@redhat.com> wrote:
    >
    > Hi,
    >
    > On 03-06-19 15:55, Benjamin Tissoires wrote:
    > > On Mon, Jun 3, 2019 at 11:51 AM Hans de Goede <hdegoede@redhat.com> wrote:
    > >>
    > >> Hi Again,
    > >>
    > >> On 03-06-19 11:11, Hans de Goede wrote:
    > >> <snip>
    > >>
    > >>>> not sure about the rest of logitech issues yet) next week.
    > >>>
    > >>> The main problem seems to be the request_module patches. Although I also
    > >
    > > Can't we use request_module_nowait() instead, and set a reasonable
    > > timeout that we detect only once to check if userspace is compatible:
    > >
    > > In pseudo-code:
    > > if (!request_module_checked) {
    > > request_module_nowait(name);
    > > use_request_module = wait_event_timeout(wq,
    > > first_module_loaded, 10 seconds in jiffies);
    > > request_module_checked = true;
    > > } else if (use_request_module) {
    > > request_module(name);
    > > }
    >
    > Well looking at the just attached dmesg , the modprobe
    > when triggered by udev from userspace succeeds in about
    > 0.5 seconds, so it seems that the modprobe hangs happens
    > when called from within the kernel rather then from within
    > userspace.
    >
    > What I do not know if is the hang is inside userspace, or
    > maybe it happens when modprobe calls back into the kernel,
    > if the hang happens when modprobe calls back into the kernel,
    > then other modprobes (done from udev) likely will hang too
    > since I think only 1 modprobe can happen at a time.
    >
    > I really wish we knew what distinguished working systems
    > from non working systems :|
    >
    > I cannot find a common denominator; other then the systems
    > are not running Fedora. So far we've reports from both Ubuntu 16.04
    > and Tumbleweed, so software version wise these 2 are wide apart.

    I am trying to reproduce the lock locally, and installed an opensuse
    Tumbleweed in a VM. When forwarding a Unifying receiver to the VM, I
    do not see the lock with either my vanilla compiled kernel and the rpm
    found in http://download.opensuse.org/repositories/Kernel:/HEAD/standard/x86_64/

    Next step is install Tumbleweed on bare metal, but I do not see how
    this could introduce a difference (maybe USB2 vs 3).

    >
    > >>> have 2 reports of problems with hid-logitech-dj driving the 0xc52f product-id,
    > >>> so we may need to drop that product-id from hid-logitech-dj, I'm working on
    > >>> that one...
    > >>
    > >> Besides the modprobe hanging issue, the only other issues all
    > >> (2 reporters) seem to be with 0xc52f receivers. We have a bug
    > >> open for this:
    > >>
    > >> https://bugzilla.kernel.org/show_bug.cgi?id=203619
    > >>
    > >> And I've asked the reporter of the second bug to add his logs
    > >> to that bug.
    > >
    > > We should likely just remove c52f from the list of supported devices.
    > > C52f receivers seem to have a different firmware as they are meant to
    > > work with different devices than C534. So I guess it is safer to not
    > > handle those right now and get the code in when it is ready.
    >
    > Ack. Can you prepare a patch to drop the c52f id?

    Yes. I have an other revert never submitted that I need to push, so I
    guess I can do a revert session today.

    I think I'll also buy one device with hopefully the C52F receiver as
    the report descriptors attached in
    https://bugzilla.kernel.org/show_bug.cgi?id=203619 seems different to
    what I would have expected.

    Cheers,
    Benjamin

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