linux-kernel - Re: hid-related 5.2-rc1 boot hang

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Message-ID: <CAO-hwJ+5UYJMnuCS0UL4g45Xc181LraAzc-CMuYB2rcqKGe_Sw@mail.gmail.com>
Date:   Tue, 4 Jun 2019 09:51:03 +0200
From:   Benjamin Tissoires <benjamin.tissoires@...hat.com>
To:     Hans de Goede <hdegoede@...hat.com>
Cc:     Jiri Kosina <jikos@...nel.org>,
        Dave Hansen <dave.hansen@...el.com>,
        "open list:HID CORE LAYER" <linux-input@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: hid-related 5.2-rc1 boot hang

On Mon, Jun 3, 2019 at 4:17 PM Hans de Goede <hdegoede@...hat.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@...hat.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