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

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Message-ID: <e431dafc-0fb4-4be3-ac29-dcf125929090@redhat.com>
Date:   Mon, 3 Jun 2019 16:17:23 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     Benjamin Tissoires <benjamin.tissoires@...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

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.

>>> 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?

Regards,

Hans