linux-kernel - Re: [PATCH v2 BlueZ] hid2hci: Fix udev rules for linux-4.14+

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Message-ID: <c2f9f862-0bf1-be6b-ad9f-8c375d4b8ff0@bakke.com>
Date:   Wed, 5 Dec 2018 20:09:35 +0100
From:   Dag B <dag@...ke.com>
To:     Ville Syrjälä <ville.syrjala@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-bluetooth@...r.kernel.org,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Marcel Holtmann <marcel@...tmann.org>,
        Kay Sievers <kay.sievers@...y.org>,
        Zbigniew Jędrzejewski-Szmek <zbyszek@...waw.pl>,
        systemd-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 BlueZ] hid2hci: Fix udev rules for linux-4.14+



On 05.12.2018 16:40, Ville Syrjälä wrote:
> On Wed, Dec 05, 2018 at 08:06:21AM +0100, Greg Kroah-Hartman wrote:
>> On Tue, Dec 04, 2018 at 10:41:17PM +0200, Ville Syrjala wrote:
>>> From: Ville Syrjälä <ville.syrjala@...ux.intel.com>
>>>
>>> Since commit 1455cf8dbfd0 ("driver core: emit uevents when
>>> device is bound to a driver") the kernel started emitting
>>> "bind" and "unbind" uevents which confuse the hid2hci
>>> udev rules.
>>>
>>> The symptoms on an affected machine (Dell E5400 in my case)
>>> include bluetooth devices not appearing and udev hogging
>>> the cpu as it's busy processing a constant stream of these
>>> "bind"+"unbind" uevents.
>> What is causing a "stream" of bind and unbind events?  This only happens
>> when a device is attached to a driver or removed from a driver, which is
>> caused by something else happening.
> Not sure if it's just due to this thing causing devices to
> appear/disappear during bind/unbind events or what.
>
>> This should not be a normal
>> occurance, unless something odd is happening to your hardware?
> It's not specific to my hardware. Lot's of people are affected.
> See eg.
> https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1759836
>
> Acutally looking through that bug it seems someone else noticed
> hid2hci failing lot in the logs. So maybe it's just that we already
> switched the mode during "add", and then we try to redo the same
> thing during "bind" which fails, and that then causes and unbind?
> Dunno, udev is beyond me.
>
>
There is another bluetooth scenario where a cpu core peaks at 100%.
This is when a bluetooth keyboard goes out to lunch/suspends/disappears.
No idea if this is related to the original issue, asking forgiveness if 
it is not.
I have found it challenging to attract any attention to the problem, 
despite it not being an entirely new or uncommon occurence.

Google the following terms: bluetooth keyboard bluetoothd linux 100% cpu



By chance, I discovered a supposed fix for this on github today. I have 
not had the chance to test it (or if it even applies) yet:

https://github.com/peak3d/bluez/commit/9cc3c1afd793e40b1a0cdc4a13e08b5e2575759e

Could someone please shine a light on the sanity of this patch?



Dag B