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

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Date:   Wed, 5 Dec 2018 20:21:45 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Dag B <dag@...ke.com>
Cc:     Ville Syrjälä 
        <ville.syrjala@...ux.intel.com>, 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 Wed, Dec 05, 2018 at 08:09:35PM +0100, Dag B wrote:
> 
> 
> 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 bluetooth keyboards working just fine here, again, more specifics
would be good to have.

> 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?

That's a userspace bluez patch, I think you are asking on the wrong
list, sorry.

greg k-h