Bug#966703: linux-image-4.19.0-10-amd64: kworker process with permanent high CPU load

[Salvatore Bonaccorso <carnil@debian.org>]

Hi Dirk,

Thanks for testing that.

On Sat, Aug 29, 2020 at 11:04:43AM +0200, Dirk Kostrewa wrote:
> Hi Salvatore,
> 
> I have enabled the verbose debugging mode on the command line and have
> appended the first 5000 lines of the dmesg output to this e-mail, running
> the current kernel from the Buster backports with the two kworker processes
> with high CPU load present.
> 
> After that, I have applied your patch to this kernel and rebooted with the
> patched kernel:
> 
> 5.7.0-0.bpo.2-amd64 #1 SMP Debian 5.7.10-1~bpo10+1a~test (2020-08-28) x86_64
> GNU/Linux
> 
> With your patch applied, the two kworker processes with high CPU load
> completely disappeared!

Unfortunately I suspect this indicates either a HW fault or a HW
design error as stated in the found kernel-thread which was just
uncovered by the mentioned kernel fix (which we temporarily reverted
with the patch). I can try to ask Alan Stern.

There might be a workaround workarble for you, the issue should
disapear if you prevent the system to automatically try to suspend
usb2 root hub (but you have the same on usb1 root hub).

# echo on >/sys/bus/usb/devices/usb2/power/control

will do that for the usb2 root hub.

Regards,
Salvatore