Re: [4.3] kworker busy in pm_runtime_work

[Daniel J Blueman]

On 16 November 2015 at 23:22, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:
> On Mon, 16 Nov 2015, Daniel J Blueman wrote:
>
>> Tuning USB suspend [1] in 4.3 on a Dell XPS 15 9553 (Skylake), I see a
>> kworker thread spinning in rpm_suspend [2].
>>
>> What is the most useful debug to get here beyond the immediate [3]?
>
> You can try doing:
>
>         echo 'module usbcore =p' >/sys/kernel/debug/dynamic_debug/control

kworker and ksoftirqd spinning occurs when I echo 'auto' to all the
USB control entries. Using Alan's excellent tip, we see this being
logged repeatedly at a high rate:
[  353.245180] usb usb1-port4: status 0107 change 0000
[  353.245194] usb usb1-port12: status 0507 change 0000
[  353.245202] hub 1-0:1.0: state 7 ports 16 chg 0000 evt 0000
[  353.245203] hub 1-0:1.0: hub_suspend
[  353.245205] usb usb1: bus auto-suspend, wakeup 1
[  353.245206] usb usb1: bus suspend fail, err -16
[  353.245207] hub 1-0:1.0: hub_resume
...

So, EBUSY. Both the webcam is not open, and the bluetooth interface
[1] is rfkill'd; the situation occurs even if I unload all related
modules.

What further debug would be useful?

Thanks!
  Daniel

-- [1]

Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 002: ID 0a5c:6410 Broadcom Corp.
Bus 001 Device 003: ID 1bcf:2b95 Sunplus Innovation Technology Inc.
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
-- 
Daniel J Blueman
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