usb: dwc2: NMI watchdog: BUG: soft lockup - CPU#0 stuck for 146s

[Doug Anderson]

Hi,

On Mon, Oct 16, 2017 at 1:49 PM, Julius Werner <jwerner at chromium.org> wrote:
>> d9a14b00 339317035 C Ii:1:004:1 -32:1 0
>> d9a14b00 339317049 S Ii:1:004:1 -115:1 10 <
>> d9a14b00 339318040 C Ii:1:004:1 -32:1 0
>> d9a14b00 339318057 S Ii:1:004:1 -115:1 10 <
>> d9a14b00 339319042 C Ii:1:004:1 -32:1 0
>> d9a14b00 339319056 S Ii:1:004:1 -115:1 10 <
>> d9a14b00 339329551 C Ii:1:004:1 -32:1 0
>> d9a14b00 339329571 S Ii:1:004:1 -115:1 10 <
>> d9a14b00 339330586 C Ii:1:004:1 -32:1 0
>> d9a14b00 339330601 S Ii:1:004:1 -115:1 10 <
>> d9a14b00 339331035 C Ii:1:004:1 -32:1 0
>
> Sorry for necromancing an old thread, but I just happened to read
> through this and thought someone might care:
>
> If I read that right, the usbmon output shows that the interrupt
> endpoint is stalled (keeps returning -EPIPE). A STALL is a special
> device-side USB condition that tells the host something is wrong and
> will persist until cleared manually. It seems that the driver isn't
> prepared for this (see
> drivers/usb/serial/pl2303.c#pl2303_read_int_callback) and just keeps
> resubmitting the URB, so it will stall again as fast as the endpoint
> allows it to. This may be the reason why you get so many transfers
> that it overwhelms the CPU.
>
> A fix would be to catch -EPIPE in that function and handle it
> explicitly (with either a CLEAR_STALL to the endpoint or a full USB
> reset... would have to look at the documentation for PL2303 to see
> what the stall actually means and how you're supposed to treat it).

To further comment on this old thread, I just posted another patch at
<https://patchwork.kernel.org/patch/10027237/> that could also make
pl2303 less able to bring dwc2-based controllers to a screeching halt.
I added many of the people who had taken part in this thread, but if
you were just lurking here then hopefully you can dig it up and try it
out.

-Doug