Hi,

I rarely use a Realtek USB 3.0 Gigabit Ethernet adapter (vid/pid
0bda:8153), but when I did last night, it resulted in a lockup of
processes doing networking ("ip link", "ping", "ethtool", ...).

A (few) minute(s) before that event, I noticed that there was no network
connectivity (ping hung) which was somehow solved by invoking "ethtool
eth1" (triggering runtime pm wakeup?). This same trick did not work at
the next event. Invoking "ethtool eth1", "ip link", etc. hung completely
and interrupt (^C) did not work at all.

Since that did not work, I pulled the USB adapter and re-inserted it,
hoping it would reset things. That did not work at all, there was a
"usb disconnect" message, but no further driver messages.

Fast forward an hour, and it has become a disaster. I have terminated
and killed many programs via SysRq but am still unable to get a stable
system that does not hang on network I/O. Even the suspend process
fails so in the end I attempted to shutdown the system. After half an
hour after getting the poweroff message, I issued SysRq + B to reboot
(since SysRq + O did not shut down either).

Attached are logs with various various backtraces from SysRq and failed
suspend. Let me know if you need more information!

By the way, often I have to rmmod xhci and re-insert it, otherwise
plugging it in does not result in a detection. A USB 2.0 port does not
have this problem (runtime PM is enabled for all devices). This is the
USB 3.0 port:

    02:00.0 USB controller [0c03]: NEC Corporation uPD720200 USB 3.0
    Host Controller [1033:0194] (rev 03)
-- 
Kind regards,
Peter Wu
https://lekensteyn.nl