On Mon, Jul 20, 2020 at 06:33:55PM +0200, Michal Hocko wrote: > On Mon 20-07-20 11:12:55, Alan Stern wrote: > [...] > > sudo echo 'module usbcore =p' >/debug/dynamic_debug/control > > > > Then wait long enough for some interesting messages to appear in the > > kernel log (it should only take a few seconds if the worker thread is as > > busy as you say) and collect the output from the dmesg command. > > > > To turn dynamic debugging back off when you're finished, use the same > > command with "=p" changed to "-p". > > [ 95.395815] hub 2-0:1.0: state 7 ports 6 chg 0006 evt 0000 > [ 95.395824] usb usb2-port1: status 0088, change 0000, 5.0 Gb/s > [ 95.395838] usb usb2-port2: status 0088, change 0000, 5.0 Gb/s > [ 95.396016] hub 2-0:1.0: hub_suspend > [ 95.396023] usb usb2: bus auto-suspend, wakeup 1 > [ 95.396029] usb usb2: bus suspend fail, err -16 Okay, that's the problem. You may get more specific information about the suspend failure if you turn on dynamic debugging for the xhci-hcd module (same command as above but with xhci-hcd instead of usbcore). If you want a quick way to prevent this from happening, you can do: sudo echo on >/sys/bus/usb/devices/usb2/power/control That won't actually fix anything, but it will stop the system from automatically trying to suspend usb2 root hub. Alan Stern
