On Wed, 7 May 2014, Dan Williams wrote: > If a port is powered-off, or in the process of being powered-off, prevent > khubd from operating on it. Otherwise, the following sequence of events > leading to an unintended disconnect may occur: > > Events: > (0) <set pm_qos_no_poweroff to '0' for port1> > (1) hub 2-2:1.0: hub_resume > (2) hub 2-2:1.0: port 1: status 0301 change 0000 > (3) hub 2-2:1.0: state 7 ports 4 chg 0002 evt 0000 > (4) hub 2-2:1.0: port 1, power off status 0000, change 0000, 12 Mb/s > (5) usb 2-2.1: USB disconnect, device number 5 > > Description: > (1) hub is resumed before sending a ClearPortFeature request > (2) hub_activate() notices the port is connected and sets > hub->change_bits for the port > (3) hub_events() starts, but at the same time the port suspends > (4) hub_connect_change() sees the disabled port and triggers disconnect > > Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx> Acked-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
