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Commit 097a155f authored by Dan Williams's avatar Dan Williams Committed by Greg Kroah-Hartman
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usb: synchronize port poweroff and khubd 



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

Acked-by: default avatarAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent af376a46

drivers/usb/core/hub.c

+20 −1
Original line number Diff line number Diff line
@@ -4784,6 +4784,10 @@ static void port_event(struct usb_hub *hub, int port1) 
				USB_PORT_FEAT_C_PORT_CONFIG_ERROR);

	}



	/* skip port actions that require the port to be powered on */

	if (!pm_runtime_active(&port_dev->dev))

		return;



	if (hub_handle_remote_wakeup(hub, port1, portstatus, portchange))

		connect_change = 1;
@@ -4910,11 +4914,26 @@ static void hub_events(void) 


		/* deal with port status changes */

		for (i = 1; i <= hdev->maxchild; i++) {

			struct usb_port *port_dev = hub->ports[i - 1];



			if (!test_bit(i, hub->busy_bits)

					&& (test_bit(i, hub->event_bits)

						|| test_bit(i, hub->change_bits)

						|| test_bit(i, hub->wakeup_bits)))

						|| test_bit(i, hub->wakeup_bits))) {

				/*

				 * The get_noresume and barrier ensure that if

				 * the port was in the process of resuming, we

				 * flush that work and keep the port active for

				 * the duration of the port_event().  However,

				 * if the port is runtime pm suspended

				 * (powered-off), we leave it in that state, run

				 * an abbreviated port_event(), and move on.

				 */

				pm_runtime_get_noresume(&port_dev->dev);

				pm_runtime_barrier(&port_dev->dev);

				port_event(hub, i);

				pm_runtime_put_sync(&port_dev->dev);

			}

		}



		/* deal with hub status changes */