[PATCH v6 part2 4/8] usb: synchronize port poweroff and khubd

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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

Most of the code thrash here is just indenting the portions of
port_event() that require the port to be runtime pm active.

Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
 drivers/usb/core/hub.c |   61 ++++++++++++++++++++++++++++--------------------
 1 files changed, 36 insertions(+), 25 deletions(-)

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index c021ce51e682..d1c0d2d2f1af 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -4749,33 +4749,38 @@ static void port_event(struct usb_hub *hub, int port1)
 				USB_PORT_FEAT_C_PORT_CONFIG_ERROR);
 	}
 
-	if (hub_handle_remote_wakeup(hub, port1, portstatus, portchange))
-		connect_change = 1;
-
-	/*
-	 * Warm reset a USB3 protocol port if it's in
-	 * SS.Inactive state.
-	 */
-	if (hub_port_warm_reset_required(hub, portstatus)) {
-		int status;
+	/* take port actions that require the port to be powered on */
+	if (pm_runtime_active(&port_dev->dev)) {
+		if (hub_handle_remote_wakeup(hub, port1,
+				portstatus, portchange))
+			connect_change = 1;
 
-		dev_dbg(&port_dev->dev, "do warm reset\n");
-		if (!udev || !(portstatus & USB_PORT_STAT_CONNECTION)
-				|| udev->state == USB_STATE_NOTATTACHED) {
-			status = hub_port_reset(hub, port1, NULL,
-					HUB_BH_RESET_TIME, true);
-			if (status < 0)
-				hub_port_disable(hub, port1, 1);
-		} else {
-			usb_lock_device(udev);
-			status = usb_reset_device(udev);
-			usb_unlock_device(udev);
-			connect_change = 0;
+		/*
+		 * Warm reset a USB3 protocol port if it's in
+		 * SS.Inactive state.
+		 */
+		if (hub_port_warm_reset_required(hub, portstatus)) {
+			int status;
+
+			dev_dbg(&port_dev->dev, "do warm reset\n");
+			if (!udev || !(portstatus & USB_PORT_STAT_CONNECTION)
+					|| udev->state == USB_STATE_NOTATTACHED) {
+				status = hub_port_reset(hub, port1, NULL,
+						HUB_BH_RESET_TIME, true);
+				if (status < 0)
+					hub_port_disable(hub, port1, 1);
+			} else {
+				usb_lock_device(udev);
+				status = usb_reset_device(udev);
+				usb_unlock_device(udev);
+				connect_change = 0;
+			}
 		}
-	}
 
-	if (connect_change)
-		hub_port_connect_change(hub, port1, portstatus, portchange);
+		if (connect_change)
+			hub_port_connect_change(hub, port1, portstatus,
+					portchange);
+	}
 }
 
 
@@ -4862,11 +4867,17 @@ 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_and_clear_bit(i, hub->event_bits)
 					|| test_bit(i, hub->change_bits)
-					|| test_bit(i, hub->wakeup_bits)))
+					|| test_bit(i, hub->wakeup_bits))) {
+				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 */

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