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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: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Dan Williams 2014-05-20 18:09:20 -07:00 committed by Greg Kroah-Hartman
parent af376a461c
commit 097a155f05
1 changed files with 20 additions and 1 deletions
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21
drivers/usb/core/hub.c
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@ -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 */