On Wed, 19 Mar 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
>
> 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 | 91 +++++++++++++++++++++++++++---------------------
> 1 files changed, 51 insertions(+), 40 deletions(-)
>
> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> index e0c593ea7a0e..10f420626204 100644
> --- a/drivers/usb/core/hub.c
> +++ b/drivers/usb/core/hub.c
> @@ -4761,51 +4761,56 @@ 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)) {
How about avoiding all the churn by doing this?
+ /* The following actions aren't needed if the port is powered off */
+ if (!pm_runtime_active(&port_dev->dev))
+ return;
+
> @@ -4892,11 +4897,17 @@ 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))) {
Please add a comment here, explaining that this is to prevent any
runtime suspends from powering-off the port while we're handling the
events.
> + pm_runtime_get_noresume(&port_dev->dev);
> + pm_runtime_barrier(&port_dev->dev);
> port_event(hub, i);
> + pm_runtime_put_sync(&port_dev->dev);
> + }
> }
Alan Stern
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