On Tue, 30 Jul 2013, Julius Werner wrote:
> The USB hub driver's event handler contains a check to catch SuperSpeed
> devices that transitioned into the SS.Inactive state and tries to fix
> them with a reset. It decides whether to do a plain hub port reset or
> call the usb_reset_device() function based on whether there was a device
> attached to the port.
>
> However, there are device/hub combinations (found with a JetFlash
> Transcend mass storage stick (8564:1000) on the root hub of an Intel
> LynxPoint PCH) which can transition to the SS.Inactive state on
> disconnect (and stay there long enough for the host to notice). In this
> case, above-mentioned reset check will call usb_reset_device() on the
> stale device data structure. The kernel will send pointless LPM control
> messages to the no longer connected device address and can even cause
> several 5 second khubd stalls on some (buggy?) host controllers, before
> finally accepting the device's fate amongst a flurry of error messages.
>
> This patch makes the choice of reset dependent on the port status that
> has just been read from the hub in addition to the existence of an
> in-kernel data structure for the device, and only proceeds with the more
> extensive reset if both are valid.
>
> Signed-off-by: Julius Werner <jwerner@xxxxxxxxxxxx>
> ---
> drivers/usb/core/hub.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> index 4a8a1d6..558313d 100644
> --- a/drivers/usb/core/hub.c
> +++ b/drivers/usb/core/hub.c
> @@ -4798,7 +4798,8 @@ static void hub_events(void)
> hub->ports[i - 1]->child;
>
> dev_dbg(hub_dev, "warm reset port %d\n", i);
> - if (!udev) {
> + if (!udev || !(portstatus &
> + USB_PORT_STAT_CONNECTION)) {
> status = hub_port_reset(hub, i,
> NULL, HUB_BH_RESET_TIME,
> true);
> @@ -4808,8 +4809,8 @@ static void hub_events(void)
> usb_lock_device(udev);
> status = usb_reset_device(udev);
> usb_unlock_device(udev);
> + connect_change = 0;
> }
> - connect_change = 0;
> }
>
> if (connect_change)
This version looks better.
Acked-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
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