On Thu, 4 Feb 2016, Chris Bainbridge wrote: > The XHCI controller presents two USB buses to the system - one for USB 2 > and one for USB 3. When only one bus is locked there is a race condition > during hub init that results in errors like: > > [ 13.183701] usb 3-3: device descriptor read/all, error -110
What exactly is the race condition? Why does locking both buses fix it? > @@ -4312,7 +4312,7 @@ hub_port_init(struct usb_hub *hub, struct usb_device > *udev, int port1, > if (oldspeed == USB_SPEED_LOW) > delay = HUB_LONG_RESET_TIME; > > - mutex_lock(&hdev->bus->usb_address0_mutex); > + mutex_lock(&hdev->bus->controller->mutex); > > /* Reset the device; full speed may morph to high speed */ > /* FIXME a USB 2.0 device may morph into SuperSpeed on reset. */ > @@ -4588,7 +4588,7 @@ fail: > hub_port_disable(hub, port1, 0); > update_devnum(udev, devnum); /* for disconnect processing */ > } > - mutex_unlock(&hdev->bus->usb_address0_mutex); > + mutex_unlock(&hdev->bus->controller->mutex); > return retval; > } I don't think this is a good idea. The driver core needs to be able to access the controller while this function is running. You can introduce a new mutex if you want, perhaps in the primary hcd structure, but don't use bus->controller->mutex. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
