[--cc Alan Cox] On Tue, 2013-03-05 at 21:50 +0100, Sebastian Andrzej Siewior wrote: > * Peter Hurley | 2013-02-05 15:20:15 [-0500]: > > > Please re-test with your dummy_hcd/g_nokia testcase, although > > I'm not convinced that usb gadget is using tty_hangup() appropriately. > > tty drivers use this for async carrier loss coming from an IRQ > > which will be disabled if the tty has been shutdown. Does gserial > > prevent async hangup to a dead tty in a similar fashion? > > Not sure I understood. tty_hangup() is only called from within > gserial_disconnect() which calls right after usb_ep_disable(). After > usb_ep_disable() no further serial packets can be received until the > endpoints are re-enabled. This happens in gserial_connect(). That's why I asked. There are two potential issues: First, tty_hangup() is asynchronous -- ie., it returns immediately. It does not wait for the tty device to actually perform the hangup. So if the gadget layers start cleanup immediately after, expecting that they won't get a flurry of tty calls, that would be bad. tty_vhangup() is synchronous -- ie., you wait while it cleans up. This is what the usb serial core does on it's disconnect() method. But I didn't research further if the circumstances were the same. Second, when the hangup actually does run -- in __tty_hangup() -- it expects the tty to exist. I didn't go looking through the gadget layers to see if the tty was disposed some other way, which might race the asynchronous tty hangup. Thanks, Peter Hurley -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
