On Mon, 20 Feb 2012, Sebastian Andrzej Siewior wrote: > > What's the issue here? > > > > If a driver calls usb_unlink_urb() while holding a lock, and the > > completion routine tries to acquire the same lock, then deadlock is > > possible. The fact that usb_unlink_urb() is asynchronous is not a > > guarantee of anything; the HCD is allowed to call the completion > > handler from within usb_unlink_urb(). > > > > It's true that the kerneldoc for usb_unlink_urb() says "This request is > > always asynchronous". It might be a good idea to remove the word > > "always", because it seems to give people the wrong idea. > > I see. So you approve that patch and suggest to remove the "always" > wording plus adding something like "the hcd might call complete routine > during unlink" ? Well, I haven't read the patch and don't really understand what issue it tries to solve. But if that issue is the one I talked about above then yes, it makes sense. And changing the documentation as you suggest would be a good thing to do in any case. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
