On Fri, Apr 25, 2014 at 10:16:57AM +0800, Li Zhong wrote: > On Thu, 2014-04-24 at 16:52 +0200, Johan Hovold wrote: > > No, this isn't self removal. The driver-attribute (not device-attribute) > > store operation simply grabs a lock that is also held while the driver > > is being deregistered at module unload. Taking a reference to the module > > in this case will prevent deregistration while store is running. > > > > But it seems like this can be solved for usb-serial by simply not > > holding the lock while deregistering. > > I didn't look carefully about this lock. > > But I'm not sure whether there are such requirements for driver > attributes: > > some lock needs be grabbed in the driver attributes store callbacks, and > the same lock also needs to be grabbed during driver unregister. > > If we have such requirements currently or in the future, I think they > could all be solved by breaking active protection after get the module > reference. Yes, if we find any such cases, but I don't think it should be done generally (as in one of your earlier posts). Active protection is usually exactly what prevents the driver from being deregistered, and would only need to be broken to avoid any ABBA deadlocks from being reported by lockdep (the module reference would be enough to prevent the actual deadlock). Thanks, Johan -- 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
