On Fri, Jun 21, 2013 at 9:12 AM, Ming Lei <ming.lei@xxxxxxxxxxxxx> wrote: > On Fri, Jun 21, 2013 at 12:52 AM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: >> On Thu, 20 Jun 2013, Ming Lei wrote: >> >>> On Thu, Jun 20, 2013 at 10:59 PM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: >>> > >>> > By the way, did you consider the race that Oliver pointed out? When an >>> > HCD is removed, all the outstanding URBs for all devices on its bus get >>> > cancelled. The core waits until the urb_list for each endpoint is >>> > empty. >>> >>> This should be enough since during remove path usbcore will wait for all >>> URBs' completion which is only triggered by tasklet, so once all URBs are >>> finished, the tasklet list has been empty already. >> >> No, usbcore only waits until the urb_list for each endpoint is empty. >> It doesn't keep track of the individual URB completions. Look at >> usb_hcd_flush_endpoint() and you'll see. > > But, if URBs still aren't completed after usb_disconnect(), it should be > bug of usbcore or driver, shouldn't it? Thought about the problem further, there should be one problem: - we can't let URBs survive from deleting the interface, otherwise the module in which the completion handler lives might have been removed - so tasklet_kill() should be added into usb_hcd_synchronize_unlinks() to make sure the above point, although it is a bit tricky since tasklet_kill() flushes global list, but it does work. Thanks, -- Ming Lei -- 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
