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. > > (Probably it's sufficient to wait until the tasklet lists are empty. I > > assume tasklet_kill() won't stop a tasklet that's currently running.) > > From the implementation of tasklet_kill(), it will wait for the completion > of the tasklet. > > Actually the tasklet_kill() should not be necessary, I think. You're probably right. But we should wait until the tasklet's list is empty; we don't want to deallocate an hcd structure until all the URBs are taken off. 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
