On Mon, 4 Jun 2012, Sarah Sharp wrote: > This patch changes the xHCI ring handling code to allow the URB > completion handler to run before ringing the doorbell on an endpoint > ring. This means adding a new flag to prevent the doorbell ring > (EP_STAY_HALTED), to avoid a race condition with the URB completion > handler and a completing Set TR Dequeue Pointer command (which will > restart the ring). The new flag temporarily stops the ring until the > URB completion function has a chance to cancel any pending URBs. That > will set a different cancellation pending flag, which will also halt the > endpoint ring. > > Make sure to set the new EP_STAY_HALTED flag before calling > xhci_cleanup_halted_endpoint(). That function will queue a Set TR > Dequeue command, which will ring the doorbell and restart the ring after > it completes. We need to make sure that the URB completion handlers > have a chance to run before the ring is restarted. I really don't understand the structure of your driver, but this sounds like it's more complicated than necessary. The general approach for handling a stopped endpoint ring should be: Give back all the URBs that are complete; Clean up the ring; Restart it if any URBs remain queued. As far as I can see, the only state you need to keep track of is whether the ring is active, stopping, or stopped. There shouldn't be any need for an EP_STAY_HALTED flag. 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
