On Mon, 17 Dec 2012, Chen Gang wrote: > are all kfree for urb->hcpriv in lock protected ? Yes. The only one is in urb_free_priv, and it is always called with the lock held. > (set urb->hcpriv = NULL in usb_hcd_giveback_urb, not in lock protected). > can you be sure that it is no synchronization issue ? Yes. > if you can be sure > would you please explain to me (I am learning). It is pretty much as I explained in my previous email. finish_urb calls usb_free_priv while holding the lock. Then while still holding the lock, it calls usb_hcd_unlink_urb_from_ep. In addition, ohci_urb_dequeue calls usb_hcd_check_unlink_urb while holding the lock, and does nothing if the return value is nonzero. So all you need to do is verify that after usb_hcd_unlink_urb_from_ep runs, usb_hcd_check_unlink_urb will always return a nonzero value. In fact, it will return -EIDRM -- until the next time the URB is submitted and usb_hcd_link_urb_to_ep is called. 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
