On Fri, Mar 22, 2013 at 3:31 AM, Eric Wong <normalper...@yhbt.net> wrote: > Arve Hjønnevåg <a...@android.com> wrote: >> On Thu, Mar 21, 2013 at 8:24 PM, Eric Wong <normalper...@yhbt.net> wrote: >> > >> > With EPOLLET and improper usage (not hitting EAGAIN), the event now >> > has a larger window to be lost (as mentioned in my changelog). >> > >> >> What about the case where EPOLLET is not set? The old code did not >> drop events in that case. > > Nothing is dropped, if the event wasn't on the ready list before, > ep_poll_callback may still append the ready list while __put_user > is running. > > If the event was on the ready list: > > 1) It does not matter for EPOLLONESHOT, it'll get masked out and > discarded in the next ep_send_events call until ep_modify reenables > it. Since ep_modify and ep_send_events both take ep->mtx, there's > no conflict. > > 2) Level Trigger - event stays ready, so nothing is dropped. >
At some point the level triggered event has to get cleared. As far as I can tell, your new code will drop new events that occur between "revents = ep_item_poll(epi, &pt);" and "epi->state = EP_STATE_IDLE;" in that case. -- Arve Hjønnevåg -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
