Hi Jamal, J Hadi Salim <[EMAIL PROTECTED]> wrote on 05/09/2007 09:22:44 PM:
> > Since I am holding a lock in these two changed areas till I return > > back to __qdisc_run (which clears the RUNNING bit) and then drop the > > lock, there is no way packets can be on the queue while I falsely > > return 0, or no packets on the queue while I falsely return -1. > > If you relinquish yourself from being a dequeuer by letting go of > RUNNING then it is possible during that short window one of the other > N-1 CPUs could have been enqueueing; that packet will never be dequeued > unless a new packet shows up some X amount of time later. But RUNNING is never relinquished till all the way back out to __qdisc_run. Only the lock is dropped before calling xmit and re-got after xmit is finished (all the while holding RUNNING). After xmit both queue_lock and RUNNING are held. If some other cpu enqueue'd during this release window (and they would have returned after dropping the lock as they are pure enqueuer's), qdisc_restart will find those skbs. Similarly if no skbs were added, qdisc_restart will return 0. Thanks, - KK > I hope what i described above helps. Off for about a day. CCing Herbert > who last made changes to that area incase i missed something .. > > cheers, > jamal > > PS:- Please dont use my temporary gmail account to respond; a reply-to > will pick the right address (@cyberus.ca). > - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
