On Thu, Jan 21, 2016 at 06:02:34PM -0500, Waiman Long wrote: > This patch attempts to fix this live-lock condition by enabling the > a woken task in the wait list to enter optimistic spinning loop itself > with precedence over the ones in the OSQ. This should prevent the > live-lock > condition from happening.
So I think having the top waiter going back in to contend on the OSQ is an excellent idea, but I'm not sure the wlh_spinning thing is important. The OSQ itself is FIFO fair, and the waiters retain the wait_list position. So having the top wait_list entry contending on the OSQ ensures we cannot starve (I think). Also, as Davidlohr said, we cannot copy/paste this much code.
