Messages in this thread | | | Subject | Re: [PATCH] sched: Remove WAKEUP_PREEMPT feature check in entity_tick | From | Peter Zijlstra <> | Date | Fri, 29 Jul 2011 13:45:33 +0200 |
| |
On Fri, 2011-07-29 at 16:46 +0800, Yong Zhang wrote: > Let's take UP for example, we have cpu-hug task A and threadirq B. > > n tick ---> n+1 tick > set_tsk_need_resched(A); > B comes in and > wake up thread-B; > > So for system on which we disable WAKEUP_PREEMPT, > if we don't have that check, thread-B will wait until n+1 tick comes > to get to run. > But if we have that check, thread-B will get to run after IRQ-B returns.
But that's exactly what wakeup preemption is about, waking tasks don't get to preempt running tasks. So no doing that preemption is exactly right for !WAKEUP_PREEMPT.
Anyway, I've queued the removal patch since that removes all confusion ;-)
| |