On 02/24/2014 07:12 AM, Peter Zijlstra wrote:
Anyway, the below seems to work; it avoids playing tricks with the idle thread and instead uses a magic constant.The comparison should be faster too; seeing how we avoid dereferencing p->sched_class. --- Subject: sched: Guarantee task priority in pick_next_task() From: Peter Zijlstra<[email protected]> Date: Fri Feb 14 12:25:08 CET 2014 Michael spotted that the idle_balance() push down created a task priority problem. Previously, when we called idle_balance() before pick_next_task() it wasn't a problem when -- because of the rq->lock droppage -- an rt/dl task slipped in. Similarly for pre_schedule(), rt pre-schedule could have a dl task slip in. But by pulling it into the pick_next_task() loop, we'll not try a higher task priority again. Cure this by creating a re-start condition in pick_next_task(); and triggering this from pick_next_task_{rt,fair}(). Fixes: 38033c37faab ("sched: Push down pre_schedule() and idle_balance()") Cc: Juri Lelli<[email protected]> Cc: Ingo Molnar<[email protected]> Cc: Steven Rostedt<[email protected]> Reported-by: Michael Wang<[email protected]> Signed-off-by: Peter Zijlstra<[email protected]>
Sign me up to the fan club of this patch, I love it.After running it for a bit I see that all the hangs I've seen before are gone, even those that I didn't assume were sched related.
Thanks, Sasha
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