Messages in this thread | | | Date | Wed, 3 Jun 2015 10:55:27 +0200 | From | Peter Zijlstra <> | Subject | Re: [RFC][PATCH 1/7] sched: Replace post_schedule with a balance callback list |
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A: Because it messes up the order in which people normally read text. Q: Why is top-posting such a bad thing? A: Top-posting. Q: What is the most annoying thing in e-mail?
On Wed, Jun 03, 2015 at 04:24:05PM +0800, pang.xunlei@zte.com.cn wrote: > Hi Peter, > > This may increase the overhead of schedule() a bit, as it will have > more work to do.
How so? It replaces the post_schedule() muck and should not be more expensive than that.
It will make sched_setscheduler() etc.. a little more expensive, but that doesn't matter, those are not critical things at all.
> check_class_changed(): > if (prev_class->switched_from) > prev_class->switched_from(rq, p); > /* Possble rq->lock 'hole'. */ > p->sched_class->switched_to(rq, p); > > For above cases, why can't we just add a judgement in switched_to_fair() > as follows: > if (rq != task_rq(p)) > return;
Because its too easy to get wrong. There have been many instances of bugs caused by this dropping of rq->lock.
And sure you can patch it up, once you find it, but I would really rather prevent these things if at all possible.
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