linux-kernel - Re: [PATCH] sched: resched proper CPU on yield

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Message-ID: <4D6DBA7F.7010203@redhat.com>
Date:	Tue, 01 Mar 2011 22:33:19 -0500
From:	Rik van Riel <riel@...hat.com>
To:	Venkatesh Pallipadi <venki@...gle.com>
CC:	Mike Galbraith <efault@....de>, a.p.zijlstra@...llo.nl,
	mingo@...hat.com, hpa@...or.com, linux-kernel@...r.kernel.org,
	mtosatti@...hat.com, tglx@...utronix.de, mingo@...e.hu
Subject: Re: [PATCH] sched: resched proper CPU on yield_to

On 03/01/2011 07:28 PM, Venkatesh Pallipadi wrote:
> yield_to_task_fair() has code to resched the CPU of yielding task when the
> intention is to resched the CPU of the task that is being yielded to.
>
> Change here fixes the problem and also makes the resched conditional on
> rq != p_rq.

That would result in not rescheduling when current and p are
on the same runqueue, in effect making yield_to a noop for the
easiest case...

When rq != p_rq, we need to ensure both get rescheduled.

We want to have current not run right now (because it is waiting
on a resource that's not available), and we do want p to run.

I'm about to fall over, so I'll go to sleep now.

I can send a patch tomorrow morning, unless you beat me to it :)

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