linux-kernel - Re: [RFC -v3 PATCH 2/3] sched: add yield

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Message-ID: <1294167213.9334.38.camel@marge.simson.net>
Date:	Tue, 04 Jan 2011 19:53:33 +0100
From:	Mike Galbraith <efault@....de>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Rik van Riel <riel@...hat.com>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, Avi Kiviti <avi@...hat.com>,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	Chris Wright <chrisw@...s-sol.org>
Subject: Re: [RFC -v3 PATCH 2/3] sched: add yield_to function

On Tue, 2011-01-04 at 19:04 +0100, Peter Zijlstra wrote:

> > +		p_cfs_rq = cfs_rq_of(pse);
> > +		yield = 1;
> > +	}
> > +#endif
> > +
> > +	if (yield)
> > +		clear_buddies(cfs_rq, se);
> > +	else if (preempt)
> > +		clear_buddies(p_cfs_rq, curr);
> > +
> > +	/* Tell the scheduler that we'd really like pse to run next. */
> > +	p_cfs_rq->next = pse;
> > +
> > +	if (!yield && preempt)
> > +		resched_task(task_of(p_cfs_rq->curr));
> 
> I don't get this.. Why would you resched the remote cpu, surely you
> didn't just pull its current task over..

:) hope not.   Caller bails on task_running(p_rq, p).  wants a comment
too I suppose.

Target doesn't live here, preempt is still set/allowed, so we want the
remote cpu to schedule.

	-Mike

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