linux-kernel - Re: [PATCH v3] sched/deadline: do not try to push tasks if pinned task switches to dl

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Message-ID: <20160330064455.GQ3408@twins.programming.kicks-ass.net>
Date:	Wed, 30 Mar 2016 08:44:55 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Juri Lelli <juri.lelli@....com>,
	Wanpeng Li <wanpeng.li@...ux.intel.com>,
	Ingo Molnar <mingo@...hat.com>,
	Kirill V Tkhai <tkhai@...dex.ru>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] sched/deadline: do not try to push tasks if pinned
 task switches to dl

On Tue, Mar 29, 2016 at 06:47:22PM -0400, Steven Rostedt wrote:
> I'm looking at some old changes for sched-deadline, and I stumbled
> across this. As I'm working on sched deadline tests, I've discovered
> that they can't have cpu affinity. They are limited to their sched
> domains. That is, sched deadline tasks have whatever affinity that the
> domain they happen to be in has.
> 
> Is there a condition where rq != task_rq(p) and p->nr_cpus_allowed > 1
> isn't true?

When holding rq->lock, no. I suppose the patch was just to mirror rt and
someone 'forgot' about the extra constraints on dl tasks.