linux-kernel - Re: [PATCH 07/10] sched: Migrate sched to use new tick dependency mask model

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Message-ID: <20150729130147.GB11554@lerouge>
Date:	Wed, 29 Jul 2015 15:01:48 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Chris Metcalf <cmetcalf@...hip.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Preeti U Murthy <preeti@...ux.vnet.ibm.com>,
	Christoph Lameter <cl@...ux.com>,
	Ingo Molnar <mingo@...nel.org>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Rik van Riel <riel@...hat.com>
Subject: Re: [PATCH 07/10] sched: Migrate sched to use new tick dependency
 mask model

On Fri, Jul 24, 2015 at 12:56:42PM -0400, Chris Metcalf wrote:
> On 07/23/2015 12:42 PM, Frederic Weisbecker wrote:
> >+static inline void sched_update_tick_dependency(struct rq *rq)
> >+{
> >+	int cpu;
> >+
> >+	if (!tick_nohz_full_enabled())
> >+		return;
> >+
> >+	cpu = cpu_of(rq);
> >+
> >+	if (!tick_nohz_full_cpu(rq->cpu))
> >+		return;
> >+
> >+	if (sched_can_stop_tick(rq))
> >+		tick_nohz_clear_tick_dependency_cpu(TICK_SCHED_BIT, cpu);
> >+	else
> >+		tick_nohz_set_tick_dependency_cpu(TICK_SCHED_BIT, cpu);
> >+}
> 
> Is it worth asserting that the rq is locked at this point? Presumably that's
> a requirement so that the cpu can't change out from under you.

Indeed it has become a requirement here. I'll add a check.

Thanks.
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