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

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Date:	Fri, 24 Jul 2015 12:56:42 -0400
From:	Chris Metcalf <cmetcalf@...hip.com>
To:	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>
CC:	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 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.
-- 
Chris Metcalf, EZChip Semiconductor
http://www.ezchip.com
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