Date: Tue, 11 Nov 2014 18:30:23 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>
Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
        mturquette@linaro.org, amit.kucheria@linaro.org,
        vincent.guittot@linaro.org, daniel.lezcano@linaro.org,
        Morten.Rasmussen@arm.com, efault@gmx.de, nicolas.pitre@linaro.org,
        dietmar.eggemann@arm.com, pjt@google.com, bsegall@google.com,
        mingo@kernel.org, linaro-kernel@lists.linaro.org,
        Preeti U Murthy <preeti@linux.vnet.ibm.com>
Subject: Re: [RFC 1/2] sched/fair: Add cumulative average of load_avg_contrib
 to a task
Message-ID: <20141111173023.GP10501@worktop.programming.kicks-ass.net>
References: <1415598358-26505-1-git-send-email-shilpa.bhat@linux.vnet.ibm.com>
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 <20141110134911.GG29390@twins.programming.kicks-ass.net>
 <546222C7.2030000@linux.vnet.ibm.com>
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On Tue, Nov 11, 2014 at 08:22:55PM +0530, Shilpasri G Bhat wrote:
> On 11/10/2014 07:19 PM, Peter Zijlstra wrote:
> > It it broken because who says rq->prev still exists?
> 
> 'task_cumulative_load()' is handled by the cpufreq governor's kworker.
> And the kworker is queued only if there is task running on cpu which
> guarantees the existence of rq->prev in a running state.

Not so, there is no guarantee it will still be running by the time the
kworker actually comes around to running.
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