linux-kernel - [Query]: tick-sched: why don't we stop tick when we are running idle task?

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Date:	Wed, 9 Apr 2014 16:03:00 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Frédéric Weisbecker <fweisbec@...il.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Lists linaro-kernel <linaro-kernel@...ts.linaro.org>
Subject: [Query]: tick-sched: why don't we stop tick when we are running idle task?

Hi Frederic,

File: kernel/time/tick-sched.c
Function: tick_nohz_full_stop_tick()

We are doing this:

if (!tick_nohz_full_cpu(cpu) || is_idle_task(current))
        return;

Which means: if a FULL_NO_HZ cpu is running idle task currently,
don't stop its tick..

I couldn't understand why. Can you please help here?

--
viresh
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