Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Thu, 9 Aug 2018 12:45:49 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Leo Yan <leo.yan@linaro.org>
Cc:     Ingo Molnar <mingo@redhat.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] sched: idle: Reenable sched tick for cpuidle request
Message-ID: <20180809104549.GS2494@hirez.programming.kicks-ass.net>
References: <1533793647-5628-1-git-send-email-leo.yan@linaro.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <1533793647-5628-1-git-send-email-leo.yan@linaro.org>
User-Agent: Mutt/1.10.0 (2018-05-17)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Thu, Aug 09, 2018 at 01:47:27PM +0800, Leo Yan wrote:
> diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
> index 1a3e9bd..802286e 100644
> --- a/kernel/sched/idle.c
> +++ b/kernel/sched/idle.c
> @@ -190,10 +190,18 @@ static void cpuidle_idle_call(void)
>  		 */
>  		next_state = cpuidle_select(drv, dev, &stop_tick);
>  
> -		if (stop_tick)
> +		if (stop_tick) {
>  			tick_nohz_idle_stop_tick();
> -		else
> +		} else {
> +			/*
> +			 * The cpuidle framework says to not stop tick but
> +			 * the tick has been stopped yet, so restart it.
> +			 */
> +			if (tick_nohz_tick_stopped())
> +				tick_nohz_idle_restart_tick();
> +

I suspect you want an 'else' here. restart_tick already calls
timer_clear_idle().

>  			tick_nohz_idle_retain_tick();
> +		}
>  

However, I would rather we stuff all this into retain_tick.