From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1753337AbbDBNeU (ORCPT <rfc822;w@1wt.eu>);
	Thu, 2 Apr 2015 09:34:20 -0400
Received: from bombadil.infradead.org ([198.137.202.9]:51577 "EHLO
	bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1752640AbbDBNeR (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Thu, 2 Apr 2015 09:34:17 -0400
Date: Thu, 2 Apr 2015 15:34:03 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Ingo Molnar <mingo@redhat.com>, Thomas Gleixner <tglx@linutronix.de>,
        linaro-kernel@lists.linaro.org, linux-kernel@vger.kernel.org,
        Kevin Hilman <khilman@linaro.org>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        Preeti U Murthy <preeti@linux.vnet.ibm.com>,
        Frederic Weisbecker <fweisbec@gmail.com>
Subject: Re: [PATCH 2/3] clockevents: Restart clockevent device before using
 it again
Message-ID: <20150402133403.GY23123@twins.programming.kicks-ass.net>
References: <cover.1427475606.git.viresh.kumar@linaro.org>
 <a8bce41503c36f6de6be94b0f8854ab646f6745d.1427475606.git.viresh.kumar@linaro.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <a8bce41503c36f6de6be94b0f8854ab646f6745d.1427475606.git.viresh.kumar@linaro.org>
User-Agent: Mutt/1.5.21 (2012-12-30)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Fri, Mar 27, 2015 at 10:44:28PM +0530, Viresh Kumar wrote:
> Only hrtimer_reprogram() is responsible for programming the clockevent device
> for next event, if the clockevent device is stopped earlier. And updating that
> alone is sufficient here.

> +++ b/kernel/time/hrtimer.c
> @@ -566,6 +566,7 @@ static int hrtimer_reprogram(struct hrtimer *timer,
>  {
>  	struct hrtimer_cpu_base *cpu_base = this_cpu_ptr(&hrtimer_bases);
>  	ktime_t expires = ktime_sub(hrtimer_get_expires(timer), base->offset);
> +	struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
>  	int res;
>  
>  	WARN_ON_ONCE(hrtimer_get_expires_tv64(timer) < 0);
> @@ -610,6 +611,10 @@ static int hrtimer_reprogram(struct hrtimer *timer,
>  	if (cpu_base->hang_detected)
>  		return 0;
>  
> +	/* Switchback to ONESHOT state */
> +	if (unlikely(dev->state == CLOCK_EVT_STATE_ONESHOT_STOPPED))
> +		clockevents_set_state(dev, CLOCK_EVT_STATE_ONESHOT);
> +
>  	/*
>  	 * Clockevents returns -ETIME, when the event was in the past.
>  	 */

Should we not do this in tick_program_event() instead? Note that there
are a few more places that call that, the two in the hrtimer_interrupt()
should be safe because if we're handling the interrupt its cannot be
stopped anyhow.

hrtimer_force_reprogram() seems to need the annotation regardless.

Furthermore, by putting it in tick_program_event() you also don't need
to fixup tick_nohz_restart().

Or am I completely missing something?