linux-kernel - Re: [PATCH 1/4] time: alarmtimer: Add the trcepoints for alarmtimer

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Date:   Mon, 21 Nov 2016 09:13:01 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     John Stultz <john.stultz@...aro.org>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        Baolin Wang <baolin.wang@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Richard Cochran <richardcochran@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH 1/4] time: alarmtimer: Add the trcepoints for alarmtimer


* John Stultz <john.stultz@...aro.org> wrote:

> @@ -222,7 +226,7 @@ static int alarmtimer_suspend(struct device *dev)
>  	ktime_t min, now;
>  	unsigned long flags;
>  	struct rtc_device *rtc;
> -	int i;
> +	int i, type = 0;
>  	int ret;
>  
>  	spin_lock_irqsave(&freezer_delta_lock, flags);
> @@ -247,8 +251,10 @@ static int alarmtimer_suspend(struct device *dev)
>  		if (!next)
>  			continue;
>  		delta = ktime_sub(next->expires, base->gettime());
> -		if (!min.tv64 || (delta.tv64 < min.tv64))
> +		if (!min.tv64 || (delta.tv64 < min.tv64)) {
>  			min = delta;
> +			type = i;
> +		}
>  	}
>  	if (min.tv64 == 0)
>  		return 0;
> @@ -264,6 +270,8 @@ static int alarmtimer_suspend(struct device *dev)
>  	now = rtc_tm_to_ktime(tm);
>  	now = ktime_add(now, min);
>  
> +	trace_alarmtimer_suspend(now, type);
> +
>  	/* Set alarm, if in the past reject suspend briefly to handle */
>  	ret = rtc_timer_start(rtc, &rtctimer, now, ktime_set(0, 0));
>  	if (ret < 0)

Hm, there's a weirdness here: if freezer_delta != 0 when alarmtimer_suspend() is 
called then type might be '0', although it's not alarm_bases[0] this value is 
picked up from.

Wouldn't it be better to initialize 'type' to -1 instead? (And rename it to 
min_type or so.)

That would disambiguate the freezer_delta special case in the trace.

(Unless I missed something.)

Thanks,

	Ingo