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

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Date:   Mon, 21 Nov 2016 16:46:34 +0800
From:   Baolin Wang <baolin.wang@...aro.org>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     John Stultz <john.stultz@...aro.org>,
        lkml <linux-kernel@...r.kernel.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

Hi Ingo,

On 21 November 2016 at 16:13, Ingo Molnar <mingo@...nel.org> wrote:
>
> * 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.)

Make sense. I will send out new patch to fix this. Thanks for your comments.

>
> That would disambiguate the freezer_delta special case in the trace.
>
> (Unless I missed something.)
>
> Thanks,
>
>         Ingo



-- 
Baolin.wang
Best Regards