linux-kernel - Re: [PATCH V2 3/5] cpuidle: idle: menu: Don't reflect when a state selection failed

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Date:	Tue, 28 Oct 2014 20:15:52 +0100
From:	Daniel Lezcano <daniel.lezcano@...aro.org>
To:	Len Brown <lenb@...nel.org>
CC:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Linux PM list <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	linaro-kernel@...ts.linaro.org, Patch Tracking <patches@...aro.org>
Subject: Re: [PATCH V2 3/5] cpuidle: idle: menu: Don't reflect when a state
 selection failed

On 10/28/2014 03:01 AM, Len Brown wrote:
> On Thu, Oct 23, 2014 at 5:01 AM, Daniel Lezcano
> <daniel.lezcano@...aro.org> wrote:
>> In the current code, the check to reflect or not the outcoming state is done
>> against the idle state which has been chosen and its value.
>>
>> Instead of doing a check in each of the reflect functions, just don't call reflect
>> if something went wrong in the idle path.
>>
>> Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
>> Acked-by: Nicolas Pitre <nico@...aro.org>
>> ---
>>   drivers/cpuidle/governors/ladder.c | 3 +--
>>   drivers/cpuidle/governors/menu.c   | 4 +---
>>   kernel/sched/idle.c                | 3 ++-
>>   3 files changed, 4 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/cpuidle/governors/ladder.c b/drivers/cpuidle/governors/ladder.c
>> index fb396d6..c0b36a8 100644
>> --- a/drivers/cpuidle/governors/ladder.c
>> +++ b/drivers/cpuidle/governors/ladder.c
>> @@ -165,8 +165,7 @@ static int ladder_enable_device(struct cpuidle_driver *drv,
>>   static void ladder_reflect(struct cpuidle_device *dev, int index)
>>   {
>>          struct ladder_device *ldev = &__get_cpu_var(ladder_devices);
>> -       if (index > 0)
>> -               ldev->last_state_idx = index;
>
> Before this patch, last_state_idx was never set to 0 here.
> After this patch, last_state_idx will be set to 0 when entered_state is 0.
> Is that okay?

Yes, I think so because the state zero won't be never selected on x86 
but on the other arch it will. So before this patch, on the other archs, 
the state 0 was never reflected as it should do.

This is resulting from the CPUIDLE_DRIVER_STATE_START macro (I hope I 
can kill this macro in a couple of patchset after this one).

>> +       ldev->last_state_idx = index;
>>   }
>>
>>   static struct cpuidle_governor ladder_governor = {
>> diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
>> index a17515f..3907301 100644
>> --- a/drivers/cpuidle/governors/menu.c
>> +++ b/drivers/cpuidle/governors/menu.c
>> @@ -365,9 +365,7 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev,
>>   static void menu_reflect(struct cpuidle_device *dev, int index)
>>   {
>>          struct menu_device *data = &__get_cpu_var(menu_devices);
>> -       data->last_state_idx = index;
>> -       if (index >= 0)
>> -               data->needs_update = 1;
>> +       data->needs_update = 1;
>>   }
>>
>>   /**
>> diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
>> index 58c7522..49dcc7d 100644
>> --- a/kernel/sched/idle.c
>> +++ b/kernel/sched/idle.c
>> @@ -162,7 +162,8 @@ use_default:
>>          /*
>>           * Give the governor an opportunity to reflect on the outcome
>>           */
>> -       cpuidle_reflect(dev, entered_state);
>> +       if (entered_state >= 0)
>> +               cpuidle_reflect(dev, entered_state);
>>
>>   exit_idle:
>>          __current_set_polling();
>> --
>> 1.9.1
>>
>> --
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>
>
>


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