diff mbox

[3/5] cpuidle: idle: menu: Don't reflect when a state selection failed

Message ID 1413822343-1972-3-git-send-email-daniel.lezcano@linaro.org
State New
Headers show

Commit Message

Daniel Lezcano Oct. 20, 2014, 4:25 p.m. UTC
In the current code, the check to reflect or not the outcoming state is done
against the idle state which has been choose 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@linaro.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(-)

Comments

Nicolas Pitre Oct. 22, 2014, 8:41 p.m. UTC | #1
On Mon, 20 Oct 2014, Daniel Lezcano wrote:

> In the current code, the check to reflect or not the outcoming state is done
> against the idle state which has been choose and its value.

s/choose/chosen/

> 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@linaro.org>

Acked-by: Nicolas Pitre <nico@linaro.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;
> +	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 f439161..9ac7322 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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Peter Zijlstra Oct. 24, 2014, 1:24 p.m. UTC | #2
On Mon, Oct 20, 2014 at 06:25:41PM +0200, Daniel Lezcano wrote:
> -	if (index > 0)
> -	if (index >= 0)

That's not the same condition.
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Daniel Lezcano Oct. 24, 2014, 1:32 p.m. UTC | #3
On 10/24/2014 03:24 PM, Peter Zijlstra wrote:
> On Mon, Oct 20, 2014 at 06:25:41PM +0200, Daniel Lezcano wrote:
>> -	if (index > 0)
>> -	if (index >= 0)
>
> That's not the same condition.

Yes and it is wrong. That is the result of the 
CPUIDLE_DRIVER_STATE_START dance.

The ladder governor is avoiding to use the POLL state as it was running 
on x86. But on, eg. ARM, we will never reflect the state 0 because 
CPUIDLE_DRIVER_STATE_START is equal to zero for all non-x86 platform.

If I am not wrong the ladder select function will never choose the state 
0 for x86, so it will never reflect the state 0 (after applying the 
patch 1/5). For the other arch it will reflect the state 0 as it should.
Peter Zijlstra Oct. 24, 2014, 1:38 p.m. UTC | #4
On Mon, Oct 20, 2014 at 06:25:41PM +0200, Daniel Lezcano wrote:
> +++ 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);
>  

Given we'll do use_default: when next_state < 0, we actually never get
here unless this is true.
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Daniel Lezcano Oct. 24, 2014, 1:43 p.m. UTC | #5
On 10/24/2014 03:38 PM, Peter Zijlstra wrote:
> On Mon, Oct 20, 2014 at 06:25:41PM +0200, Daniel Lezcano wrote:
>> +++ 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);
>>
>
> Given we'll do use_default: when next_state < 0, we actually never get
> here unless this is true.

There is the 'cpuidle_enter' call in between which may fail.
Peter Zijlstra Oct. 24, 2014, 1:56 p.m. UTC | #6
On Fri, Oct 24, 2014 at 03:43:53PM +0200, Daniel Lezcano wrote:
> On 10/24/2014 03:38 PM, Peter Zijlstra wrote:
> >On Mon, Oct 20, 2014 at 06:25:41PM +0200, Daniel Lezcano wrote:
> >>+++ 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);
> >>
> >
> >Given we'll do use_default: when next_state < 0, we actually never get
> >here unless this is true.
> 
> There is the 'cpuidle_enter' call in between which may fail.

Hmm, indeed there is. I had not expected that one to fail like this.
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diff mbox

Patch

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;
+	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 f439161..9ac7322 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();