linux-kernel - Re: [PATCH 3/3] cpuidle: Using the wake_up_all_idle

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Message-ID: <540862AA.7060907@linaro.org>
Date:	Thu, 04 Sep 2014 15:01:30 +0200
From:	Daniel Lezcano <daniel.lezcano@...aro.org>
To:	Chuansheng Liu <chuansheng.liu@...el.com>, peterz@...radead.org,
	luto@...capital.net, rjw@...ysocki.net, mingo@...hat.com
CC:	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	changcheng.liu@...el.com, xiaoming.wang@...el.com,
	souvik.k.chakravarty@...el.com
Subject: Re: [PATCH 3/3] cpuidle: Using the wake_up_all_idle_cpus() to wake
 up all idle cpus

On 09/04/2014 09:17 AM, Chuansheng Liu wrote:
> Currently kick_all_cpus_sync() or smp_call_function() can not
> break the polling idle cpu immediately.
>
> Here using wake_up_all_idle_cpus() which can wake up the polling idle
> cpu quickly is much helpful for power.

Acked-by: Daniel Lezcano <daniel.lezcano@...aro.org>

So IIUC, kick_all_cpus_sync is a broken function, right ?

Wouldn't make sense to replace all calls to kick_all_cpus by 
wake_up_all_idle_cpus ? and remove this broken function ?

> Signed-off-by: Chuansheng Liu <chuansheng.liu@...el.com>
> ---
>   drivers/cpuidle/cpuidle.c |    9 ++-------
>   1 file changed, 2 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
> index ee9df5e..d31e04c 100644
> --- a/drivers/cpuidle/cpuidle.c
> +++ b/drivers/cpuidle/cpuidle.c
> @@ -223,7 +223,7 @@ void cpuidle_uninstall_idle_handler(void)
>   {
>   	if (enabled_devices) {
>   		initialized = 0;
> -		kick_all_cpus_sync();
> +		wake_up_all_idle_cpus();
>   	}
>   }
>
> @@ -530,11 +530,6 @@ EXPORT_SYMBOL_GPL(cpuidle_register);
>
>   #ifdef CONFIG_SMP
>
> -static void smp_callback(void *v)
> -{
> -	/* we already woke the CPU up, nothing more to do */
> -}
> -
>   /*
>    * This function gets called when a part of the kernel has a new latency
>    * requirement.  This means we need to get all processors out of their C-state,
> @@ -544,7 +539,7 @@ static void smp_callback(void *v)
>   static int cpuidle_latency_notify(struct notifier_block *b,
>   		unsigned long l, void *v)
>   {
> -	smp_call_function(smp_callback, NULL, 1);
> +	wake_up_all_idle_cpus();
>   	return NOTIFY_OK;
>   }
>
>


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