linux-kernel - Re: [PATCH 4/9] idle: move the cpuidle entry point to the generic idle loop

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Date:	Mon, 27 Jan 2014 09:32:19 +0100
From:	Daniel Lezcano <daniel.lezcano@...aro.org>
To:	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Russell King <linux@....linux.org.uk>,
	Catalin Marinas <catalin.marinas@....com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mundt <lethal@...ux-sh.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>
CC:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linuxppc-dev@...ts.ozlabs.org, linux-sh@...r.kernel.org,
	linux-pm@...r.kernel.org, linaro-kernel@...ts.linaro.org
Subject: Re: [PATCH 4/9] idle: move the cpuidle entry point to the generic
 idle loop

On 01/27/2014 07:08 AM, Nicolas Pitre wrote:
> In order to integrate cpuidle with the scheduler, we must have a better
> proximity in the core code with what cpuidle is doing and not delegate
> such interaction to arch code.
>
> Architectures implementing arch_cpu_idle() should simply enter
> a cheap idle mode in the absence of a proper cpuidle driver.
>
> Signed-off-by: Nicolas Pitre <nico@...aro.org>

This patch without the next ones will lead to an extra call to 
cpuidle_idle_call.

	cpuidle_idle_call
		arch_cpu_idle
			cpuidle_idle_call
				x86_idle

But I guess it is acceptable as it is fixed with the next patches of the 
serie.

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

> ---
>   kernel/cpu/idle.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/cpu/idle.c b/kernel/cpu/idle.c
> index 4e327e211b..a6f40ad9f8 100644
> --- a/kernel/cpu/idle.c
> +++ b/kernel/cpu/idle.c
> @@ -3,6 +3,7 @@
>    */
>   #include <linux/sched.h>
>   #include <linux/cpu.h>
> +#include <linux/cpuidle.h>
>   #include <linux/tick.h>
>   #include <linux/mm.h>
>   #include <linux/stackprotector.h>
> @@ -94,7 +95,8 @@ static void cpu_idle_loop(void)
>   				if (!current_clr_polling_and_test()) {
>   					stop_critical_timings();
>   					rcu_idle_enter();
> -					arch_cpu_idle();
> +					if (cpuidle_idle_call())
> +						arch_cpu_idle();
>   					WARN_ON_ONCE(irqs_disabled());
>   					rcu_idle_exit();
>   					start_critical_timings();
>


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