Re: [PATCH 1/2] cpuidle: Clean up fallback handling in cpuidle_idle_call()

From: Lorenzo Pieralisi
Date: Mon Mar 02 2015 - 11:05:47 EST


On Mon, Mar 02, 2015 at 02:51:35PM +0000, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
>
> Move the fallback code path in cpuidle_idle_call() to the end of the
> function to avoid jumping to a label in a an if () branch.

Nit: "in an if () branch"

> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> ---
> kernel/sched/idle.c | 29 +++++++++++++++--------------
> 1 file changed, 15 insertions(+), 14 deletions(-)
>
> Index: linux-pm/kernel/sched/idle.c
> ===================================================================
> --- linux-pm.orig/kernel/sched/idle.c
> +++ linux-pm/kernel/sched/idle.c
> @@ -124,20 +124,8 @@ static void cpuidle_idle_call(void)
> * Fall back to the default arch idle method on errors.
> */
> next_state = cpuidle_select(drv, dev);
> - if (next_state < 0) {
> -use_default:
> - /*
> - * We can't use the cpuidle framework, let's use the default
> - * idle routine.
> - */
> - if (current_clr_polling_and_test())
> - local_irq_enable();
> - else
> - arch_cpu_idle();
> -
> - goto exit_idle;
> - }
> -
> + if (next_state < 0)
> + goto use_default;
>
> /*
> * The idle task must be scheduled, it is pointless to
> @@ -195,6 +183,19 @@ exit_idle:
>
> rcu_idle_exit();
> start_critical_timings();
> + return;
> +
> +use_default:
> + /*
> + * We can't use the cpuidle framework, let's use the default
> + * idle routine.
> + */
> + if (current_clr_polling_and_test())
> + local_irq_enable();
> + else
> + arch_cpu_idle();
> +
> + goto exit_idle;

I wonder whether making the code at label use_default a function saves us
some jumping around, not sure it is worth the churn, your call, I am ok as
it is.

Lorenzo
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