Re: [PATCH 4/4] sched / idle: Call default_idle_call() from cpuidle_enter_state()

Daniel Lezcano
2015-05-04T15:04:19Z

On 05/04/2015 03:58 PM, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>
> The check of the cpuidle_enter() return value against -EBUSY
> made in call_cpuidle() will not be necessary any more if
> cpuidle_enter_state() calls default_idle_call() directly when it
> is about to return -EBUSY, so make that happen and eliminate the
> check.
>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>
> ---
> drivers/cpuidle/cpuidle.c | 4 +++-
> drivers/cpuidle/cpuidle.h | 2 ++
> kernel/sched/idle.c | 14 ++++++--------
> 3 files changed, 11 insertions(+), 9 deletions(-)
>
> Index: linux-pm/drivers/cpuidle/cpuidle.c
> ===================================================================
> --- linux-pm.orig/drivers/cpuidle/cpuidle.c
> +++ linux-pm/drivers/cpuidle/cpuidle.c
> @@ -167,8 +167,10 @@ int cpuidle_enter_state(struct cpuidle_d
> * local timer will be shut down. If a local timer is used from another
> * CPU as a broadcast timer, this call may fail if it is not available.
> */
> - if (broadcast && tick_broadcast_enter())
> + if (broadcast && tick_broadcast_enter()) {
> + default_idle_call();
> return -EBUSY;
> + }
>
> trace_cpu_idle_rcuidle(index, dev->cpu);
> time_start = ktime_get();
> Index: linux-pm/drivers/cpuidle/cpuidle.h
> ===================================================================
> --- linux-pm.orig/drivers/cpuidle/cpuidle.h
> +++ linux-pm/drivers/cpuidle/cpuidle.h
> @@ -18,6 +18,8 @@ extern int cpuidle_enter_state(struct cp
> /* idle loop */
> extern void cpuidle_install_idle_handler(void);
> extern void cpuidle_uninstall_idle_handler(void);
> +/* kernel/sched/idle.c */
> +extern void default_idle_call(void);

There is a cyclic dependency introduced with this function.

idle.c <=> cpuidle.c

Are we sure we want them to be mutually dependent ?

> /* governors */
> extern int cpuidle_switch_governor(struct cpuidle_governor *gov);
> Index: linux-pm/kernel/sched/idle.c
> ===================================================================
> --- linux-pm.orig/kernel/sched/idle.c
> +++ linux-pm/kernel/sched/idle.c
> @@ -67,11 +67,12 @@ void __weak arch_cpu_idle(void)
> local_irq_enable();
> }
>
> -static void default_idle_call(void) {
> - /*
> - * We can't use the cpuidle framework, let's use the default idle
> - * routine.
> - */
> +/**
> + * default_idle_call - Default CPU idle routine.
> + *
> + * To use when the cpuidle framework cannot be used.
> + */
> +void default_idle_call(void) {

Same comment as Peter on the patch 1/4.

> if (current_clr_polling_and_test())
> local_irq_enable();
> else
> @@ -112,9 +113,6 @@ static int call_cpuidle(struct cpuidle_d
> /* The cpu is no longer idle or about to enter idle. */
> idle_set_state(this_rq(), NULL);
>
> - if (entered_state == -EBUSY)
> - default_idle_call();
> -
> return entered_state;
> }
>
>

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