Re: [PATCH v2 2/2] cpuidle: Change :enter_dead() driver callback return type to void

[Mario Limonciello]

On 11/19/2024 09:09, Gautham R. Shenoy wrote:
> Hello Rafael,
>
> On Fri, Nov 15, 2024 at 10:00:25PM +0100, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> >
> > After a previous change, cpuidle_play_dead(), which is the only caller
> > of idle state :enter_dead() callbacks, ignores their return values, so
> > they may as well be void.
> >
> > Suggested-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
>
> > ---
> >
> > v1 -> v2: New patch
> >
> > Interestingly enough, the only user of :enter_dead() idle state callbacks
> > in the current mainline turns out to be ACPI idle.
>
> For that matter, the only user of cpuidle_play_dead() is the
> native_play_dead(). Was that always the case?
>
> Some of the other architectures select the deepest available idle
> state at boot time, and enter that state when a CPU is offlined.
>
> In any case I am ok with this.
>
> Reviewed-by: Gautham R. Shenoy <gautham.shenoy@xxxxxxx>
Reviewed-by: Mario Limonciello <mario.limonciello@xxxxxxx>

> --
> Thanks and Regards
> gautham.
> > ---
> >   drivers/acpi/processor_idle.c |    7 ++-----
> >   include/linux/cpuidle.h       |    2 +-
> >   2 files changed, 3 insertions(+), 6 deletions(-)
> >
> > Index: linux-pm/include/linux/cpuidle.h
> > ===================================================================
> > --- linux-pm.orig/include/linux/cpuidle.h
> > +++ linux-pm/include/linux/cpuidle.h
> > @@ -61,7 +61,7 @@ struct cpuidle_state {
> >   			struct cpuidle_driver *drv,
> >   			int index);
> >   
> > -	int (*enter_dead) (struct cpuidle_device *dev, int index);
> > +	void (*enter_dead) (struct cpuidle_device *dev, int index);
> >   
> >   	/*
> >   	 * CPUs execute ->enter_s2idle with the local tick or entire timekeeping
> > Index: linux-pm/drivers/acpi/processor_idle.c
> > ===================================================================
> > --- linux-pm.orig/drivers/acpi/processor_idle.c
> > +++ linux-pm/drivers/acpi/processor_idle.c
> > @@ -578,7 +578,7 @@ static void __cpuidle acpi_idle_do_entry
> >    * @dev: the target CPU
> >    * @index: the index of suggested state
> >    */
> > -static int acpi_idle_play_dead(struct cpuidle_device *dev, int index)
> > +static void acpi_idle_play_dead(struct cpuidle_device *dev, int index)
> >   {
> >   	struct acpi_processor_cx *cx = per_cpu(acpi_cstate[index], dev->cpu);
> >   
> > @@ -591,11 +591,8 @@ static int acpi_idle_play_dead(struct cp
> >   		else if (cx->entry_method == ACPI_CSTATE_SYSTEMIO) {
> >   			io_idle(cx->address);
> >   		} else
> > -			return -ENODEV;
> > +			return;
> >   	}
> > -
> > -	/* Never reached */
> > -	return 0;
> >   }
> >   
> >   static __always_inline bool acpi_idle_fallback_to_c1(struct acpi_processor *pr)