[PATCH v2 5/7] sched/preempt: add PREEMPT_DYNAMIC using static keys

[Frederic Weisbecker]

On Fri, Feb 04, 2022 at 03:05:55PM +0000, Mark Rutland wrote:
> diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h
> index dfd84c59b144..141952f4fee8 100644
> --- a/include/linux/entry-common.h
> +++ b/include/linux/entry-common.h
> @@ -456,13 +456,19 @@ irqentry_state_t noinstr irqentry_enter(struct pt_regs *regs);
>   */
>  void raw_irqentry_exit_cond_resched(void);
>  #ifdef CONFIG_PREEMPT_DYNAMIC
> +#if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL)
>  #define irqentry_exit_cond_resched_dynamic_enabled	raw_irqentry_exit_cond_resched
>  #define irqentry_exit_cond_resched_dynamic_disabled	NULL
>  DECLARE_STATIC_CALL(irqentry_exit_cond_resched, raw_irqentry_exit_cond_resched);
>  #define irqentry_exit_cond_resched()	static_call(irqentry_exit_cond_resched)()
> -#else
> -#define irqentry_exit_cond_resched()	raw_irqentry_exit_cond_resched()
> +#elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY)
> +DECLARE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched);

If CONFIG_PREEMPT && CONFIG_PREEMPT_DYNAMIC and no "preempt=" parameter is
passed, nothing is overriden on boot. So you need to either have cond_resched
and might_resched initially disabled (STATIC_KEY_FALSE?) or call
sched_dynamic_update() from preempt_dynamic_init() also when CONFIG_PREEMPT=y.

Thanks.