Re: [PATCH RESEND] sched: Move some scheduler fields to new static branch API

[Shrikanth Hegde <sshegde@linux.ibm.com>]

Hi Hongyan.

On 8/19/26 1:39 PM, Hongyan Xia wrote:
> From: Hongyan Xia <hongyan.xia@transsion.com>
> 
> __cfs_bandwidth_used uses struct static_key directly which is
> deprecated. Fix.

A bit of context on why it is deprecated would help.

>
> sk_dynamic_* uses static_key_{enable/disable}(), which aren't really
> deprecated, but take the opportunity to move to the new static_branch_*
> APIs to be consistent.
>

Mark had a series to remove a few of them completely. IIRC only lazy
check will remain.

https://lore.kernel.org/all/20260803191731.3244294-1-mark.rutland@arm.com/
  
> No functional change.
> 
> Signed-off-by: Hongyan Xia <hongyan.xia@transsion.com>
> ---
> Changed in RESEND:
> - Separate the original series into individual patches. They aren't easy
>    to review as a series.
> - Move sk_dynamic_* to the new API as well.
> 
>   kernel/sched/core.c | 18 +++++++++---------
>   kernel/sched/fair.c |  8 ++++----
>   2 files changed, 13 insertions(+), 13 deletions(-)
> 
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 96226707c2f6..5c07d53e43b5 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -7933,15 +7933,15 @@ int sched_dynamic_mode(const char *str)
>   	return -EINVAL;
>   }
>   
> -# define preempt_dynamic_key_enable(f)	static_key_enable(&sk_dynamic_##f.key)
> -# define preempt_dynamic_key_disable(f)	static_key_disable(&sk_dynamic_##f.key)
> +# define preempt_dynamic_branch_enable(f)	static_branch_enable(&sk_dynamic_##f)
> +# define preempt_dynamic_branch_disable(f)	static_branch_disable(&sk_dynamic_##f)

Also, doc doesn't about mention about static_branch_enable vs static_key_enable.
is static_key_enable also deprecated.

>   
>   # if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL)
>   #  define preempt_dynamic_enable(f)	static_call_update(f, f##_dynamic_enabled)
>   #  define preempt_dynamic_disable(f)	static_call_update(f, f##_dynamic_disabled)
>   # elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY)
> -#  define preempt_dynamic_enable(f)	preempt_dynamic_key_enable(f)
> -#  define preempt_dynamic_disable(f)	preempt_dynamic_key_disable(f)
> +#  define preempt_dynamic_enable(f)	preempt_dynamic_branch_enable(f)
> +#  define preempt_dynamic_disable(f)	preempt_dynamic_branch_disable(f)
>   # else
>   #  error "Unsupported PREEMPT_DYNAMIC mechanism"
>   # endif
> @@ -7959,7 +7959,7 @@ static void __sched_dynamic_update(int mode)
>   	preempt_dynamic_enable(preempt_schedule);
>   	preempt_dynamic_enable(preempt_schedule_notrace);
>   	preempt_dynamic_enable(irqentry_exit_cond_resched);
> -	preempt_dynamic_key_disable(preempt_lazy);
> +	preempt_dynamic_branch_disable(preempt_lazy);
>   
>   	switch (mode) {
>   	case preempt_dynamic_none:
> @@ -7968,7 +7968,7 @@ static void __sched_dynamic_update(int mode)
>   		preempt_dynamic_disable(preempt_schedule);
>   		preempt_dynamic_disable(preempt_schedule_notrace);
>   		preempt_dynamic_disable(irqentry_exit_cond_resched);
> -		preempt_dynamic_key_disable(preempt_lazy);
> +		preempt_dynamic_branch_disable(preempt_lazy);
>   		if (mode != preempt_dynamic_mode)
>   			pr_info("Dynamic Preempt: none\n");
>   		break;
> @@ -7979,7 +7979,7 @@ static void __sched_dynamic_update(int mode)
>   		preempt_dynamic_disable(preempt_schedule);
>   		preempt_dynamic_disable(preempt_schedule_notrace);
>   		preempt_dynamic_disable(irqentry_exit_cond_resched);
> -		preempt_dynamic_key_disable(preempt_lazy);
> +		preempt_dynamic_branch_disable(preempt_lazy);
>   		if (mode != preempt_dynamic_mode)
>   			pr_info("Dynamic Preempt: voluntary\n");
>   		break;
> @@ -7990,7 +7990,7 @@ static void __sched_dynamic_update(int mode)
>   		preempt_dynamic_enable(preempt_schedule);
>   		preempt_dynamic_enable(preempt_schedule_notrace);
>   		preempt_dynamic_enable(irqentry_exit_cond_resched);
> -		preempt_dynamic_key_disable(preempt_lazy);
> +		preempt_dynamic_branch_disable(preempt_lazy);
>   		if (mode != preempt_dynamic_mode)
>   			pr_info("Dynamic Preempt: full\n");
>   		break;
> @@ -8001,7 +8001,7 @@ static void __sched_dynamic_update(int mode)
>   		preempt_dynamic_enable(preempt_schedule);
>   		preempt_dynamic_enable(preempt_schedule_notrace);
>   		preempt_dynamic_enable(irqentry_exit_cond_resched);
> -		preempt_dynamic_key_enable(preempt_lazy);
> +		preempt_dynamic_branch_enable(preempt_lazy);
>   		if (mode != preempt_dynamic_mode)
>   			pr_info("Dynamic Preempt: lazy\n");
>   		break;
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 762dd8a4647c..4b65be5ec471 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -6442,21 +6442,21 @@ entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
>   #ifdef CONFIG_CFS_BANDWIDTH
>   
>   #ifdef CONFIG_JUMP_LABEL
> -static struct static_key __cfs_bandwidth_used;
> +static DEFINE_STATIC_KEY_FALSE(__cfs_bandwidth_used);
>   
>   static inline bool cfs_bandwidth_used(void)
>   {
> -	return static_key_false(&__cfs_bandwidth_used);
> +	return static_branch_unlikely(&__cfs_bandwidth_used);
>   }
>   


We will still have two left.

core.c: if (static_key_false((&paravirt_steal_rq_enabled))) {
cputime.c:      if (static_key_false(&paravirt_steal_enabled)) {

>   void cfs_bandwidth_usage_inc(void)
>   {
> -	static_key_slow_inc_cpuslocked(&__cfs_bandwidth_used);
> +	static_branch_inc_cpuslocked(&__cfs_bandwidth_used);
>   }
>   
>   void cfs_bandwidth_usage_dec(void)
>   {
> -	static_key_slow_dec_cpuslocked(&__cfs_bandwidth_used);
> +	static_branch_dec_cpuslocked(&__cfs_bandwidth_used);
>   }
>   #else /* !CONFIG_JUMP_LABEL: */
>   static bool cfs_bandwidth_used(void)