Re: [PATCH RESEND] sched: Move some scheduler fields to new static branch API
From: Hongyan Xia
Date: Wed Aug 19 2026 - 22:22:07 EST
On 8/19/2026 8:19 PM, Shrikanth Hegde wrote:
>
> Hi Hongyan.
>
> On 8/19/26 1:39 PM, Hongyan Xia wrote:
>> From: Hongyan Xia <hongyan.xia@xxxxxxxxxxxxx>
>>
>> __cfs_bandwidth_used uses struct static_key directly which is
>> deprecated. Fix.
>
> A bit of context on why it is deprecated would help.
Sure. Will add some context in the next rev.
>>
>> 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://apc01.safelinks.protection.outlook.com/?
> url=https%3A%2F%2Flore.kernel.org%2Fall%2F20260803191731.3244294-1-
> mark.rutland%40arm.com%2F&data=05%7C02%7Chongyan.xia%40transsion.com%7C65194a86312643aed75b08defdec3f5a%7C2e8503a62d0143338e366ab7c8cd7ae2%7C0%7C0%7C639227388298975336%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=KbAcWOiQg%2Bir4%2FzKW2KG66IkxSnbq79m2I9IUlLe4os%3D&reserved=0
>
I see. These two do conflict. Would be nice if Mark's patch gets merged
first, then it makes this diff smaller.
>> No functional change.
>>
>> Signed-off-by: Hongyan Xia <hongyan.xia@xxxxxxxxxxxxx>
>> ---
>> 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.
Right, like mentioned in the commit message, this change here is a
nice-to-have, not really deprecation. The trend is to move from untyped
static_key_* variants to typed static_branch_* ones, so I took the
opportunity to fix it.
>>
>> # 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((¶virt_steal_rq_enabled))) {
> cputime.c: if (static_key_false(¶virt_steal_enabled)) {
>
That has been sent, at
https://lore.kernel.org/all/20260819081207.12150-1-hongyan.xia@xxxxxxxxxxxxx/
That touches all archs and may need review from Xen folks, so I split it
into a separate patch.
>> 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)
>