Re: [PATCH v2] sched: Convert last bits of deprecated static key usage

[Hongyan Xia]

On 10/6/2026 6:50 PM, Valentin Schneider wrote:
> On 03/09/26 11:57, Hongyan Xia wrote:
>> From: Hongyan Xia <hongyan.xia@xxxxxxxxxxxxx>
>>
>> Raw static keys have no type information and do not prevent mis-matches
>> (like static_key_false() on a default TRUE key). The helper names
>> static_key_{true/false}() are also confusing, hence the deprecation.
>>
>> We have already converted other sites in previous patches. Convert the
>> last sites of deprecated static key APIs. After this fix, scheduler code
>> has zero deprecated static key APIs now.
>>
>> 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.
>>
>> No functional change.
>>
>> Signed-off-by: Hongyan Xia <hongyan.xia@xxxxxxxxxxxxx>
> 
> Some comprehension/changelog explanation nit below, otherwise:
> 
> Reviewed-by: Valentin Schneider <vschneid@xxxxxxxxxx>
> 
>> @@ -6575,21 +6575,21 @@ 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);
>>   }
> 
> Usual likely/unlikely/true/false static key confusion for me here;
> 
> The previous definition was pretty much
>   = STATIC_KEY_INIT_FALSE
> due to static storage initialization.
> 
> And then for the static_key_*() naming, false == unlikely.
> 
> Because it's all #define magic I assume the compilation delta will be zero,
> but I can't be bothered given I'm on a laptop running power saver mode.

This is exactly what I checked before sending this patch. The good news 
is that at least on my machine, the delta in the machine code is zero 
under aarch64 and x86.