sched: cleanup sched_update_scaling() return type and usage

[PATCH] sched: cleanup sched_update_scaling() return type and usage

Posted by Zhan Xusheng 2 weeks, 4 days ago

The function sched_update_scaling() always returned 0 and callers never
checked its return value. This patch removes the return value and changes
the function to return void for clarity.

The usage of the return value in kernel/sched/debug.c has also been
updated to reflect this change. This cleanup improves code readability
and eliminates unnecessary logic.

Tested:
- Kernel compiled successfully
- sched_update_scaling() invoked without errors
- No regressions in scheduler-related functionality

Signed-off-by: Zhan Xusheng <zhanxusheng@xiaomi.com>
---
 kernel/sched/debug.c | 3 +--
 kernel/sched/fair.c  | 4 +---
 kernel/sched/sched.h | 2 +-
 3 files changed, 3 insertions(+), 6 deletions(-)

diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index 41caa22e0680..d74c02297b42 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -189,8 +189,7 @@ static ssize_t sched_scaling_write(struct file *filp, const char __user *ubuf,
 		return -EINVAL;
 
 	sysctl_sched_tunable_scaling = scaling;
-	if (sched_update_scaling())
-		return -EINVAL;
+	sched_update_scaling();
 
 	*ppos += cnt;
 	return cnt;
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index e71302282671..234437ddd4c0 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1004,7 +1004,7 @@ struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
 /**************************************************************
  * Scheduling class statistics methods:
  */
-int sched_update_scaling(void)
+void sched_update_scaling(void)
 {
 	unsigned int factor = get_update_sysctl_factor();
 
@@ -1012,8 +1012,6 @@ int sched_update_scaling(void)
 	(normalized_sysctl_##name = sysctl_##name / (factor))
 	WRT_SYSCTL(sched_base_slice);
 #undef WRT_SYSCTL
-
-	return 0;
 }
 
 static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se);
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 93fce4bbff5e..c9ef6cd7b754 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2168,7 +2168,7 @@ extern int group_balance_cpu(struct sched_group *sg);
 extern void update_sched_domain_debugfs(void);
 extern void dirty_sched_domain_sysctl(int cpu);
 
-extern int sched_update_scaling(void);
+extern void sched_update_scaling(void);
 
 static inline const struct cpumask *task_user_cpus(struct task_struct *p)
 {
-- 
2.43.0

Re: [PATCH] sched: cleanup sched_update_scaling() return type and usage

Posted by Shubhang Kaushik 2 weeks, 4 days ago

Hello Zhan,

On Tue, 20 Jan 2026, Zhan Xusheng wrote:

> The function sched_update_scaling() always returned 0 and callers never
> checked its return value. This patch removes the return value and changes
> the function to return void for clarity.
>
> The usage of the return value in kernel/sched/debug.c has also been
> updated to reflect this change. This cleanup improves code readability
> and eliminates unnecessary logic.
>
> Tested:
> - Kernel compiled successfully
> - sched_update_scaling() invoked without errors
> - No regressions in scheduler-related functionality
>
> Signed-off-by: Zhan Xusheng <zhanxusheng@xiaomi.com>
> ---
> kernel/sched/debug.c | 3 +--
> kernel/sched/fair.c  | 4 +---
> kernel/sched/sched.h | 2 +-
> 3 files changed, 3 insertions(+), 6 deletions(-)
>
> diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
> index 41caa22e0680..d74c02297b42 100644
> --- a/kernel/sched/debug.c
> +++ b/kernel/sched/debug.c
> @@ -189,8 +189,7 @@ static ssize_t sched_scaling_write(struct file *filp, const char __user *ubuf,
> 		return -EINVAL;
>
> 	sysctl_sched_tunable_scaling = scaling;
> -	if (sched_update_scaling())
> -		return -EINVAL;
> +	sched_update_scaling();

Okay. Good to remove a vestigial return value and dead -EINVAL check, as 
the function performs 'no-fail' math.

>
> 	*ppos += cnt;
> 	return cnt;
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index e71302282671..234437ddd4c0 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -1004,7 +1004,7 @@ struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
> /**************************************************************
>  * Scheduling class statistics methods:
>  */
> -int sched_update_scaling(void)
> +void sched_update_scaling(void)
> {
> 	unsigned int factor = get_update_sysctl_factor();
>
> @@ -1012,8 +1012,6 @@ int sched_update_scaling(void)
> 	(normalized_sysctl_##name = sysctl_##name / (factor))
> 	WRT_SYSCTL(sched_base_slice);
> #undef WRT_SYSCTL
> -
> -	return 0;
> }

By changing this to void, we are asserting that the update is 
'fire-and-forget'. If we later need to add sanity check preventing 
for eg. slice that is too small, the return type might  need to
revert to int.

>
> static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se);
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index 93fce4bbff5e..c9ef6cd7b754 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -2168,7 +2168,7 @@ extern int group_balance_cpu(struct sched_group *sg);
> extern void update_sched_domain_debugfs(void);
> extern void dirty_sched_domain_sysctl(int cpu);
>
> -extern int sched_update_scaling(void);
> +extern void sched_update_scaling(void);
>
> static inline const struct cpumask *task_user_cpus(struct task_struct *p)
> {
> -- 
> 2.43.0
>
>

Regards,
Shubhang Kaushik