[PATCH] sched_ext: Fix stale errno in scx_sub_enable_workfn()

[PATCH] sched_ext: Fix stale errno in scx_sub_enable_workfn()

[Cui Jian]

scx_sub_enable_workfn() drops the return value of validate_ops().
When validate_ops() fails, the function jumps to err_disable with
ret still holding 0 from the previous call, so the fallback error
added by commit db4e9defd2e8 ("sched_ext: Record an error on
errno-only sub-enable failure") reports "scx_sub_enable() failed
(0)".

This is currently harmless because validate_ops() records its own
scx_error() first and the first error wins, but it leaves the
fallback broken for this path. Save the return value into ret,
like scx_root_enable_workfn() already does.

The nesting depth check and the cgroup online check also reach
err_disable without setting ret. Set -EINVAL and -ENODEV there so
the fallback always reports a real errno.

Signed-off-by: Cui Jian <cjian720@163.com>
---
 kernel/sched/ext/ext.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/ext/ext.c b/kernel/sched/ext/ext.c
index e3fa7b2fac9d..e623d6375f66 100644
--- a/kernel/sched/ext/ext.c
+++ b/kernel/sched/ext/ext.c
@@ -7559,6 +7559,7 @@ static void scx_sub_enable_workfn(struct kthread_work *work)
 	if (sch->level >= SCX_SUB_MAX_DEPTH) {
 		scx_error(sch, "max nesting depth %d violated",
 			  SCX_SUB_MAX_DEPTH);
+		ret = -EINVAL;
 		goto err_disable;
 	}
 
@@ -7580,7 +7581,8 @@ static void scx_sub_enable_workfn(struct kthread_work *work)
 	if (ret)
 		goto err_disable;
 
-	if (validate_ops(sch, ops))
+	ret = validate_ops(sch, ops);
+	if (ret)
 		goto err_disable;
 
 	struct scx_sub_attach_args sub_attach_args = {
@@ -7613,6 +7615,7 @@ static void scx_sub_enable_workfn(struct kthread_work *work)
 	set_cgroup_sched(sch_cgroup(sch), sch);
 	if (!(cgrp->self.flags & CSS_ONLINE)) {
 		scx_error(sch, "cgroup is not online");
+		ret = -ENODEV;
 		goto err_unlock_and_disable;
 	}
 

base-commit: 1229e2e57a5c2980ccd457b9b53ea0eed5a22ab3
-- 
2.34.1

Re: [PATCH] sched_ext: Fix stale errno in scx_sub_enable_workfn()

[Andrea Righi]

Hi Cui,

On Sun, Jul 19, 2026 at 04:17:13AM +0800, Cui Jian wrote:
> scx_sub_enable_workfn() drops the return value of validate_ops().
> When validate_ops() fails, the function jumps to err_disable with
> ret still holding 0 from the previous call, so the fallback error
> added by commit db4e9defd2e8 ("sched_ext: Record an error on
> errno-only sub-enable failure") reports "scx_sub_enable() failed
> (0)".
> 
> This is currently harmless because validate_ops() records its own
> scx_error() first and the first error wins, but it leaves the
> fallback broken for this path. Save the return value into ret,
> like scx_root_enable_workfn() already does.
> 
> The nesting depth check and the cgroup online check also reach
> err_disable without setting ret. Set -EINVAL and -ENODEV there so
> the fallback always reports a real errno.
> 
> Signed-off-by: Cui Jian <cjian720@163.com>

This doesn't apply anymore, but the logic should still be valid. Can you rebase
it to the latest branch?

 git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext.git for-7.3

Thanks,
-Andrea

> ---
>  kernel/sched/ext/ext.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/sched/ext/ext.c b/kernel/sched/ext/ext.c
> index e3fa7b2fac9d..e623d6375f66 100644
> --- a/kernel/sched/ext/ext.c
> +++ b/kernel/sched/ext/ext.c
> @@ -7559,6 +7559,7 @@ static void scx_sub_enable_workfn(struct kthread_work *work)
>  	if (sch->level >= SCX_SUB_MAX_DEPTH) {
>  		scx_error(sch, "max nesting depth %d violated",
>  			  SCX_SUB_MAX_DEPTH);
> +		ret = -EINVAL;
>  		goto err_disable;
>  	}
>  
> @@ -7580,7 +7581,8 @@ static void scx_sub_enable_workfn(struct kthread_work *work)
>  	if (ret)
>  		goto err_disable;
>  
> -	if (validate_ops(sch, ops))
> +	ret = validate_ops(sch, ops);
> +	if (ret)
>  		goto err_disable;
>  
>  	struct scx_sub_attach_args sub_attach_args = {
> @@ -7613,6 +7615,7 @@ static void scx_sub_enable_workfn(struct kthread_work *work)
>  	set_cgroup_sched(sch_cgroup(sch), sch);
>  	if (!(cgrp->self.flags & CSS_ONLINE)) {
>  		scx_error(sch, "cgroup is not online");
> +		ret = -ENODEV;
>  		goto err_unlock_and_disable;
>  	}
>  
> 
> base-commit: 1229e2e57a5c2980ccd457b9b53ea0eed5a22ab3
> -- 
> 2.34.1
> 

[PATCH v2] sched_ext: Fix stale errno in scx_sub_enable_workfn()

[Cui Jian]

The nesting depth check and the cgroup online check in
scx_sub_enable_workfn() reach err_disable without setting ret, so
the fallback error added by commit db4e9defd2e8 ("sched_ext: Record
an error on errno-only sub-enable failure") reports
"scx_sub_enable() failed (0)".

This is currently harmless because both paths record their own
scx_error() first and the first error wins, but it leaves the
fallback broken for these paths. Set -EINVAL and -ENODEV there
so the fallback always reports a real errno.

v2: The validate_ops() path from v1 is already fixed in for-7.3
    (sub.c already has ret = scx_validate_ops()), so only the two
    remaining paths are addressed.

Signed-off-by: Cui Jian <cjian720@163.com>
---
 kernel/sched/ext/sub.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/sched/ext/sub.c b/kernel/sched/ext/sub.c
index d7842a609d96..6da6c91e4287 100644
--- a/kernel/sched/ext/sub.c
+++ b/kernel/sched/ext/sub.c
@@ -1331,6 +1331,7 @@ void scx_sub_enable_workfn(struct kthread_work *work)
 	if (sch->level >= SCX_SUB_MAX_DEPTH) {
 		scx_error(sch, "max nesting depth %d violated",
 			  SCX_SUB_MAX_DEPTH);
+		ret = -EINVAL;
 		goto err_disable;
 	}
 
@@ -1378,6 +1379,7 @@ void scx_sub_enable_workfn(struct kthread_work *work)
 	set_cgroup_sched(sch_cgroup(sch), sch);
 	if (!(cgrp->self.flags & CSS_ONLINE)) {
 		scx_error(sch, "cgroup is not online");
+		ret = -ENODEV;
 		goto err_unlock_and_disable;
 	}
 
-- 
2.34.1

Re: [PATCH v2] sched_ext: Fix stale errno in scx_sub_enable_workfn()

[Andrea Righi]

Hi Cui,

On Wed, Jul 22, 2026 at 06:03:52PM +0800, Cui Jian wrote:
> The nesting depth check and the cgroup online check in
> scx_sub_enable_workfn() reach err_disable without setting ret, so
> the fallback error added by commit db4e9defd2e8 ("sched_ext: Record
> an error on errno-only sub-enable failure") reports
> "scx_sub_enable() failed (0)".
> 
> This is currently harmless because both paths record their own
> scx_error() first and the first error wins, but it leaves the
> fallback broken for these paths. Set -EINVAL and -ENODEV there
> so the fallback always reports a real errno.
> 
> v2: The validate_ops() path from v1 is already fixed in for-7.3
>     (sub.c already has ret = scx_validate_ops()), so only the two
>     remaining paths are addressed.
> 
> Signed-off-by: Cui Jian <cjian720@163.com>

Looks good to me now.

Reviewed-by: Andrea Righi <arighi@nvidia.com>

Thanks,
-Andrea

> ---
>  kernel/sched/ext/sub.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/kernel/sched/ext/sub.c b/kernel/sched/ext/sub.c
> index d7842a609d96..6da6c91e4287 100644
> --- a/kernel/sched/ext/sub.c
> +++ b/kernel/sched/ext/sub.c
> @@ -1331,6 +1331,7 @@ void scx_sub_enable_workfn(struct kthread_work *work)
>  	if (sch->level >= SCX_SUB_MAX_DEPTH) {
>  		scx_error(sch, "max nesting depth %d violated",
>  			  SCX_SUB_MAX_DEPTH);
> +		ret = -EINVAL;
>  		goto err_disable;
>  	}
>  
> @@ -1378,6 +1379,7 @@ void scx_sub_enable_workfn(struct kthread_work *work)
>  	set_cgroup_sched(sch_cgroup(sch), sch);
>  	if (!(cgrp->self.flags & CSS_ONLINE)) {
>  		scx_error(sch, "cgroup is not online");
> +		ret = -ENODEV;
>  		goto err_unlock_and_disable;
>  	}
>  
> -- 
> 2.34.1
> 

Re: [PATCH v2] sched_ext: Fix stale errno in scx_sub_enable_workfn()

[Tejun Heo]

Hello,

On Wed, Jul 22, 2026 at 06:03:52PM +0800, Cui Jian wrote:
> The nesting depth check and the cgroup online check in
> scx_sub_enable_workfn() reach err_disable without setting ret, so
> the fallback error added by commit db4e9defd2e8 ("sched_ext: Record
> an error on errno-only sub-enable failure") reports
> "scx_sub_enable() failed (0)".

Applied to sched_ext/for-7.3.

Thanks.

-- 
tejun