[PATCH] Documentation: index.rst: add entry of other sub-directory

[PATCH] Documentation: index.rst: add entry of other sub-directory

[Manuel Ebner]

add reference to scheduler/sched-rt-group.rst

Signed-off-by: Manuel Ebner <manuelebner@mailbox.org>
---
 Documentation/core-api/real-time/index.rst | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Documentation/core-api/real-time/index.rst b/Documentation/core-api/real-time/index.rst
index f08d2395a22c..661b419e7f8f 100644
--- a/Documentation/core-api/real-time/index.rst
+++ b/Documentation/core-api/real-time/index.rst
@@ -15,3 +15,4 @@ the required changes compared to a non-PREEMPT_RT configuration.
    differences
    hardware
    architecture-porting
+   Real-Time group scheduling <../../scheduler/sched-rt-group>
-- 
2.54.0

[PATCH] Documentation: real-time/index: add entry

[Manuel Ebner]

I figured out the subject and changelog aren't good. It should be:

[PATCH] Documentation: real-time/index: add entry

Add reference to realtime/index.rst pointing to scheduler/sched-rt-group.rst

Signed-off-by: Manuel Ebner <manuelebner@mailbox.org>
---

I'm waiting for feedback before making [v2].

Thanks 
 Manuel

Re: [PATCH] Documentation: index.rst: add entry of other sub-directory

[Sebastian Andrzej Siewior]

On 2026-06-03 10:04:31 [+0200], Manuel Ebner wrote:
> add reference to scheduler/sched-rt-group.rst
> 
> Signed-off-by: Manuel Ebner <manuelebner@mailbox.org>
> ---
>  Documentation/core-api/real-time/index.rst | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/Documentation/core-api/real-time/index.rst b/Documentation/core-api/real-time/index.rst
> index f08d2395a22c..661b419e7f8f 100644
> --- a/Documentation/core-api/real-time/index.rst
> +++ b/Documentation/core-api/real-time/index.rst
> @@ -15,3 +15,4 @@ the required changes compared to a non-PREEMPT_RT configuration.
>     differences
>     hardware
>     architecture-porting
> +   Real-Time group scheduling <../../scheduler/sched-rt-group>

Have you been using this and are referencing this because it is useful
or did you just happen to find it?
People have been complaining about this and I *think* it fails to work
in multi-CPU scenarios (it might work if the task is restricted to
single CPU usage). Not entirely certain. But complains, that I am
certain of.
There is replacement underway to utilize SCHED_DL for this as in
"Hierarchical Constant Bandwidth Server (HCBS)"
	https://lore.kernel.org/all/20260430213835.62217-1-yurand2000@gmail.com/

Sebastian

Re: [PATCH] Documentation: index.rst: add entry of other sub-directory

[Manuel Ebner]

On Wed, 2026-06-03 at 12:20 +0200, Sebastian Andrzej Siewior wrote:
> On 2026-06-03 10:04:31 [+0200], Manuel Ebner wrote:
> > add reference to scheduler/sched-rt-group.rst
> > 
> > Signed-off-by: Manuel Ebner <manuelebner@mailbox.org>
> > ---
> >  Documentation/core-api/real-time/index.rst | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/Documentation/core-api/real-time/index.rst b/Documentation/core-api/real-
> > time/index.rst
> > index f08d2395a22c..661b419e7f8f 100644
> > --- a/Documentation/core-api/real-time/index.rst
> > +++ b/Documentation/core-api/real-time/index.rst
> > @@ -15,3 +15,4 @@ the required changes compared to a non-PREEMPT_RT configuration.
> >     differences
> >     hardware
> >     architecture-porting
> > +   Real-Time group scheduling <../../scheduler/sched-rt-group>
> 
> Have you been using this and are referencing this because it is useful
> or did you just happen to find it?

I happened to find it.

> People have been complaining about this 

Maybe with the help of them we can figure out what's happening.
adding linux-rt-user@vger.kernel.org 

> and I *think* it fails to work
> in multi-CPU scenarios (it might work if the task is restricted to
> single CPU usage). Not entirely certain. But complains, that I am
> certain of.
> There is replacement underway to utilize SCHED_DL for this as in
> "Hierarchical Constant Bandwidth Server (HCBS)"
> 	https://lore.kernel.org/all/20260430213835.62217-1-yurand2000@gmail.com/

will look into this.
> 
> Sebastian

Thanks for the feedback
 Manuel

Re: [PATCH] Documentation: index.rst: add entry of other sub-directory

[Sebastian Andrzej Siewior]

On 2026-06-03 12:55:57 [+0200], Manuel Ebner wrote:
> > People have been complaining about this 
> 
> Maybe with the help of them we can figure out what's happening.
> adding linux-rt-user@vger.kernel.org 

good luck. What I managed to find out is that those, that did not copy
statements but run into trouble themself, were using in a multi-CPU
scenario. Based on other details I *think* it should not happen single
CPU usage but nobody confirmed.

But this HCBS thingy aims at replacing/ removing it entirely…

Sebastian

Re: [PATCH] Documentation: index.rst: add entry of other sub-directory

[Jonathan Corbet]

Manuel Ebner <manuelebner@mailbox.org> writes:

> add reference to scheduler/sched-rt-group.rst
>
> Signed-off-by: Manuel Ebner <manuelebner@mailbox.org>
> ---
>  Documentation/core-api/real-time/index.rst | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/Documentation/core-api/real-time/index.rst b/Documentation/core-api/real-time/index.rst
> index f08d2395a22c..661b419e7f8f 100644
> --- a/Documentation/core-api/real-time/index.rst
> +++ b/Documentation/core-api/real-time/index.rst
> @@ -15,3 +15,4 @@ the required changes compared to a non-PREEMPT_RT configuration.
>     differences
>     hardware
>     architecture-porting
> +   Real-Time group scheduling <../../scheduler/sched-rt-group>

This file already appears in the toctree in
Documentation/scheduler/index.rst; adding it elsewhere can create build
problems.  If you really want a link here, the way to do it is to add a
cross reference instead.

jon

Re: [PATCH] Documentation: index.rst: add entry of other sub-directory

[Sebastian Andrzej Siewior]

On 2026-06-12 13:30:13 [-0600], Jonathan Corbet wrote:
> Manuel Ebner <manuelebner@mailbox.org> writes:
> 
> > add reference to scheduler/sched-rt-group.rst
> >
> > Signed-off-by: Manuel Ebner <manuelebner@mailbox.org>
> > ---
> >  Documentation/core-api/real-time/index.rst | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/Documentation/core-api/real-time/index.rst b/Documentation/core-api/real-time/index.rst
> > index f08d2395a22c..661b419e7f8f 100644
> > --- a/Documentation/core-api/real-time/index.rst
> > +++ b/Documentation/core-api/real-time/index.rst
> > @@ -15,3 +15,4 @@ the required changes compared to a non-PREEMPT_RT configuration.
> >     differences
> >     hardware
> >     architecture-porting
> > +   Real-Time group scheduling <../../scheduler/sched-rt-group>
> 
> This file already appears in the toctree in
> Documentation/scheduler/index.rst; adding it elsewhere can create build
> problems.  If you really want a link here, the way to do it is to add a
> cross reference instead.

The long term goal is to remove sched-rt-group and replace it with
something else. Manuel stated that he just found it and was not/ is not
using it. Maybe just drop it entirely.

> jon

Sebastian