Re: [PATCH 2/2] docs: sched-preemption: Fix the list of runtime-selectable models

[Sebastian Andrzej Siewior]

On 2026-10-28 10:43:33 [+0800], Jinjie Ruan wrote:
> --- a/Documentation/scheduler/sched-preemption.rst
> +++ b/Documentation/scheduler/sched-preemption.rst
> @@ -20,9 +20,6 @@ change.
>  The models selectable at runtime are:
>  
>  	=========	====================================================
> -	none		No preemption of kernel code other than at explicit
> -			``cond_resched()`` / blocking points.
> -	voluntary	As ``none``, plus ``might_sleep()`` sites.
>  	full		Any section that is not explicitly preempt disabled
>  			may be preempted at any time.
>  	lazy		As ``full``, except that the scheduling request is

This is fine.

> @@ -31,10 +28,12 @@ The models selectable at runtime are:
>  			apply to real-time tasks.
>  	=========	====================================================
>  
> -Not every model is available on every kernel.  An architecture that provides
> -lazy-preempt support offers only ``full`` and ``lazy``, and ``none`` and
> -``voluntary`` are rejected there.  A PREEMPT_RT kernel always offers ``full``,
> -and ``lazy`` as well if the architecture provides it.
> +CONFIG_PREEMPT_DYNAMIC depends on CONFIG_ARCH_HAS_PREEMPT_LAZY, so ``none``
> +and ``voluntary`` are never selectable at runtime; passing either is
> +rejected with "Dynamic Preempt: unsupported mode".  The two models are only
> +left as build-time choices on architectures without lazy-preempt support.
> +A PREEMPT_RT kernel always offers ``full``, and ``lazy`` as well if the
> +architecture provides it.

What about:
 Not every model is available on every kernel.  An architecture that provides
 preemption support supports ``full``. If additionally lazy-preempt is
 supported then the choice ``lazy`` becomes available. An architecture
 without preemption support can not enable CONFIG_PREEMPT_DYNAMIC. On
 such an architecture the preemption model can only be selected at
 compile time. 

Sebastian