Re: [PATCH v3 1/4] rcutorture: Update due to x86 not supporting none/voluntary preemption

[Joel Fernandes <joelagnelf@nvidia.com>]

On 3/4/2026 7:01 PM, Paul E. McKenney wrote:
> As of v7.0-rc1, architectures that support preemption, including x86 and
> arm64, no longer support CONFIG_PREEMPT_NONE or CONFIG_PREEMPT_VOLUNTARY.
> Attempting to build kernels with these two Kconfig options results in
> .config errors.  This commit therefore switches such rcutorture scenarios
> to CONFIG_PREEMPT_LAZY.
> 
> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
> 
> ---
> 
> Changes since v2:
> 
> o	Fold in c69ac5693540 ("rcutorture: Adjust scenarios for default
> 	lazy preemption")
> 
> Changes since v1:
> 
> o	Add CONFIG_PREEMPT_DYNAMIC=n in order to test non-preemptible RCU.
> 
> o	Remove CONFIG_PREEMPT_COUNT=n because it conflicts with
> 	CONFIG_PREEMPT_LAZY=y.
> 
> o	Remove some stray conflicting CONFIG_PREEMPT_LAZY=n instances.
> 
[...]
> diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE04 b/tools/testing/selftests/rcutorture/configs/rcu/TREE04
> index 34aee1acb8662..ac857d5bcb222 100644
> --- a/tools/testing/selftests/rcutorture/configs/rcu/TREE04
> +++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE04
> @@ -1,11 +1,12 @@
>  CONFIG_SMP=y
>  CONFIG_NR_CPUS=8
> +CONFIG_PREEMPT_LAZY=y
>  CONFIG_PREEMPT_NONE=n
> -CONFIG_PREEMPT_VOLUNTARY=y
> +CONFIG_PREEMPT_VOLUNTARY=n
>  CONFIG_PREEMPT=n
>  CONFIG_PREEMPT_DYNAMIC=n
> -CONFIG_PREEMPT_LAZY=n
>  #CHECK#CONFIG_TREE_RCU=y
> +#CHECK#CONFIG_PREEMPT_RCU=n

nit: Let us add this #CHECK# to the other configs you changed too? Otherwise it
is a bit confusing because it took some digging to clearly see that
PREEMPT_DYNAMIC=n and PREEMPT_LAZY=y implies CONFIG_PREEMPT_RCU=n ;-)

Otherwise, I could not find any other flaws in the approach and it makes sense, so:
Reviewed-by: Joel Fernandes <joelagnelf@nvidia.com>

Boqun, you will be taking this through the 7.0-rc tree right? So that 7.0
release tests don't fail.

Also I will drop the 2 related rcutorture patches for 7.1 and rebase on top of a
7.0-rc fixes branch Boqun might be creating.

Thanks!

--
Joel Fernandes

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