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

[Paul E. McKenney]

On Thu, Mar 05, 2026 at 12:53:48PM -0500, Joel Fernandes wrote:
> 
> 
> 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@xxxxxxxxxx>
> > 
> > ---
> > 
> > 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 ;-)

Tell me about it.  ;-)

I will add "#CHECK#CONFIG_PREEMPT_RCU=n" as a separate non-urgent commit.

> Otherwise, I could not find any other flaws in the approach and it makes sense, so:
> Reviewed-by: Joel Fernandes <joelagnelf@xxxxxxxxxx>
> 
> Boqun, you will be taking this through the 7.0-rc tree right? So that 7.0
> release tests don't fail.

Unless I hear otherwise, I will assume that Boqun will apply your
Reviewed-by.  Easy for me to do, just no point in its being done twice.

> 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.

Sounds good, and thank you both!

								Thanx, Paul

> Thanks!
> 
> --
> Joel Fernandes
> 
> [...]
>