Re: [PATCH 26/28] hazptrtorture: Add torture_type=none clean skip for rcuscale coexistence

[Paul E. McKenney]

On Thu, Nov 05, 2026 at 12:54:44AM +0800, Kunwu Chan wrote:
> When both HAZPTR_TORTURE_TEST and RCU_SCALE_TEST are built into
> the same kernel, hazptrtorture calls torture_init_begin() first
> and rcuscale fails with -EBUSY.  torture_type=none makes
> hazptrtorture return early without registering, allowing the
> rcuscale hazptr scale type to run in the same boot.
> 
> Signed-off-by: Kunwu Chan <kunwu.chan@xxxxxxxxx>

You are only supposed to build one of them into the kernel at a time,
so the intent of the torture_init_begin() failure paths is to enforce
this rule.  If you want to run both in the same kernel, the way to do
that is to build both as kernel modules, then do modprobe and then rmmod
of the first one, followed by modprobe and rmmod of the second one.

So please help me out here.  Why do we need to allow both rcuscale and
hazptrtorture to be built into the same kernel?

If your desire is simply better handling of an error condition, an
alternative is to force either a Kconfig or build failure when more than
one of the modules invoking torture_init_begin() is built into the same
kernel at the same time.

							Thanx, Paul

> ---
>  .../selftests/rcutorture/configs/rcuscale/HAZPTR    | 13 +++++++++++++
>  .../rcutorture/configs/rcuscale/HAZPTR.boot         |  1 +
>  2 files changed, 14 insertions(+)
>  create mode 100644 tools/testing/selftests/rcutorture/configs/rcuscale/HAZPTR
>  create mode 100644 tools/testing/selftests/rcutorture/configs/rcuscale/HAZPTR.boot
> 
> diff --git a/tools/testing/selftests/rcutorture/configs/rcuscale/HAZPTR b/tools/testing/selftests/rcutorture/configs/rcuscale/HAZPTR
> new file mode 100644
> index 000000000000..c5e9cf0184ae
> --- /dev/null
> +++ b/tools/testing/selftests/rcutorture/configs/rcuscale/HAZPTR
> @@ -0,0 +1,13 @@
> +CONFIG_SMP=y
> +CONFIG_NR_CPUS=128
> +CONFIG_PREEMPT=y
> +CONFIG_HZ_PERIODIC=n
> +CONFIG_NO_HZ_IDLE=y
> +CONFIG_HOTPLUG_CPU=y
> +CONFIG_DEBUG_KERNEL=y
> +CONFIG_HAZPTR_TORTURE_TEST=y
> +CONFIG_HAZPTR_DEBUG=y
> +CONFIG_HAZPTR_STALL_DETECTOR=y
> +CONFIG_HAZPTR_STALL_TIMEOUT=1000
> +CONFIG_HAZPTR_DRAIN_ASSIST=y
> +CONFIG_RCU_SCALE_TEST=y
> diff --git a/tools/testing/selftests/rcutorture/configs/rcuscale/HAZPTR.boot b/tools/testing/selftests/rcutorture/configs/rcuscale/HAZPTR.boot
> new file mode 100644
> index 000000000000..e9cca4cf453b
> --- /dev/null
> +++ b/tools/testing/selftests/rcutorture/configs/rcuscale/HAZPTR.boot
> @@ -0,0 +1 @@
> +hazptrtorture.torture_type=none
> -- 
> 2.43.0
>