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Date:   Thu, 20 Jul 2023 12:53:05 -0700
From:   "Paul E. McKenney" <paulmck@kernel.org>
To:     Valentin Schneider <vschneid@redhat.com>
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Subject: Re: [RFC PATCH v2 17/20] rcutorture: Add a test config to torture
 test low RCU_DYNTICKS width
Message-ID: <24b55289-1c35-41cc-9ad3-baa957f1c9cb@paulmck-laptop>
Reply-To: paulmck@kernel.org
References: <20230720163056.2564824-1-vschneid@redhat.com>
 <20230720163056.2564824-18-vschneid@redhat.com>
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On Thu, Jul 20, 2023 at 05:30:53PM +0100, Valentin Schneider wrote:
> We now have an RCU_EXPORT knob for configuring the size of the dynticks
> counter: CONFIG_RCU_DYNTICKS_BITS.
> 
> Add a torture config for a ridiculously small counter (2 bits). This is ac
> opy of TREE4 with the added counter size restriction.
> 
> Link: http://lore.kernel.org/r/4c2cb573-168f-4806-b1d9-164e8276e66a@paulmck-laptop
> Suggested-by: Paul E. McKenney <paulmck@kernel.org>
> Signed-off-by: Valentin Schneider <vschneid@redhat.com>
> ---
>  .../selftests/rcutorture/configs/rcu/TREE11   | 19 +++++++++++++++++++
>  .../rcutorture/configs/rcu/TREE11.boot        |  1 +
>  2 files changed, 20 insertions(+)
>  create mode 100644 tools/testing/selftests/rcutorture/configs/rcu/TREE11
>  create mode 100644 tools/testing/selftests/rcutorture/configs/rcu/TREE11.boot
> 
> diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE11 b/tools/testing/selftests/rcutorture/configs/rcu/TREE11
> new file mode 100644
> index 0000000000000..aa7274efd9819
> --- /dev/null
> +++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE11
> @@ -0,0 +1,19 @@
> +CONFIG_SMP=y
> +CONFIG_NR_CPUS=8
> +CONFIG_PREEMPT_NONE=n
> +CONFIG_PREEMPT_VOLUNTARY=y
> +CONFIG_PREEMPT=n
> +CONFIG_PREEMPT_DYNAMIC=n
> +#CHECK#CONFIG_TREE_RCU=y
> +CONFIG_HZ_PERIODIC=n
> +CONFIG_NO_HZ_IDLE=n
> +CONFIG_NO_HZ_FULL=y
> +CONFIG_RCU_TRACE=y
> +CONFIG_RCU_FANOUT=4
> +CONFIG_RCU_FANOUT_LEAF=3
> +CONFIG_DEBUG_LOCK_ALLOC=n
> +CONFIG_DEBUG_OBJECTS_RCU_HEAD=n
> +CONFIG_RCU_EXPERT=y
> +CONFIG_RCU_EQS_DEBUG=y
> +CONFIG_RCU_LAZY=y
> +CONFIG_RCU_DYNTICKS_BITS=2

Why not just add this last line to the existing TREE04 scenario?
That would ensure that it gets tested regularly without extending the
time required to run a full set of rcutorture tests.

> diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE11.boot b/tools/testing/selftests/rcutorture/configs/rcu/TREE11.boot
> new file mode 100644
> index 0000000000000..a8d94caf7d2fd
> --- /dev/null
> +++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE11.boot
> @@ -0,0 +1 @@
> +rcutree.rcu_fanout_leaf=4 nohz_full=1-N
> -- 
> 2.31.1
>