Re: [RFC PATCH v2 17/20] rcutorture: Add a test config to torture test low RCU_DYNTICKS width

On Thu, Jul 20, 2023 at 12:53:05PM -0700, Paul E. McKenney wrote:

On Thu, Jul 20, 2023 at 05:30:53PM +0100, Valentin Schneider wrote:

quoted

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 (local)
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.

Please see below for the version of this patch that I am running overnight
tests with.  Does this one work for you?

							Thanx, Paul

------------------------------------------------------------------------

commit 1aa13731e665193cd833edac5ebc86a9c3fea2b7
Author: Valentin Schneider [off-list ref]
Date:   Thu Jul 20 20:58:41 2023 -0700

    rcutorture: Add a test config to torture test low RCU_DYNTICKS width
    
    We now have an RCU_EXPORT knob for configuring the size of the dynticks
    counter: CONFIG_RCU_DYNTICKS_BITS.
    
    Modify scenario TREE04 to exercise a a ridiculously small counter
    (2 bits).
    
    Link: http://lore.kernel.org/r/4c2cb573-168f-4806-b1d9-164e8276e66a@paulmck-laptop (local)
    Suggested-by: Paul E. McKenney [off-list ref]
    Signed-off-by: Valentin Schneider [off-list ref]
    Signed-off-by: Paul E. McKenney [off-list ref]

diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE04 b/tools/testing/selftests/rcutorture/configs/rcu/TREE04
index dc4985064b3a..aa7274efd981 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/TREE04
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE04

@@ -16,3 +16,4 @@ CONFIG_DEBUG_OBJECTS_RCU_HEAD=n
 CONFIG_RCU_EXPERT=y
 CONFIG_RCU_EQS_DEBUG=y
 CONFIG_RCU_LAZY=y
+CONFIG_RCU_DYNTICKS_BITS=2