From 4df002d908796c1ff87b985af1d31a0e36e6c66f Mon Sep 17 00:00:00 2001
From: "Paul E. McKenney" <paulmck@kernel.org>
Date: Fri, 25 Mar 2022 16:39:01 -0700
Subject: [PATCH] rcuscale: Allow rcuscale without RCU Tasks

Currently, a CONFIG_PREEMPT_NONE=y kernel substitutes normal RCU for
RCU Tasks.  Unless that kernel builds rcuscale, whether built-in or as
a module, in which case RCU Tasks is (unnecessarily) built.  This both
increases kernel size and increases the complexity of certain tracing
operations.  This commit therefore decouples the presence of rcuscale
from the presence of RCU Tasks.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/Kconfig.debug                             |  1 -
 kernel/rcu/rcuscale.c                                | 12 +++++++++++-
 .../selftests/rcutorture/configs/rcuscale/CFcommon   |  4 ++--
 .../selftests/rcutorture/configs/rcuscale/TREE       |  2 ++
 4 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/kernel/rcu/Kconfig.debug b/kernel/rcu/Kconfig.debug
index dceaa3e754e5..71e73fceff87 100644
--- a/kernel/rcu/Kconfig.debug
+++ b/kernel/rcu/Kconfig.debug
@@ -28,7 +28,6 @@ config RCU_SCALE_TEST
 	depends on DEBUG_KERNEL
 	select TORTURE_TEST
 	select SRCU
-	select TASKS_RCU
 	select TASKS_RUDE_RCU
 	select TASKS_TRACE_RCU
 	default n
diff --git a/kernel/rcu/rcuscale.c b/kernel/rcu/rcuscale.c
index 5e4f1f83d38e..311dbcb064ed 100644
--- a/kernel/rcu/rcuscale.c
+++ b/kernel/rcu/rcuscale.c
@@ -268,6 +268,8 @@ static struct rcu_scale_ops srcud_ops = {
 	.name		= "srcud"
 };
 
+#ifdef CONFIG_TASKS_RCU
+
 /*
  * Definitions for RCU-tasks scalability testing.
  */
@@ -295,6 +297,14 @@ static struct rcu_scale_ops tasks_ops = {
 	.name		= "tasks"
 };
 
+#define TASKS_OPS &tasks_ops,
+
+#else // #ifdef CONFIG_TASKS_RCU
+
+#define TASKS_OPS
+
+#endif // #else // #ifdef CONFIG_TASKS_RCU
+
 /*
  * Definitions for RCU-tasks-trace scalability testing.
  */
@@ -797,7 +807,7 @@ rcu_scale_init(void)
 	long i;
 	int firsterr = 0;
 	static struct rcu_scale_ops *scale_ops[] = {
-		&rcu_ops, &srcu_ops, &srcud_ops, &tasks_ops, &tasks_tracing_ops
+		&rcu_ops, &srcu_ops, &srcud_ops, TASKS_OPS &tasks_tracing_ops
 	};
 
 	if (!torture_init_begin(scale_type, verbose))
diff --git a/tools/testing/selftests/rcutorture/configs/rcuscale/CFcommon b/tools/testing/selftests/rcutorture/configs/rcuscale/CFcommon
index 90942bb5bebc..2ed3b46a9c37 100644
--- a/tools/testing/selftests/rcutorture/configs/rcuscale/CFcommon
+++ b/tools/testing/selftests/rcutorture/configs/rcuscale/CFcommon
@@ -1,5 +1,5 @@
 CONFIG_RCU_SCALE_TEST=y
 CONFIG_PRINTK_TIME=y
 CONFIG_TASKS_RCU_GENERIC=y
-CONFIG_TASKS_RCU=y
-CONFIG_TASKS_TRACE_RCU=y
+CONFIG_FORCE_TASKS_RCU=y
+#CHECK#CONFIG_TASKS_RCU=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcuscale/TREE b/tools/testing/selftests/rcutorture/configs/rcuscale/TREE
index f110d9ffbe4c..b10706fd03a4 100644
--- a/tools/testing/selftests/rcutorture/configs/rcuscale/TREE
+++ b/tools/testing/selftests/rcutorture/configs/rcuscale/TREE
@@ -16,3 +16,5 @@ CONFIG_RCU_BOOST=n
 CONFIG_DEBUG_OBJECTS_RCU_HEAD=n
 CONFIG_RCU_EXPERT=y
 CONFIG_RCU_TRACE=y
+CONFIG_KPROBES=n
+CONFIG_FTRACE=n