rcu: Remove *_SLOW_* Kconfig options

The RCU_TORTURE_TEST_SLOW_PREINIT, RCU_TORTURE_TEST_SLOW_PREINIT_DELAY,
RCU_TORTURE_TEST_SLOW_PREINIT_DELAY, RCU_TORTURE_TEST_SLOW_INIT,
RCU_TORTURE_TEST_SLOW_INIT_DELAY, RCU_TORTURE_TEST_SLOW_CLEANUP,
and RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY Kconfig options are only
useful for torture testing, and there are the rcutree.gp_cleanup_delay,
rcutree.gp_init_delay, and rcutree.gp_preinit_delay kernel boot parameters
that rcutorture can use instead.  The effect of these parameters is to
artificially slow down grace period initialization and cleanup in order
to make some types of race conditions happen more often.

This commit therefore simplifies Tree RCU a bit by removing the Kconfig
options and adding the corresponding kernel parameters to rcutorture's
.boot files instead.  However, this commit also leaves out the kernel
parameters for TREE02, TREE04, and TREE07 in order to have about the
same number of tests slowed as not slowed.  TREE01, TREE03, TREE05,
and TREE06 are slowed, and the rest are not slowed.

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Documentation/admin-guide/kernel-parameters.txt

@@ -3229,21 +3229,17 @@
 
 	rcutree.gp_cleanup_delay=	[KNL]
 			Set the number of jiffies to delay each step of
-			RCU grace-period cleanup.  This only has effect
-			when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
+			RCU grace-period cleanup.
 
 	rcutree.gp_init_delay=	[KNL]
 			Set the number of jiffies to delay each step of
-			RCU grace-period initialization.  This only has
-			effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
-			is set.
+			RCU grace-period initialization.
 
 	rcutree.gp_preinit_delay=	[KNL]
 			Set the number of jiffies to delay each step of
 			RCU grace-period pre-initialization, that is,
 			the propagation of recent CPU-hotplug changes up
-			the rcu_node combining tree.  This only has effect
-			when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
+			the rcu_node combining tree.
 
 	rcutree.rcu_fanout_exact= [KNL]
 			Disable autobalancing of the rcu_node combining

kernel/rcu/tree.c

@@ -177,26 +177,12 @@ module_param(kthread_prio, int, 0644);
 
 /* Delay in jiffies for grace-period initialization delays, debug only. */
 
-#ifdef CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT
-static int gp_preinit_delay = CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT_DELAY;
-module_param(gp_preinit_delay, int, 0644);
-#else /* #ifdef CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT */
-static const int gp_preinit_delay;
-#endif /* #else #ifdef CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT */
-
-#ifdef CONFIG_RCU_TORTURE_TEST_SLOW_INIT
-static int gp_init_delay = CONFIG_RCU_TORTURE_TEST_SLOW_INIT_DELAY;
-module_param(gp_init_delay, int, 0644);
-#else /* #ifdef CONFIG_RCU_TORTURE_TEST_SLOW_INIT */
-static const int gp_init_delay;
-#endif /* #else #ifdef CONFIG_RCU_TORTURE_TEST_SLOW_INIT */
-
-#ifdef CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP
-static int gp_cleanup_delay = CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY;
-module_param(gp_cleanup_delay, int, 0644);
-#else /* #ifdef CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP */
-static const int gp_cleanup_delay;
-#endif /* #else #ifdef CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP */
+static int gp_preinit_delay;
+module_param(gp_preinit_delay, int, 0444);
+static int gp_init_delay;
+module_param(gp_init_delay, int, 0444);
+static int gp_cleanup_delay;
+module_param(gp_cleanup_delay, int, 0444);
 
 /*
  * Number of grace periods between delays, normalized by the duration of

kernel/rcu/tree_plugin.h

@@ -109,11 +109,11 @@ static void __init rcu_bootup_announce_oddness(void)
 		pr_info("\tKick kthreads if too-long grace period.\n");
 	if (IS_ENABLED(CONFIG_DEBUG_OBJECTS_RCU_HEAD))
 		pr_info("\tRCU callback double-/use-after-free debug enabled.\n");
-	if (IS_ENABLED(CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT))
+	if (gp_preinit_delay)
 		pr_info("\tRCU debug GP pre-init slowdown %d jiffies.\n", gp_preinit_delay);
-	if (IS_ENABLED(CONFIG_RCU_TORTURE_TEST_SLOW_INIT))
+	if (gp_init_delay)
 		pr_info("\tRCU debug GP init slowdown %d jiffies.\n", gp_init_delay);
-	if (IS_ENABLED(CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP))
+	if (gp_cleanup_delay)
 		pr_info("\tRCU debug GP init slowdown %d jiffies.\n", gp_cleanup_delay);
 	if (IS_ENABLED(CONFIG_RCU_EQS_DEBUG))
 		pr_info("\tRCU debug extended QS entry/exit.\n");

lib/Kconfig.debug

@@ -1373,81 +1373,6 @@ config RCU_TORTURE_TEST
 	  Say M if you want the RCU torture tests to build as a module.
 	  Say N if you are unsure.
 
-config RCU_TORTURE_TEST_SLOW_PREINIT
-	bool "Slow down RCU grace-period pre-initialization to expose races"
-	depends on RCU_TORTURE_TEST
-	help
-	  This option delays grace-period pre-initialization (the
-	  propagation of CPU-hotplug changes up the rcu_node combining
-	  tree) for a few jiffies between initializing each pair of
-	  consecutive rcu_node structures.  This helps to expose races
-	  involving grace-period pre-initialization, in other words, it
-	  makes your kernel less stable.  It can also greatly increase
-	  grace-period latency, especially on systems with large numbers
-	  of CPUs.  This is useful when torture-testing RCU, but in
-	  almost no other circumstance.
-
-	  Say Y here if you want your system to crash and hang more often.
-	  Say N if you want a sane system.
-
-config RCU_TORTURE_TEST_SLOW_PREINIT_DELAY
-	int "How much to slow down RCU grace-period pre-initialization"
-	range 0 5
-	default 3
-	depends on RCU_TORTURE_TEST_SLOW_PREINIT
-	help
-	  This option specifies the number of jiffies to wait between
-	  each rcu_node structure pre-initialization step.
-
-config RCU_TORTURE_TEST_SLOW_INIT
-	bool "Slow down RCU grace-period initialization to expose races"
-	depends on RCU_TORTURE_TEST
-	help
-	  This option delays grace-period initialization for a few
-	  jiffies between initializing each pair of consecutive
-	  rcu_node structures.	This helps to expose races involving
-	  grace-period initialization, in other words, it makes your
-	  kernel less stable.  It can also greatly increase grace-period
-	  latency, especially on systems with large numbers of CPUs.
-	  This is useful when torture-testing RCU, but in almost no
-	  other circumstance.
-
-	  Say Y here if you want your system to crash and hang more often.
-	  Say N if you want a sane system.
-
-config RCU_TORTURE_TEST_SLOW_INIT_DELAY
-	int "How much to slow down RCU grace-period initialization"
-	range 0 5
-	default 3
-	depends on RCU_TORTURE_TEST_SLOW_INIT
-	help
-	  This option specifies the number of jiffies to wait between
-	  each rcu_node structure initialization.
-
-config RCU_TORTURE_TEST_SLOW_CLEANUP
-	bool "Slow down RCU grace-period cleanup to expose races"
-	depends on RCU_TORTURE_TEST
-	help
-	  This option delays grace-period cleanup for a few jiffies
-	  between cleaning up each pair of consecutive rcu_node
-	  structures.  This helps to expose races involving grace-period
-	  cleanup, in other words, it makes your kernel less stable.
-	  It can also greatly increase grace-period latency, especially
-	  on systems with large numbers of CPUs.  This is useful when
-	  torture-testing RCU, but in almost no other circumstance.
-
-	  Say Y here if you want your system to crash and hang more often.
-	  Say N if you want a sane system.
-
-config RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY
-	int "How much to slow down RCU grace-period cleanup"
-	range 0 5
-	default 3
-	depends on RCU_TORTURE_TEST_SLOW_CLEANUP
-	help
-	  This option specifies the number of jiffies to wait between
-	  each rcu_node structure cleanup operation.
-
 config RCU_CPU_STALL_TIMEOUT
 	int "RCU CPU stall timeout in seconds"
 	depends on RCU_STALL_COMMON

tools/testing/selftests/rcutorture/configs/rcu/TREE01

@@ -17,6 +17,3 @@ CONFIG_DEBUG_LOCK_ALLOC=n
 CONFIG_RCU_BOOST=n
 CONFIG_DEBUG_OBJECTS_RCU_HEAD=n
 CONFIG_RCU_EXPERT=y
-CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP=y
-CONFIG_RCU_TORTURE_TEST_SLOW_INIT=y
-CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT=y

tools/testing/selftests/rcutorture/configs/rcu/TREE01.boot

@@ -1 +1,4 @@
 rcutorture.torture_type=rcu_bh maxcpus=8
+rcutree.gp_preinit_delay=3
+rcutree.gp_init_delay=3
+rcutree.gp_cleanup_delay=3

tools/testing/selftests/rcutorture/configs/rcu/TREE02

@@ -19,8 +19,5 @@ CONFIG_DEBUG_LOCK_ALLOC=y
 CONFIG_PROVE_LOCKING=n
 CONFIG_RCU_BOOST=n
 CONFIG_RCU_EXPERT=y
-CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP=y
-CONFIG_RCU_TORTURE_TEST_SLOW_INIT=y
-CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT=y
 CONFIG_DEBUG_OBJECTS=y
 CONFIG_DEBUG_OBJECTS_RCU_HEAD=y

tools/testing/selftests/rcutorture/configs/rcu/TREE03

@@ -17,6 +17,3 @@ CONFIG_RCU_BOOST=y
 CONFIG_RCU_KTHREAD_PRIO=2
 CONFIG_DEBUG_OBJECTS_RCU_HEAD=n
 CONFIG_RCU_EXPERT=y
-CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP=y
-CONFIG_RCU_TORTURE_TEST_SLOW_INIT=y
-CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT=y

tools/testing/selftests/rcutorture/configs/rcu/TREE03.boot

@@ -1 +1,4 @@
 rcutorture.onoff_interval=1 rcutorture.onoff_holdoff=30
+rcutree.gp_preinit_delay=3
+rcutree.gp_init_delay=3
+rcutree.gp_cleanup_delay=3

tools/testing/selftests/rcutorture/configs/rcu/TREE04

@@ -18,7 +18,4 @@ CONFIG_RCU_FANOUT_LEAF=3
 CONFIG_DEBUG_LOCK_ALLOC=n
 CONFIG_DEBUG_OBJECTS_RCU_HEAD=n
 CONFIG_RCU_EXPERT=y
-CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP=y
-CONFIG_RCU_TORTURE_TEST_SLOW_INIT=y
-CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT=y
 CONFIG_RCU_EQS_DEBUG=y

tools/testing/selftests/rcutorture/configs/rcu/TREE05

@@ -19,6 +19,3 @@ CONFIG_PROVE_LOCKING=y
 #CHECK#CONFIG_PROVE_RCU=y
 CONFIG_DEBUG_OBJECTS_RCU_HEAD=n
 CONFIG_RCU_EXPERT=y
-CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP=y
-CONFIG_RCU_TORTURE_TEST_SLOW_INIT=y
-CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT=y

tools/testing/selftests/rcutorture/configs/rcu/TREE05.boot

@@ -1,2 +1,5 @@
 rcutorture.torture_type=sched
 rcupdate.rcu_self_test_sched=1
+rcutree.gp_preinit_delay=3
+rcutree.gp_init_delay=3
+rcutree.gp_cleanup_delay=3

tools/testing/selftests/rcutorture/configs/rcu/TREE06

@@ -21,6 +21,3 @@ CONFIG_PROVE_LOCKING=y
 CONFIG_DEBUG_OBJECTS=y
 CONFIG_DEBUG_OBJECTS_RCU_HEAD=y
 CONFIG_RCU_EXPERT=y
-CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP=y
-CONFIG_RCU_TORTURE_TEST_SLOW_INIT=y
-CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT=y

tools/testing/selftests/rcutorture/configs/rcu/TREE06.boot

@@ -2,3 +2,6 @@ rcupdate.rcu_self_test=1
 rcupdate.rcu_self_test_bh=1
 rcupdate.rcu_self_test_sched=1
 rcutree.rcu_fanout_exact=1
+rcutree.gp_preinit_delay=3
+rcutree.gp_init_delay=3
+rcutree.gp_cleanup_delay=3

tools/testing/selftests/rcutorture/configs/rcu/TREE07

@@ -17,6 +17,3 @@ CONFIG_RCU_FANOUT_LEAF=2
 CONFIG_DEBUG_LOCK_ALLOC=n
 CONFIG_DEBUG_OBJECTS_RCU_HEAD=n
 CONFIG_RCU_EXPERT=y
-CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP=y
-CONFIG_RCU_TORTURE_TEST_SLOW_INIT=y
-CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT=y

tools/testing/selftests/rcutorture/doc/TREE_RCU-kconfig.txt

@@ -28,9 +28,6 @@ CONFIG_RCU_TRACE -- Do half.
 CONFIG_SMP -- Need one !SMP for PREEMPT_RCU.
 CONFIG_RCU_EXPERT=n -- Do a few, but these have to be vanilla configurations.
 CONFIG_RCU_EQS_DEBUG -- Do at least one for CONFIG_NO_HZ_FULL and not.
-CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP -- Do for all but a couple TREE scenarios.
-CONFIG_RCU_TORTURE_TEST_SLOW_INIT -- Do for all but a couple TREE scenarios.
-CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT -- Do for all but a couple TREE scenarios.
 
 RCU-bh: Do one with PREEMPT and one with !PREEMPT.
 RCU-sched: Do one with PREEMPT but not BOOST.
@@ -78,12 +75,6 @@ CONFIG_RCU_TORTURE_TEST_RUNNABLE
 
 	Always used in KVM testing.
 
-CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT_DELAY
-CONFIG_RCU_TORTURE_TEST_SLOW_INIT_DELAY
-CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY
-
-	Inspection suffices, ignore.
-
 CONFIG_PREEMPT_RCU
 CONFIG_TREE_RCU
 CONFIG_TINY_RCU