rcutorture: Change units of onoff_interval to jiffies

Some RCU bugs have been sensitive to the frequency of CPU-hotplug
operations, which have been gradually increased over time.  But this
frequency is now at the one-second lower limit that can be specified using
the rcutorture.onoff_interval kernel parameter.  This commit therefore
changes the units of rcutorture.onoff_interval from seconds to jiffies,
and also sets the value specified for this kernel parameter in the TREE03
rcutorture scenario to 200, which is 200 milliseconds for HZ=1000.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Documentation/admin-guide/kernel-parameters.txt

@@ -3632,8 +3632,8 @@
 			Set time (s) after boot for CPU-hotplug testing.
 
 	rcutorture.onoff_interval= [KNL]
-			Set time (s) between CPU-hotplug operations, or
-			zero to disable CPU-hotplug testing.
+			Set time (jiffies) between CPU-hotplug operations,
+			or zero to disable CPU-hotplug testing.
 
 	rcutorture.shuffle_interval= [KNL]
 			Set task-shuffle interval (s).  Shuffling tasks

kernel/rcu/rcutorture.c

@@ -87,7 +87,7 @@ torture_param(int, object_debug, 0,
 	     "Enable debug-object double call_rcu() testing");
 torture_param(int, onoff_holdoff, 0, "Time after boot before CPU hotplugs (s)");
 torture_param(int, onoff_interval, 0,
-	     "Time between CPU hotplugs (s), 0=disable");
+	     "Time between CPU hotplugs (jiffies), 0=disable");
 torture_param(int, shuffle_interval, 3, "Number of seconds between shuffles");
 torture_param(int, shutdown_secs, 0, "Shutdown time (s), <= zero to disable.");
 torture_param(int, stall_cpu, 0, "Stall duration (s), zero to disable.");
@@ -1889,7 +1889,7 @@ rcu_torture_init(void)
 	firsterr = torture_shutdown_init(shutdown_secs, rcu_torture_cleanup);
 	if (firsterr)
 		goto unwind;
-	firsterr = torture_onoff_init(onoff_holdoff * HZ, onoff_interval * HZ);
+	firsterr = torture_onoff_init(onoff_holdoff * HZ, onoff_interval);
 	if (firsterr)
 		goto unwind;
 	firsterr = rcu_torture_stall_init();

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

-rcutorture.onoff_interval=1 rcutorture.onoff_holdoff=30
+rcutorture.onoff_interval=200 rcutorture.onoff_holdoff=30
 rcutree.gp_preinit_delay=12
 rcutree.gp_init_delay=3
 rcutree.gp_cleanup_delay=3

tools/testing/selftests/rcutorture/configs/rcu/ver_functions.sh

@@ -39,7 +39,7 @@ rcutorture_param_onoff () {
 	if ! bootparam_hotplug_cpu "$1" && configfrag_hotplug_cpu "$2"
 	then
 		echo CPU-hotplug kernel, adding rcutorture onoff. 1>&2
-		echo rcutorture.onoff_interval=3 rcutorture.onoff_holdoff=30
+		echo rcutorture.onoff_interval=1000 rcutorture.onoff_holdoff=30
 	fi
 }