rcutorture: Permit holding off CPU-hotplug operations during boot

When rcutorture is started automatically at boot time, it might well
also start CPU-hotplug operations at that time, which might not be
desirable.  This commit therefore adds an rcutorture parameter that
allows CPU-hotplug operations to be held off for the specified number
of seconds after the start of boot.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

1 files changed, 10 insertions, 2 deletions

diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c
index a52b3217c160..2914cafe171b 100644
--- a/kernel/rcutorture.c
+++ b/kernel/rcutorture.c
@@ -65,6 +65,7 @@ static int fqs_duration;	/* Duration of bursts (us), 0 to disable. */
 static int fqs_holdoff;         /* Hold time within burst (us). */
 static int fqs_stutter = 3;     /* Wait time between bursts (s). */
 static int onoff_interval;      /* Wait time between CPU hotplugs, 0=disable. */
+static int onoff_holdoff;       /* Seconds after boot before CPU hotplugs. */
 static int shutdown_secs;       /* Shutdown time (s).  <=0 for no shutdown. */
 static int test_boost = 1;      /* Test RCU prio boost: 0=no, 1=maybe, 2=yes. */
 static int test_boost_interval = 7; /* Interval between boost tests, seconds. */
@@ -95,6 +96,8 @@ module_param(fqs_stutter, int, 0444);
 MODULE_PARM_DESC(fqs_stutter, "Wait time between fqs bursts (s)");
 module_param(onoff_interval, int, 0444);
 MODULE_PARM_DESC(onoff_interval, "Time between CPU hotplugs (s), 0=disable");
+module_param(onoff_holdoff, int, 0444);
+MODULE_PARM_DESC(onoff_holdoff, "Time after boot before CPU hotplugs (s)");
 module_param(shutdown_secs, int, 0444);
 MODULE_PARM_DESC(shutdown_secs, "Shutdown time (s), zero to disable.");
 module_param(test_boost, int, 0444);
@@ -1300,13 +1303,13 @@ rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, char *tag)
                 "fqs_duration=%d fqs_holdoff=%d fqs_stutter=%d "
                 "test_boost=%d/%d test_boost_interval=%d "
                 "test_boost_duration=%d shutdown_secs=%d "
-                "onoff_interval=%d\n",
+                "onoff_interval=%d onoff_holdoff=%d\n",
                 torture_type, tag, nrealreaders, nfakewriters,
                 stat_interval, verbose, test_no_idle_hz, shuffle_interval,
                 stutter, irqreader, fqs_duration, fqs_holdoff, fqs_stutter,
                 test_boost, cur_ops->can_boost,
                 test_boost_interval, test_boost_duration, shutdown_secs,
-                onoff_interval);
+                onoff_interval, onoff_holdoff);
 }
 
 static struct notifier_block rcutorture_shutdown_nb = {
@@ -1410,6 +1413,11 @@ rcu_torture_onoff(void *arg)
         for_each_online_cpu(cpu)
                 maxcpu = cpu;
         WARN_ON(maxcpu < 0);
+        if (onoff_holdoff > 0) {
+                VERBOSE_PRINTK_STRING("rcu_torture_onoff begin holdoff");
+                schedule_timeout_interruptible(onoff_holdoff * HZ);
+                VERBOSE_PRINTK_STRING("rcu_torture_onoff end holdoff");
+        }
         while (!kthread_should_stop()) {
                 cpu = (rcu_random(&rand) >> 4) % (maxcpu + 1);
                 if (cpu_online(cpu) && cpu_is_hotpluggable(cpu)) {