2 files changed, 63 insertions, 4 deletions

diff --git a/Documentation/RCU/torture.txt b/Documentation/RCU/torture.txt
index 2967a65269d8..02b3d14c0209 100644
--- a/Documentation/RCU/torture.txt
+++ b/Documentation/RCU/torture.txt
@@ -46,9 +46,15 @@ stat_interval	The number of seconds between output of torture
 
 shuffle_interval
                 The number of seconds to keep the test threads affinitied
-                to a particular subset of the CPUs, defaults to 5 seconds.
+                to a particular subset of the CPUs, defaults to 3 seconds.
                 Used in conjunction with test_no_idle_hz.
 
+stutter         The length of time to run the test before pausing for this
+                same period of time.  Defaults to "stutter=5", so as
+                to run and pause for (roughly) five-second intervals.
+                Specifying "stutter=0" causes the test to run continuously
+                without pausing, which is the old default behavior.
+
 test_no_idle_hz Whether or not to test the ability of RCU to operate in
                 a kernel that disables the scheduling-clock interrupt to
                 idle CPUs.  Boolean parameter, "1" to test, "0" otherwise.
diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c
index 0ca7e9b290b0..98ae7d168225 100644
--- a/kernel/rcutorture.c
+++ b/kernel/rcutorture.c
@@ -57,7 +57,8 @@ static int stat_interval;	/* Interval between stats, in seconds. */
                                 /*  Defaults to "only at end of test". */
 static int verbose;             /* Print more debug info. */
 static int test_no_idle_hz;     /* Test RCU's support for tickless idle CPUs. */
-static int shuffle_interval = 5; /* Interval between shuffles (in sec)*/
+static int shuffle_interval = 3; /* Interval between shuffles (in sec)*/
+static int stutter = 5;         /* Start/stop testing interval (in sec) */
 static char *torture_type = "rcu"; /* What RCU implementation to torture. */
 
 module_param(nreaders, int, 0444);
@@ -72,6 +73,8 @@ module_param(test_no_idle_hz, bool, 0444);
 MODULE_PARM_DESC(test_no_idle_hz, "Test support for tickless idle CPUs");
 module_param(shuffle_interval, int, 0444);
 MODULE_PARM_DESC(shuffle_interval, "Number of seconds between shuffles");
+module_param(stutter, int, 0444);
+MODULE_PARM_DESC(stutter, "Number of seconds to run/halt test");
 module_param(torture_type, charp, 0444);
 MODULE_PARM_DESC(torture_type, "Type of RCU to torture (rcu, rcu_bh, srcu)");
 
@@ -91,6 +94,7 @@ static struct task_struct **fakewriter_tasks;
 static struct task_struct **reader_tasks;
 static struct task_struct *stats_task;
 static struct task_struct *shuffler_task;
+static struct task_struct *stutter_task;
 
 #define RCU_TORTURE_PIPE_LEN 10
 
@@ -119,6 +123,8 @@ static atomic_t n_rcu_torture_mberror;
 static atomic_t n_rcu_torture_error;
 static struct list_head rcu_torture_removed;
 
+static int stutter_pause_test = 0;
+
 /*
  * Allocate an element from the rcu_tortures pool.
  */
@@ -179,6 +185,13 @@ rcu_random(struct rcu_random_state *rrsp)
         return swahw32(rrsp->rrs_state);
 }
 
+static void
+rcu_stutter_wait(void)
+{
+        while (stutter_pause_test)
+                schedule_timeout_interruptible(1);
+}
+
 /*
  * Operations vector for selecting different types of tests.
  */
@@ -563,6 +576,7 @@ rcu_torture_writer(void *arg)
                 }
                 rcu_torture_current_version++;
                 oldbatch = cur_ops->completed();
+                rcu_stutter_wait();
         } while (!kthread_should_stop() && !fullstop);
         VERBOSE_PRINTK_STRING("rcu_torture_writer task stopping");
         while (!kthread_should_stop())
@@ -586,6 +600,7 @@ rcu_torture_fakewriter(void *arg)
                 schedule_timeout_uninterruptible(1 + rcu_random(&rand)%10);
                 udelay(rcu_random(&rand) & 0x3ff);
                 cur_ops->sync();
+                rcu_stutter_wait();
         } while (!kthread_should_stop() && !fullstop);
 
         VERBOSE_PRINTK_STRING("rcu_torture_fakewriter task stopping");
@@ -641,6 +656,7 @@ rcu_torture_reader(void *arg)
                 preempt_enable();
                 cur_ops->readunlock(idx);
                 schedule();
+                rcu_stutter_wait();
         } while (!kthread_should_stop() && !fullstop);
         VERBOSE_PRINTK_STRING("rcu_torture_reader task stopping");
         while (!kthread_should_stop())
@@ -812,15 +828,34 @@ rcu_torture_shuffle(void *arg)
         return 0;
 }
 
+/* Cause the rcutorture test to "stutter", starting and stopping all
+ * threads periodically.
+ */
+static int
+rcu_torture_stutter(void *arg)
+{
+        VERBOSE_PRINTK_STRING("rcu_torture_stutter task started");
+        do {
+                schedule_timeout_interruptible(stutter * HZ);
+                stutter_pause_test = 1;
+                if (!kthread_should_stop())
+                        schedule_timeout_interruptible(stutter * HZ);
+                stutter_pause_test = 0;
+        } while (!kthread_should_stop());
+        VERBOSE_PRINTK_STRING("rcu_torture_stutter task stopping");
+        return 0;
+}
+
 static inline void
 rcu_torture_print_module_parms(char *tag)
 {
         printk(KERN_ALERT "%s" TORTURE_FLAG
                 "--- %s: nreaders=%d nfakewriters=%d "
                 "stat_interval=%d verbose=%d test_no_idle_hz=%d "
-                "shuffle_interval = %d\n",
+                "shuffle_interval=%d stutter=%d\n",
                 torture_type, tag, nrealreaders, nfakewriters,
-                stat_interval, verbose, test_no_idle_hz, shuffle_interval);
+                stat_interval, verbose, test_no_idle_hz, shuffle_interval,
+                stutter);
 }
 
 static void
@@ -829,6 +864,11 @@ rcu_torture_cleanup(void)
         int i;
 
         fullstop = 1;
+        if (stutter_task) {
+                VERBOSE_PRINTK_STRING("Stopping rcu_torture_stutter task");
+                kthread_stop(stutter_task);
+        }
+        stutter_task = NULL;
         if (shuffler_task) {
                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_shuffle task");
                 kthread_stop(shuffler_task);
@@ -1017,6 +1057,19 @@ rcu_torture_init(void)
                         goto unwind;
                 }
         }
+        if (stutter < 0)
+                stutter = 0;
+        if (stutter) {
+                /* Create the stutter thread */
+                stutter_task = kthread_run(rcu_torture_stutter, NULL,
+                                          "rcu_torture_stutter");
+                if (IS_ERR(stutter_task)) {
+                        firsterr = PTR_ERR(stutter_task);
+                        VERBOSE_PRINTK_ERRSTRING("Failed to create stutter");
+                        stutter_task = NULL;
+                        goto unwind;
+                }
+        }
         return 0;
 
 unwind: