+static int rcu_idle_cpu; /* Force all torture tasks off this CPU */
+
+/* Shuffle tasks such that we allow @rcu_idle_cpu to become idle. A special case
+ * is when @rcu_idle_cpu = -1, when we allow the tasks to run on all CPUs.
+ */
+void rcu_torture_shuffle_tasks(void)
+{
+ cpumask_t tmp_mask = CPU_MASK_ALL;
+ int i;
+
+ lock_cpu_hotplug();
+
+ /* No point in shuffling if there is only one online CPU (ex: UP) */
+ if (num_online_cpus() == 1) {
+ unlock_cpu_hotplug();
+ return;
+ }
+
+ if (rcu_idle_cpu != -1)
+ cpu_clear(rcu_idle_cpu, tmp_mask);
+
+ set_cpus_allowed(current, tmp_mask);
+
+ if (reader_tasks != NULL) {
+ for (i = 0; i < nrealreaders; i++)
+ if (reader_tasks[i])
+ set_cpus_allowed(reader_tasks[i], tmp_mask);
+ }
+
+ if (writer_task)
+ set_cpus_allowed(writer_task, tmp_mask);
+
+ if (stats_task)
+ set_cpus_allowed(stats_task, tmp_mask);
+
+ if (rcu_idle_cpu == -1)
+ rcu_idle_cpu = num_online_cpus() - 1;
+ else
+ rcu_idle_cpu--;
+
+ unlock_cpu_hotplug();
+}
+
+/* Shuffle tasks across CPUs, with the intent of allowing each CPU in the
+ * system to become idle at a time and cut off its timer ticks. This is meant
+ * to test the support for such tickless idle CPU in RCU.
+ */
+static int
+rcu_torture_shuffle(void *arg)
+{
+ VERBOSE_PRINTK_STRING("rcu_torture_shuffle task started");
+ do {
+ schedule_timeout_interruptible(shuffle_interval * HZ);
+ rcu_torture_shuffle_tasks();
+ } while (!kthread_should_stop());
+ VERBOSE_PRINTK_STRING("rcu_torture_shuffle task stopping");
+ return 0;
+}
+
+static inline void
+rcu_torture_print_module_parms(char *tag)
+{
+ printk(KERN_ALERT TORTURE_FLAG "--- %s: nreaders=%d "
+ "stat_interval=%d verbose=%d test_no_idle_hz=%d "
+ "shuffle_interval = %d\n",
+ tag, nrealreaders, stat_interval, verbose, test_no_idle_hz,
+ shuffle_interval);
+}
+