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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2014-01-28 15:29:21 -0800
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2014-02-23 09:01:05 -0800
commit3808dc9fab05913060626d7f0edd0f195cb9dcab (patch)
tree5db578f420dc657197fd34b3a9a2c20bf79e0de3 /kernel/torture.c
parentf67a33561e6e5463b548219df98130da95f2e4a7 (diff)
rcutorture: Abstract torture_shuffle()
The torture_shuffle() function forces each CPU in turn to go idle periodically in order to check for problems interacting with per-CPU variables and with dyntick-idle mode. Because this sort of debugging is not specific to RCU, this commit abstracts that functionality. This in turn requires abstracting some additional infrastructure. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Diffstat (limited to 'kernel/torture.c')
-rw-r--r--kernel/torture.c151
1 files changed, 151 insertions, 0 deletions
diff --git a/kernel/torture.c b/kernel/torture.c
index f05042036ae8..26058f20ee83 100644
--- a/kernel/torture.c
+++ b/kernel/torture.c
@@ -76,6 +76,157 @@ torture_random(struct torture_random_state *trsp)
EXPORT_SYMBOL_GPL(torture_random);
/*
+ * Variables for shuffling. The idea is to ensure that each CPU stays
+ * idle for an extended period to test interactions with dyntick idle,
+ * as well as interactions with any per-CPU varibles.
+ */
+struct shuffle_task {
+ struct list_head st_l;
+ struct task_struct *st_t;
+};
+
+static long shuffle_interval; /* In jiffies. */
+static struct task_struct *shuffler_task;
+static cpumask_var_t shuffle_tmp_mask;
+static int shuffle_idle_cpu; /* Force all torture tasks off this CPU */
+static struct list_head shuffle_task_list = LIST_HEAD_INIT(shuffle_task_list);
+static DEFINE_MUTEX(shuffle_task_mutex);
+
+/*
+ * Register a task to be shuffled. If there is no memory, just splat
+ * and don't bother registering.
+ */
+void torture_shuffle_task_register(struct task_struct *tp)
+{
+ struct shuffle_task *stp;
+
+ if (WARN_ON_ONCE(tp == NULL))
+ return;
+ stp = kmalloc(sizeof(*stp), GFP_KERNEL);
+ if (WARN_ON_ONCE(stp == NULL))
+ return;
+ stp->st_t = tp;
+ mutex_lock(&shuffle_task_mutex);
+ list_add(&stp->st_l, &shuffle_task_list);
+ mutex_unlock(&shuffle_task_mutex);
+}
+EXPORT_SYMBOL_GPL(torture_shuffle_task_register);
+
+/*
+ * Unregister all tasks, for example, at the end of the torture run.
+ */
+static void torture_shuffle_task_unregister_all(void)
+{
+ struct shuffle_task *stp;
+ struct shuffle_task *p;
+
+ mutex_lock(&shuffle_task_mutex);
+ list_for_each_entry_safe(stp, p, &shuffle_task_list, st_l) {
+ list_del(&stp->st_l);
+ kfree(stp);
+ }
+ mutex_unlock(&shuffle_task_mutex);
+}
+
+/* Shuffle tasks such that we allow shuffle_idle_cpu to become idle.
+ * A special case is when shuffle_idle_cpu = -1, in which case we allow
+ * the tasks to run on all CPUs.
+ */
+static void torture_shuffle_tasks(void)
+{
+ struct shuffle_task *stp;
+
+ cpumask_setall(shuffle_tmp_mask);
+ get_online_cpus();
+
+ /* No point in shuffling if there is only one online CPU (ex: UP) */
+ if (num_online_cpus() == 1) {
+ put_online_cpus();
+ return;
+ }
+
+ /* Advance to the next CPU. Upon overflow, don't idle any CPUs. */
+ shuffle_idle_cpu = cpumask_next(shuffle_idle_cpu, shuffle_tmp_mask);
+ if (shuffle_idle_cpu >= nr_cpu_ids)
+ shuffle_idle_cpu = -1;
+ if (shuffle_idle_cpu != -1) {
+ cpumask_clear_cpu(shuffle_idle_cpu, shuffle_tmp_mask);
+ if (cpumask_empty(shuffle_tmp_mask)) {
+ put_online_cpus();
+ return;
+ }
+ }
+
+ mutex_lock(&shuffle_task_mutex);
+ list_for_each_entry(stp, &shuffle_task_list, st_l)
+ set_cpus_allowed_ptr(stp->st_t, shuffle_tmp_mask);
+ mutex_unlock(&shuffle_task_mutex);
+
+ put_online_cpus();
+}
+
+/* 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 torture_shuffle(void *arg)
+{
+ VERBOSE_TOROUT_STRING("torture_shuffle task started");
+ do {
+ schedule_timeout_interruptible(shuffle_interval);
+ torture_shuffle_tasks();
+ torture_shutdown_absorb("torture_shuffle");
+ } while (!torture_must_stop());
+ VERBOSE_TOROUT_STRING("torture_shuffle task stopping");
+ return 0;
+}
+
+/*
+ * Start the shuffler, with shuffint in jiffies.
+ */
+int torture_shuffle_init(long shuffint)
+{
+ int ret;
+
+ shuffle_interval = shuffint;
+
+ shuffle_idle_cpu = -1;
+
+ if (!alloc_cpumask_var(&shuffle_tmp_mask, GFP_KERNEL)) {
+ VERBOSE_TOROUT_ERRSTRING("Failed to alloc mask");
+ return -ENOMEM;
+ }
+
+ /* Create the shuffler thread */
+ shuffler_task = kthread_run(torture_shuffle, NULL, "torture_shuffle");
+ if (IS_ERR(shuffler_task)) {
+ ret = PTR_ERR(shuffler_task);
+ free_cpumask_var(shuffle_tmp_mask);
+ VERBOSE_TOROUT_ERRSTRING("Failed to create shuffler");
+ shuffler_task = NULL;
+ return ret;
+ }
+ torture_shuffle_task_register(shuffler_task);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(torture_shuffle_init);
+
+/*
+ * Stop the shuffling.
+ */
+void torture_shuffle_cleanup(void)
+{
+ torture_shuffle_task_unregister_all();
+ if (shuffler_task) {
+ VERBOSE_TOROUT_STRING("Stopping torture_shuffle task");
+ kthread_stop(shuffler_task);
+ free_cpumask_var(shuffle_tmp_mask);
+ }
+ shuffler_task = NULL;
+}
+EXPORT_SYMBOL_GPL(torture_shuffle_cleanup);
+
+/*
* Absorb kthreads into a kernel function that won't return, so that
* they won't ever access module text or data again.
*/