[PATCH v2 1/1] rcu-tasks: Add RCU-tasks self tests

[Uladzislau Rezki (Sony)]

This commit adds self tests for early-boot use of RCU-tasks grace periods.
It tests all three variants (Rude, Tasks, and Tasks Trace) and covers
both synchronous (e.g., synchronize_rcu_tasks()) and asynchronous (e.g.,
call_rcu_tasks()) grace-period APIs.

Self-tests are run only in kernels built with CONFIG_PROVE_RCU=y.

Signed-off-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
---
 kernel/rcu/tasks.h | 69 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 69 insertions(+)

diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index 36607551f966..7478d912734a 100644
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -1224,6 +1224,35 @@ void show_rcu_tasks_gp_kthreads(void)
 }
 #endif /* #ifndef CONFIG_TINY_RCU */

+struct test_desc {
+       struct rcu_head rh;
+       const char *name;
+       bool run;
+};
+
+static struct test_desc tests[] = {
+       { .name = "call_rcu_tasks()" },
+       { .name = "call_rcu_rude()"  },
+       { .name = "call_rcu_trace()" },
+};
+
+static int rcu_executed_test_counter;
+
+static void test_rcu_tasks_callback(struct rcu_head *rhp)
+{
+       int i;
+
+       pr_info("RCU-tasks test callback executed %d\n",
+               ++rcu_executed_test_counter);
+
+       for (i = 0; i < ARRAY_SIZE(tests); i++) {
+               if (rhp == &tests[i].rh) {
+                       tests[i].run = false;
+                       break;
+               }
+       }
+}
+
 void __init rcu_init_tasks_generic(void)
 {
 #ifdef CONFIG_TASKS_RCU
@@ -1237,7 +1266,47 @@ void __init rcu_init_tasks_generic(void)
 #ifdef CONFIG_TASKS_TRACE_RCU
        rcu_spawn_tasks_trace_kthread();
 #endif
+
+       // Run the self-tests.
+       if (IS_ENABLED(CONFIG_PROVE_RCU)) {
+               pr_info("Running RCU-tasks wait API self tests\n");
+#ifdef CONFIG_TASKS_RCU
+               tests[0].run = true;
+               call_rcu_tasks(&tests[0].rh, test_rcu_tasks_callback);
+               synchronize_rcu_tasks();
+#endif
+
+#ifdef CONFIG_TASKS_RUDE_RCU
+               tests[1].run = true;
+               call_rcu_tasks_rude(&tests[1].rh, test_rcu_tasks_callback);
+               synchronize_rcu_tasks_rude();
+#endif
+
+#ifdef CONFIG_TASKS_TRACE_RCU
+               tests[2].run = true;
+               call_rcu_tasks_trace(&tests[2].rh, test_rcu_tasks_callback);
+               synchronize_rcu_tasks_trace();
+#endif
+       }
+}
+
+static int rcu_tasks_verify_self_tests(void)
+{
+       int ret, i;
+
+       for (i = 0, ret = 0; i < ARRAY_SIZE(tests); i++) {
+               if (tests[i].run) {             // still hanging.
+                       pr_err("%s has been failed.\n", tests[i].name);
+                       ret = -1;
+               }
+       }
+
+       if (ret)
+               WARN_ON(1);
+
+       return ret;
 }
+late_initcall(rcu_tasks_verify_self_tests);

 #else /* #ifdef CONFIG_TASKS_RCU_GENERIC */
 static inline void rcu_tasks_bootup_oddness(void) {}
-- 
2.20.1

--
Vlad Rezki