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Date:   Wed, 16 Dec 2020 16:49:59 +0100
From:   Uladzislau Rezki <urezki@...il.com>
To:     "Paul E . McKenney" <paulmck@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>, RCU <rcu@...r.kernel.org>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Daniel Axtens <dja@...ens.net>,
        Frederic Weisbecker <frederic@...nel.org>,
        Neeraj Upadhyay <neeraju@...eaurora.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Michal Hocko <mhocko@...e.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Theodore Y . Ts'o" <tytso@....edu>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Oleksiy Avramchenko <oleksiy.avramchenko@...ymobile.com>
Subject: Re: [PATCH 2/2] rcu-tasks: add RCU-tasks self tests

> Add self tests for checking of RCU-tasks API functionality.
> It covers:
>     - wait API functions;
>     - invoking/completion call_rcu_tasks*().
> 
> Self-tests are run when CONFIG_PROVE_RCU kernel parameter is set.
> 
> Signed-off-by: Uladzislau Rezki (Sony) <urezki@...il.com>
> ---
>  kernel/rcu/tasks.h | 44 ++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 44 insertions(+)
> 
> diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
> index 67a162949763..9407772780c1 100644
> --- a/kernel/rcu/tasks.h
> +++ b/kernel/rcu/tasks.h
> @@ -1225,6 +1225,16 @@ void show_rcu_tasks_gp_kthreads(void)
>  }
>  #endif /* #ifndef CONFIG_TINY_RCU */
>  
> +static struct rcu_head rhp;
> +static int rcu_execurted_test_counter;
> +static int rcu_run_test_counter;
> +
> +static void test_rcu_tasks_callback(struct rcu_head *r)
> +{
> +	pr_info("RCU-tasks test callback executed %d\n",
> +		++rcu_execurted_test_counter);
> +}
> +
>  void __init rcu_init_tasks_generic(void)
>  {
>  #ifdef CONFIG_TASKS_RCU
> @@ -1238,7 +1248,41 @@ void __init rcu_init_tasks_generic(void)
>  #ifdef CONFIG_TASKS_TRACE_RCU
>  	rcu_spawn_tasks_trace_kthread();
>  #endif
> +
> +	if (IS_ENABLED(CONFIG_PROVE_RCU)) {
> +		pr_info("Running RCU-tasks wait API self tests\n");
> +#ifdef CONFIG_TASKS_RCU
> +		rcu_run_test_counter++;
> +		call_rcu_tasks(&rhp, test_rcu_tasks_callback);
> +		synchronize_rcu_tasks();
> +#endif
> +
> +#ifdef CONFIG_TASKS_RUDE_RCU
> +		rcu_run_test_counter++;
> +		call_rcu_tasks_trace(&rhp, test_rcu_tasks_callback);
> +		synchronize_rcu_tasks_rude();
> +#endif
> +
> +#ifdef CONFIG_TASKS_TRACE_RCU
> +		rcu_run_test_counter++;
> +		call_rcu_tasks_trace(&rhp, test_rcu_tasks_callback);
> +		synchronize_rcu_tasks_trace();
> +#endif
> +	}
> +}
> +
> +static int rcu_tasks_verify_self_tests(void)
> +{
> +	int ret = 0;
> +
> +	if (rcu_run_test_counter != rcu_execurted_test_counter) {
> +		WARN_ON(1);
> +		ret = -1;
> +	}
> +
> +	return ret;
>  }
> +late_initcall(rcu_tasks_verify_self_tests);
>  
>  #else /* #ifdef CONFIG_TASKS_RCU_GENERIC */
>  static inline void rcu_tasks_bootup_oddness(void) {}
Please find a v2 of the patch that is in question. First version
uses the same rhp for all RCU flavors what is wrong. Initially
i had three different one per one flavor. But for some reason
end up with only one.


>From e7c6096af5a7916f29c0b4b05e1644b3b3a6c589 Mon Sep 17 00:00:00 2001
From: "Uladzislau Rezki (Sony)" <urezki@...il.com>
Date: Wed, 9 Dec 2020 21:27:32 +0100
Subject: [PATCH v2 1/1] rcu-tasks: Add RCU-tasks self tests

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@...il.com>
---
 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

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