linux-kernel - Re: [PATCH 2/2] rcu-tasks: add RCU-tasks self tests

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Date:   Mon, 21 Dec 2020 09:18:05 -0800
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Uladzislau Rezki <urezki@...il.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, RCU <rcu@...r.kernel.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

On Mon, Dec 21, 2020 at 04:38:09PM +0100, Uladzislau Rezki wrote:
> On Wed, Dec 16, 2020 at 03:29:55PM -0800, Paul E. McKenney wrote:
> > On Wed, Dec 16, 2020 at 04:49:59PM +0100, Uladzislau Rezki wrote:

[ . . . ]

> > > 2.20.1
> > 
> > Again, much improved!
> > 
> See below the v3 version. I hope i fixed all comments :)
> 
> >From 06f7adfd84cbb1994d0e2693ee9dcdfd272a9bd0 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 v3 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>

Much better!

I pulled this in, but made one small additional change.  Please let me
know if this is problematic.

							Thanx, Paul

------------------------------------------------------------------------

commit 93372198b5c9efdfd288aa3b3ee41c1f90866886
Author: Uladzislau Rezki (Sony) <urezki@...il.com>
Date:   Wed Dec 9 21:27:32 2020 +0100

    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>
    Signed-off-by: Paul E. McKenney <paulmck@...nel.org>

diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index 3660755..35a2cd5 100644
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -1224,6 +1224,40 @@ void show_rcu_tasks_gp_kthreads(void)
 }
 #endif /* #ifndef CONFIG_TINY_RCU */
 
+struct rcu_tasks_test_desc {
+	struct rcu_head rh;
+	const char *name;
+	bool notrun;
+};
+
+static struct rcu_tasks_test_desc tests[] = {
+	{
+		.name = "call_rcu_tasks()",
+		/* If not defined, the test is skipped. */
+		.notrun = !IS_ENABLED(CONFIG_TASKS_RCU),
+	},
+	{
+		.name = "call_rcu_tasks_rude()",
+		/* If not defined, the test is skipped. */
+		.notrun = !IS_ENABLED(CONFIG_TASKS_RUDE_RCU),
+	},
+	{
+		.name = "call_rcu_tasks_trace()",
+		/* If not defined, the test is skipped. */
+		.notrun = !IS_ENABLED(CONFIG_TASKS_TRACE_RCU)
+	}
+};
+
+static void test_rcu_tasks_callback(struct rcu_head *rhp)
+{
+	struct rcu_tasks_test_desc *rttd =
+		container_of(rhp, struct rcu_tasks_test_desc, rh);
+
+	pr_info("Callback from %s invoked.\n", rttd->name);
+
+	rttd->notrun = true;
+}
+
 void __init rcu_init_tasks_generic(void)
 {
 #ifdef CONFIG_TASKS_RCU
@@ -1237,7 +1271,45 @@ 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
+		synchronize_rcu_tasks();
+		call_rcu_tasks(&tests[0].rh, test_rcu_tasks_callback);
+#endif
+
+#ifdef CONFIG_TASKS_RUDE_RCU
+		synchronize_rcu_tasks_rude();
+		call_rcu_tasks_rude(&tests[1].rh, test_rcu_tasks_callback);
+#endif
+
+#ifdef CONFIG_TASKS_TRACE_RCU
+		synchronize_rcu_tasks_trace();
+		call_rcu_tasks_trace(&tests[2].rh, test_rcu_tasks_callback);
+#endif
+	}
+}
+
+static int rcu_tasks_verify_self_tests(void)
+{
+	int ret = 0;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(tests); i++) {
+		if (!tests[i].notrun) {		// 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) {}