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

["Paul E. McKenney" <paulmck@kernel.org>]

On Mon, Dec 21, 2020 at 07:45:39PM +0100, Uladzislau Rezki wrote:
> On Mon, Dec 21, 2020 at 09:18:05AM -0800, Paul E. McKenney wrote:
> > 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@gmail.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@gmail.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@gmail.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@gmail.com>
> >     Signed-off-by: Paul E. McKenney <paulmck@kernel.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);
> That is fine! We can output the name instead of executed counter.
> Doing so makes it completely clear who triggers the callback.

And we also need to make it not trigger when CONFIG_PROVE_RCU=n.
While in the area, we might as well leave anything that is needed only
by CONFIG_PROVE_RCU=y undefined when CONFIG_PROVE_RCU=n.

How about the following?

							Thanx, Paul

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

commit f7a1ac0d3504e0518745da7f98573c1b13587f3e
Author: Uladzislau Rezki (Sony) <urezki@gmail.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@gmail.com>
    [ paulmck: Handle CONFIG_PROVE_RCU=n and identify test cases' callbacks. ]
    Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index 3660755..af7c194 100644
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -1224,6 +1224,82 @@ void show_rcu_tasks_gp_kthreads(void)
 }
 #endif /* #ifndef CONFIG_TINY_RCU */
 
+#ifdef CONFIG_PROVE_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;
+}
+
+static void rcu_tasks_initiate_self_tests(void)
+{
+	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_PROVE_RCU */
+static void rcu_tasks_initiate_self_tests(void) { }
+#endif /* #else #ifdef CONFIG_PROVE_RCU */
+
 void __init rcu_init_tasks_generic(void)
 {
 #ifdef CONFIG_TASKS_RCU
@@ -1237,6 +1313,9 @@ void __init rcu_init_tasks_generic(void)
 #ifdef CONFIG_TASKS_TRACE_RCU
 	rcu_spawn_tasks_trace_kthread();
 #endif
+
+	// Run the self-tests.
+	rcu_tasks_initiate_self_tests();
 }
 
 #else /* #ifdef CONFIG_TASKS_RCU_GENERIC */