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Date: Mon, 21 Dec 2020 16:38:09 +0100
From: Uladzislau Rezki <urezki@...il.com>
To: "Paul E. McKenney" <paulmck@...nel.org>
Cc: Uladzislau Rezki <urezki@...il.com>,
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 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:
> > > 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>
>
> Much improved, thank you! A few more comments below.
>
> > ---
> > 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 {
>
> Please use something like "struct rcu_tasks_test_desc" to help the poor
> people who might need to grep for this. Feel free to shorten it, but
> please make it descriptive and thus more likely to stay unique.
>
> > + struct rcu_head rh;
> > + const char *name;
> > + bool run;
>
> If you make this "bool notrun" you don't need to initialize.
>
> > +};
> > +
> > +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)
> > +{
>
> struct rcu_tasks_test_desc *rttdp;
>
> > + int i;
> > +
> > + pr_info("RCU-tasks test callback executed %d\n",
> > + ++rcu_executed_test_counter);
>
> rttdp = container_of(rhp, rh, struct rcu_tasks_test_desc);
> rttdp->notrun = true;
>
> Or I suppose:
>
> container_of(rhp, rh, struct rcu_tasks_test_desc)->notrun = true;
>
> Then the loop below can go away.
>
> > +
> > + 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;
>
> The s/run/notrun/ allows the three initializations of .run to go away.
>
> > + call_rcu_tasks(&tests[0].rh, test_rcu_tasks_callback);
> > + synchronize_rcu_tasks();
>
> Why not reverse the order of these two statements? That would test
> call_rcu_tasks*()'s ability to do a grace period on their own, without
> help from the corresponding 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;
>
> Why not initialize "ret" in the declaration?
>
> > +
> > + 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
>
> 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>
---
kernel/rcu/tasks.h | 75 ++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 75 insertions(+)
diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index 36607551f966..670212ed9648 100644
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -1224,6 +1224,43 @@ 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 int rcu_executed_test_counter;
+
+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("RCU-tasks test callback executed %d\n",
+ ++rcu_executed_test_counter);
+
+ rttd->notrun = true;
+}
+
void __init rcu_init_tasks_generic(void)
{
#ifdef CONFIG_TASKS_RCU
@@ -1237,7 +1274,45 @@ 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) {}
--
2.20.1
--
Vlad Rezki
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