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[94.245.46.61]) by smtp.gmail.com with ESMTPSA id a11sm2242049lfl.22.2020.12.21.13.28.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 21 Dec 2020 13:28:07 -0800 (PST) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Mon, 21 Dec 2020 22:28:05 +0100 To: "Paul E. McKenney" Cc: Uladzislau Rezki , LKML , RCU , Michael Ellerman , Andrew Morton , Daniel Axtens , Frederic Weisbecker , Neeraj Upadhyay , Joel Fernandes , Peter Zijlstra , Michal Hocko , Thomas Gleixner , "Theodore Y . Ts'o" , Sebastian Andrzej Siewior , Oleksiy Avramchenko Subject: Re: [PATCH 2/2] rcu-tasks: add RCU-tasks self tests Message-ID: <20201221212805.GA28289@pc638.lan> References: <20201209202732.5896-1-urezki@gmail.com> <20201209202732.5896-2-urezki@gmail.com> <20201216154959.GA2408@pc638.lan> <20201216232955.GO2657@paulmck-ThinkPad-P72> <20201221153809.GA24756@pc638.lan> <20201221171805.GW2657@paulmck-ThinkPad-P72> <20201221184539.GA24895@pc638.lan> <20201221192906.GX2657@paulmck-ThinkPad-P72> <20201221194848.GA2558@pc638.lan> <20201221204513.GY2657@paulmck-ThinkPad-P72> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201221204513.GY2657@paulmck-ThinkPad-P72> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Dec 21, 2020 at 12:45:13PM -0800, Paul E. McKenney wrote: > On Mon, Dec 21, 2020 at 08:48:48PM +0100, Uladzislau Rezki wrote: > > On Mon, Dec 21, 2020 at 11:29:06AM -0800, Paul E. McKenney wrote: > > > 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)" > > > > > > 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) > > > > > > > > > > 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) > > > > > 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) > > > > > Signed-off-by: Paul E. McKenney > > > > > > > > > > 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) > > > 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) > > > [ paulmck: Handle CONFIG_PROVE_RCU=n and identify test cases' callbacks. ] > > > Signed-off-by: Paul E. McKenney > > > > > > 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 */ > > That makes sense to me. I missed that point. There is no > > reason in wasting of extra cycles which affect a boot up > > time if built without CONFIG_PROVE_RCU. > > If CONFIG_PROVE_RCU=n, then rcu_tasks_initiate_self_tests is an empty > function. So the compiler should be able to eliminate all runtime > overhead from rcu_tasks_initiate_self_tests() when CONFIG_PROVE_RCU=n. > > Or am I missing your point? > That is correct, i mean your description. I wanted to underline that the late_initcall(rcu_tasks_verify_self_tests); was called even for CONFIG_PROVE_RCU=n, what would affect a boot time with disabled option. Of-course that extra time would be negligible. >From the other hand, why we should introduce it if it can be avoided. Your last change fixes that :) -- Vlad Rezki