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

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Date:   Fri, 12 Feb 2021 20:20:59 +0100
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     "Uladzislau Rezki (Sony)" <urezki@...il.com>
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>,
        Oleksiy Avramchenko <oleksiy.avramchenko@...ymobile.com>
Subject: Re: [PATCH 2/2] rcu-tasks: add RCU-tasks self tests

On 2020-12-09 21:27:32 [+0100], Uladzislau Rezki (Sony) 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.

I just bisected to this commit. By booting with `threadirqs' I end up
with:
[    0.176533] Running RCU-tasks wait API self tests

No stall warning or so.
It boots again with:

diff --git a/init/main.c b/init/main.c
--- a/init/main.c
+++ b/init/main.c
@@ -1489,6 +1489,7 @@ void __init console_on_rootfs(void)
 	fput(file);
 }
 
+void rcu_tasks_initiate_self_tests(void);
 static noinline void __init kernel_init_freeable(void)
 {
 	/*
@@ -1514,6 +1515,7 @@ static noinline void __init kernel_init_freeable(void)
 
 	rcu_init_tasks_generic();
 	do_pre_smp_initcalls();
+	rcu_tasks_initiate_self_tests();
 	lockup_detector_init();
 
 	smp_init();
diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -1266,7 +1266,7 @@ static void test_rcu_tasks_callback(struct rcu_head *rhp)
 	rttd->notrun = true;
 }
 
-static void rcu_tasks_initiate_self_tests(void)
+void rcu_tasks_initiate_self_tests(void)
 {
 	pr_info("Running RCU-tasks wait API self tests\n");
 #ifdef CONFIG_TASKS_RCU
@@ -1322,7 +1322,6 @@ void __init rcu_init_tasks_generic(void)
 #endif
 
 	// Run the self-tests.
-	rcu_tasks_initiate_self_tests();
 }
 
 #else /* #ifdef CONFIG_TASKS_RCU_GENERIC */

> Signed-off-by: Uladzislau Rezki (Sony) <urezki@...il.com>

Sebastian