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[94.245.46.61]) by smtp.gmail.com with ESMTPSA id j16sm366852lfk.68.2021.02.19.02.49.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 19 Feb 2021 02:50:00 -0800 (PST) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Fri, 19 Feb 2021 11:49:58 +0100 To: Sebastian Andrzej Siewior Cc: "Paul E. McKenney" , Masami Hiramatsu , Ingo Molnar , Steven Rostedt , Peter Zijlstra , Thomas Gleixner , Uladzislau Rezki , LKML , RCU , Michael Ellerman , Andrew Morton , Daniel Axtens , Frederic Weisbecker , Neeraj Upadhyay , Joel Fernandes , Michal Hocko , "Theodore Y . Ts'o" , Oleksiy Avramchenko Subject: Re: [PATCH] kprobes: Fix to delay the kprobes jump optimization Message-ID: <20210219104958.GA34308@pc638.lan> References: <161365856280.719838.12423085451287256713.stgit@devnote2> <20210218151554.GQ2743@paulmck-ThinkPad-P72> <20210219081755.eucq4srbam6wg2gm@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210219081755.eucq4srbam6wg2gm@linutronix.de> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Feb 19, 2021 at 09:17:55AM +0100, Sebastian Andrzej Siewior wrote: > On 2021-02-18 07:15:54 [-0800], Paul E. McKenney wrote: > > Thank you, but the original report of a problem was from Sebastian > > and the connection to softirq was Uladzislau. So could you please > > add these before (or even in place of) my Reported-by? > > > > Reported-by: Sebastian Andrzej Siewior > > Reported-by: Uladzislau Rezki > > > > Other than that, looks good! > > Perfect. I'm kind of lost here, nevertheless ;) Does this mean that the > RCU selftest can now be delayed? > If above fix works, we can initialize rcu_init_tasks_generic() from the core_initcall() including selftst. It means that such initialization can be done later: diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 5cc6deaa5df2..ae7d0cdfa9bd 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -88,12 +88,6 @@ void rcu_sched_clock_irq(int user); void rcu_report_dead(unsigned int cpu); void rcutree_migrate_callbacks(int cpu); -#ifdef CONFIG_TASKS_RCU_GENERIC -void rcu_init_tasks_generic(void); -#else -static inline void rcu_init_tasks_generic(void) { } -#endif - #ifdef CONFIG_RCU_STALL_COMMON void rcu_sysrq_start(void); void rcu_sysrq_end(void); diff --git a/init/main.c b/init/main.c index c68d784376ca..3024c4db17a9 100644 --- a/init/main.c +++ b/init/main.c @@ -1512,7 +1512,6 @@ static noinline void __init kernel_init_freeable(void) init_mm_internals(); - rcu_init_tasks_generic(); do_pre_smp_initcalls(); lockup_detector_init(); diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index 17c8ebe131af..2797f9a042f4 100644 --- a/kernel/rcu/tasks.h +++ b/kernel/rcu/tasks.h @@ -966,11 +966,6 @@ static void rcu_tasks_trace_pregp_step(void) static void rcu_tasks_trace_pertask(struct task_struct *t, struct list_head *hop) { - // During early boot when there is only the one boot CPU, there - // is no idle task for the other CPUs. Just return. - if (unlikely(t == NULL)) - return; - WRITE_ONCE(t->trc_reader_special.b.need_qs, false); WRITE_ONCE(t->trc_reader_checked, false); t->trc_ipi_to_cpu = -1; @@ -1300,7 +1295,7 @@ late_initcall(rcu_tasks_verify_self_tests); static void rcu_tasks_initiate_self_tests(void) { } #endif /* #else #ifdef CONFIG_PROVE_RCU */ -void __init rcu_init_tasks_generic(void) +static void __init rcu_init_tasks_generic(void) { #ifdef CONFIG_TASKS_RCU rcu_spawn_tasks_kthread(); @@ -1318,6 +1313,7 @@ void __init rcu_init_tasks_generic(void) rcu_tasks_initiate_self_tests(); } +core_initcall(rcu_init_tasks_generic); #else /* #ifdef CONFIG_TASKS_RCU_GENERIC */ static inline void rcu_tasks_bootup_oddness(void) {} void show_rcu_tasks_gp_kthreads(void) {} -- Vlad Rezki