From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-11.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 37353C2D0A3 for ; Fri, 6 Nov 2020 14:43:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 83806208B8 for ; Fri, 6 Nov 2020 14:43:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604673795; bh=Fj8awA6Fcy8YY7k4CfGwBYzsc5wO+RhyNYKCMKn+Tgw=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:List-ID: From; b=IBCZXeZwhIXynKDE0cHNIiQwkckig0T3vMET2QBJOPOhqcI6Pcm9+FpHcUlmadv6J FzMqEd/I/v3RQ/5LhfXwJ0v9fOBJKnO1rjYqrMuuNTQFEmWjHm1opL+bpkCHCSNGed iJeqwotos+7DOk193iVc2deIUVOuInOOZVhTdAf4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727233AbgKFOnO (ORCPT ); Fri, 6 Nov 2020 09:43:14 -0500 Received: from mail.kernel.org ([198.145.29.99]:34546 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726565AbgKFOnO (ORCPT ); Fri, 6 Nov 2020 09:43:14 -0500 Received: from paulmck-ThinkPad-P72.home (50-39-104-11.bvtn.or.frontiernet.net [50.39.104.11]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 1DF4A20724; Fri, 6 Nov 2020 14:43:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604673793; bh=Fj8awA6Fcy8YY7k4CfGwBYzsc5wO+RhyNYKCMKn+Tgw=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=WVaTpqyzRDjE84irSOloXbMBATmZDFNKMDSBKQd6owGZ6BzV6xpSBKGSHmFv1dwuz IlGycO1W8Of5jO850yWfaG4HRtUWnmlYwtSOffGtdlAjqdctCeNhHF/nAPkClaWDuO 4+pTL5/ZfaiDit4KSZ1J7qqm4vua8OmPqb6Gw0HU= Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id AB157352097B; Fri, 6 Nov 2020 06:43:12 -0800 (PST) Date: Fri, 6 Nov 2020 06:43:12 -0800 From: "Paul E. McKenney" To: Will Deacon Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kernel-team@android.com, Catalin Marinas , Qian Cai Subject: Re: [PATCH 2/2] arm64: smp: Tell RCU about CPUs that fail to come online Message-ID: <20201106144312.GU3249@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <20201106103602.9849-1-will@kernel.org> <20201106103602.9849-3-will@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201106103602.9849-3-will@kernel.org> User-Agent: Mutt/1.9.4 (2018-02-28) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Nov 06, 2020 at 10:36:02AM +0000, Will Deacon wrote: > Commit ce3d31ad3cac ("arm64/smp: Move rcu_cpu_starting() earlier") ensured > that RCU is informed early about incoming CPUs that might end up calling > into printk() before they are online. However, if such a CPU fails the > early CPU feature compatibility checks in check_local_cpu_capabilities(), > then it will be powered off or parked without informing RCU, leading to > an endless stream of stalls: > > | rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: > | rcu: 2-O...: (0 ticks this GP) idle=002/1/0x4000000000000000 softirq=0/0 fqs=2593 > | (detected by 0, t=5252 jiffies, g=9317, q=136) > | Task dump for CPU 2: > | task:swapper/2 state:R running task stack: 0 pid: 0 ppid: 1 flags:0x00000028 > | Call trace: > | ret_from_fork+0x0/0x30 > > Ensure that the dying CPU invokes rcu_report_dead() prior to being powered > off or parked. > > Cc: Qian Cai > Cc: "Paul E. McKenney" > Suggested-by: Qian Cai > Signed-off-by: Will Deacon Reviewed-by: Paul E. McKenney > --- > arch/arm64/kernel/smp.c | 1 + > kernel/rcu/tree.c | 2 +- > 2 files changed, 2 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c > index 09c96f57818c..18e9727d3f64 100644 > --- a/arch/arm64/kernel/smp.c > +++ b/arch/arm64/kernel/smp.c > @@ -413,6 +413,7 @@ void cpu_die_early(void) > > /* Mark this CPU absent */ > set_cpu_present(cpu, 0); > + rcu_report_dead(cpu); > > if (IS_ENABLED(CONFIG_HOTPLUG_CPU)) { > update_cpu_boot_status(CPU_KILL_ME); > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index 2a52f42f64b6..bd04b09b84b3 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -4077,7 +4077,6 @@ void rcu_cpu_starting(unsigned int cpu) > smp_mb(); /* Ensure RCU read-side usage follows above initialization. */ > } > > -#ifdef CONFIG_HOTPLUG_CPU > /* > * The outgoing function has no further need of RCU, so remove it from > * the rcu_node tree's ->qsmaskinitnext bit masks. > @@ -4117,6 +4116,7 @@ void rcu_report_dead(unsigned int cpu) > rdp->cpu_started = false; > } > > +#ifdef CONFIG_HOTPLUG_CPU > /* > * The outgoing CPU has just passed through the dying-idle state, and we > * are being invoked from the CPU that was IPIed to continue the offline > -- > 2.29.1.341.ge80a0c044ae-goog >