From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757276AbcCCKES (ORCPT ); Thu, 3 Mar 2016 05:04:18 -0500 Received: from torg.zytor.com ([198.137.202.12]:39550 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1756709AbcCCKEQ (ORCPT ); Thu, 3 Mar 2016 05:04:16 -0500 Date: Thu, 3 Mar 2016 02:03:35 -0800 From: tip-bot for Thomas Gleixner Message-ID: Cc: hpa@zytor.com, linux-kernel@vger.kernel.org, peterz@infradead.org, tglx@linutronix.de, mingo@kernel.org, paulmck@linux.vnet.ibm.com Reply-To: paulmck@linux.vnet.ibm.com, mingo@kernel.org, peterz@infradead.org, tglx@linutronix.de, linux-kernel@vger.kernel.org, hpa@zytor.com In-Reply-To: <20160302201127.GA23440@linux.vnet.ibm.com> References: <20160302201127.GA23440@linux.vnet.ibm.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:smp/hotplug] cpu/hotplug: Plug death reporting race Git-Commit-ID: 71f87b2fc64c2e9b6d53cb817f28711b959d3dfe X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 71f87b2fc64c2e9b6d53cb817f28711b959d3dfe Gitweb: http://git.kernel.org/tip/71f87b2fc64c2e9b6d53cb817f28711b959d3dfe Author: Thomas Gleixner AuthorDate: Thu, 3 Mar 2016 10:52:10 +0100 Committer: Thomas Gleixner CommitDate: Thu, 3 Mar 2016 10:52:10 +0100 cpu/hotplug: Plug death reporting race Paul noticed that the conversion of the death reporting introduced a race where the outgoing cpu might be delayed after waking the controll processor, so it might not be able to call rcu_report_dead() before being physically removed, leading to RCU stalls. We cant call complete after rcu_report_dead(), so instead of going back to busy polling, simply issue a function call to do the completion. Fixes: 27d50c7eeb0f "rcu: Make CPU_DYING_IDLE an explicit call" Reported-by: Paul E. McKenney Link: http://lkml.kernel.org/r/20160302201127.GA23440@linux.vnet.ibm.com Signed-off-by: Thomas Gleixner Acked-by: Peter Zijlstra --- kernel/cpu.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/kernel/cpu.c b/kernel/cpu.c index ff8059b..93e9d89 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -755,14 +755,26 @@ static int notify_dead(unsigned int cpu) return 0; } +static void cpuhp_complete_idle_dead(void *arg) +{ + struct cpuhp_cpu_state *st = arg; + + complete(&st->done); +} + void cpuhp_report_idle_dead(void) { struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state); BUG_ON(st->state != CPUHP_AP_OFFLINE); - st->state = CPUHP_AP_IDLE_DEAD; - complete(&st->done); rcu_report_dead(smp_processor_id()); + st->state = CPUHP_AP_IDLE_DEAD; + /* + * We cannot call complete after rcu_report_dead() so we delegate it + * to an online cpu. + */ + smp_call_function_single(cpumask_first(cpu_online_mask), + cpuhp_complete_idle_dead, st, 0); } #else