From mboxrd@z Thu Jan 1 00:00:00 1970 From: paulmck@linux.vnet.ibm.com (Paul E. McKenney) Date: Tue, 12 Dec 2017 09:20:59 -0800 Subject: [PATCH] ARM: CPU hotplug: Delegate complete() to surviving CPU Message-ID: <20171212172059.GA11875@linux.vnet.ibm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org The ARM implementation of arch_cpu_idle_dead() invokes complete(), but does so after RCU has stopped watching the outgoing CPU, which results in lockdep complaints because complete() invokes functions containing RCU readers. This patch therefore uses Thomas Gleixner's trick of delegating the complete() call to a surviving CPU via smp_call_function_single(). Reported-by: Peng Fan Reported-by: Russell King - ARM Linux Signed-off-by: Paul E. McKenney Tested-by: Tested-by: Fabio Estevam Cc: Russell King Cc: Ingo Molnar Cc: "Peter Zijlstra (Intel)" Cc: Michal Hocko Cc: Thomas Gleixner Cc: diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c index b4fbf00ee4ad..75f85e20aafa 100644 --- a/arch/arm/kernel/smp.c +++ b/arch/arm/kernel/smp.c @@ -267,6 +267,14 @@ void __cpu_die(unsigned int cpu) } /* + * Invoke complete() on behalf of the outgoing CPU. + */ +static void arch_cpu_idle_dead_complete(void *arg) +{ + complete(&cpu_died); +} + +/* * Called from the idle thread for the CPU which has been shutdown. * * Note that we disable IRQs here, but do not re-enable them @@ -293,9 +301,11 @@ void arch_cpu_idle_dead(void) /* * Tell __cpu_die() that this CPU is now safe to dispose of. Once * this returns, power and/or clocks can be removed at any point - * from this CPU and its cache by platform_cpu_kill(). + * from this CPU and its cache by platform_cpu_kill(). We cannot + * call complete() this late, so we delegate it to an online CPU. */ - complete(&cpu_died); + smp_call_function_single(cpumask_first(cpu_online_mask), + arch_cpu_idle_dead_complete, NULL, 0); /* * Ensure that the cache lines associated with that completion are From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752498AbdLLRVJ (ORCPT ); Tue, 12 Dec 2017 12:21:09 -0500 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:48774 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751643AbdLLRVE (ORCPT ); Tue, 12 Dec 2017 12:21:04 -0500 Date: Tue, 12 Dec 2017 09:20:59 -0800 From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Cc: Russell King - ARM Linux , Peng Fan , Fabio Estevam , Ingo Molnar , "Peter Zijlstra (Intel)" , Michal Hocko , Thomas Gleixner Subject: [PATCH] ARM: CPU hotplug: Delegate complete() to surviving CPU Reply-To: paulmck@linux.vnet.ibm.com MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 17121217-2213-0000-0000-0000024951E3 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00008194; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000244; SDB=6.00959219; UDB=6.00485093; IPR=6.00739241; BA=6.00005738; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00018504; XFM=3.00000015; UTC=2017-12-12 17:21:01 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17121217-2214-0000-0000-0000586C33D9 Message-Id: <20171212172059.GA11875@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-12-12_10:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1712120247 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The ARM implementation of arch_cpu_idle_dead() invokes complete(), but does so after RCU has stopped watching the outgoing CPU, which results in lockdep complaints because complete() invokes functions containing RCU readers. This patch therefore uses Thomas Gleixner's trick of delegating the complete() call to a surviving CPU via smp_call_function_single(). Reported-by: Peng Fan Reported-by: Russell King - ARM Linux Signed-off-by: Paul E. McKenney Tested-by: Tested-by: Fabio Estevam Cc: Russell King Cc: Ingo Molnar Cc: "Peter Zijlstra (Intel)" Cc: Michal Hocko Cc: Thomas Gleixner Cc: diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c index b4fbf00ee4ad..75f85e20aafa 100644 --- a/arch/arm/kernel/smp.c +++ b/arch/arm/kernel/smp.c @@ -267,6 +267,14 @@ void __cpu_die(unsigned int cpu) } /* + * Invoke complete() on behalf of the outgoing CPU. + */ +static void arch_cpu_idle_dead_complete(void *arg) +{ + complete(&cpu_died); +} + +/* * Called from the idle thread for the CPU which has been shutdown. * * Note that we disable IRQs here, but do not re-enable them @@ -293,9 +301,11 @@ void arch_cpu_idle_dead(void) /* * Tell __cpu_die() that this CPU is now safe to dispose of. Once * this returns, power and/or clocks can be removed at any point - * from this CPU and its cache by platform_cpu_kill(). + * from this CPU and its cache by platform_cpu_kill(). We cannot + * call complete() this late, so we delegate it to an online CPU. */ - complete(&cpu_died); + smp_call_function_single(cpumask_first(cpu_online_mask), + arch_cpu_idle_dead_complete, NULL, 0); /* * Ensure that the cache lines associated with that completion are