From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752644AbaBNH52 (ORCPT ); Fri, 14 Feb 2014 02:57:28 -0500 Received: from e28smtp08.in.ibm.com ([122.248.162.8]:49735 "EHLO e28smtp08.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752620AbaBNH5Z (ORCPT ); Fri, 14 Feb 2014 02:57:25 -0500 From: "Srivatsa S. Bhat" Subject: [PATCH v2 12/52] s390, smp: Fix CPU hotplug callback registration To: paulus@samba.org, oleg@redhat.com, mingo@kernel.org, rusty@rustcorp.com.au, peterz@infradead.org, tglx@linutronix.de, akpm@linux-foundation.org Cc: paulmck@linux.vnet.ibm.com, tj@kernel.org, walken@google.com, ego@linux.vnet.ibm.com, linux@arm.linux.org.uk, rjw@rjwysocki.net, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, srivatsa.bhat@linux.vnet.ibm.com, Martin Schwidefsky , Heiko Carstens , Thomas Gleixner , Ingo Molnar , linux-s390@vger.kernel.org, "Srivatsa S. Bhat" Date: Fri, 14 Feb 2014 13:21:55 +0530 Message-ID: <20140214075155.22701.59797.stgit@srivatsabhat.in.ibm.com> In-Reply-To: <20140214074750.22701.47330.stgit@srivatsabhat.in.ibm.com> References: <20140214074750.22701.47330.stgit@srivatsabhat.in.ibm.com> User-Agent: StGIT/0.14.3 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14021407-2000-0000-0000-00000FBA3659 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Subsystems that want to register CPU hotplug callbacks, as well as perform initialization for the CPUs that are already online, often do it as shown below: get_online_cpus(); for_each_online_cpu(cpu) init_cpu(cpu); register_cpu_notifier(&foobar_cpu_notifier); put_online_cpus(); This is wrong, since it is prone to ABBA deadlocks involving the cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently with CPU hotplug operations). Instead, the correct and race-free way of performing the callback registration is: cpu_notifier_register_begin(); for_each_online_cpu(cpu) init_cpu(cpu); /* Note the use of the double underscored version of the API */ __register_cpu_notifier(&foobar_cpu_notifier); cpu_notifier_register_done(); Fix the smp code in s390 by using this latter form of callback registration. Cc: Martin Schwidefsky Cc: Heiko Carstens Cc: Thomas Gleixner Cc: Ingo Molnar Cc: linux-s390@vger.kernel.org Signed-off-by: Srivatsa S. Bhat --- arch/s390/kernel/smp.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c index a7125b6..e10be35 100644 --- a/arch/s390/kernel/smp.c +++ b/arch/s390/kernel/smp.c @@ -1057,19 +1057,24 @@ static DEVICE_ATTR(rescan, 0200, NULL, rescan_store); static int __init s390_smp_init(void) { - int cpu, rc; + int cpu, rc = 0; - hotcpu_notifier(smp_cpu_notify, 0); #ifdef CONFIG_HOTPLUG_CPU rc = device_create_file(cpu_subsys.dev_root, &dev_attr_rescan); if (rc) return rc; #endif + cpu_notifier_register_begin(); for_each_present_cpu(cpu) { rc = smp_add_present_cpu(cpu); if (rc) - return rc; + goto out; } - return 0; + + __hotcpu_notifier(smp_cpu_notify, 0); + +out: + cpu_notifier_register_done(); + return rc; } subsys_initcall(s390_smp_init); From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Srivatsa S. Bhat" Subject: [PATCH v2 12/52] s390, smp: Fix CPU hotplug callback registration Date: Fri, 14 Feb 2014 13:21:55 +0530 Message-ID: <20140214075155.22701.59797.stgit@srivatsabhat.in.ibm.com> References: <20140214074750.22701.47330.stgit@srivatsabhat.in.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20140214074750.22701.47330.stgit@srivatsabhat.in.ibm.com> Sender: linux-kernel-owner@vger.kernel.org List-Archive: List-Post: To: paulus@samba.org, oleg@redhat.com, rusty@rustcorp.com.au, peterz@infradead.org, akpm@linux-foundation.org Cc: paulmck@linux.vnet.ibm.com, tj@kernel.org, walken@google.com, ego@linux.vnet.ibm.com, linux@arm.linux.org.uk, rjw@rjwysocki.net, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, srivatsa.bhat@linux.vnet.ibm.com, Martin Schwidefsky , Heiko Carstens , Thomas Gleixner , Ingo Molnar , linux-s390@vger.kernel.org"Srivatsa S. Bhat" List-ID: Subsystems that want to register CPU hotplug callbacks, as well as perform initialization for the CPUs that are already online, often do it as shown below: get_online_cpus(); for_each_online_cpu(cpu) init_cpu(cpu); register_cpu_notifier(&foobar_cpu_notifier); put_online_cpus(); This is wrong, since it is prone to ABBA deadlocks involving the cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently with CPU hotplug operations). Instead, the correct and race-free way of performing the callback registration is: cpu_notifier_register_begin(); for_each_online_cpu(cpu) init_cpu(cpu); /* Note the use of the double underscored version of the API */ __register_cpu_notifier(&foobar_cpu_notifier); cpu_notifier_register_done(); Fix the smp code in s390 by using this latter form of callback registration. Cc: Martin Schwidefsky Cc: Heiko Carstens Cc: Thomas Gleixner Cc: Ingo Molnar Cc: linux-s390@vger.kernel.org Signed-off-by: Srivatsa S. Bhat --- arch/s390/kernel/smp.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c index a7125b6..e10be35 100644 --- a/arch/s390/kernel/smp.c +++ b/arch/s390/kernel/smp.c @@ -1057,19 +1057,24 @@ static DEVICE_ATTR(rescan, 0200, NULL, rescan_store); static int __init s390_smp_init(void) { - int cpu, rc; + int cpu, rc = 0; - hotcpu_notifier(smp_cpu_notify, 0); #ifdef CONFIG_HOTPLUG_CPU rc = device_create_file(cpu_subsys.dev_root, &dev_attr_rescan); if (rc) return rc; #endif + cpu_notifier_register_begin(); for_each_present_cpu(cpu) { rc = smp_add_present_cpu(cpu); if (rc) - return rc; + goto out; } - return 0; + + __hotcpu_notifier(smp_cpu_notify, 0); + +out: + cpu_notifier_register_done(); + return rc; } subsys_initcall(s390_smp_init); From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e28smtp08.in.ibm.com ([122.248.162.8]:49734 "EHLO e28smtp08.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752619AbaBNH50 (ORCPT ); Fri, 14 Feb 2014 02:57:26 -0500 Received: from /spool/local by e28smtp08.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 14 Feb 2014 13:27:23 +0530 From: "Srivatsa S. Bhat" Subject: [PATCH v2 12/52] s390, smp: Fix CPU hotplug callback registration Date: Fri, 14 Feb 2014 13:21:55 +0530 Message-ID: <20140214075155.22701.59797.stgit@srivatsabhat.in.ibm.com> In-Reply-To: <20140214074750.22701.47330.stgit@srivatsabhat.in.ibm.com> References: <20140214074750.22701.47330.stgit@srivatsabhat.in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-arch-owner@vger.kernel.org List-ID: To: paulus@samba.org, oleg@redhat.com, mingo@kernel.org, rusty@rustcorp.com.au, peterz@infradead.org, tglx@linutronix.de, akpm@linux-foundation.org Cc: paulmck@linux.vnet.ibm.com, tj@kernel.org, walken@google.com, ego@linux.vnet.ibm.com, linux@arm.linux.org.uk, rjw@rjwysocki.net, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, srivatsa.bhat@linux.vnet.ibm.com, Martin Schwidefsky , Heiko Carstens , linux-s390@vger.kernel.org"Srivatsa S. Bhat" Message-ID: <20140214075155.FoZh1ydMpK46fHxXuO5lLUukn3Qb1MXnqlXsX1mdA-w@z> Subsystems that want to register CPU hotplug callbacks, as well as perform initialization for the CPUs that are already online, often do it as shown below: get_online_cpus(); for_each_online_cpu(cpu) init_cpu(cpu); register_cpu_notifier(&foobar_cpu_notifier); put_online_cpus(); This is wrong, since it is prone to ABBA deadlocks involving the cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently with CPU hotplug operations). Instead, the correct and race-free way of performing the callback registration is: cpu_notifier_register_begin(); for_each_online_cpu(cpu) init_cpu(cpu); /* Note the use of the double underscored version of the API */ __register_cpu_notifier(&foobar_cpu_notifier); cpu_notifier_register_done(); Fix the smp code in s390 by using this latter form of callback registration. Cc: Martin Schwidefsky Cc: Heiko Carstens Cc: Thomas Gleixner Cc: Ingo Molnar Cc: linux-s390@vger.kernel.org Signed-off-by: Srivatsa S. Bhat --- arch/s390/kernel/smp.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c index a7125b6..e10be35 100644 --- a/arch/s390/kernel/smp.c +++ b/arch/s390/kernel/smp.c @@ -1057,19 +1057,24 @@ static DEVICE_ATTR(rescan, 0200, NULL, rescan_store); static int __init s390_smp_init(void) { - int cpu, rc; + int cpu, rc = 0; - hotcpu_notifier(smp_cpu_notify, 0); #ifdef CONFIG_HOTPLUG_CPU rc = device_create_file(cpu_subsys.dev_root, &dev_attr_rescan); if (rc) return rc; #endif + cpu_notifier_register_begin(); for_each_present_cpu(cpu) { rc = smp_add_present_cpu(cpu); if (rc) - return rc; + goto out; } - return 0; + + __hotcpu_notifier(smp_cpu_notify, 0); + +out: + cpu_notifier_register_done(); + return rc; } subsys_initcall(s390_smp_init);