Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756104AbaBEWRh (ORCPT ); Wed, 5 Feb 2014 17:17:37 -0500 Received: from e23smtp01.au.ibm.com ([202.81.31.143]:49652 "EHLO e23smtp01.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754744AbaBEWRb (ORCPT ); Wed, 5 Feb 2014 17:17:31 -0500 From: "Srivatsa S. Bhat" Subject: [PATCH 42/51] hwmon, coretemp: Fix CPU hotplug callback registration To: paulus@samba.org, oleg@redhat.com, rusty@rustcorp.com.au, peterz@infradead.org, tglx@linutronix.de, akpm@linux-foundation.org Cc: mingo@kernel.org, paulmck@linux.vnet.ibm.com, tj@kernel.org, walken@google.com, ego@linux.vnet.ibm.com, linux@arm.linux.org.uk, linux-kernel@vger.kernel.org, srivatsa.bhat@linux.vnet.ibm.com, Fenghua Yu , Jean Delvare , Guenter Roeck , lm-sensors@lm-sensors.org, "Srivatsa S. Bhat" Date: Thu, 06 Feb 2014 03:42:06 +0530 Message-ID: <20140205221205.19080.15108.stgit@srivatsabhat.in.ibm.com> In-Reply-To: <20140205220251.19080.92336.stgit@srivatsabhat.in.ibm.com> References: <20140205220251.19080.92336.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: 14020522-1618-0000-0000-0000056295D2 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_maps_update_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_maps_update_done(); Fix the hwmon coretemp code by using this latter form of callback registration. Cc: Fenghua Yu Cc: Jean Delvare Cc: Guenter Roeck Cc: lm-sensors@lm-sensors.org Signed-off-by: Srivatsa S. Bhat --- drivers/hwmon/coretemp.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) diff --git a/drivers/hwmon/coretemp.c b/drivers/hwmon/coretemp.c index bbb0b0d..43c436b 100644 --- a/drivers/hwmon/coretemp.c +++ b/drivers/hwmon/coretemp.c @@ -849,20 +849,20 @@ static int __init coretemp_init(void) if (err) goto exit; - get_online_cpus(); + cpu_maps_update_begin(); for_each_online_cpu(i) get_core_online(i); #ifndef CONFIG_HOTPLUG_CPU if (list_empty(&pdev_list)) { - put_online_cpus(); + cpu_maps_update_done(); err = -ENODEV; goto exit_driver_unreg; } #endif - register_hotcpu_notifier(&coretemp_cpu_notifier); - put_online_cpus(); + __register_hotcpu_notifier(&coretemp_cpu_notifier); + cpu_maps_update_done(); return 0; #ifndef CONFIG_HOTPLUG_CPU @@ -877,8 +877,8 @@ static void __exit coretemp_exit(void) { struct pdev_entry *p, *n; - get_online_cpus(); - unregister_hotcpu_notifier(&coretemp_cpu_notifier); + cpu_maps_update_begin(); + __unregister_hotcpu_notifier(&coretemp_cpu_notifier); mutex_lock(&pdev_list_mutex); list_for_each_entry_safe(p, n, &pdev_list, list) { platform_device_unregister(p->pdev); @@ -886,7 +886,7 @@ static void __exit coretemp_exit(void) kfree(p); } mutex_unlock(&pdev_list_mutex); - put_online_cpus(); + cpu_maps_update_done(); platform_driver_unregister(&coretemp_driver); } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/