Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753924AbaBFAoO (ORCPT ); Wed, 5 Feb 2014 19:44:14 -0500 Received: from mail-pa0-f68.google.com ([209.85.220.68]:54901 "EHLO mail-pa0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753230AbaBFAoM (ORCPT ); Wed, 5 Feb 2014 19:44:12 -0500 Date: Wed, 5 Feb 2014 16:44:12 -0800 From: Guenter Roeck To: "Srivatsa S. Bhat" Cc: paulus@samba.org, oleg@redhat.com, rusty@rustcorp.com.au, peterz@infradead.org, tglx@linutronix.de, akpm@linux-foundation.org, 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, Fenghua Yu , Jean Delvare , lm-sensors@lm-sensors.org Subject: Re: [PATCH 42/51] hwmon, coretemp: Fix CPU hotplug callback registration Message-ID: <20140206004412.GA1308@roeck-us.net> References: <20140205220251.19080.92336.stgit@srivatsabhat.in.ibm.com> <20140205221205.19080.15108.stgit@srivatsabhat.in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140205221205.19080.15108.stgit@srivatsabhat.in.ibm.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 06, 2014 at 03:42:06AM +0530, Srivatsa S. Bhat wrote: > 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 Applied. Guenter -- 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/