Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756568AbaBFQJ2 (ORCPT ); Thu, 6 Feb 2014 11:09:28 -0500 Received: from e23smtp01.au.ibm.com ([202.81.31.143]:50835 "EHLO e23smtp01.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756533AbaBFQJ0 (ORCPT ); Thu, 6 Feb 2014 11:09:26 -0500 Message-ID: <52F3B270.20005@linux.vnet.ibm.com> Date: Thu, 06 Feb 2014 21:34:00 +0530 From: "Srivatsa S. Bhat" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20120828 Thunderbird/15.0 MIME-Version: 1.0 To: "Rafael J. Wysocki" CC: Len Brown , 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, linux-pm@vger.kernel.org Subject: Re: [PATCH 38/51] intel-idle: Fix CPU hotplug callback registration References: <20140205220251.19080.92336.stgit@srivatsabhat.in.ibm.com> <20140205221122.19080.64763.stgit@srivatsabhat.in.ibm.com> <87012016.ZnbTpcb5sN@vostro.rjw.lan> In-Reply-To: <87012016.ZnbTpcb5sN@vostro.rjw.lan> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14020616-1618-0000-0000-0000056533D6 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/06/2014 06:13 PM, Rafael J. Wysocki wrote: > On Thursday, February 06, 2014 03:41:23 AM 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 intel-idle code by using this latter form of callback registration. >> >> Cc: Len Brown >> Cc: "Rafael J. Wysocki" >> Cc: linux-pm@vger.kernel.org >> Signed-off-by: Srivatsa S. Bhat > > This looks good to me. Len, what do you think? > Thanks a lot Rafael! > Srivatsa, how does it depend on the rest of your series? > It depends only on the first patch in the series: http://article.gmane.org/gmane.linux.kernel/1641640 But don't take this patch yet, we are discussing a possible rename of the function cpu_maps_update_begin()/done(). So I'll post a v2 after the name is finalized. Thank you! Regards, Srivatsa S. Bhat -- 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/