Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752755AbaBNSIr (ORCPT ); Fri, 14 Feb 2014 13:08:47 -0500 Received: from e28smtp07.in.ibm.com ([122.248.162.7]:54749 "EHLO e28smtp07.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752486AbaBNSIo (ORCPT ); Fri, 14 Feb 2014 13:08:44 -0500 Message-ID: <52FE5A62.90100@linux.vnet.ibm.com> Date: Fri, 14 Feb 2014 23:33:14 +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: Bjorn Helgaas CC: "paulus@samba.org" , oleg@redhat.com, Ingo Molnar , Rusty Russell , Peter Zijlstra , Thomas Gleixner , Andrew Morton , Paul McKenney , Tejun Heo , Michel Lespinasse , ego@linux.vnet.ibm.com, Russell King , "Rafael J. Wysocki" , "linux-kernel@vger.kernel.org" , Linux-Arch , "H. Peter Anvin" , "x86@kernel.org" , "linux-pci@vger.kernel.org" Subject: Re: [PATCH v2 27/52] x86, pci, amd-bus: Fix CPU hotplug callback registration References: <20140214074750.22701.47330.stgit@srivatsabhat.in.ibm.com> <20140214075511.22701.15084.stgit@srivatsabhat.in.ibm.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14021418-8878-0000-0000-00000AE283CE Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/14/2014 11:05 PM, Bjorn Helgaas wrote: > On Fri, Feb 14, 2014 at 12:55 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_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 amd-bus code in x86 by using this latter form of callback >> registration. >> >> Cc: Bjorn Helgaas >> Cc: Thomas Gleixner >> Cc: Ingo Molnar >> Cc: "H. Peter Anvin" >> Cc: x86@kernel.org >> Cc: linux-pci@vger.kernel.org >> Signed-off-by: Srivatsa S. Bhat > > This looks fine to me. > > Acked-by: Bjorn Helgaas > > I think it makes sense for you to merge it along with all your other > similar changes. I don't foresee any conflicts with things in my PCI > tree. > Great! 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/