Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752338AbaBNRf1 (ORCPT ); Fri, 14 Feb 2014 12:35:27 -0500 Received: from mail-ie0-f172.google.com ([209.85.223.172]:55225 "EHLO mail-ie0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751277AbaBNRfY (ORCPT ); Fri, 14 Feb 2014 12:35:24 -0500 MIME-Version: 1.0 In-Reply-To: <20140214075511.22701.15084.stgit@srivatsabhat.in.ibm.com> References: <20140214074750.22701.47330.stgit@srivatsabhat.in.ibm.com> <20140214075511.22701.15084.stgit@srivatsabhat.in.ibm.com> From: Bjorn Helgaas Date: Fri, 14 Feb 2014 10:35:03 -0700 Message-ID: Subject: Re: [PATCH v2 27/52] x86, pci, amd-bus: Fix CPU hotplug callback registration To: "Srivatsa S. Bhat" 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" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. > --- > > arch/x86/pci/amd_bus.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/pci/amd_bus.c b/arch/x86/pci/amd_bus.c > index a48be98..f05cbf0 100644 > --- a/arch/x86/pci/amd_bus.c > +++ b/arch/x86/pci/amd_bus.c > @@ -380,10 +380,13 @@ static int __init pci_io_ecs_init(void) > if (early_pci_allowed()) > pci_enable_pci_io_ecs(); > > - register_cpu_notifier(&amd_cpu_notifier); > + cpu_notifier_register_begin(); > for_each_online_cpu(cpu) > amd_cpu_notify(&amd_cpu_notifier, (unsigned long)CPU_ONLINE, > (void *)(long)cpu); > + __register_cpu_notifier(&amd_cpu_notifier); > + cpu_notifier_register_done(); > + > pci_probe |= PCI_HAS_IO_ECS; > > return 0; > -- 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/