From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932114AbaBEWOk (ORCPT ); Wed, 5 Feb 2014 17:14:40 -0500 Received: from e28smtp07.in.ibm.com ([122.248.162.7]:54322 "EHLO e28smtp07.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752261AbaBEWOe (ORCPT ); Wed, 5 Feb 2014 17:14:34 -0500 From: "Srivatsa S. Bhat" Subject: [PATCH 25/51] x86, pci, amd-bus: 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, Bjorn Helgaas , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, linux-pci@vger.kernel.org, "Srivatsa S. Bhat" Date: Thu, 06 Feb 2014 03:39:12 +0530 Message-ID: <20140205220912.19080.11413.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: 14020522-8878-0000-0000-00000ABF35BA 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 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 --- 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..7cd5d84 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_maps_update_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_maps_update_done(); + pci_probe |= PCI_HAS_IO_ECS; return 0;