From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e28smtp06.in.ibm.com (e28smtp06.in.ibm.com [122.248.162.6]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 681432C0144 for ; Tue, 11 Mar 2014 07:38:53 +1100 (EST) Received: from /spool/local by e28smtp06.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 11 Mar 2014 02:08:51 +0530 Received: from d28relay01.in.ibm.com (d28relay01.in.ibm.com [9.184.220.58]) by d28dlp02.in.ibm.com (Postfix) with ESMTP id 1BEB33940023 for ; Tue, 11 Mar 2014 02:08:50 +0530 (IST) Received: from d28av04.in.ibm.com (d28av04.in.ibm.com [9.184.220.66]) by d28relay01.in.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id s2AKckIA24707258 for ; Tue, 11 Mar 2014 02:08:46 +0530 Received: from d28av04.in.ibm.com (localhost [127.0.0.1]) by d28av04.in.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id s2AKcmIH009873 for ; Tue, 11 Mar 2014 02:08:49 +0530 From: "Srivatsa S. Bhat" Subject: [PATCH v3 27/52] x86, pci, amd-bus: Fix CPU hotplug callback registration To: paulus@samba.org, oleg@redhat.com, mingo@kernel.org, rjw@rjwysocki.net, rusty@rustcorp.com.au, peterz@infradead.org, tglx@linutronix.de, akpm@linux-foundation.org Date: Tue, 11 Mar 2014 02:08:43 +0530 Message-ID: <20140310203842.10746.18948.stgit@srivatsabhat.in.ibm.com> In-Reply-To: <20140310203312.10746.310.stgit@srivatsabhat.in.ibm.com> References: <20140310203312.10746.310.stgit@srivatsabhat.in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Cc: linux-arch@vger.kernel.org, ego@linux.vnet.ibm.com, walken@google.com, linux@arm.linux.org.uk, linux-pm@vger.kernel.org, linux-pci@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org, "Srivatsa S. Bhat" , "H. Peter Anvin" , tj@kernel.org, Thomas Gleixner , paulmck@linux.vnet.ibm.com, Bjorn Helgaas , Ingo Molnar List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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: Thomas Gleixner Cc: Ingo Molnar Cc: "H. Peter Anvin" Cc: x86@kernel.org Cc: linux-pci@vger.kernel.org Acked-by: Bjorn Helgaas 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..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;