Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752721AbaBNH6Z (ORCPT ); Fri, 14 Feb 2014 02:58:25 -0500 Received: from e23smtp05.au.ibm.com ([202.81.31.147]:44702 "EHLO e23smtp05.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751145AbaBNH6W (ORCPT ); Fri, 14 Feb 2014 02:58:22 -0500 From: "Srivatsa S. Bhat" Subject: [PATCH v2 15/52] x86, msr: Fix CPU hotplug callback registration To: paulus@samba.org, oleg@redhat.com, mingo@kernel.org, rusty@rustcorp.com.au, peterz@infradead.org, tglx@linutronix.de, akpm@linux-foundation.org Cc: paulmck@linux.vnet.ibm.com, tj@kernel.org, walken@google.com, ego@linux.vnet.ibm.com, linux@arm.linux.org.uk, rjw@rjwysocki.net, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, srivatsa.bhat@linux.vnet.ibm.com, "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , x86@kernel.org, "Srivatsa S. Bhat" Date: Fri, 14 Feb 2014 13:22:30 +0530 Message-ID: <20140214075229.22701.93673.stgit@srivatsabhat.in.ibm.com> In-Reply-To: <20140214074750.22701.47330.stgit@srivatsabhat.in.ibm.com> References: <20140214074750.22701.47330.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: 14021407-1396-0000-0000-0000044B35FB 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_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 msr code in x86 by using this latter form of callback registration. Cc: "H. Peter Anvin" Cc: Thomas Gleixner Cc: Ingo Molnar Cc: x86@kernel.org Signed-off-by: Srivatsa S. Bhat --- arch/x86/kernel/msr.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) diff --git a/arch/x86/kernel/msr.c b/arch/x86/kernel/msr.c index 05266b5..c9603ac 100644 --- a/arch/x86/kernel/msr.c +++ b/arch/x86/kernel/msr.c @@ -259,14 +259,15 @@ static int __init msr_init(void) goto out_chrdev; } msr_class->devnode = msr_devnode; - get_online_cpus(); + + cpu_notifier_register_begin(); for_each_online_cpu(i) { err = msr_device_create(i); if (err != 0) goto out_class; } - register_hotcpu_notifier(&msr_class_cpu_notifier); - put_online_cpus(); + __register_hotcpu_notifier(&msr_class_cpu_notifier); + cpu_notifier_register_done(); err = 0; goto out; @@ -275,7 +276,7 @@ out_class: i = 0; for_each_online_cpu(i) msr_device_destroy(i); - put_online_cpus(); + cpu_notifier_register_done(); class_destroy(msr_class); out_chrdev: __unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr"); @@ -286,13 +287,14 @@ out: static void __exit msr_exit(void) { int cpu = 0; - get_online_cpus(); + + cpu_notifier_register_begin(); for_each_online_cpu(cpu) msr_device_destroy(cpu); class_destroy(msr_class); __unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr"); - unregister_hotcpu_notifier(&msr_class_cpu_notifier); - put_online_cpus(); + __unregister_hotcpu_notifier(&msr_class_cpu_notifier); + cpu_notifier_register_done(); } module_init(msr_init); -- 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/