Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755396AbaBEWVU (ORCPT ); Wed, 5 Feb 2014 17:21:20 -0500 Received: from e28smtp08.in.ibm.com ([122.248.162.8]:57840 "EHLO e28smtp08.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753981AbaBEWQp (ORCPT ); Wed, 5 Feb 2014 17:16:45 -0500 From: "Srivatsa S. Bhat" Subject: [PATCH 38/51] intel-idle: 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, Len Brown , "Rafael J. Wysocki" , linux-pm@vger.kernel.org, "Srivatsa S. Bhat" Date: Thu, 06 Feb 2014 03:41:23 +0530 Message-ID: <20140205221122.19080.64763.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: 14020522-2000-0000-0000-00000F986B5C 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 intel-idle code by using this latter form of callback registration. Cc: Len Brown Cc: "Rafael J. Wysocki" Cc: linux-pm@vger.kernel.org Signed-off-by: Srivatsa S. Bhat --- drivers/idle/intel_idle.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c index 8e1939f..716ee5a 100644 --- a/drivers/idle/intel_idle.c +++ b/drivers/idle/intel_idle.c @@ -681,14 +681,19 @@ static int __init intel_idle_init(void) if (intel_idle_cpuidle_devices == NULL) return -ENOMEM; + cpu_maps_update_begin(); + for_each_online_cpu(i) { retval = intel_idle_cpu_init(i); if (retval) { + cpu_maps_update_done(); cpuidle_unregister_driver(&intel_idle_driver); return retval; } } - register_cpu_notifier(&cpu_hotplug_notifier); + __register_cpu_notifier(&cpu_hotplug_notifier); + + cpu_maps_update_done(); return 0; } @@ -698,10 +703,13 @@ static void __exit intel_idle_exit(void) intel_idle_cpuidle_devices_uninit(); cpuidle_unregister_driver(&intel_idle_driver); + cpu_maps_update_begin(); if (lapic_timer_reliable_states != LAPIC_TIMER_ALWAYS_RELIABLE) on_each_cpu(__setup_broadcast_timer, (void *)false, 1); - unregister_cpu_notifier(&cpu_hotplug_notifier); + __unregister_cpu_notifier(&cpu_hotplug_notifier); + + cpu_maps_update_done(); return; } -- 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/