Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755977AbaBEWQa (ORCPT ); Wed, 5 Feb 2014 17:16:30 -0500 Received: from e23smtp05.au.ibm.com ([202.81.31.147]:50605 "EHLO e23smtp05.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753356AbaBEWQ0 (ORCPT ); Wed, 5 Feb 2014 17:16:26 -0500 From: "Srivatsa S. Bhat" Subject: [PATCH 36/51] drivers/base/topology.c: 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, Greg Kroah-Hartman , "Srivatsa S. Bhat" Date: Thu, 06 Feb 2014 03:41:02 +0530 Message-ID: <20140205221101.19080.43968.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: 14020522-1396-0000-0000-0000043F172E 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 topology code by using this latter form of callback registration. Cc: Greg Kroah-Hartman Signed-off-by: Srivatsa S. Bhat --- drivers/base/topology.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/drivers/base/topology.c b/drivers/base/topology.c index 94ffee3..9db29cc 100644 --- a/drivers/base/topology.c +++ b/drivers/base/topology.c @@ -161,16 +161,20 @@ static int topology_cpu_callback(struct notifier_block *nfb, static int topology_sysfs_init(void) { int cpu; - int rc; + int rc = 0; + + cpu_maps_update_begin(); for_each_online_cpu(cpu) { rc = topology_add_dev(cpu); if (rc) - return rc; + goto out; } - hotcpu_notifier(topology_cpu_callback, 0); + __hotcpu_notifier(topology_cpu_callback, 0); - return 0; +out: + cpu_maps_update_done(); + return rc; } device_initcall(topology_sysfs_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/