Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754781AbaBEWMX (ORCPT ); Wed, 5 Feb 2014 17:12:23 -0500 Received: from e28smtp06.in.ibm.com ([122.248.162.6]:50182 "EHLO e28smtp06.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752647AbaBEWMT (ORCPT ); Wed, 5 Feb 2014 17:12:19 -0500 From: "Srivatsa S. Bhat" Subject: [PATCH 13/51] powerpc, sysfs: 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, Benjamin Herrenschmidt , Paul Mackerras , Madhavan Srinivasan , Olof Johansson , Wang Dongsheng , linuxppc-dev@lists.ozlabs.org, "Srivatsa S. Bhat" Date: Thu, 06 Feb 2014 03:36:54 +0530 Message-ID: <20140205220654.19080.11341.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: 14020522-9574-0000-0000-00000BCF36AA 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 sysfs code in powerpc by using this latter form of callback registration. Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Cc: Madhavan Srinivasan Cc: Olof Johansson Cc: Wang Dongsheng Cc: linuxppc-dev@lists.ozlabs.org Signed-off-by: Srivatsa S. Bhat --- arch/powerpc/kernel/sysfs.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c index 97e1dc9..c29ad44 100644 --- a/arch/powerpc/kernel/sysfs.c +++ b/arch/powerpc/kernel/sysfs.c @@ -975,7 +975,8 @@ static int __init topology_init(void) int cpu; register_nodes(); - register_cpu_notifier(&sysfs_cpu_nb); + + cpu_maps_update_begin(); for_each_possible_cpu(cpu) { struct cpu *c = &per_cpu(cpu_devices, cpu); @@ -999,6 +1000,11 @@ static int __init topology_init(void) if (cpu_online(cpu)) register_cpu_online(cpu); } + + __register_cpu_notifier(&sysfs_cpu_nb); + + cpu_maps_update_done(); + #ifdef CONFIG_PPC64 sysfs_create_dscr_default(); #endif /* CONFIG_PPC64 */ -- 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/