Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756202AbaBEWTP (ORCPT ); Wed, 5 Feb 2014 17:19:15 -0500 Received: from e28smtp04.in.ibm.com ([122.248.162.4]:45248 "EHLO e28smtp04.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755307AbaBEWTI (ORCPT ); Wed, 5 Feb 2014 17:19:08 -0500 From: "Srivatsa S. Bhat" Subject: [PATCH 50/51] net/core/flow.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, "David S. Miller" , Li RongQing , Sasha Levin , Andrew Morton , Chris Metcalf , netdev@vger.kernel.org, "Srivatsa S. Bhat" Date: Thu, 06 Feb 2014 03:43:46 +0530 Message-ID: <20140205221345.19080.20784.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: 14020522-5564-0000-0000-00000BE034B2 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 code in net/core/flow.c by using this latter form of callback registration. Cc: "David S. Miller" Cc: Li RongQing Cc: Sasha Levin Cc: Andrew Morton Cc: Chris Metcalf Cc: netdev@vger.kernel.org Signed-off-by: Srivatsa S. Bhat --- net/core/flow.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/net/core/flow.c b/net/core/flow.c index dfa602c..0f2c995 100644 --- a/net/core/flow.c +++ b/net/core/flow.c @@ -456,6 +456,8 @@ static int __init flow_cache_init(struct flow_cache *fc) if (!fc->percpu) return -ENOMEM; + cpu_maps_update_begin(); + for_each_online_cpu(i) { if (flow_cache_cpu_prepare(fc, i)) goto err; @@ -463,7 +465,9 @@ static int __init flow_cache_init(struct flow_cache *fc) fc->hotcpu_notifier = (struct notifier_block){ .notifier_call = flow_cache_cpu, }; - register_hotcpu_notifier(&fc->hotcpu_notifier); + __register_hotcpu_notifier(&fc->hotcpu_notifier); + + cpu_maps_update_done(); setup_timer(&fc->rnd_timer, flow_cache_new_hashrnd, (unsigned long) fc); @@ -479,6 +483,8 @@ err: fcp->hash_table = NULL; } + cpu_maps_update_done(); + free_percpu(fc->percpu); fc->percpu = NULL; -- 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/