Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755854AbaBEWPw (ORCPT ); Wed, 5 Feb 2014 17:15:52 -0500 Received: from e28smtp04.in.ibm.com ([122.248.162.4]:51321 "EHLO e28smtp04.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755756AbaBEWPr (ORCPT ); Wed, 5 Feb 2014 17:15:47 -0500 From: "Srivatsa S. Bhat" Subject: [PATCH 32/51] scsi, bnx2fc: 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, Eddie Wai , "James E.J. Bottomley" , linux-scsi@vger.kernel.org, "Srivatsa S. Bhat" Date: Thu, 06 Feb 2014 03:40:25 +0530 Message-ID: <20140205221024.19080.30665.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: 14020522-5564-0000-0000-00000BE032E8 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 bnx2fc code in scsi by using this latter form of callback registration. Cc: Eddie Wai Cc: "James E.J. Bottomley" Cc: linux-scsi@vger.kernel.org Signed-off-by: Srivatsa S. Bhat --- drivers/scsi/bnx2fc/bnx2fc_fcoe.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/drivers/scsi/bnx2fc/bnx2fc_fcoe.c b/drivers/scsi/bnx2fc/bnx2fc_fcoe.c index 9b94850..f6c10c5 100644 --- a/drivers/scsi/bnx2fc/bnx2fc_fcoe.c +++ b/drivers/scsi/bnx2fc/bnx2fc_fcoe.c @@ -2586,12 +2586,16 @@ static int __init bnx2fc_mod_init(void) spin_lock_init(&p->fp_work_lock); } + cpu_maps_update_begin(); + for_each_online_cpu(cpu) { bnx2fc_percpu_thread_create(cpu); } /* Initialize per CPU interrupt thread */ - register_hotcpu_notifier(&bnx2fc_cpu_notifier); + __register_hotcpu_notifier(&bnx2fc_cpu_notifier); + + cpu_maps_update_done(); cnic_register_driver(CNIC_ULP_FCOE, &bnx2fc_cnic_cb); @@ -2656,13 +2660,17 @@ static void __exit bnx2fc_mod_exit(void) if (l2_thread) kthread_stop(l2_thread); - unregister_hotcpu_notifier(&bnx2fc_cpu_notifier); + cpu_maps_update_begin(); /* Destroy per cpu threads */ for_each_online_cpu(cpu) { bnx2fc_percpu_thread_destroy(cpu); } + __unregister_hotcpu_notifier(&bnx2fc_cpu_notifier); + + cpu_maps_update_done(); + destroy_workqueue(bnx2fc_wq); /* * detach from scsi transport -- 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/