From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e28smtp04.in.ibm.com (e28smtp04.in.ibm.com [122.248.162.4]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 2B0242C05D0 for ; Tue, 11 Mar 2014 07:40:03 +1100 (EST) Received: from /spool/local by e28smtp04.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 11 Mar 2014 02:10:02 +0530 Received: from d28relay03.in.ibm.com (d28relay03.in.ibm.com [9.184.220.60]) by d28dlp01.in.ibm.com (Postfix) with ESMTP id 644E2E0057 for ; Tue, 11 Mar 2014 02:13:44 +0530 (IST) Received: from d28av04.in.ibm.com (d28av04.in.ibm.com [9.184.220.66]) by d28relay03.in.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id s2AKduM627656296 for ; Tue, 11 Mar 2014 02:09:56 +0530 Received: from d28av04.in.ibm.com (localhost [127.0.0.1]) by d28av04.in.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id s2AKdwTX012284 for ; Tue, 11 Mar 2014 02:09:59 +0530 From: "Srivatsa S. Bhat" Subject: [PATCH v3 35/52] scsi, fcoe: Fix CPU hotplug callback registration To: paulus@samba.org, oleg@redhat.com, mingo@kernel.org, rjw@rjwysocki.net, rusty@rustcorp.com.au, peterz@infradead.org, tglx@linutronix.de, akpm@linux-foundation.org Date: Tue, 11 Mar 2014 02:09:52 +0530 Message-ID: <20140310203952.10746.35946.stgit@srivatsabhat.in.ibm.com> In-Reply-To: <20140310203312.10746.310.stgit@srivatsabhat.in.ibm.com> References: <20140310203312.10746.310.stgit@srivatsabhat.in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Cc: linux-arch@vger.kernel.org, ego@linux.vnet.ibm.com, walken@google.com, linux@arm.linux.org.uk, linux-scsi@vger.kernel.org, Robert Love , linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, "James E.J. Bottomley" , fcoe-devel@open-fcoe.org, linuxppc-dev@ozlabs.org, "Srivatsa S. Bhat" , tj@kernel.org, paulmck@linux.vnet.ibm.com, Ingo Molnar List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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_notifier_register_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_notifier_register_done(); Fix the fcoe code in scsi by using this latter form of callback registration. Cc: Robert Love Cc: "James E.J. Bottomley" Cc: Ingo Molnar Cc: fcoe-devel@open-fcoe.org Cc: linux-scsi@vger.kernel.org Signed-off-by: Srivatsa S. Bhat --- drivers/scsi/fcoe/fcoe.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/drivers/scsi/fcoe/fcoe.c b/drivers/scsi/fcoe/fcoe.c index f317000..d5e105b 100644 --- a/drivers/scsi/fcoe/fcoe.c +++ b/drivers/scsi/fcoe/fcoe.c @@ -2633,14 +2633,18 @@ static int __init fcoe_init(void) skb_queue_head_init(&p->fcoe_rx_list); } + cpu_notifier_register_begin(); + for_each_online_cpu(cpu) fcoe_percpu_thread_create(cpu); /* Initialize per CPU interrupt thread */ - rc = register_hotcpu_notifier(&fcoe_cpu_notifier); + rc = __register_hotcpu_notifier(&fcoe_cpu_notifier); if (rc) goto out_free; + cpu_notifier_register_done(); + /* Setup link change notification */ fcoe_dev_setup(); @@ -2655,6 +2659,9 @@ out_free: for_each_online_cpu(cpu) { fcoe_percpu_thread_destroy(cpu); } + + cpu_notifier_register_done(); + mutex_unlock(&fcoe_config_mutex); destroy_workqueue(fcoe_wq); return rc; @@ -2687,11 +2694,15 @@ static void __exit fcoe_exit(void) } rtnl_unlock(); - unregister_hotcpu_notifier(&fcoe_cpu_notifier); + cpu_notifier_register_begin(); for_each_online_cpu(cpu) fcoe_percpu_thread_destroy(cpu); + __unregister_hotcpu_notifier(&fcoe_cpu_notifier); + + cpu_notifier_register_done(); + mutex_unlock(&fcoe_config_mutex); /*