From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e23smtp02.au.ibm.com (e23smtp02.au.ibm.com [202.81.31.144]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 2C83C2C0AF3 for ; Tue, 11 Mar 2014 07:42:43 +1100 (EST) Received: from /spool/local by e23smtp02.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 11 Mar 2014 06:42:42 +1000 Received: from d23relay03.au.ibm.com (d23relay03.au.ibm.com [9.190.235.21]) by d23dlp03.au.ibm.com (Postfix) with ESMTP id 0EC2E3578057 for ; Tue, 11 Mar 2014 07:42:40 +1100 (EST) Received: from d23av01.au.ibm.com (d23av01.au.ibm.com [9.190.234.96]) by d23relay03.au.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id s2AKgQdR8847718 for ; Tue, 11 Mar 2014 07:42:26 +1100 Received: from d23av01.au.ibm.com (localhost [127.0.0.1]) by d23av01.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id s2AKgchc008543 for ; Tue, 11 Mar 2014 07:42:39 +1100 From: "Srivatsa S. Bhat" Subject: [PATCH v3 49/52] mm, vmstat: 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 02:12:27 +0530 Message-ID: <20140310204226.10746.64059.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, Christoph Lameter , walken@google.com, linux@arm.linux.org.uk, linux-pm@vger.kernel.org, Rik van Riel , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linuxppc-dev@ozlabs.org, Dave Hansen , "Srivatsa S. Bhat" , Johannes Weiner , tj@kernel.org, Toshi Kani , Andrew Morton , paulmck@linux.vnet.ibm.com, Cody P Schafer , 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 vmstat code in the MM subsystem by using this latter form of callback registration. Cc: Andrew Morton Cc: Johannes Weiner Cc: Cody P Schafer Cc: Toshi Kani Cc: Dave Hansen Cc: Ingo Molnar Cc: linux-mm@kvack.org Acked-by: Christoph Lameter Acked-by: Rik van Riel Reviewed-by: Yasuaki Ishimatsu Signed-off-by: Srivatsa S. Bhat --- mm/vmstat.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/mm/vmstat.c b/mm/vmstat.c index def5dd2..58c6f3d 100644 --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -1292,14 +1292,14 @@ static int __init setup_vmstat(void) #ifdef CONFIG_SMP int cpu; - register_cpu_notifier(&vmstat_notifier); + cpu_notifier_register_begin(); + __register_cpu_notifier(&vmstat_notifier); - get_online_cpus(); for_each_online_cpu(cpu) { start_cpu_timer(cpu); node_set_state(cpu_to_node(cpu), N_CPU); } - put_online_cpus(); + cpu_notifier_register_done(); #endif #ifdef CONFIG_PROC_FS proc_create("buddyinfo", S_IRUGO, NULL, &fragmentation_file_operations);