From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e23smtp04.au.ibm.com (e23smtp04.au.ibm.com [202.81.31.146]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 33B202C0543 for ; Tue, 11 Mar 2014 07:36:13 +1100 (EST) Received: from /spool/local by e23smtp04.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 11 Mar 2014 06:36:12 +1000 Received: from d23relay05.au.ibm.com (d23relay05.au.ibm.com [9.190.235.152]) by d23dlp03.au.ibm.com (Postfix) with ESMTP id 5B27C3578055 for ; Tue, 11 Mar 2014 07:36:09 +1100 (EST) Received: from d23av02.au.ibm.com (d23av02.au.ibm.com [9.190.235.138]) by d23relay05.au.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id s2AKG02T6488470 for ; Tue, 11 Mar 2014 07:16:00 +1100 Received: from d23av02.au.ibm.com (localhost [127.0.0.1]) by d23av02.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id s2AKa7cT027705 for ; Tue, 11 Mar 2014 07:36:09 +1100 From: "Srivatsa S. Bhat" Subject: [PATCH v3 12/52] s390, smp: 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 02:05:58 +0530 Message-ID: <20140310203557.10746.48924.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-pm@vger.kernel.org, linux-s390@vger.kernel.org, Heiko Carstens , linux-kernel@vger.kernel.org, Ingo Molnar , linuxppc-dev@ozlabs.org, "Srivatsa S. Bhat" , tj@kernel.org, Thomas Gleixner , paulmck@linux.vnet.ibm.com, Martin Schwidefsky 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 smp code in s390 by using this latter form of callback registration. Cc: Martin Schwidefsky Cc: Heiko Carstens Cc: Thomas Gleixner Cc: Ingo Molnar Cc: linux-s390@vger.kernel.org Signed-off-by: Srivatsa S. Bhat --- arch/s390/kernel/smp.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c index a7125b6..e10be35 100644 --- a/arch/s390/kernel/smp.c +++ b/arch/s390/kernel/smp.c @@ -1057,19 +1057,24 @@ static DEVICE_ATTR(rescan, 0200, NULL, rescan_store); static int __init s390_smp_init(void) { - int cpu, rc; + int cpu, rc = 0; - hotcpu_notifier(smp_cpu_notify, 0); #ifdef CONFIG_HOTPLUG_CPU rc = device_create_file(cpu_subsys.dev_root, &dev_attr_rescan); if (rc) return rc; #endif + cpu_notifier_register_begin(); for_each_present_cpu(cpu) { rc = smp_add_present_cpu(cpu); if (rc) - return rc; + goto out; } - return 0; + + __hotcpu_notifier(smp_cpu_notify, 0); + +out: + cpu_notifier_register_done(); + return rc; } subsys_initcall(s390_smp_init);