Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755491AbaBEWO2 (ORCPT ); Wed, 5 Feb 2014 17:14:28 -0500 Received: from e23smtp08.au.ibm.com ([202.81.31.141]:39281 "EHLO e23smtp08.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752261AbaBEWOY (ORCPT ); Wed, 5 Feb 2014 17:14:24 -0500 From: "Srivatsa S. Bhat" Subject: [PATCH 24/51] x86, hpet: 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, Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, "Srivatsa S. Bhat" Date: Thu, 06 Feb 2014 03:39:00 +0530 Message-ID: <20140205220859.19080.7550.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: 14020522-5140-0000-0000-000004839F20 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 hpet code in x86 by using this latter form of callback registration. Cc: Thomas Gleixner Cc: Ingo Molnar Cc: "H. Peter Anvin" Cc: x86@kernel.org Signed-off-by: Srivatsa S. Bhat --- arch/x86/kernel/hpet.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c index da85a8e..199aaae 100644 --- a/arch/x86/kernel/hpet.c +++ b/arch/x86/kernel/hpet.c @@ -943,12 +943,14 @@ static __init int hpet_late_init(void) if (boot_cpu_has(X86_FEATURE_ARAT)) return 0; + cpu_maps_update_begin(); for_each_online_cpu(cpu) { hpet_cpuhp_notify(NULL, CPU_ONLINE, (void *)(long)cpu); } /* This notifier should be called after workqueue is ready */ - hotcpu_notifier(hpet_cpuhp_notify, -20); + __hotcpu_notifier(hpet_cpuhp_notify, -20); + cpu_maps_update_done(); return 0; } -- 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/