Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756538AbaBFM3a (ORCPT ); Thu, 6 Feb 2014 07:29:30 -0500 Received: from v094114.home.net.pl ([79.96.170.134]:62650 "HELO v094114.home.net.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1756238AbaBFM32 (ORCPT ); Thu, 6 Feb 2014 07:29:28 -0500 From: "Rafael J. Wysocki" To: "Srivatsa S. Bhat" Cc: paulus@samba.org, oleg@redhat.com, rusty@rustcorp.com.au, peterz@infradead.org, tglx@linutronix.de, akpm@linux-foundation.org, 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, Viresh Kumar , cpufreq@vger.kernel.org, linux-pm@vger.kernel.org Subject: Re: [PATCH 35/51] acpi-cpufreq: Fix CPU hotplug callback registration Date: Thu, 06 Feb 2014 13:43:59 +0100 Message-ID: <6272120.pzpJuaTe2d@vostro.rjw.lan> User-Agent: KMail/4.11.4 (Linux/3.13.0+; KDE/4.11.4; x86_64; ; ) In-Reply-To: <20140205221052.19080.77507.stgit@srivatsabhat.in.ibm.com> References: <20140205220251.19080.92336.stgit@srivatsabhat.in.ibm.com> <20140205221052.19080.77507.stgit@srivatsabhat.in.ibm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="utf-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thursday, February 06, 2014 03:40:53 AM Srivatsa S. Bhat wrote: > 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 acpi-cpufreq code by using this latter form of callback registration. > > Cc: "Rafael J. Wysocki" > Cc: Viresh Kumar > Cc: cpufreq@vger.kernel.org > Cc: linux-pm@vger.kernel.org > Signed-off-by: Srivatsa S. Bhat Looks OK to me. How does it depend on the rest of your series? > --- > > drivers/cpufreq/acpi-cpufreq.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c > index 18448a7..e2eb471 100644 > --- a/drivers/cpufreq/acpi-cpufreq.c > +++ b/drivers/cpufreq/acpi-cpufreq.c > @@ -907,15 +907,16 @@ static void __init acpi_cpufreq_boost_init(void) > > acpi_cpufreq_driver.boost_supported = true; > acpi_cpufreq_driver.boost_enabled = boost_state(0); > - get_online_cpus(); > + > + cpu_maps_update_begin(); > > /* Force all MSRs to the same value */ > boost_set_msrs(acpi_cpufreq_driver.boost_enabled, > cpu_online_mask); > > - register_cpu_notifier(&boost_nb); > + __register_cpu_notifier(&boost_nb); > > - put_online_cpus(); > + cpu_maps_update_done(); > } > } > > > -- > To unsubscribe from this list: send the line "unsubscribe cpufreq" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- 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/