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" <rjw@xxxxxxxxxxxxx> > Cc: Viresh Kumar <viresh.kumar@xxxxxxxxxx> > Cc: cpufreq@xxxxxxxxxxxxxxx > Cc: linux-pm@xxxxxxxxxxxxxxx > Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@xxxxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxx > 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 cpufreq" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
