On 02/06/2014 06:13 PM, Rafael J. Wysocki wrote: > 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? > Thank you! Same here, every patch depends only on the first patch in the series. (Except the raid5 and the xen/balloon patches which don't have any dependency). But I'll be posting a v2 of this patchset soon with a rename of the API.. Regards, Srivatsa S. Bhat >> --- >> >> 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 > -- Regards, Srivatsa S. Bhat -- 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
