On Wed, 28 Jan 2015, lizf@xxxxxxxxxx wrote: > From: Jiri Kosina <jkosina@xxxxxxx> > > 3.4.105-rc1 review patch. If anyone has any objections, please let me know. Please don't forget to include followup deadlock fix as well: https://lkml.org/lkml/2015/1/20/983 > > ------------------ > > > commit 6726655dfdd2dc60c035c690d9f10cb69d7ea075 upstream. > > There is a following AB-BA dependency between cpu_hotplug.lock and > cpuidle_lock: > > 1) cpu_hotplug.lock -> cpuidle_lock > enable_nonboot_cpus() > _cpu_up() > cpu_hotplug_begin() > LOCK(cpu_hotplug.lock) > cpu_notify() > ... > acpi_processor_hotplug() > cpuidle_pause_and_lock() > LOCK(cpuidle_lock) > > 2) cpuidle_lock -> cpu_hotplug.lock > acpi_os_execute_deferred() workqueue > ... > acpi_processor_cst_has_changed() > cpuidle_pause_and_lock() > LOCK(cpuidle_lock) > get_online_cpus() > LOCK(cpu_hotplug.lock) > > Fix this by reversing the order acpi_processor_cst_has_changed() does > thigs -- let it first execute the protection against CPU hotplug by > calling get_online_cpus() and obtain the cpuidle lock only after that (and > perform the symmentric change when allowing CPUs hotplug again and > dropping cpuidle lock). > > Spotted by lockdep. > > Signed-off-by: Jiri Kosina <jkosina@xxxxxxx> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> > Signed-off-by: Zefan Li <lizefan@xxxxxxxxxx> > --- > drivers/acpi/processor_idle.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c > index 6cba428..e1180ce 100644 > --- a/drivers/acpi/processor_idle.c > +++ b/drivers/acpi/processor_idle.c > @@ -1195,9 +1195,9 @@ int acpi_processor_cst_has_changed(struct acpi_processor *pr) > > if (pr->id == 0 && cpuidle_get_driver() == &acpi_idle_driver) { > > - cpuidle_pause_and_lock(); > /* Protect against cpu-hotplug */ > get_online_cpus(); > + cpuidle_pause_and_lock(); > > /* Disable all cpuidle devices */ > for_each_online_cpu(cpu) { > @@ -1222,8 +1222,8 @@ int acpi_processor_cst_has_changed(struct acpi_processor *pr) > cpuidle_enable_device(&_pr->power.dev); > } > } > - put_online_cpus(); > cpuidle_resume_and_unlock(); > + put_online_cpus(); > } > > return 0; > -- > 1.9.1 > -- Jiri Kosina SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html