[PATCH v2] thermal: use a custom lock class for intel x86_pkg_temp

[Benjamin Berg <benjamin@sipsolutions.net>]

From: Benjamin Berg <benjamin.berg@intel.com>

The intel driver has code paths that will take the tz->lock while the
cpuhp_state-up lock is held. As the cpuhp_state-up lock is used in other
code paths, it may happen that lockdep detects possible deadlocks
through unrelated thermal zone devices.

Fix these false positives by using a separate lockdep class for the
x86_pkg_temp thermal device.

Reported-by: Hans de Goede <hansg@kernel.org>
Closes: https://lore.kernel.org/linux-pm/e9d7ef79-6a24-4515-aa35-d1f2357da798@kernel.org/
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>

---

Hi,

I believe that this should solve the lockdep warning that Hans was
seeing. That said, I have not tested it much.

v2:
- Fix function name
- Mark lock class variable static

Benjamin
---
 drivers/thermal/intel/x86_pkg_temp_thermal.c | 2 ++
 drivers/thermal/thermal_core.c               | 7 +++++++
 include/linux/thermal.h                      | 8 ++++++++
 3 files changed, 17 insertions(+)

diff --git a/drivers/thermal/intel/x86_pkg_temp_thermal.c b/drivers/thermal/intel/x86_pkg_temp_thermal.c
index 3fc679b6f11b..15d3c904eaa3 100644
--- a/drivers/thermal/intel/x86_pkg_temp_thermal.c
+++ b/drivers/thermal/intel/x86_pkg_temp_thermal.c
@@ -310,6 +310,7 @@ static int pkg_temp_thermal_trips_init(int cpu, int tj_max,
 
 static int pkg_temp_thermal_device_add(unsigned int cpu)
 {
+	static struct lock_class_key x86_pkg_temp_class;
 	struct thermal_trip trips[MAX_NUMBER_OF_TRIPS] = { 0 };
 	int id = topology_logical_die_id(cpu);
 	u32 eax, ebx, ecx, edx;
@@ -349,6 +350,7 @@ static int pkg_temp_thermal_device_add(unsigned int cpu)
 		err = PTR_ERR(zonedev->tzone);
 		goto out_kfree_zonedev;
 	}
+	thermal_zone_device_set_lock_class(zonedev->tzone, &x86_pkg_temp_class);
 	err = thermal_zone_device_enable(zonedev->tzone);
 	if (err)
 		goto out_unregister_tz;
diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
index 17ca5c082643..ff5c2e01904a 100644
--- a/drivers/thermal/thermal_core.c
+++ b/drivers/thermal/thermal_core.c
@@ -1657,6 +1657,13 @@ struct thermal_zone_device *thermal_tripless_zone_device_register(
 }
 EXPORT_SYMBOL_GPL(thermal_tripless_zone_device_register);
 
+void thermal_zone_device_set_lock_class(struct thermal_zone_device *tz,
+					struct lock_class_key *lock_class)
+{
+	lockdep_set_class_and_name(&tz->lock, lock_class, tz->type);
+}
+EXPORT_SYMBOL_GPL(thermal_zone_device_set_lock_class);
+
 void *thermal_zone_device_priv(struct thermal_zone_device *tzd)
 {
 	return tzd->devdata;
diff --git a/include/linux/thermal.h b/include/linux/thermal.h
index 0b5ed6821080..3cb4cf60b66d 100644
--- a/include/linux/thermal.h
+++ b/include/linux/thermal.h
@@ -240,6 +240,9 @@ struct thermal_zone_device *thermal_tripless_zone_device_register(
 					const struct thermal_zone_device_ops *ops,
 					const struct thermal_zone_params *tzp);
 
+void thermal_zone_device_set_lock_class(struct thermal_zone_device *tz,
+					struct lock_class_key *lock_class);
+
 void thermal_zone_device_unregister(struct thermal_zone_device *tz);
 
 void *thermal_zone_device_priv(struct thermal_zone_device *tzd);
@@ -290,6 +293,11 @@ static inline struct thermal_zone_device *thermal_tripless_zone_device_register(
 					const struct thermal_zone_params *tzp)
 { return ERR_PTR(-ENODEV); }
 
+static inline void
+thermal_zone_device_set_lock_class(struct thermal_zone_device *tz,
+				   struct lock_class_key *lock_class)
+{ }
+
 static inline void thermal_zone_device_unregister(struct thermal_zone_device *tz)
 { }
 
-- 
2.50.0