thermal: netlink: Improve the initcall ordering

The initcalls like to play joke. In our case, the thermal-netlink
initcall is called after the thermal-core initcall but this one sends
a notification before the former is initialized. No issue was spotted,
but it could lead to a memory corruption, so instead of relying on the
core_initcall for the thermal-netlink, let's initialize directly from
the thermal-core init routine, so we have full control of the init
ordering.

Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Amit Kucheria <amit.kucheria@linaro.org>
Link: https://lore.kernel.org/r/20200717164217.18819-1-daniel.lezcano@linaro.org

drivers/thermal/thermal_core.c

@@ -1640,6 +1640,10 @@ static int __init thermal_init(void)
 {
 	int result;
 
+	result = thermal_netlink_init();
+	if (result)
+		goto error;
+
 	mutex_init(&poweroff_lock);
 	result = thermal_register_governors();
 	if (result)

drivers/thermal/thermal_netlink.c

@@ -641,8 +641,7 @@ static struct genl_family thermal_gnl_family __ro_after_init = {
 	.n_mcgrps	= ARRAY_SIZE(thermal_genl_mcgrps),
 };
 
-static int __init thermal_netlink_init(void)
+int __init thermal_netlink_init(void)
 {
 	return genl_register_family(&thermal_gnl_family);
 }
-core_initcall(thermal_netlink_init);

drivers/thermal/thermal_netlink.h

@@ -6,6 +6,7 @@
 
 /* Netlink notification function */
 #ifdef CONFIG_THERMAL_NETLINK
+int __init thermal_netlink_init(void);
 int thermal_notify_tz_create(int tz_id, const char *name);
 int thermal_notify_tz_delete(int tz_id);
 int thermal_notify_tz_enable(int tz_id);
@@ -23,6 +24,11 @@ int thermal_notify_cdev_delete(int cdev_id);
 int thermal_notify_tz_gov_change(int tz_id, const char *name);
 int thermal_genl_sampling_temp(int id, int temp);
 #else
+static inline int thermal_netlink_init(void)
+{
+	return 0;
+}
+
 static inline int thermal_notify_tz_create(int tz_id, const char *name)
 {
 	return 0;