stm class: Fix stm device initialization order

BugLink: https://bugs.launchpad.net/bugs/1826212

[ Upstream commit 389b6699 ]

Currently, stm_register_device() makes the device visible and then
proceeds to initializing spinlocks and other properties, which leaves
a window when the device can already be opened but is not yet fully
operational.

Fix this by reversing the initialization order.
Reported-by: Alan Cox <alan.cox@intel.com>
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Reviewed-by: Laurent Fert <laurent.fert@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

drivers/hwtracing/stm/core.c

@@ -664,18 +664,11 @@ int stm_register_device(struct device *parent, struct stm_data *stm_data,
 	stm->dev.parent = parent;
 	stm->dev.release = stm_device_release;
 
-	err = kobject_set_name(&stm->dev.kobj, "%s", stm_data->name);
-	if (err)
-		goto err_device;
-
-	err = device_add(&stm->dev);
-	if (err)
-		goto err_device;
-
 	mutex_init(&stm->link_mutex);
 	spin_lock_init(&stm->link_lock);
 	INIT_LIST_HEAD(&stm->link_list);
 
+	/* initialize the object before it is accessible via sysfs */
 	spin_lock_init(&stm->mc_lock);
 	mutex_init(&stm->policy_mutex);
 	stm->sw_nmasters = nmasters;
@@ -683,6 +676,14 @@ int stm_register_device(struct device *parent, struct stm_data *stm_data,
 	stm->data = stm_data;
 	stm_data->stm = stm;
 
+	err = kobject_set_name(&stm->dev.kobj, "%s", stm_data->name);
+	if (err)
+		goto err_device;
+
+	err = device_add(&stm->dev);
+	if (err)
+		goto err_device;
+
 	return 0;
 
 err_device: