drivers: base: Free devm resources when unregistering a device

In the current code, devres_release_all() only gets called if the device
has a bus and has been probed.

This leads to issues when using bus-less or driver-less devices where
the device might never get freed if a managed resource holds a reference
to the device. This is happening in the DRM framework for example.

We should thus call devres_release_all() in the device_del() function to
make sure that the device-managed actions are properly executed when the
device is unregistered, even if it has neither a bus nor a driver.

This is effectively the same change than commit 2f8d16a ("devres:
release resources on device_del()") that got reverted by commit
a525a3d ("driver core: free devres in device_release") over
memory leaks concerns.

This patch effectively combines the two commits mentioned above to
release the resources both on device_del() and device_release() and get
the best of both worlds.

Fixes: a525a3d ("driver core: free devres in device_release")
Signed-off-by: David Gow <davidgow@google.com>
Signed-off-by: Maxime Ripard <mripard@kernel.org>
Link: https://lore.kernel.org/r/20230720-kunit-devm-inconsistencies-test-v3-3-6aa7e074f373@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: sulix

drivers/base/core.c

@@ -3817,6 +3817,17 @@ void device_del(struct device *dev)
 	device_platform_notify_remove(dev);
 	device_links_purge(dev);
 
+	/*
+	 * If a device does not have a driver attached, we need to clean
+	 * up any managed resources. We do this in device_release(), but
+	 * it's never called (and we leak the device) if a managed
+	 * resource holds a reference to the device. So release all
+	 * managed resources here, like we do in driver_detach(). We
+	 * still need to do so again in device_release() in case someone
+	 * adds a new resource after this point, though.
+	 */
+	devres_release_all(dev);
+
 	bus_notify(dev, BUS_NOTIFY_REMOVED_DEVICE);
 	kobject_uevent(&dev->kobj, KOBJ_REMOVE);
 	glue_dir = get_glue_dir(dev);

drivers/base/test/platform-device-test.c

@@ -87,8 +87,6 @@ static void platform_device_devm_register_get_unregister_with_devm_test(struct k
 	struct test_priv *priv = test->priv;
 	int ret;
 
-	kunit_skip(test, "This needs to be fixed in the core.");
-
 	pdev = platform_device_alloc(DEVICE_NAME, PLATFORM_DEVID_NONE);
 	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, pdev);
 

drivers/base/test/root-device-test.c

@@ -78,8 +78,6 @@ static void root_device_devm_register_get_unregister_with_devm_test(struct kunit
 	struct test_priv *priv = test->priv;
 	int ret;
 
-	kunit_skip(test, "This needs to be fixed in the core.");
-
 	priv->dev = root_device_register(DEVICE_NAME);
 	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, priv->dev);