cdx: Introduce lock to protect controller ops

Add a mutex lock to prevent race between controller ops initiated by
the bus subsystem and the controller registration/unregistration.

Signed-off-by: Abhijit Gangurde <abhijit.gangurde@amd.com>
Link: https://lore.kernel.org/r/20231017160505.10640-3-abhijit.gangurde@amd.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: abhijitG-xlnx

drivers/cdx/cdx.c

@@ -72,6 +72,8 @@
 
 /* IDA for CDX controllers registered with the CDX bus */
 static DEFINE_IDA(cdx_controller_ida);
+/* Lock to protect controller ops */
+static DEFINE_MUTEX(cdx_controller_lock);
 
 static char *compat_node_name = "xlnx,versal-net-cdx";
 
@@ -396,6 +398,8 @@ static ssize_t rescan_store(const struct bus_type *bus,
 	if (!val)
 		return -EINVAL;
 
+	mutex_lock(&cdx_controller_lock);
+
 	/* Unregister all the devices on the bus */
 	cdx_unregister_devices(&cdx_bus_type);
 
@@ -415,6 +419,8 @@ static ssize_t rescan_store(const struct bus_type *bus,
 		put_device(&pd->dev);
 	}
 
+	mutex_unlock(&cdx_controller_lock);
+
 	return count;
 }
 static BUS_ATTR_WO(rescan);
@@ -538,12 +544,14 @@ int cdx_register_controller(struct cdx_controller *cdx)
 		return ret;
 	}
 
+	mutex_lock(&cdx_controller_lock);
 	cdx->id = ret;
 
 	/* Scan all the devices */
 	if (cdx->ops->scan)
 		cdx->ops->scan(cdx);
 	cdx->controller_registered = true;
+	mutex_unlock(&cdx_controller_lock);
 
 	return 0;
 }
@@ -554,9 +562,13 @@ void cdx_unregister_controller(struct cdx_controller *cdx)
 	if (cdx->id >= MAX_CDX_CONTROLLERS)
 		return;
 
+	mutex_lock(&cdx_controller_lock);
+
 	cdx->controller_registered = false;
 	device_for_each_child(cdx->dev, NULL, cdx_unregister_device);
 	ida_free(&cdx_controller_ida, cdx->id);
+
+	mutex_unlock(&cdx_controller_lock);
 }
 EXPORT_SYMBOL_GPL(cdx_unregister_controller);