driver core: don't always lock parent in shutdown

Don't lock a parent device unless it is needed in device_shutdown. This
is in preparation for making device shutdown asynchronous, when it will
be needed to allow children of a common parent to shut down
simultaneously.

Signed-off-by: Stuart Hayes <[email protected]>
Signed-off-by: David Jeffery <[email protected]>
Reviewed-by: Sagi Grimberg <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Reviewed-by: Keith Busch <[email protected]>
Tested-by: Keith Busch <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: Stuart Hayes

drivers/base/core.c

@@ -4816,7 +4816,7 @@ void device_shutdown(void)
 		spin_unlock(&devices_kset->list_lock);
 
 		/* hold lock to avoid race with probe/release */
-		if (parent)
+		if (parent && dev->bus && dev->bus->need_parent_lock)
 			device_lock(parent);
 		device_lock(dev);
 
@@ -4840,7 +4840,7 @@ void device_shutdown(void)
 		}
 
 		device_unlock(dev);
-		if (parent)
+		if (parent && dev->bus && dev->bus->need_parent_lock)
 			device_unlock(parent);
 
 		put_device(dev);