x86/umwait: move to use bus_get_dev_root()

JIRA: https://issues.redhat.com/browse/RHEL-1023

commit 6026027
Author: Greg Kroah-Hartman <[email protected]>
Date:   Mon Mar 13 19:28:52 2023 +0100

Direct access to the struct bus_type dev_root pointer is going away soon
so replace that with a call to bus_get_dev_root() instead, which is what
it is there for.

Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: [email protected]
Cc: "H. Peter Anvin" <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Signed-off-by: Mark Langsdorf <[email protected]>

Author: mlangsdorf

arch/x86/kernel/cpu/umwait.c

@@ -232,7 +232,11 @@ static int __init umwait_init(void)
 	 * Add umwait control interface. Ignore failure, so at least the
 	 * default values are set up in case the machine manages to boot.
 	 */
-	dev = cpu_subsys.dev_root;
-	return sysfs_create_group(&dev->kobj, &umwait_attr_group);
+	dev = bus_get_dev_root(&cpu_subsys);
+	if (dev) {
+		ret = sysfs_create_group(&dev->kobj, &umwait_attr_group);
+		put_device(dev);
+	}
+	return ret;
 }
 device_initcall(umwait_init);