KATO Takenori 747e915757 Avoid `lock against myself' panic by following operation:
# mount -t union (or null) dir1 dir2
	# mount -t union (or null) dir2 dir1

The function namei in union_mount calls union_root.  The upper vnode
has been already locked and vn_lock in union_root causes above panic.

Add printf's included in `#ifdef DIAGNOSTIC' for EDEADLK cases.
1997-04-19 06:04:13 +00:00
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