diff -r 197c0b40423a tools/hotplug/Linux/locking.sh
--- a/tools/hotplug/Linux/locking.sh	Tue Dec 14 19:28:25 2010 +0000
+++ b/tools/hotplug/Linux/locking.sh	Wed Dec 15 11:56:04 2010 +0900
@@ -63,7 +63,7 @@ _claim_lock()
       retries=0
     else
       local pid=$(echo $owner | cut -d : -f 1)
-      if [ ! -f "/proc/$pid/status" ]
+      if [ -n "$pid" -a "$pid" != "unknown" -a ! -f "/proc/$pid/status" ]
       then
         _release_lock $lockdir
       fi