From: Philipp Hahn <hahn@univention.de>
Date: Wed, 16 Sep 2015 08:55:26 +0200
Subject: Bug #20481: Fix race during device hotplug

Sometimes qemu/the kernel takes too long for the first domain to start. The
hotplug script then finds the device still in state 1=Initialising and aborts.
Add an artifical delay of 1 seconds and try again.
---
 tools/hotplug/Linux/block | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/tools/hotplug/Linux/block b/tools/hotplug/Linux/block
index 06de5c9..f0f2601 100644
--- a/tools/hotplug/Linux/block
+++ b/tools/hotplug/Linux/block
@@ -255,12 +255,16 @@ case "$command" in
 
         # Avoid a race with the remove if the path has been deleted, or
 	# otherwise changed from "InitWait" state e.g. due to a timeout
-        xenbus_state=$(xenstore_read_default "$XENBUS_PATH/state" 'unknown')
-        if [ "$xenbus_state" != '2' ]
-        then
+        while true
+        do
+          xenbus_state=$(xenstore_read_default "$XENBUS_PATH/state" 'unknown')
+          case "$xenbus_state" in
+          1) log notice "Path still initializing: $XENBUS_PATH" ; sleep 1 ; continue ;;
+          2) break ;;
+          esac
           release_lock "block"
           fatal "Path closed or removed during hotplug add: $XENBUS_PATH state: $xenbus_state"
-        fi
+        done
 
         if [ "$mode" = 'w' ] && ! stat "$file" -c %A | grep -q w
         then