Retrieve locking block-chain

/*
--************************************************************************************
-- Description:    This script list the current locking block chain.
--            It will create 1 function: fn_GetLockChainSubTree
--                     1 table: LockChain
--
--
-- Parameters: NONE
--
-- Returns: Locking block chain
--
-- Created:     9/07/2008    John Liu
--
-- Typical Usage:    This script is typically used to find the block chain information
--
-- Comments: It also lists the dead lock (if any) at the end.
--      This script is for SQL 2005 and SQL 2008
--
--
-- Modifications:
--
-- Initials Date Description
-- -------- ---------- -----------------------------------------------------------
-- 
--************************************************************************************
*/
--***************************************Begin of create functions ********************************
--***************************************** Begin of dbo.fn_GetLockChainSubTree ************************
IF OBJECT_ID('dbo.fn_GetLockChainSubTree') IS NOT NULL DROP FUNCTION dbo.fn_GetLockChainSubTree
go

CREATE FUNCTION dbo.fn_GetLockChainSubTree(@Blocker AS INT) 
RETURNS @TREE TABLE
(
 Blocker INT NOT NULL,
 Blocked INT NOT NULL,
 lvl INT NOT NULL
)
AS
BEGIN
WITH Block_Subtree(Blocker,Blocked, lvl)
AS
( 
-- Anchor Member (AM)
SELECT 
Blocker
,Blocked
,0
FROM 
LockChain
WHERE 
Blocker = @Blocker

UNION all

-- Recursive Member (RM)
SELECT 
l.Blocker
, l.Blocked
, t.lvl+1
FROM 
LockChain AS l
INNER JOIN 
Block_Subtree AS t
ON
l.Blocker = t.Blocked
)

INSERT INTO 
@TREE
SELECT 
* 
FROM 
Block_Subtree

RETURN
END
GO
--***************************************** End of dbo.fn_GetLockChainSubTree ************************
--***************************************End of create functions ********************************

--*************************************************************************************
--**********************************         Main section         **************************
--*************************************************************************************
-- -----------------------------------------------
-- Core processing
-- -----------------------------------------------
IF OBJECT_ID('LockChain') IS NOT NULL DROP TABLE LockChain
go

--initial the LockChain table
SELECT
Blocker = Blocking_Session_ID
,Blocked = Session_ID
INTO
LockChain
FROM
sys.dm_exec_requests
WHERE
Blocking_Session_ID <> 0

--list the locking chain
SELECT
t.*,s.host_name,s.program_name,s.login_name,s.nt_user_name
FROM
LockChain l
CROSS APPLY
fn_GetLockChainSubTree(l.Blocker) as t
INNER JOIN
sys.dm_exec_sessions s
ON
l.blocker = s.session_id
WHERE
l.blocker NOT IN (
SELECT
blocked
FROM
LockChain
)

--report any dead lock
SELECT 
'Dead Lock' = 'Dead Lock'
,*
FROM 
LockChain
WHERE
blocker IN (
SELECT DISTINCT
blocked
FROM
LockChain
)
AND
blocked IN (
SELECT DISTINCT
blocker
FROM
LockChain
)

--clean up    
--DROP TABLE LockChain
--DROP FUNCTION dbo.fn_GetLockChainSubTree

-- -----------------------------------------------
-- End of Core processing
-- -----------------------------------------------
--***************************************** End of Main section **********************************