SELECT
sqltext.text,
req.session_id,
req.status,
req.start_time,
req.command,
req.cpu_time,
req.total_elapsed_time
FROM
sys.dm_exec_requests req
CROSS APPLY sys.dm_exec_sql_text(sql_handle) AS sqltext
--While running above query if you find any query which is running for long time it can be killed using following command.
KILL [session_id]