Any SQL gurus out there?

[#1]

I was wondering if there was anyway you can determine if a given procedure is running on a SQL Server Instance? (In this case SQL Server 2014 Enterprise Edition)
For example I have Procedure XXX that can take anything up to N minutes to complete. However when this procedure is running I do not want any other users to be able to execute it. I know I could set a flag in a table to say that this procedure is running, but this approach falls down in the event of a system failure.
In an ideal world it would be a real time way of knowing if the procedure was running. Maybe this can be done using the system catalogues I don't know, which is why I am asking those that might.

[#2]

Does this help? http://stackoverflow.com/questions/21582244/find-out-if-the-stored-procedure-is-already-running

[#3]

It certainly does and a lot more elegant than other options I found, thank you for that, very much appreciated.