Please attach a test project that replicates this problem. Also, specify what is in the resource? You can attach the project and the file for the resource here or in a forum PM.
@andreiem I added a random sleep time before all the procedures started. The 1st thread starts. and then 2nd thread .. 3 and 4 5 ... Since they do not do the same operations at the same time, they do not consume much processor.
