block in multi thread application

I have application that open about a 1000 thread at same time, but I have mechanism to cancel  all threads with cancellation token. when the application cancel, all log4net threads as appear in a attached picture, blocked and waiting for Sql query on log error method.

in this function :

System.Data.dll!System.Data.SqlClient.SqlCommand.ExecuteNonQuery(see pic for more info)

I want to know if you have any idea about this?