add comments

Author: Apache9

hbase-procedure/src/main/java/org/apache/hadoop/hbase/procedure2/ProcedureExecutor.java

@@ -1466,6 +1466,8 @@ private void releaseLock(Procedure<TEnvironment> proc, boolean force) {
     }
   }
 
+  // Returning null means we have already held the execution lock, so you do not need to get the
+  // lock entry for releasing
   private IdLock.Entry getLockEntryForRollback(long procId) {
     // Hold the execution lock if it is not held by us. The IdLock is not reentrant so we need
     // this check, as the worker will hold the lock before executing a procedure. This is the only