fix thread safety (#1403)

Co-authored-by: raffaelladevita <devita@ge.infn.it>

Author: baltzell

common-tools/clas-utils/src/main/java/org/jlab/utils/benchmark/Benchmark.java

@@ -39,36 +39,34 @@ public void reset(){
             bt.reset(); 
     }
 
-    public void addTimer(String name){
+    public synchronized void addTimer(String name){
         if (!timerStore.containsKey(name))
             timerStore.put(name, new BenchmarkMultiTimer(name));
-        else
-            System.err.println("[Benchmark] -----> error. timer with name ("+ name + ") already exists");
     }
 
     public void pause(String name){
         if (!timerStore.containsKey(name))
-            timerStore.put(name, new BenchmarkMultiTimer(name));
+            addTimer(name);
         else
             timerStore.get(name).pause();
     }
 
     public void resume(String name){
         if (!timerStore.containsKey(name))
-            timerStore.put(name, new BenchmarkMultiTimer(name));
+            addTimer(name);
         timerStore.get(name).resume();
     }
 
     public void pause(int thread, String name){
         if (!timerStore.containsKey(name))
-            timerStore.put(name, new BenchmarkMultiTimer(name));
+            addTimer(name);
         else
             timerStore.get(name).pause(thread);
     }
 
     public void resume(int thread, String name){
         if (!timerStore.containsKey(name))
-            timerStore.put(name, new BenchmarkMultiTimer(name));
+            addTimer(name);
         timerStore.get(name).resume(thread);
     }