diff --git a/CHANGES.txt b/CHANGES.txt
index c92c2cf8b..45b226567 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -1,5 +1,6 @@
 Current
 
+Fixed: GITHUB-727 : Fixing data races (Krishnan Mahadevan)
 Fixed: GITHUB-2913: Maps containing nulls can be incorrectly considered equal (Alex Heneveld)
 
 7.8.0
diff --git a/testng-collections/src/main/java/org/testng/collections/Sets.java b/testng-collections/src/main/java/org/testng/collections/Sets.java
index af616522e..c375623b1 100644
--- a/testng-collections/src/main/java/org/testng/collections/Sets.java
+++ b/testng-collections/src/main/java/org/testng/collections/Sets.java
@@ -5,6 +5,7 @@
 import java.util.HashSet;
 import java.util.LinkedHashSet;
 import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
 
 public final class Sets {
 
@@ -14,6 +15,10 @@ public static <V> Set<V> newHashSet() {
     return new HashSet<>();
   }
 
+  public static <V> Set<V> newConcurrentHashSet() {
+    return ConcurrentHashMap.newKeySet();
+  }
+
   public static <V> Set<V> newHashSet(Collection<V> c) {
     return new HashSet<>(c);
   }
diff --git a/testng-core/src/main/java/org/testng/internal/ExitCodeListener.java b/testng-core/src/main/java/org/testng/internal/ExitCodeListener.java
index 440525613..adbc9d581 100644
--- a/testng-core/src/main/java/org/testng/internal/ExitCodeListener.java
+++ b/testng-core/src/main/java/org/testng/internal/ExitCodeListener.java
@@ -12,7 +12,7 @@
 import org.testng.xml.XmlSuite;
 
 public class ExitCodeListener implements ITestListener, IReporter, IExecutionListener {
-  private boolean hasTests = false;
+  private volatile boolean hasTests = false;
   private final ExitCode status = new ExitCode();
   private boolean failIfAllTestsSkipped = false;
 
@@ -64,12 +64,6 @@ public void onTestFailedButWithinSuccessPercentage(ITestResult result) {
     this.hasTests = true;
   }
 
-  @Override
-  public void onStart(ITestContext context) {}
-
-  @Override
-  public void onFinish(ITestContext context) {}
-
   @Override
   public void onExecutionFinish() {
     if (failIfAllTestsSkipped && (getStatus().getExitCode() == ExitCode.SKIPPED)) {
diff --git a/testng-core/src/main/java/org/testng/internal/invokers/TestMethodWorker.java b/testng-core/src/main/java/org/testng/internal/invokers/TestMethodWorker.java
index 77f6db75d..a192f309c 100644
--- a/testng-core/src/main/java/org/testng/internal/invokers/TestMethodWorker.java
+++ b/testng-core/src/main/java/org/testng/internal/invokers/TestMethodWorker.java
@@ -161,7 +161,7 @@ protected void invokeBeforeClassMethods(ITestClass testClass, IMethodInstance mi
     Map<ITestClass, Set<Object>> invokedBeforeClassMethods =
         m_classMethodMap.getInvokedBeforeClassMethods();
     Set<Object> instances =
-        invokedBeforeClassMethods.computeIfAbsent(testClass, key -> Sets.newHashSet());
+        invokedBeforeClassMethods.computeIfAbsent(testClass, key -> Sets.newConcurrentHashSet());
     Object instance = mi.getInstance();
     if (!instances.contains(instance)) {
       instances.add(instance);