Merge pull request #1035 from mariofusco/q41314b

Replace synchronized block with ReentrantLock in LazyFaultTolerance

implementation/core/src/main/java/io/smallrye/faulttolerance/core/apiimpl/LazyFaultTolerance.java

@@ -1,6 +1,7 @@
 package io.smallrye.faulttolerance.core.apiimpl;
 
 import java.util.concurrent.Callable;
+import java.util.concurrent.locks.ReentrantLock;
 import java.util.function.Supplier;
 
 import io.smallrye.faulttolerance.api.FaultTolerance;
@@ -9,6 +10,8 @@ public final class LazyFaultTolerance<T> implements FaultTolerance<T> {
     private final Supplier<FaultTolerance<T>> builder;
     private final Class<?> asyncType;
 
+    private final ReentrantLock lock = new ReentrantLock();
+
     private volatile FaultTolerance<T> instance;
 
     LazyFaultTolerance(Supplier<FaultTolerance<T>> builder, Class<?> asyncType) {
@@ -38,12 +41,15 @@ public void run(Runnable action) {
     private FaultTolerance<T> instance() {
         FaultTolerance<T> instance = this.instance;
         if (instance == null) {
-            synchronized (this) {
+            lock.lock();
+            try {
                 instance = this.instance;
                 if (instance == null) {
                     instance = builder.get();
                     this.instance = instance;
                 }
+            } finally {
+                lock.unlock();
             }
         }
         return instance;