From 30bb3094c16f8c3bf0f570f34f62a4a098cdb9b6 Mon Sep 17 00:00:00 2001
From: Norman Maurer <norman_maurer@apple.com>
Date: Wed, 11 May 2016 11:53:31 +0200
Subject: [PATCH] [#5227] Fix race-condition in PooledByteBufAllocatorTest

Motivation:

PooledByteBufAllocatorTest.testNumThreadCachesWithNoDirrectArenas() had a race as it just used LockSupport.parkNanos(). We should better use a CountdownLatch and so be sure we really have init everything.

Modifications:

Replace LockSupport.parkNanos(...) with CountdownLatch usage

Result:

No more race in test.
---
 .../buffer/PooledByteBufAllocatorTest.java    | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/buffer/src/test/java/io/netty/buffer/PooledByteBufAllocatorTest.java b/buffer/src/test/java/io/netty/buffer/PooledByteBufAllocatorTest.java
index 9bdd2431c0..b3ab27e948 100644
--- a/buffer/src/test/java/io/netty/buffer/PooledByteBufAllocatorTest.java
+++ b/buffer/src/test/java/io/netty/buffer/PooledByteBufAllocatorTest.java
@@ -126,7 +126,7 @@ public class PooledByteBufAllocatorTest {
     }
 
     @Test
-    public void testNumThreadCachesWithNoDirectArenas() {
+    public void testNumThreadCachesWithNoDirectArenas() throws InterruptedException {
         int numHeapArenas = 1;
         final PooledByteBufAllocator allocator =
             new PooledByteBufAllocator(numHeapArenas, 0, 8192, 1);
@@ -188,17 +188,20 @@ public class PooledByteBufAllocatorTest {
         LockSupport.parkNanos(MILLISECONDS.toNanos(100));
     }
 
-    private static CountDownLatch createNewThreadCache(final PooledByteBufAllocator allocator) {
+    private static CountDownLatch createNewThreadCache(final PooledByteBufAllocator allocator)
+            throws InterruptedException {
         final CountDownLatch latch = new CountDownLatch(1);
-
+        final CountDownLatch cacheLatch = new CountDownLatch(1);
         Thread t = new FastThreadLocalThread(new Runnable() {
 
             @Override
             public void run() {
                 ByteBuf buf = allocator.newHeapBuffer(1024, 1024);
-                for (int i = 0; i < buf.capacity(); i++) {
-                    buf.writeByte(0);
-                }
+
+                // Countdown the latch after we allocated a buffer. At this point the cache must exists.
+                cacheLatch.countDown();
+
+                buf.writeZero(buf.capacity());
 
                 try {
                     latch.await();
@@ -213,8 +216,8 @@ public class PooledByteBufAllocatorTest {
         });
         t.start();
 
-        // Wait a bit for the thread & thread cache to be created.
-        LockSupport.parkNanos(MILLISECONDS.toNanos(100));
+        // Wait until we allocated a buffer and so be sure the thread was started and the cache exists.
+        cacheLatch.await();
 
         return latch;
     }