From ab7ecd6a0f1e067147c1e155692c9b0114cb64ad Mon Sep 17 00:00:00 2001
From: paulward24 <52216289+paulward24@users.noreply.github.com>
Date: Fri, 28 Jun 2019 16:06:43 -0700
Subject: [PATCH] HDFS-14618. Incorrect synchronization of ArrayList field
 (ArrayList is thread-unsafe). Contributed by Paul Ward.

(cherry picked from commit d203045c3024b134d7a0417d1ea3a60d03a1534a)
---
 .../server/blockmanagement/PendingReconstructionBlocks.java   | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/PendingReconstructionBlocks.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/PendingReconstructionBlocks.java
index 0f20daae397..d0af60c6d2b 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/PendingReconstructionBlocks.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/PendingReconstructionBlocks.java
@@ -132,7 +132,9 @@ class PendingReconstructionBlocks {
   public void clear() {
     synchronized (pendingReconstructions) {
       pendingReconstructions.clear();
-      timedOutItems.clear();
+      synchronized (timedOutItems) {
+        timedOutItems.clear();
+      }
       timedOutCount = 0L;
     }
   }