From fa69c791607dbb0959a66f6187cff5eb8f328a1f Mon Sep 17 00:00:00 2001
From: dordsor21 <dordsor21@gmail.com>
Date: Thu, 14 Jan 2021 15:42:38 +0000
Subject: [PATCH] lock when editing the chunks cache in
 SingletThreadQueueExtent  - Long2ObjectLinkedOpenHashMap is not thread-safe
 and should not be used from multiple threads at once  - Fixes #851

---
 .../beta/implementation/queue/SingleThreadQueueExtent.java  | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/worldedit-core/src/main/java/com/boydti/fawe/beta/implementation/queue/SingleThreadQueueExtent.java b/worldedit-core/src/main/java/com/boydti/fawe/beta/implementation/queue/SingleThreadQueueExtent.java
index 5f03b4cab..da9a517ff 100644
--- a/worldedit-core/src/main/java/com/boydti/fawe/beta/implementation/queue/SingleThreadQueueExtent.java
+++ b/worldedit-core/src/main/java/com/boydti/fawe/beta/implementation/queue/SingleThreadQueueExtent.java
@@ -114,7 +114,9 @@ public class SingleThreadQueueExtent extends ExtentBatchProcessorHolder implemen
             for (IChunk chunk : this.chunks.values()) {
                 chunk.recycle();
             }
+            getChunkLock.lock();
             this.chunks.clear();
+            getChunkLock.unlock();
         }
         this.enabledQueue = true;
         this.lastChunk = null;
@@ -163,7 +165,9 @@ public class SingleThreadQueueExtent extends ExtentBatchProcessorHolder implemen
             lastChunk = null;
         }
         final long index = MathMan.pairInt(chunk.getX(), chunk.getZ());
+        getChunkLock.lock();
         chunks.remove(index, chunk);
+        getChunkLock.unlock();
         V future = submitUnchecked(chunk);
         submissions.add(future);
         return future;
@@ -374,7 +378,9 @@ public class SingleThreadQueueExtent extends ExtentBatchProcessorHolder implemen
                     }
                 }
             }
+            getChunkLock.lock();
             chunks.clear();
+            getChunkLock.unlock();
         }
         pollSubmissions(0, true);
     }