From 45cc1dd2c7ada0d2bc291105b83f06a518ad5e1b Mon Sep 17 00:00:00 2001
From: themode <themode@outlook.fr>
Date: Sun, 27 Sep 2020 19:04:08 +0200
Subject: [PATCH] Made InstanceManager#unregisterInstance thread-safe

---
 .../server/instance/InstanceManager.java       | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/src/main/java/net/minestom/server/instance/InstanceManager.java b/src/main/java/net/minestom/server/instance/InstanceManager.java
index 61a881057..57cfcb68a 100644
--- a/src/main/java/net/minestom/server/instance/InstanceManager.java
+++ b/src/main/java/net/minestom/server/instance/InstanceManager.java
@@ -111,15 +111,17 @@ public final class InstanceManager {
     public void unregisterInstance(Instance instance) {
         Check.stateCondition(!instance.getPlayers().isEmpty(), "You cannot unregister an instance with players");
 
-        // Unload all chunks
-        if (instance instanceof InstanceContainer) {
-            InstanceContainer instanceContainer = (InstanceContainer) instance;
-            instanceContainer.scheduledChunksToRemove.addAll(instanceContainer.getChunks());
-            instanceContainer.UNSAFE_unloadChunks();
-        }
+        synchronized (instance) {
+            // Unload all chunks
+            if (instance instanceof InstanceContainer) {
+                InstanceContainer instanceContainer = (InstanceContainer) instance;
+                instanceContainer.scheduledChunksToRemove.addAll(instanceContainer.getChunks());
+                instanceContainer.UNSAFE_unloadChunks();
+            }
 
-        instance.setRegistered(false);
-        this.instances.remove(instance);
+            instance.setRegistered(false);
+            this.instances.remove(instance);
+        }
     }
 
     /**