From e94e3b7b05c33b23f284fded10de986c8a8c6829 Mon Sep 17 00:00:00 2001
From: dordsor21 <dordsor21@gmail.com>
Date: Wed, 13 Jan 2021 18:17:18 +0000
Subject: [PATCH] Only forcefully submit a chunk if we hold the monitor.  -
 Properly ensures we don't try to submit chunks that already have a monitor
 (prevent the FAWE-freezing)  - We can't detect if "no" threads hold the
 chunk's monitor, but equally that would also be kinda very bad practice.

---
 .../queue/SingleThreadQueueExtent.java            | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

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 25c64cbcf..6569ec61c 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
@@ -250,8 +250,19 @@ public class SingleThreadQueueExtent extends ExtentBatchProcessorHolder implemen
             //  - memory is low & queue size > num threads + 8
             //  - queue size > target size and primary queue has less than num threads submissions
             if (enabledQueue && ((lowMem && size > Settings.IMP.QUEUE.PARALLEL_THREADS + 8) || (size > Settings.IMP.QUEUE.TARGET_SIZE && Fawe.get().getQueueHandler().isUnderutilized()))) {
-                chunk = chunks.removeFirst();
-                final Future future = submitUnchecked(chunk);
+                int i = 0;
+                boolean found = false;
+                while (i < chunks.size() && (chunk = chunks.get(i)) != null) {
+                    if (Thread.holdsLock(chunk)) {
+                        found = true;
+                        break;
+                    }
+                    i++;
+                }
+                Future future = null;
+                if (found) {
+                    future = submitUnchecked(chunk);
+                }
                 if (future != null && !future.isDone()) {
                     final int targetSize;
                     if (lowMem) {