queue = this.queues[i];
++
++ if (queue.peek() != null) {
++ return true;
++ }
++ }
++ return false;
++ }
++
++ /**
+ * Prevent further additions to this queue. Attempts to add after this call has completed (potentially during) will
+ * result in {@link IllegalStateException} being thrown.
+ *
@@ -1317,7 +1335,7 @@ index 000000000..c3ca3c4a1
+}
diff --git a/src/main/java/com/destroystokyo/paper/io/QueueExecutorThread.java b/src/main/java/com/destroystokyo/paper/io/QueueExecutorThread.java
new file mode 100644
-index 000000000..f127ef236
+index 000000000..ee906b594
--- /dev/null
+++ b/src/main/java/com/destroystokyo/paper/io/QueueExecutorThread.java
@@ -0,0 +0,0 @@
@@ -1342,11 +1360,7 @@ index 000000000..f127ef236
+ protected final AtomicBoolean parked = new AtomicBoolean();
+
+ protected volatile ConcurrentLinkedQueue flushQueue = new ConcurrentLinkedQueue<>();
-+
-+ // this is required to synchronize LockSupport#park()
-+ // LockSupport explicitly states that it will only follow ordering with respect to volatile access
-+ // see flush() for more details
-+ protected volatile long flushCounter;
++ protected volatile long flushCycles;
+
+ public QueueExecutorThread(final PrioritizedTaskQueue queue) {
+ this(queue, (int)(1.e6)); // 1.0ms
@@ -1392,20 +1406,14 @@ index 000000000..f127ef236
+ }
+
+ this.parked.set(true);
++
+ // We need to parse here to avoid a race condition where a thread queues a task before we set parked to true
+ // (i.e it will not notify us)
-+
-+ // it also resolves race condition where we've overriden a concurrent thread's flush call which set parked to false
-+ // the important ordering: (volatile guarantees we cannot re-order the below events)
-+ // us: parked -> true, parse tasks -> writeCounter + 1 -> drain flush queue
-+ // them: read write counter -> add to flush queue -> write parked to false -> park loop
-+
-+ // if we overwrite their set parked to false call then they're in the park loop or about to be, and we're about to
-+ // drain the flush queue
+ if (this.pollTasks(true)) {
+ this.parked.set(false);
+ continue;
+ }
++
+ if (this.handleClose()) {
+ return;
+ }
@@ -1452,19 +1460,22 @@ index 000000000..f127ef236
+ }
+
+ protected void handleFlushThreads(final boolean shutdown) {
-+ final ConcurrentLinkedQueue flushQueue = this.flushQueue; // Note: this can be a plain read
++ Thread parking;
++ ConcurrentLinkedQueue flushQueue = this.flushQueue;
++ do {
++ ++flushCycles; // may be plain read opaque write
++ while ((parking = flushQueue.poll()) != null) {
++ LockSupport.unpark(parking);
++ }
++ } while (this.pollTasks(false));
++
+ if (shutdown) {
-+ this.flushQueue = null; // Note: this can be a release write
-+ }
++ this.flushQueue = null;
+
-+ Thread current;
-+
-+ while ((current = flushQueue.poll()) != null) {
-+ this.pollTasks(false);
-+ // increment flush counter so threads will wake up after being unparked()
-+ //noinspection NonAtomicOperationOnVolatileField
-+ ++this.flushCounter; // may be plain read plain write if we order before poll() (also would need to re-order pollTasks)
-+ LockSupport.unpark(current);
++ // defend against a race condition where a flush thread double-checks right before we set to null
++ while ((parking = flushQueue.poll()) != null) {
++ LockSupport.unpark(parking);
++ }
+ }
+ }
+
@@ -1485,7 +1496,6 @@ index 000000000..f127ef236
+ this.notifyTasks();
+ }
+
-+
+ /**
+ * Waits until this thread's queue is empty.
+ *
@@ -1501,42 +1511,47 @@ index 000000000..f127ef236
+
+ // order is important
+
-+ long flushCounter = this.flushCounter;
++ int successes = 0;
++ long lastCycle = -1L;
+
-+ ConcurrentLinkedQueue flushQueue = this.flushQueue;
++ do {
++ final ConcurrentLinkedQueue flushQueue = this.flushQueue;
++ if (flushQueue == null) {
++ return;
++ }
+
-+ // it's important to read the flush queue after the flush counter to ensure that if we proceed from here
-+ // we have a flush counter that would be different from the final flush counter if the queue executor shuts down
-+ // the double read of the flush queue is not enough to account for this since
-+ if (flushQueue == null) {
-+ return; // queue executor has received shutdown and emptied queue
-+ }
++ flushQueue.add(currentThread);
+
-+ flushQueue.add(currentThread);
++ // double check flush queue
++ if (this.flushQueue == null) {
++ return;
++ }
+
-+ // re-check null flush queue, we need to guarantee the executor is not shutting down before parking
++ final long currentCycle = this.flushCycles; // may be opaque read
+
-+ if (this.flushQueue == null) {
-+ // cannot guarantee state of flush queue now, the executor is done though
-+ return;
-+ }
++ if (currentCycle == lastCycle) {
++ Thread.yield();
++ continue;
++ }
+
-+ // force a response from the IO thread, we're not sure of its state currently
-+ this.parked.set(false);
-+ LockSupport.unpark(this);
++ // force response
++ this.parked.set(false);
++ LockSupport.unpark(this);
+
-+ // Note: see the run() function for handling of a race condition where the queue executor overwrites our parked write
++ LockSupport.park("flushing queue executor thread");
+
-+ boolean interrupted = false; // preserve interrupted status
++ // returns whether there are tasks queued, does not return whether there are tasks executing
++ // this is why we cycle twice twice through flush (we know a pollTask call is made after a flush cycle)
++ // we really only need to guarantee that the tasks this thread has queued has gone through, and can leave
++ // tasks queued concurrently that are unsychronized with this thread as undefined behavior
++ if (this.queue.hasTasks()) {
++ successes = 0;
++ } else {
++ ++successes;
++ }
+
-+ while (this.flushCounter == flushCounter) {
-+ interrupted |= Thread.interrupted();
-+ LockSupport.park();
-+ }
++ } while (successes != 2);
+
-+ if (interrupted) {
-+ Thread.currentThread().interrupt();
-+ }
+ }
+
+ /**