From 4abf4aecad100eb8768da16ac7314f0848cc653b Mon Sep 17 00:00:00 2001
From: "Dylan K. Taylor" <dktapps@pmmp.io>
Date: Sun, 28 Mar 2021 18:10:23 +0100
Subject: [PATCH] MainLogger: fixed potential deadlock during syncFlushBuffer()
 the notify() to flush the buffer might arrive in between the writeLogStream()
 and synchronized() calls in the thread body, resulting in a deadlock if the
 logger thread managed to call wait() before the main thread did.

---
 src/pocketmine/utils/MainLogger.php | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/src/pocketmine/utils/MainLogger.php b/src/pocketmine/utils/MainLogger.php
index 4e34a1610..2846e0bfd 100644
--- a/src/pocketmine/utils/MainLogger.php
+++ b/src/pocketmine/utils/MainLogger.php
@@ -331,10 +331,11 @@ class MainLogger extends \AttachableThreadedLogger{
 	 * @return void
 	 */
 	public function syncFlushBuffer(){
-		$this->syncFlush = true;
 		$this->synchronized(function() : void{
+			$this->syncFlush = true;
 			$this->notify(); //write immediately
-
+		});
+		$this->synchronized(function() : void{
 			while($this->syncFlush){
 				$this->wait(); //block until it's all been written to disk
 			}
@@ -371,7 +372,7 @@ class MainLogger extends \AttachableThreadedLogger{
 		while(!$this->shutdown){
 			$this->writeLogStream($logResource);
 			$this->synchronized(function() : void{
-				if(!$this->shutdown){
+				if(!$this->shutdown && !$this->syncFlush){
 					$this->wait();
 				}
 			});