From 024ec3cd966a0875ef36642d8b45829bab1a2f8e Mon Sep 17 00:00:00 2001
From: daoge_cmd <3523206925@qq.com>
Date: Mon, 28 Oct 2024 17:27:29 +0800
Subject: [PATCH] fix: fix deadlock in finding world spawn point

---
 .../org/allaymc/server/world/AllayWorld.java  | 24 +++++++++++--------
 1 file changed, 14 insertions(+), 10 deletions(-)

diff --git a/server/src/main/java/org/allaymc/server/world/AllayWorld.java b/server/src/main/java/org/allaymc/server/world/AllayWorld.java
index 6ec32b20c..75a262798 100644
--- a/server/src/main/java/org/allaymc/server/world/AllayWorld.java
+++ b/server/src/main/java/org/allaymc/server/world/AllayWorld.java
@@ -161,20 +161,24 @@ protected void checkFirstTick() {
         }
         isFirstTick = true;
 
-        // Check spawn point
-        if (!isSafeStandingPos(new Position3i(worldData.getSpawnPoint(), getOverWorld()))) {
-            var newSpawnPoint = getOverWorld().findSuitableGroundPosAround(this::isSafeStandingPos, 0, 0, 32);
-            if (newSpawnPoint == null) {
-                log.warn("Cannot find a safe spawn point in the overworld dimension of world {}", worldData.getName());
-                newSpawnPoint = new Vector3i(0, getOverWorld().getHeight(0, 0) + 1, 0);
-            }
-            worldData.setSpawnPoint(newSpawnPoint);
-        }
-
         if (Server.SETTINGS.worldSettings().loadSpawnPointChunks()) {
             // Add spawn point chunk loader
             getOverWorld().getChunkService().addChunkLoader(new SpawnPointChunkLoader());
         }
+
+        // Shouldn't block world tick poll here, otherwise there will be a deadlock because
+        // Dimension#findSuitableGroundPosAround() -wait-> Dimension#getBlockState() -wait-> ChunkService#getOrLoadChunkSync()
+        // -wait-> WorldGenerator#generateChunk(), and WorldGenerator should be ticked in order to generate chunk normally
+        Thread.ofVirtual().name("World " + worldData.getName() + " Spawn Point Finding Thread").start(() -> {
+            if (!isSafeStandingPos(new Position3i(worldData.getSpawnPoint(), getOverWorld()))) {
+                var newSpawnPoint = getOverWorld().findSuitableGroundPosAround(this::isSafeStandingPos, 0, 0, 32);
+                if (newSpawnPoint == null) {
+                    log.warn("Cannot find a safe spawn point in the overworld dimension of world {}", worldData.getName());
+                    newSpawnPoint = new Vector3i(0, getOverWorld().getHeight(0, 0) + 1, 0);
+                }
+                worldData.setSpawnPoint(newSpawnPoint);
+            }
+        });
     }
 
     protected boolean isSafeStandingPos(Position3ic pos) {