From 3b56f00b825d9da1ccb935c585c6ede04287460c Mon Sep 17 00:00:00 2001
From: embeddedt <42941056+embeddedt@users.noreply.github.com>
Date: Wed, 12 Apr 2023 14:42:11 -0400
Subject: [PATCH] Fix world load freezing if mods access the previous server
 world

---
 .../core/config/ModernFixEarlyConfig.java     |  1 +
 .../chunk_deadlock/ServerChunkCacheMixin.java | 32 +++++++++++++++++++
 src/main/resources/modernfix.mixins.json      |  1 +
 3 files changed, 34 insertions(+)
 create mode 100644 src/main/java/org/embeddedt/modernfix/mixin/bugfix/chunk_deadlock/ServerChunkCacheMixin.java

diff --git a/src/main/java/org/embeddedt/modernfix/core/config/ModernFixEarlyConfig.java b/src/main/java/org/embeddedt/modernfix/core/config/ModernFixEarlyConfig.java
index 9bf69c7e..d4f7a59c 100644
--- a/src/main/java/org/embeddedt/modernfix/core/config/ModernFixEarlyConfig.java
+++ b/src/main/java/org/embeddedt/modernfix/core/config/ModernFixEarlyConfig.java
@@ -49,6 +49,7 @@ public class ModernFixEarlyConfig {
         this.addMixinRule("bugfix.packet_leak", false);
         this.addMixinRule("bugfix.structure_manager_crash", true);
         this.addMixinRule("bugfix.mc218112", true);
+        this.addMixinRule("bugfix.chunk_deadlock", true);
         this.addMixinRule("bugfix.tf_cme_on_load", modPresent("twilightforest"));
         this.addMixinRule("bugfix.refinedstorage", modPresent("refinedstorage"));
         this.addMixinRule("perf.async_jei", modPresent("jei"));
diff --git a/src/main/java/org/embeddedt/modernfix/mixin/bugfix/chunk_deadlock/ServerChunkCacheMixin.java b/src/main/java/org/embeddedt/modernfix/mixin/bugfix/chunk_deadlock/ServerChunkCacheMixin.java
new file mode 100644
index 00000000..9ebcac80
--- /dev/null
+++ b/src/main/java/org/embeddedt/modernfix/mixin/bugfix/chunk_deadlock/ServerChunkCacheMixin.java
@@ -0,0 +1,32 @@
+package org.embeddedt.modernfix.mixin.bugfix.chunk_deadlock;
+
+import net.minecraft.server.level.ServerChunkCache;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.chunk.ChunkStatus;
+import net.minecraft.world.level.chunk.EmptyLevelChunk;
+import org.embeddedt.modernfix.ModernFix;
+import org.spongepowered.asm.mixin.Final;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Shadow;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;
+
+@Mixin(value = ServerChunkCache.class, priority = 1100)
+public abstract class ServerChunkCacheMixin {
+    @Shadow @Final private Thread mainThread;
+    @Shadow @Final public ServerLevel level;
+    private final boolean debugDeadServerAccess = Boolean.getBoolean("modernfix.debugBadChunkloading");
+    @Inject(method = "getChunk", at = @At("HEAD"), cancellable = true)
+    private void bailIfServerDead(int chunkX, int chunkZ, ChunkStatus requiredStatus, boolean load, CallbackInfoReturnable<ChunkAccess> cir) {
+        if(!this.mainThread.isAlive()) {
+            ModernFix.LOGGER.fatal("A mod is accessing chunks from a stopped server (this will also cause memory leaks)");
+            if(debugDeadServerAccess) {
+                new Exception().printStackTrace();
+            }
+            cir.setReturnValue(new EmptyLevelChunk(this.level, new ChunkPos(chunkX, chunkZ)));
+        }
+    }
+}
diff --git a/src/main/resources/modernfix.mixins.json b/src/main/resources/modernfix.mixins.json
index ae37e36b..78067ad7 100644
--- a/src/main/resources/modernfix.mixins.json
+++ b/src/main/resources/modernfix.mixins.json
@@ -15,6 +15,7 @@
     "bugfix.refinedstorage.te_bug.FluidExternalStorageMixin",
     "bugfix.refinedstorage.te_bug.ItemExternalStorageCacheMixin",
     "bugfix.refinedstorage.te_bug.ItemExternalStorageMixin",
+    "bugfix.chunk_deadlock.ServerChunkCacheMixin",
     "perf.remove_biome_temperature_cache.BiomeMixin",
     "perf.resourcepacks.ModFileResourcePackMixin",
     "perf.resourcepacks.VanillaPackMixin",