Use wrapped StructureManager to prevent worldgen deadlock

Spigot-Server-Patches/0576-Use-wrapped-StructureManager-to-prevent-worldgen-dea.patch

@@ -0,0 +1,34 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: MiniDigger <admin@minidigger.me>
+Date: Wed, 2 Sep 2020 13:56:18 +0200
+Subject: [PATCH] Use wrapped StructureManager to prevent worldgen deadlock
+
+
+diff --git a/src/main/java/net/minecraft/server/RegionLimitedWorldAccess.java b/src/main/java/net/minecraft/server/RegionLimitedWorldAccess.java
+index e9fbeaf309735ea5fcb0c53b8b2485b0c5dd43be..9172c679c874d42750d2adc32124ecda29ea43cf 100644
+--- a/src/main/java/net/minecraft/server/RegionLimitedWorldAccess.java
++++ b/src/main/java/net/minecraft/server/RegionLimitedWorldAccess.java
+@@ -30,6 +30,7 @@ public class RegionLimitedWorldAccess implements GeneratorAccessSeed {
+     private final BiomeManager m;
+     private final ChunkCoordIntPair n;
+     private final ChunkCoordIntPair o;
++    private final StructureManager structureManager; // Paper - cache wrapped structure manager
+ 
+     public RegionLimitedWorldAccess(WorldServer worldserver, List<IChunkAccess> list) {
+         int i = MathHelper.floor(Math.sqrt((double) list.size()));
+@@ -51,6 +52,7 @@ public class RegionLimitedWorldAccess implements GeneratorAccessSeed {
+             this.m = new BiomeManager(this, BiomeManager.a(this.g), worldserver.getDimensionManager().getGenLayerZoomer());
+             this.n = ((IChunkAccess) list.get(0)).getPos();
+             this.o = ((IChunkAccess) list.get(list.size() - 1)).getPos();
++            this.structureManager = this.f.getStructureManager().a(this); // Paper - cache wrapped structure manager
+         }
+     }
+ 
+@@ -379,6 +381,6 @@ public class RegionLimitedWorldAccess implements GeneratorAccessSeed {
+ 
+     @Override
+     public Stream<? extends StructureStart<?>> a(SectionPosition sectionposition, StructureGenerator<?> structuregenerator) {
+-        return this.f.a(sectionposition, structuregenerator);
++        return structureManager.a(sectionposition, structuregenerator); // Paper - wrapped structure manager to prevent deadlock, see #4272 and MC-199487
+     }
+ }