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PaperMC/patches/server/0408-Fix-Concurrency-issue-in-ShufflingList.patch
2024-12-05 12:20:56 +01:00

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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Mon, 6 Jul 2020 18:36:41 -0400
Subject: [PATCH] Fix Concurrency issue in ShufflingList
if multiple threads from worldgen sort at same time, it will crash.
So make a copy of the list for sorting purposes.
diff --git a/src/main/java/net/minecraft/world/entity/ai/behavior/GateBehavior.java b/src/main/java/net/minecraft/world/entity/ai/behavior/GateBehavior.java
index 334962f1bf5988059fec506f0d3aaf4302205220..6a270c9adb044a6e0b1c8e09b9106d51989fd761 100644
--- a/src/main/java/net/minecraft/world/entity/ai/behavior/GateBehavior.java
+++ b/src/main/java/net/minecraft/world/entity/ai/behavior/GateBehavior.java
@@ -18,7 +18,7 @@ public class GateBehavior<E extends LivingEntity> implements BehaviorControl<E>
private final Set<MemoryModuleType<?>> exitErasedMemories;
private final GateBehavior.OrderPolicy orderPolicy;
private final GateBehavior.RunningPolicy runningPolicy;
- private final ShufflingList<BehaviorControl<? super E>> behaviors = new ShufflingList<>();
+ private final ShufflingList<BehaviorControl<? super E>> behaviors = new ShufflingList<>(false); // Paper - Fix Concurrency issue in ShufflingList during worldgen
private Behavior.Status status = Behavior.Status.STOPPED;
public GateBehavior(
diff --git a/src/main/java/net/minecraft/world/entity/ai/behavior/ShufflingList.java b/src/main/java/net/minecraft/world/entity/ai/behavior/ShufflingList.java
index 195eea55fabc7a9a665e0a8f04934a3aaf9f8b71..3fac11bf02652b5f51f30f99bdf516504467d0d2 100644
--- a/src/main/java/net/minecraft/world/entity/ai/behavior/ShufflingList.java
+++ b/src/main/java/net/minecraft/world/entity/ai/behavior/ShufflingList.java
@@ -16,12 +16,25 @@ import net.minecraft.util.RandomSource;
public class ShufflingList<U> implements Iterable<U> {
protected final List<ShufflingList.WeightedEntry<U>> entries;
private final RandomSource random = RandomSource.create();
+ private final boolean isUnsafe; // Paper - Fix Concurrency issue in ShufflingList during worldgen
public ShufflingList() {
+ // Paper start - Fix Concurrency issue in ShufflingList during worldgen
+ this(true);
+ }
+ public ShufflingList(boolean isUnsafe) {
+ this.isUnsafe = isUnsafe;
+ // Paper end - Fix Concurrency issue in ShufflingList during worldgen
this.entries = Lists.newArrayList();
}
private ShufflingList(List<ShufflingList.WeightedEntry<U>> list) {
+ // Paper start - Fix Concurrency issue in ShufflingList during worldgen
+ this(list, true);
+ }
+ private ShufflingList(List<ShufflingList.WeightedEntry<U>> list, boolean isUnsafe) {
+ this.isUnsafe = isUnsafe;
+ // Paper end - Fix Concurrency issue in ShufflingList during worldgen
this.entries = Lists.newArrayList(list);
}
@@ -35,9 +48,12 @@ public class ShufflingList<U> implements Iterable<U> {
}
public ShufflingList<U> shuffle() {
- this.entries.forEach(entry -> entry.setRandom(this.random.nextFloat()));
- this.entries.sort(Comparator.comparingDouble(ShufflingList.WeightedEntry::getRandWeight));
- return this;
+ // Paper start - Fix Concurrency issue in ShufflingList during worldgen
+ List<ShufflingList.WeightedEntry<U>> list = this.isUnsafe ? Lists.newArrayList(this.entries) : this.entries;
+ list.forEach(entry -> entry.setRandom(this.random.nextFloat()));
+ list.sort(Comparator.comparingDouble(ShufflingList.WeightedEntry::getRandWeight));
+ return this.isUnsafe ? new ShufflingList<>(list, this.isUnsafe) : this;
+ // Paper end - Fix Concurrency issue in ShufflingList during worldgen
}
public Stream<U> stream() {