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 WeightedList 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 893c37cc7e33f4baa98131afca45a258600ddc75..09998d160a6d79fdb5a5041a5d572649a1532e6a 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 @@ -16,7 +16,7 @@ public class GateBehavior<E extends LivingEntity> extends Behavior<E> { private final Set<MemoryModuleType<?>> exitErasedMemories; private final GateBehavior.OrderPolicy orderPolicy; private final GateBehavior.RunningPolicy runningPolicy; - private final ShufflingList<Behavior<? super E>> behaviors = new ShufflingList<>(); + private final ShufflingList<Behavior<? super E>> behaviors = new ShufflingList<>(false); // Paper - don't use a clone public GateBehavior(Map<MemoryModuleType<?>, MemoryStatus> requiredMemoryState, Set<MemoryModuleType<?>> memoriesToForgetWhenStopped, GateBehavior.OrderPolicy order, GateBehavior.RunningPolicy runMode, List<Pair<Behavior<? super E>, Integer>> tasks) { super(requiredMemoryState); 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 d4c9def80154c3e62a0b6928057062a0808f339f..4fa64b1e2004810906bb0b174436c8e687a75ada 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 @@ -14,12 +14,25 @@ import java.util.stream.Stream; public class ShufflingList<U> { protected final List<ShufflingList.WeightedEntry<U>> entries; private final Random random = new Random(); + private final boolean isUnsafe; // Paper public ShufflingList() { + // Paper start + this(true); + } + public ShufflingList(boolean isUnsafe) { + this.isUnsafe = isUnsafe; + // Paper end this.entries = Lists.newArrayList(); } private ShufflingList(List<ShufflingList.WeightedEntry<U>> list) { + // Paper start + this(list, true); + } + private ShufflingList(List<ShufflingList.WeightedEntry<U>> list, boolean isUnsafe) { + this.isUnsafe = isUnsafe; + // Paper end this.entries = Lists.newArrayList(list); } @@ -35,11 +48,12 @@ public class ShufflingList<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 - make concurrent safe, work off a clone of the list + 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 } public Stream<U> stream() {