Paper/patches/server/0411-Fix-Concurrency-issue-in-ShufflingList.patch
Spottedleaf 8c5b837e05 Rework async chunk api implementation
Firstly, the old methods all routed to the CompletableFuture method.
However, the CF method could not guarantee that if the caller
was off-main that the future would be "completed" on-main. Since
the callback methods used the CF one, this meant that the callback
methods did not guarantee that the callbacks were to be called on
the main thread.

Now, all methods route to getChunkAtAsync(x, z, gen, urgent, cb)
so that the methods with the callback are guaranteed to invoke
the callback on the main thread. The CF behavior remains unchanged;
it may still appear to complete on main if invoked off-main.

Secondly, remove the scheduleOnMain invocation in the async
chunk completion. This unnecessarily delays the callback
by 1 tick.

Thirdly, add getChunksAtAsync(minX, minZ, maxX, maxZ, ...) which
will load chunks within an area. This method is provided as a helper
as keeping all chunks loaded within an area can be complicated to
implement for plugins (due to the lacking ticket API), and is
already implemented internally anyways.

Fourthly, remove the ticket addition that occured with getChunkAt
and getChunkAtAsync. The ticket addition may delay the unloading
of the chunk unnecessarily. It also fixes a very rare timing bug
where the future/callback would be completed after the chunk
unloads.
2024-11-18 23:00:59 -08:00

68 lines
3.7 KiB
Diff

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() {