Paper/patches/server/0716-Don-t-use-level-random-in-entity-constructors.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

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Diff

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Jake Potrebic <jake.m.potrebic@gmail.com>
Date: Sun, 10 Jul 2022 14:13:22 -0700
Subject: [PATCH] Don't use level random in entity constructors
Paper makes the entity random thread-safe
and constructing an entity off the main thread
should be supported. Some entities (for whatever
reason) use the level's random in some places.
diff --git a/src/main/java/net/minecraft/world/entity/item/ItemEntity.java b/src/main/java/net/minecraft/world/entity/item/ItemEntity.java
index 586257fe5c9f5cddd0ed164254f46777c6e71d66..d555fd0b200c012f30ed0c0ec09a37b25a737b76 100644
--- a/src/main/java/net/minecraft/world/entity/item/ItemEntity.java
+++ b/src/main/java/net/minecraft/world/entity/item/ItemEntity.java
@@ -72,7 +72,12 @@ public class ItemEntity extends Entity implements TraceableEntity {
}
public ItemEntity(Level world, double x, double y, double z, ItemStack stack) {
- this(world, x, y, z, stack, world.random.nextDouble() * 0.2D - 0.1D, 0.2D, world.random.nextDouble() * 0.2D - 0.1D);
+ // Paper start - Don't use level random in entity constructors (to make them thread-safe)
+ this(EntityType.ITEM, world);
+ this.setPos(x, y, z);
+ this.setDeltaMovement(this.random.nextDouble() * 0.2D - 0.1D, 0.2D, this.random.nextDouble() * 0.2D - 0.1D);
+ this.setItem(stack);
+ // Paper end - Don't use level random in entity constructors
}
public ItemEntity(Level world, double x, double y, double z, ItemStack stack, double velocityX, double velocityY, double velocityZ) {
diff --git a/src/main/java/net/minecraft/world/entity/item/PrimedTnt.java b/src/main/java/net/minecraft/world/entity/item/PrimedTnt.java
index 45c224198135e48f94dc72312c805bf451bf7b0e..de87483600e55d88176fe25db621bbd3e464729f 100644
--- a/src/main/java/net/minecraft/world/entity/item/PrimedTnt.java
+++ b/src/main/java/net/minecraft/world/entity/item/PrimedTnt.java
@@ -68,7 +68,7 @@ public class PrimedTnt extends Entity implements TraceableEntity {
public PrimedTnt(Level world, double x, double y, double z, @Nullable LivingEntity igniter) {
this(EntityType.TNT, world);
this.setPos(x, y, z);
- double d3 = world.random.nextDouble() * 6.2831854820251465D;
+ double d3 = this.random.nextDouble() * 6.2831854820251465D; // Paper - Don't use level random in entity constructors
this.setDeltaMovement(-Math.sin(d3) * 0.02D, 0.20000000298023224D, -Math.cos(d3) * 0.02D);
this.setFuse(80);