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c5a10665b8
Spigot still maintains some partial implementation of "tick skipping", a practice in which the MinecraftServer.currentTick field is updated not by an increment of one per actual tick, but instead set to System.currentTimeMillis() / 50. This behaviour means that the tracked tick may "skip" a tick value in case a previous tick took more than the expected 50ms. To compensate for this in important paths, spigot/craftbukkit implements "wall-time". Instead of incrementing/decrementing ticks on block entities/entities by one for each call to their tick() method, they instead increment/decrement important values, like an ItemEntity's age or pickupDelay, by the difference of `currentTick - lastTick`, where `lastTick` is the value of `currentTick` during the last tick() call. These "fixes" however do not play nicely with minecraft's simulation distance as entities/block entities implementing the above behaviour would "catch up" their values when moving from a non-ticking chunk to a ticking one as their `lastTick` value remains stuck on the last tick in a ticking chunk and hence lead to a large "catch up" once ticked again. Paper completely removes the "tick skipping" behaviour (See patch "Further-improve-server-tick-loop"), making the above precautions completely unnecessary, which also rids paper of the previous described incompatibility with non-ticking chunks.
68 lines
3.7 KiB
Diff
68 lines
3.7 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Aikar <aikar@aikar.co>
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Date: Mon, 6 Jul 2020 18:36:41 -0400
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Subject: [PATCH] Fix Concurrency issue in ShufflingList
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if multiple threads from worldgen sort at same time, it will crash.
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So make a copy of the list for sorting purposes.
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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
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index 334962f1bf5988059fec506f0d3aaf4302205220..6a270c9adb044a6e0b1c8e09b9106d51989fd761 100644
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--- a/src/main/java/net/minecraft/world/entity/ai/behavior/GateBehavior.java
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+++ b/src/main/java/net/minecraft/world/entity/ai/behavior/GateBehavior.java
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@@ -18,7 +18,7 @@ public class GateBehavior<E extends LivingEntity> implements BehaviorControl<E>
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private final Set<MemoryModuleType<?>> exitErasedMemories;
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private final GateBehavior.OrderPolicy orderPolicy;
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private final GateBehavior.RunningPolicy runningPolicy;
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- private final ShufflingList<BehaviorControl<? super E>> behaviors = new ShufflingList<>();
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+ private final ShufflingList<BehaviorControl<? super E>> behaviors = new ShufflingList<>(false); // Paper - Fix Concurrency issue in ShufflingList during worldgen
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private Behavior.Status status = Behavior.Status.STOPPED;
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public GateBehavior(
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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
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index 195eea55fabc7a9a665e0a8f04934a3aaf9f8b71..3fac11bf02652b5f51f30f99bdf516504467d0d2 100644
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--- a/src/main/java/net/minecraft/world/entity/ai/behavior/ShufflingList.java
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+++ b/src/main/java/net/minecraft/world/entity/ai/behavior/ShufflingList.java
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@@ -16,12 +16,25 @@ import net.minecraft.util.RandomSource;
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public class ShufflingList<U> implements Iterable<U> {
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protected final List<ShufflingList.WeightedEntry<U>> entries;
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private final RandomSource random = RandomSource.create();
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+ private final boolean isUnsafe; // Paper - Fix Concurrency issue in ShufflingList during worldgen
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public ShufflingList() {
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+ // Paper start - Fix Concurrency issue in ShufflingList during worldgen
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+ this(true);
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+ }
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+ public ShufflingList(boolean isUnsafe) {
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+ this.isUnsafe = isUnsafe;
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+ // Paper end - Fix Concurrency issue in ShufflingList during worldgen
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this.entries = Lists.newArrayList();
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}
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private ShufflingList(List<ShufflingList.WeightedEntry<U>> list) {
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+ // Paper start - Fix Concurrency issue in ShufflingList during worldgen
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+ this(list, true);
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+ }
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+ private ShufflingList(List<ShufflingList.WeightedEntry<U>> list, boolean isUnsafe) {
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+ this.isUnsafe = isUnsafe;
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+ // Paper end - Fix Concurrency issue in ShufflingList during worldgen
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this.entries = Lists.newArrayList(list);
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}
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@@ -35,9 +48,12 @@ public class ShufflingList<U> implements Iterable<U> {
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}
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public ShufflingList<U> shuffle() {
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- this.entries.forEach(entry -> entry.setRandom(this.random.nextFloat()));
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- this.entries.sort(Comparator.comparingDouble(ShufflingList.WeightedEntry::getRandWeight));
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- return this;
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+ // Paper start - Fix Concurrency issue in ShufflingList during worldgen
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+ List<ShufflingList.WeightedEntry<U>> list = this.isUnsafe ? Lists.newArrayList(this.entries) : this.entries;
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+ list.forEach(entry -> entry.setRandom(this.random.nextFloat()));
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+ list.sort(Comparator.comparingDouble(ShufflingList.WeightedEntry::getRandWeight));
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+ return this.isUnsafe ? new ShufflingList<>(list, this.isUnsafe) : this;
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+ // Paper end - Fix Concurrency issue in ShufflingList during worldgen
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}
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public Stream<U> stream() {
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