Paper/patches/server/0693-Fix-CME-in-CraftPersistentDataTypeRegistry.patch
Bjarne Koll c5a10665b8
Remove wall-time / unused skip tick protection (#11412)
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.
2024-09-19 16:36:07 +02:00

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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Gero <gecam59@gmail.com>
Date: Sat, 2 Oct 2021 20:08:30 +0200
Subject: [PATCH] Fix CME in CraftPersistentDataTypeRegistry
diff --git a/src/main/java/org/bukkit/craftbukkit/persistence/CraftPersistentDataTypeRegistry.java b/src/main/java/org/bukkit/craftbukkit/persistence/CraftPersistentDataTypeRegistry.java
index 71dc4a2285ddc86e7aa65ba1a211997ffa8fcce4..20c53aac0aef180ee12de919a8000e4b4bc619ff 100644
--- a/src/main/java/org/bukkit/craftbukkit/persistence/CraftPersistentDataTypeRegistry.java
+++ b/src/main/java/org/bukkit/craftbukkit/persistence/CraftPersistentDataTypeRegistry.java
@@ -121,7 +121,7 @@ public final class CraftPersistentDataTypeRegistry {
}
}
- private final Map<Class, TagAdapter> adapters = new HashMap<>();
+ private final Map<Class, TagAdapter> adapters = new java.util.concurrent.ConcurrentHashMap<>(); // Paper - Replace HashMap with ConcurrentHashMap to avoid CME
/**
* Creates a suitable adapter instance for the primitive class type.