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Remove wall-time / unused skip tick protection (#11412)

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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.
This commit is contained in:
Bjarne Koll 2024-09-19 16:36:07 +02:00 • committed by GitHub
parent 5c82955733
commit c5a10665b8
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GPG key ID: B5690EEEBB952194
794 changed files with 402 additions and 282 deletions
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47
patches/server/0331-Prevent-Double-PlayerChunkMap-adds-crashing-server.patch Normal file
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@ -0,0 +1,47 @@
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Thu, 2 Apr 2020 01:42:39 -0400
Subject: [PATCH] Prevent Double PlayerChunkMap adds crashing server
Suspected case would be around the technique used in .stopRiding
Stack will identify any causer of this and warn instead of crashing.
diff --git a/src/main/java/net/minecraft/server/level/ChunkMap.java b/src/main/java/net/minecraft/server/level/ChunkMap.java
index ee54706b36bd227edacea2a1b6099009bd652039..8206ec366b429858d9582e437781191e5aa0fa02 100644
--- a/src/main/java/net/minecraft/server/level/ChunkMap.java
+++ b/src/main/java/net/minecraft/server/level/ChunkMap.java
@@ -1241,6 +1241,13 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
public void addEntity(Entity entity) {
org.spigotmc.AsyncCatcher.catchOp("entity track"); // Spigot
+ // Paper start - ignore and warn about illegal addEntity calls instead of crashing server
+ if (!entity.valid || entity.level() != this.level || this.entityMap.containsKey(entity.getId())) {
+ LOGGER.error("Illegal ChunkMap::addEntity for world " + this.level.getWorld().getName()
+ + ": " + entity + (this.entityMap.containsKey(entity.getId()) ? " ALREADY CONTAINED (This would have crashed your server)" : ""), new Throwable());
+ return;
+ }
+ // Paper end - ignore and warn about illegal addEntity calls instead of crashing server
if (!(entity instanceof EnderDragonPart)) {
EntityType<?> entitytypes = entity.getType();
int i = entitytypes.clientTrackingRange() * 16;
diff --git a/src/main/java/net/minecraft/server/level/ServerLevel.java b/src/main/java/net/minecraft/server/level/ServerLevel.java
index f1fa4cb11f69e248dd55b8aa69f5d07268f182a1..89e05d9316b012a5c8103682ff9dbeae757f4f57 100644
--- a/src/main/java/net/minecraft/server/level/ServerLevel.java
+++ b/src/main/java/net/minecraft/server/level/ServerLevel.java
@@ -2149,7 +2149,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
public void onTrackingStart(Entity entity) {
org.spigotmc.AsyncCatcher.catchOp("entity register"); // Spigot
- ServerLevel.this.getChunkSource().addEntity(entity);
+ // ServerLevel.this.getChunkSource().addEntity(entity); // Paper - ignore and warn about illegal addEntity calls instead of crashing server; moved down below valid=true
if (entity instanceof ServerPlayer entityplayer) {
ServerLevel.this.players.add(entityplayer);
ServerLevel.this.updateSleepingPlayerList();
@@ -2179,6 +2179,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
entity.updateDynamicGameEventListener(DynamicGameEventListener::add);
entity.inWorld = true; // CraftBukkit - Mark entity as in world
entity.valid = true; // CraftBukkit
+ ServerLevel.this.getChunkSource().addEntity(entity); // Paper - ignore and warn about illegal addEntity calls instead of crashing server
// Paper start - Entity origin API
if (entity.getOriginVector() == null) {
entity.setOrigin(entity.getBukkitEntity().getLocation());