PaperMC/patches/server/0455-Thread-Safe-Vanilla-Command-permission-checking.patch
Spottedleaf 01a13871de
Rewrite chunk system (#8177)
Patch documentation to come

Issues with the old system that are fixed now:
- World generation does not scale with cpu cores effectively.
- Relies on the main thread for scheduling and maintaining chunk state, dropping chunk load/generate rates at lower tps.
- Unreliable prioritisation of chunk gen/load calls that block the main thread.
- Shutdown logic is utterly unreliable, as it has to wait for all chunks to unload - is it guaranteed that the chunk system is in a state on shutdown that it can reliably do this? Watchdog shutdown also typically failed due to thread checks, which is now resolved.
- Saving of data is not unified (i.e can save chunk data without saving entity data, poses problems for desync if shutdown is really abnormal.
- Entities are not loaded with chunks. This caused quite a bit of headache for Chunk#getEntities API, but now the new chunk system loads entities with chunks so that they are ready whenever the chunk loads in. Effectively brings the behavior back to 1.16 era, but still storing entities in their own separate regionfiles.

The above list is not complete. The patch documentation will complete it.

New chunk system hard relies on starlight and dataconverter, and most importantly the new concurrent utilities in ConcurrentUtil.

Some of the old async chunk i/o interface (i.e the old file io thread reroutes _some_ calls to the new file io thread) is kept for plugin compat reasons. It will be removed in the next major version of minecraft.

The old legacy chunk system patches have been moved to the removed folder in case we need them again.
2022-09-26 01:02:51 -07:00

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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Sat, 11 Jul 2020 03:54:28 -0400
Subject: [PATCH] Thread Safe Vanilla Command permission checking
Datapacks check this on load and are built concurrently. This was breaking them badly due
to race conditions.
Plus, .canUse we want to be safe for async anyways.
diff --git a/src/main/java/com/mojang/brigadier/tree/CommandNode.java b/src/main/java/com/mojang/brigadier/tree/CommandNode.java
index 20a7cdf87f307878d66922aaac0c60cff218e46c..39844531b03eb8a6c70700b4ecbf0ff1a557424d 100644
--- a/src/main/java/com/mojang/brigadier/tree/CommandNode.java
+++ b/src/main/java/com/mojang/brigadier/tree/CommandNode.java
@@ -75,10 +75,10 @@ public abstract class CommandNode<S> implements Comparable<CommandNode<S>> {
public synchronized boolean canUse(final S source) {
if (source instanceof CommandSourceStack) {
try {
- ((CommandSourceStack) source).currentCommand = this;
+ ((CommandSourceStack) source).currentCommand.put(Thread.currentThread(), this); // Paper
return this.requirement.test(source);
} finally {
- ((CommandSourceStack) source).currentCommand = null;
+ ((CommandSourceStack) source).currentCommand.remove(Thread.currentThread()); // Paper
}
}
// CraftBukkit end
diff --git a/src/main/java/net/minecraft/commands/CommandSourceStack.java b/src/main/java/net/minecraft/commands/CommandSourceStack.java
index aadddbc16aa719677c3b6fc4969b6145b9b9ee0b..6fdbe747645eb83f31b56bca77a9d7962237aed8 100644
--- a/src/main/java/net/minecraft/commands/CommandSourceStack.java
+++ b/src/main/java/net/minecraft/commands/CommandSourceStack.java
@@ -59,7 +59,7 @@ public class CommandSourceStack implements SharedSuggestionProvider, com.destroy
private final Vec2 rotation;
private final CommandSigningContext signingContext;
private final TaskChainer chatMessageChainer;
- public volatile CommandNode currentCommand; // CraftBukkit
+ public java.util.Map<Thread, CommandNode> currentCommand = new java.util.concurrent.ConcurrentHashMap<>(); // CraftBukkit // Paper
public CommandSourceStack(CommandSource output, Vec3 pos, Vec2 rot, ServerLevel world, int level, String name, Component displayName, MinecraftServer server, @Nullable Entity entity) {
this(output, pos, rot, world, level, name, displayName, server, entity, false, (commandcontext, flag, j) -> {
@@ -195,9 +195,11 @@ public class CommandSourceStack implements SharedSuggestionProvider, com.destroy
@Override
public boolean hasPermission(int level) {
// CraftBukkit start
- CommandNode currentCommand = this.currentCommand;
+ // Paper start - fix concurrency issue
+ CommandNode currentCommand = this.currentCommand.get(Thread.currentThread());
if (currentCommand != null) {
return this.hasPermission(level, org.bukkit.craftbukkit.command.VanillaCommandWrapper.getPermission(currentCommand));
+ // Paper end
}
// CraftBukkit end