Paper/patches/removed/1.19.2-legacy-chunksystem/0017-Make-CallbackExecutor-strict-again.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: Spottedleaf <spottedleaf@spottedleaf.dev>
Date: Fri, 24 Apr 2020 09:06:15 -0700
Subject: [PATCH] Make CallbackExecutor strict again
The correct fix for double scheduling is to avoid it. The reason
this class is used is because double scheduling causes issues
elsewhere, and it acts as an explicit detector of what double
schedules. Effectively, use the callback executor as a tool of
finding issues rather than hiding these issues.
diff --git a/src/main/java/net/minecraft/server/level/ChunkMap.java b/src/main/java/net/minecraft/server/level/ChunkMap.java
index ea27e6b1340a42c675bc68ed75f100569114be7a..4da0cbe58dad0f66e0d056c71684120514dcac6a 100644
--- a/src/main/java/net/minecraft/server/level/ChunkMap.java
+++ b/src/main/java/net/minecraft/server/level/ChunkMap.java
@@ -157,17 +157,28 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
public final CallbackExecutor callbackExecutor = new CallbackExecutor();
public static final class CallbackExecutor implements java.util.concurrent.Executor, Runnable {
- private final java.util.Queue<Runnable> queue = new java.util.ArrayDeque<>();
+ private Runnable queued; // Paper - revert CB changes
@Override
public void execute(Runnable runnable) {
- this.queue.add(runnable);
+ // Paper start - revert CB changes
+ org.spigotmc.AsyncCatcher.catchOp("Callback Executor execute");
+ if (this.queued != null) {
+ LOGGER.error("Failed to schedule runnable", new IllegalStateException("Already queued"));
+ throw new IllegalStateException("Already queued");
+ }
+ this.queued = runnable;
+ // Paper end - revert CB changes
}
@Override
public void run() {
- Runnable task;
- while ((task = this.queue.poll()) != null) {
+ // Paper start - revert CB changes
+ org.spigotmc.AsyncCatcher.catchOp("Callback Executor execute");
+ Runnable task = this.queued;
+ if (task != null) {
+ this.queued = null;
+ // Paper end - revert CB changes
task.run();
}
}