PaperMC/patches/removed/1.19.2-legacy-chunksystem/0722-Correctly-handle-recursion-for-chunkholder-updates.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@users.noreply.github.com>
Date: Sun, 21 Mar 2021 17:32:47 -0700
Subject: [PATCH] Correctly handle recursion for chunkholder updates
If a chunk ticket level is brought up while unloading it would
cause a recursive call which would handle the increase but then
the caller would think the chunk would be unloaded.
diff --git a/src/main/java/net/minecraft/server/level/ChunkHolder.java b/src/main/java/net/minecraft/server/level/ChunkHolder.java
index c4046b364d1896b781e23c92b241ec73c239d3a0..9c0bf31c3c362632241c95338a3f8d67bbd4fdc5 100644
--- a/src/main/java/net/minecraft/server/level/ChunkHolder.java
+++ b/src/main/java/net/minecraft/server/level/ChunkHolder.java
@@ -472,8 +472,10 @@ public class ChunkHolder {
playerchunkmap.onFullChunkStatusChange(this.pos, playerchunk_state);
}
+ protected long updateCount; // Paper - correctly handle recursion
protected void updateFutures(ChunkMap chunkStorage, Executor executor) {
io.papermc.paper.util.TickThread.ensureTickThread("Async ticket level update"); // Paper
+ long updateCount = ++this.updateCount; // Paper - correctly handle recursion
ChunkStatus chunkstatus = ChunkHolder.getStatus(this.oldTicketLevel);
ChunkStatus chunkstatus1 = ChunkHolder.getStatus(this.ticketLevel);
boolean flag = this.oldTicketLevel <= ChunkMap.MAX_CHUNK_DISTANCE;
@@ -515,6 +517,12 @@ public class ChunkHolder {
// Run callback right away if the future was already done
chunkStorage.callbackExecutor.run();
+ // Paper start - correctly handle recursion
+ if (this.updateCount != updateCount) {
+ // something else updated ticket level for us.
+ return;
+ }
+ // Paper end - correctly handle recursion
}
// CraftBukkit end