Paper/Spigot-Server-Patches/0482-Fix-Chunk-Post-Processing-deadlock-risk.patch
Aikar 57dd397155
Updated Upstream (Bukkit/CraftBukkit)
Upstream has released updates that appears to apply and compile correctly.
This update has not been tested by PaperMC and as with ANY update, please do your own testing

Bukkit Changes:
b999860d SPIGOT-2304: Add LootGenerateEvent

CraftBukkit Changes:
77fd87e4 SPIGOT-2304: Implement LootGenerateEvent
a1a705ee SPIGOT-5566: Doused campfires & fires should call EntityChangeBlockEvent
41712edd SPIGOT-5707: PersistentDataHolder not Persistent on API dropped Item
2020-05-01 18:03:57 -04:00

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3.2 KiB
Diff

From a025fb60fcd97d4a39b9d65319df173c3bc7cbb5 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Sat, 18 Apr 2020 04:36:11 -0400
Subject: [PATCH] Fix Chunk Post Processing deadlock risk
See: https://gist.github.com/aikar/dd22bbd2a3d78a2fd3d92e95e9f28dc6
as part of post processing a chunk, we can call ChunkConverter.
ChunkConverter then kicks off major physics updates, and when blocks
that have connections across chunk boundries occur, a recursive risk
can occur where A updates a block that triggers a physics request.
That physics request may trigger a chunk request, that then enqueues
a task into the Mailbox ChunkTaskQueueSorter.
If anything requests that same chunk that is in the middle of conversion,
it's mailbox queue is going to be held up, so the subsequent chunk request
will be unable to proceed.
We delay post processing of Chunk.A() 1 "pass" by re stuffing it back into
the executor so that the mailbox ChunkQueue is now considered empty.
This successfully fixed a reoccurring and highly reproduceable crash
for heightmaps.
diff --git a/src/main/java/net/minecraft/server/ChunkProviderServer.java b/src/main/java/net/minecraft/server/ChunkProviderServer.java
index c2e4e4f6f1..78a8a3cc68 100644
--- a/src/main/java/net/minecraft/server/ChunkProviderServer.java
+++ b/src/main/java/net/minecraft/server/ChunkProviderServer.java
@@ -1048,6 +1048,7 @@ public class ChunkProviderServer extends IChunkProvider {
return super.executeNext() || execChunkTask; // Paper
}
} finally {
+ playerChunkMap.chunkLoadConversionCallbackExecutor.run(); // Paper - Add chunk load conversion callback executor to prevent deadlock due to recursion in the chunk task queue sorter
playerChunkMap.callbackExecutor.run();
}
// CraftBukkit end
diff --git a/src/main/java/net/minecraft/server/PlayerChunkMap.java b/src/main/java/net/minecraft/server/PlayerChunkMap.java
index 6fa70eb08d..0e652625bb 100644
--- a/src/main/java/net/minecraft/server/PlayerChunkMap.java
+++ b/src/main/java/net/minecraft/server/PlayerChunkMap.java
@@ -108,6 +108,8 @@ public class PlayerChunkMap extends IChunkLoader implements PlayerChunk.d {
};
// CraftBukkit end
+ final CallbackExecutor chunkLoadConversionCallbackExecutor = new CallbackExecutor(); // Paper
+
// Paper start - distance maps
private final com.destroystokyo.paper.util.misc.PooledLinkedHashSets<EntityPlayer> pooledLinkedPlayerHashSets = new com.destroystokyo.paper.util.misc.PooledLinkedHashSets<>();
@@ -1007,7 +1009,7 @@ public class PlayerChunkMap extends IChunkLoader implements PlayerChunk.d {
return Either.left(chunk);
});
}, (runnable) -> {
- this.mailboxMain.a(ChunkTaskQueueSorter.a(playerchunk, runnable)); // CraftBukkit - decompile error
+ this.mailboxMain.a(ChunkTaskQueueSorter.a(playerchunk, () -> PlayerChunkMap.this.chunkLoadConversionCallbackExecutor.execute(runnable))); // CraftBukkit - decompile error // Paper - delay running Chunk post processing until outside of the sorter to prevent a deadlock scenario when post processing causes another chunk request.
});
completablefuture1.thenAcceptAsync((either) -> {
--
2.26.2