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Fix recursive deadlock in CraftWorld.isChunkGenerated #34

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Fix recursive deadlock in CraftWorld.isChunkGenerated #34

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50 changes: 47 additions & 3 deletions ...per-server/paper-patches/files/src/main/java/org/bukkit/craftbukkit/CraftWorld.java.patch
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Original file line number Diff line number Diff line change
Expand Up @@ -23,6 +23,14 @@
import java.util.function.Consumer;
import java.util.function.Predicate;
import java.util.stream.Collectors;
@@ -182,6 +_,7 @@
private final BlockMetadataStore blockMetadata = new BlockMetadataStore(this);
private final Object2IntOpenHashMap<SpawnCategory> spawnCategoryLimit = new Object2IntOpenHashMap<>();
private final CraftPersistentDataContainer persistentDataContainer = new CraftPersistentDataContainer(CraftWorld.DATA_TYPE_REGISTRY);
+ private static final ThreadLocal<Boolean> isInsideIsChunkGenerated = ThreadLocal.withInitial(() -> Boolean.FALSE); // ShreddedPaper - track recursive isChunkGenerated calls
// Paper start - void damage configuration
private boolean voidDamageEnabled;
private float voidDamageAmount;
@@ -240,7 +_,7 @@

@Override
Expand All @@ -40,7 +48,7 @@
warnUnsafeChunk("getting a faraway chunk", x, z); // Paper
net.minecraft.world.level.chunk.LevelChunk chunk = (net.minecraft.world.level.chunk.LevelChunk) this.world.getChunk(x, z, ChunkStatus.FULL, true);
return new CraftChunk(chunk);
@@ -413,10 +_,12 @@
@@ -413,26 +_,37 @@
@Override
public boolean isChunkGenerated(int x, int z) {
// Paper start - Fix this method
Expand All @@ -51,11 +59,47 @@
return CraftWorld.this.isChunkGenerated(x, z);
- }, world.getChunkSource().mainThreadProcessor).join();
+ }, world.getChunkSource().tickingRegions.executorFor(RegionPos.forChunk(x, z))); // ShreddedPaper - regions
+ if (TickThread.isTickThread()) this.getHandle().getChunkSource().mainThreadProcessor.managedBlock(future::isDone); // ShreddedPaper - run tick thread tasks (this might be one tick thread accessing a chunk in another tick thread)
+ return future.join(); // ShreddedPaper - regions
+ return future.join(); // ShreddedPaper - don't use managedBlock to avoid deadlocks in multi-threaded context
}
ChunkAccess chunk = world.getChunkSource().getChunkAtImmediately(x, z);
if (chunk != null) {
return chunk instanceof ImposterProtoChunk || chunk instanceof net.minecraft.world.level.chunk.LevelChunk;
}
- final java.util.concurrent.CompletableFuture<ChunkAccess> future = new java.util.concurrent.CompletableFuture<>();
- ca.spottedleaf.moonrise.common.PlatformHooks.get().scheduleChunkLoad(
- this.world, x, z, false, ChunkStatus.EMPTY, true, ca.spottedleaf.concurrentutil.util.Priority.NORMAL, future::complete
- );
- world.getChunkSource().mainThreadProcessor.managedBlock(future::isDone);
- return future.thenApply(c -> {
- if (c != null) {
- return c.getPersistedStatus() == ChunkStatus.FULL;
- }
- return false;
- }).join();
+ // ShreddedPaper start - avoid recursive deadlock by returning false for recursive calls when chunk not in memory
+ if (isInsideIsChunkGenerated.get()) {
+ return false; // Conservative answer: assume not generated if we can't check without blocking
+ }
+ isInsideIsChunkGenerated.set(Boolean.TRUE);
+ try {
+ // ShreddedPaper end
+ final java.util.concurrent.CompletableFuture<ChunkAccess> future = new java.util.concurrent.CompletableFuture<>();
+ ca.spottedleaf.moonrise.common.PlatformHooks.get().scheduleChunkLoad(
+ this.world, x, z, false, ChunkStatus.EMPTY, true, ca.spottedleaf.concurrentutil.util.Priority.NORMAL, future::complete
+ );
+ world.getChunkSource().mainThreadProcessor.managedBlock(future::isDone);
+ return future.thenApply(c -> {
+ if (c != null) {
+ return c.getPersistedStatus() == ChunkStatus.FULL;
+ }
+ return false;
+ }).join();
+ } finally {
+ isInsideIsChunkGenerated.set(Boolean.FALSE);
+ }
// Paper end - Fix this method
}

@@ -751,13 +_,15 @@

@Override
Expand Down