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Don't block the server thread when a keepalive kick moves to the player region #83

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Don't block the server thread when a keepalive kick moves to the player region #83

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37 changes: 29 additions & 8 deletions ...ft-patches/sources/net/minecraft/server/network/ServerCommonPacketListenerImpl.java.patch
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Original file line number Diff line number Diff line change
Expand Up @@ -11,12 +11,18 @@
import io.netty.channel.ChannelFutureListener;
import net.minecraft.CrashReport;
import net.minecraft.CrashReportCategory;
@@ -276,7 +_,7 @@
@@ -52,3 +_,4 @@
private volatile int latency; // Paper - improve keepalives - make volatile
private final io.papermc.paper.util.KeepAlive keepAlive; // Paper - improve keepalives
private volatile boolean suspendFlushingOnServerThread = false;
+ private final java.util.concurrent.atomic.AtomicBoolean shreddedDisconnectQueued = new java.util.concurrent.atomic.AtomicBoolean(); // ShreddedPaper - keepalive kick is handed to the player region
@@ -276,7 +_,8 @@
this.disconnect(DISCONNECT_UNEXPECTED_QUERY, io.papermc.paper.connection.DisconnectionReason.INVALID_COOKIE); // Paper - kick event cause
}

- protected void keepConnectionAlive() {
+ public void keepConnectionAlive() { // ShreddedPaper - make public
+ if (this.shreddedDisconnectQueued.get()) return; // ShreddedPaper - already queued, do not log another timeout every tick
Profiler.get().push("keepAlive");
long now = Util.getMillis();
// Paper start - improve keepalives
Expand All @@ -29,25 +35,40 @@
org.bukkit.craftbukkit.util.Waitable waitable = new org.bukkit.craftbukkit.util.Waitable() {
@Override
protected @Nullable Object evaluate() {
@@ -393,9 +_,20 @@
@@ -393,9 +_,34 @@
}
};

- this.server.processQueue.add(waitable);
+ // ShreddedPaper - run on player's thread
+ // ShreddedPaper start - run on the player's region, and never wait from a tick thread
+ if (this instanceof ServerGamePacketListenerImpl serverGamePacketListener) {
+ if (TickThread.isTickThread()) {
+ serverGamePacketListener.player.level().getChunkSource().tickingRegions.execute(RegionPos.forChunk(serverGamePacketListener.player.chunkPosition()), waitable);
+ } else {
+ ShreddedPaper.runSync(serverGamePacketListener.player, waitable); // this.server.processQueue.add(waitable);
+ // Caller does not own this player (keepalive runs on the global server thread).
+ // managedBlock() here deadlocks: the region cannot tick until this server tick returns.
+ if (!this.shreddedDisconnectQueued.compareAndSet(false, true)) {
+ return;
+ }
+ try {
+ serverGamePacketListener.player.level().getChunkSource().tickingRegions.scheduleTask(RegionPos.forChunk(serverGamePacketListener.player.chunkPosition()), () -> {
+ try {
+ waitable.run();
+ } finally {
+ ServerCommonPacketListenerImpl.this.shreddedDisconnectQueued.set(false);
+ }
+ });
+ } catch (Throwable throwable) {
+ this.shreddedDisconnectQueued.set(false);
+ throw throwable;
+ }
+ return;
+ }
+ ShreddedPaper.runSync(serverGamePacketListener.player, waitable); // this.server.processQueue.add(waitable);
+ } else {
+ this.server.processQueue.add(waitable);
+ }
+ // ShreddedPaper end - run on player's thread
+ // ShreddedPaper end - run on the player's region, and never wait from a tick thread

try {
+ if (TickThread.isTickThread()) this.server.managedBlock(waitable::isDone); // ShreddedPaper - don't block when waiting
waitable.get();
} catch (InterruptedException e) {
Thread.currentThread().interrupt();