Get rid of CHM on event loop VT start

Author: franz1981

core/src/main/java/io/netty/loom/EventLoopScheduler.java

@@ -88,15 +88,10 @@ public EventLoopScheduler(IoEventLoopGroup parent, ThreadFactory threadFactory,
 	}
 
 	private static ThreadFactory newEventLoopSchedulerFactory(SharedRef sharedRef) {
-		var rawVTFactory = Thread.ofVirtual().factory();
-		return runnable -> NettyScheduler.assignUnstarted(rawVTFactory.newThread(() -> // this can be inherited by any
-																						// thread created in the context
-																						// of this virtual thread
-																						// but only the original virtual
-																						// thread will have the correct
-																						// scheduler context
-		ScopedValue.where(CURRENT_SCHEDULER, new SchedulingContext(Thread.currentThread().threadId(), sharedRef))
-				.run(runnable)), sharedRef);
+		var rawVTFactory = Thread.ofVirtual().attach(sharedRef).factory();
+		return runnable -> rawVTFactory.newThread(() -> ScopedValue
+				.where(CURRENT_SCHEDULER, new SchedulingContext(Thread.currentThread().threadId(), sharedRef))
+				.run(runnable));
 	}
 
 	int externalContinuationsCount() {

core/src/main/java/io/netty/loom/NettyScheduler.java

@@ -2,8 +2,6 @@
 
 import io.netty.loom.EventLoopScheduler.SharedRef;
 
-import java.util.concurrent.ConcurrentHashMap;
-
 /**
  * Global Netty scheduler proxy for virtual threads.
  *
@@ -36,8 +34,6 @@ public class NettyScheduler implements Thread.VirtualThreadScheduler {
 
 	private final Thread.VirtualThreadScheduler jdkBuildinScheduler;
 
-	private final ConcurrentHashMap<Thread, SharedRef> unstartedThreads = new ConcurrentHashMap<>();
-
 	private final boolean perCarrierPollers;
 
 	private static NettyScheduler ensureInstalled() {
@@ -71,17 +67,15 @@ Thread.VirtualThreadScheduler jdkBuildinScheduler() {
 
 	@Override
 	public void onStart(Thread.VirtualThreadTask virtualThreadTask) {
-		// TODO this is not great for 2 reasons:
-		// 1. we are doing a remove on a concurrent map even for v threads which are not
-		// really interesting to us
-		// 2. if a vThread will never start, it will leak here forever
-		// HINT: if we had a VirtualThreadTask::Of(VirtualThread) method, we could
-		// perform the assignment BEFORE calling this
-		// on the vThread factory
-		// or the vThreadFactory could provide in its build method something to access
-		// the VirtualThreadTask of an unstarted VirtualThread
-		var assignedSchedulerRef = unstartedThreads.remove(virtualThreadTask.thread());
-		if (assignedSchedulerRef == null) {
+		if (virtualThreadTask.attachment() instanceof SharedRef ref) {
+			var eventLoop = ref.get();
+			if (eventLoop != null && eventLoop.execute(virtualThreadTask)) {
+				return;
+			}
+			// the v thread has been rejected by its assigned scheduler or its scheduler is
+			// gone
+			virtualThreadTask.attach(null);
+		} else {
 			if (perCarrierPollers) {
 				// Read-Poller threads should always inherit the event loop scheduler from the
 				// caller thread
@@ -105,31 +99,16 @@ public void onStart(Thread.VirtualThreadTask virtualThreadTask) {
 					}
 				}
 			}
-		} else {
-			var scheduler = assignedSchedulerRef.get();
-			if (scheduler != null) {
-				// attach the assigned scheduler to the task
-				virtualThreadTask.attach(assignedSchedulerRef);
-				if (scheduler.execute(virtualThreadTask)) {
-					return;
-				}
-			}
-			// the v thread has been rejected by its assigned scheduler or its scheduler is
-			// gone
-			virtualThreadTask.attach(null);
 		}
 		jdkBuildinScheduler.onStart(virtualThreadTask);
 	}
 
 	@Override
 	public void onContinue(Thread.VirtualThreadTask virtualThreadTask) {
-		var attachment = virtualThreadTask.attachment();
-		if (attachment instanceof SharedRef ref) {
-			var assignedScheduler = ref.get();
-			if (assignedScheduler != null) {
-				if (assignedScheduler.execute(virtualThreadTask)) {
-					return;
-				}
+		if (virtualThreadTask.attachment() instanceof SharedRef ref) {
+			var eventLoop = ref.get();
+			if (eventLoop != null && eventLoop.execute(virtualThreadTask)) {
+				return;
 			}
 			// the v thread has been rejected by its assigned scheduler or its scheduler is
 			// gone
@@ -138,11 +117,6 @@ public void onContinue(Thread.VirtualThreadTask virtualThreadTask) {
 		jdkBuildinScheduler.onContinue(virtualThreadTask);
 	}
 
-	static Thread assignUnstarted(Thread unstarted, SharedRef ref) {
-		ensureInstalled().unstartedThreads.put(unstarted, ref);
-		return unstarted;
-	}
-
 	public static boolean perCarrierPollers() {
 		return ensureInstalled().perCarrierPollers;
 	}