Replace FiberPoolThread with a plain Thread to prepare for VirtualThread

Author: eregon

src/main/java/org/truffleruby/RubyLanguage.java

@@ -50,7 +50,6 @@
 import org.truffleruby.core.exception.RubySyntaxError;
 import org.truffleruby.core.exception.RubySystemCallError;
 import org.truffleruby.core.exception.RubySystemExit;
-import org.truffleruby.core.fiber.FiberPoolThread;
 import org.truffleruby.core.fiber.RubyFiber;
 import org.truffleruby.core.hash.RubyHash;
 import org.graalvm.options.OptionValues;
@@ -192,9 +191,10 @@ public static final class ThreadLocalState {
     }
 
     private final ContextThreadLocal<ThreadLocalState> threadLocalState = createContextThreadLocal(
-            (context, thread) -> thread instanceof FiberPoolThread
-                    ? ((FiberPoolThread) thread).threadLocalState
-                    : new ThreadLocalState());
+            (context, thread) -> {
+                var state = context.getThreadManager().threadLocalStates.remove(thread);
+                return state != null ? state : new ThreadLocalState();
+            });
 
     private final CyclicAssumption tracingCyclicAssumption = new CyclicAssumption("object-space-tracing");
     @CompilationFinal private volatile Assumption tracingAssumption = tracingCyclicAssumption.getAssumption();

src/main/java/org/truffleruby/core/fiber/FiberManager.java

@@ -98,7 +98,8 @@ private void fiberMain(RubyContext context, RubyFiber fiber, RubyProc block, Nod
         assert !fiber.isRootFiber() : "Root Fibers execute threadMain() and not fiberMain()";
         assertNotEntered("Fibers should start unentered to avoid triggering multithreading");
 
-        final FiberPoolThread thread = (FiberPoolThread) Thread.currentThread();
+        final Thread thread = Thread.currentThread();
+        var threadLocalState = context.getThreadManager().threadLocalStates.get(thread);
         final SourceSection sourceSection = block.getSharedMethodInfo().getSourceSection();
         final String oldName = thread.getName();
         thread.setName(NAME_PREFIX + " id=" + thread.getId() + " from " + context.fileLine(sourceSection));
@@ -116,7 +117,7 @@ private void fiberMain(RubyContext context, RubyFiber fiber, RubyProc block, Nod
          * for multiple Fibers and multiple Ruby Threads due to the Fiber pool, but initializeThread() is only called
          * once per thread. */
         fiber.rubyThread.setCurrentFiber(fiber);
-        thread.threadLocalState.rubyThread = fiber.rubyThread;
+        threadLocalState.rubyThread = fiber.rubyThread;
 
         final Object prev = truffleContext.enter(currentNode);
 
@@ -153,7 +154,7 @@ private void fiberMain(RubyContext context, RubyFiber fiber, RubyProc block, Nod
             fiber.status = FiberStatus.TERMINATED;
             // Leave context before addToMessageQueue() -> parent Fiber starts executing
             truffleContext.leave(currentNode, prev);
-            thread.threadLocalState.rubyThread = null;
+            threadLocalState.rubyThread = null;
             cleanup(fiber, thread);
             thread.setName(oldName);
 

src/main/java/org/truffleruby/core/fiber/FiberPoolThread.java

@@ -33,6 +33,7 @@
 import com.oracle.truffle.api.object.DynamicObjectLibrary;
 import org.truffleruby.RubyContext;
 import org.truffleruby.RubyLanguage;
+import org.truffleruby.RubyLanguage.ThreadLocalState;
 import org.truffleruby.SuppressFBWarnings;
 import org.truffleruby.collections.Memo;
 import org.truffleruby.core.DummyNode;
@@ -41,7 +42,6 @@
 import org.truffleruby.core.exception.RubyException;
 import org.truffleruby.core.exception.RubySystemExit;
 import org.truffleruby.core.fiber.FiberManager;
-import org.truffleruby.core.fiber.FiberPoolThread;
 import org.truffleruby.core.fiber.RubyFiber;
 import org.truffleruby.core.klass.RubyClass;
 import org.truffleruby.core.string.StringUtils;
@@ -151,6 +151,8 @@ public void restartMainThread(Thread mainJavaThread) {
     // spawning Thread => Fiber object
     public static final ThreadLocal<RubyFiber> FIBER_BEING_SPAWNED = new ThreadLocal<>();
 
+    public final Map<Thread, ThreadLocalState> threadLocalStates = new ConcurrentHashMap<>();
+
     private Thread createFiberJavaThread(Runnable runnable) {
         final RubyFiber fiber = FIBER_BEING_SPAWNED.get();
         assert fiber != null;
@@ -159,7 +161,9 @@ private Thread createFiberJavaThread(Runnable runnable) {
             throw new UnsupportedOperationException("fibers should not be created while pre-initializing the context");
         }
 
-        final Thread thread = new FiberPoolThread(runnable); // context.getEnv().createUnenteredThread(runnable);
+        final Thread thread = new Thread(runnable); // context.getEnv().createUnenteredThread(runnable);
+
+        threadLocalStates.put(thread, new ThreadLocalState());
         thread.setName("Ruby-FiberPool-" + thread.getName());
         thread.setDaemon(true); // GR-33255
         rubyManagedThreads.add(thread); // need to be set before initializeThread()