Handling of onSpinWait and its absence in AffinityPool (#28946)

akka-actor/src/main/java/akka/dispatch/affinity/OnSpinWait.java

@@ -0,0 +1,36 @@
+/*
+ * Copyright (C) 2009-2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.dispatch.affinity;
+
+import akka.util.Unsafe;
+import java.lang.invoke.MethodHandle;
+import java.lang.invoke.MethodHandles;
+import akka.annotation.InternalApi;
+import static java.lang.invoke.MethodType.methodType;
+
+/**
+ * INTERNAL API
+ */
+@InternalApi
+final class OnSpinWait {
+    private final static MethodHandle handle;
+
+    public final static void spinWait() throws Throwable {
+        handle.invoke(); // Will be inlined as an invokeExact since the callsite matches the MH definition of () -> void
+    }
+
+    static {
+        final MethodHandle noop = MethodHandles.constant(Object.class, null).asType(methodType(Void.TYPE));
+        MethodHandle impl;
+        try {
+          impl = MethodHandles.lookup().findStatic(Thread.class, "onSpinWait", methodType(Void.TYPE));
+        } catch (NoSuchMethodException nsme) {
+          impl = noop;
+        } catch (IllegalAccessException iae) {
+          impl = noop;
+        }
+        handle = impl;
+  };
+}

akka-actor/src/main/scala/akka/dispatch/affinity/AffinityPool.scala

@@ -5,8 +5,6 @@
 package akka.dispatch.affinity
 
 import java.lang.Integer.reverseBytes
-import java.lang.invoke.MethodHandles
-import java.lang.invoke.MethodType.methodType
 import java.util.Collections
 import java.util.concurrent._
 import java.util.concurrent.TimeUnit.MICROSECONDS
@@ -15,16 +13,18 @@ import java.util.concurrent.locks.LockSupport
 
 import scala.annotation.{ switch, tailrec }
 import scala.collection.{ immutable, mutable }
-import scala.util.control.NonFatal
 
 import com.typesafe.config.Config
 
 import akka.annotation.{ ApiMayChange, InternalApi }
 import akka.dispatch._
 import akka.event.Logging
-import akka.util.{ ImmutableIntMap, OptionVal, ReentrantGuard }
+import akka.util.{ ImmutableIntMap, ReentrantGuard }
 import akka.util.Helpers.Requiring
 
+import scala.annotation.{ switch, tailrec }
+import scala.collection.{ immutable, mutable }
+
 @InternalApi
 @ApiMayChange
 private[affinity] object AffinityPool {
@@ -42,13 +42,6 @@ private[affinity] object AffinityPool {
   // PoolState: all threads have been stopped, does not process tasks and does not accept new ones
   final val Terminated = 5
 
-  // Method handle to JDK9+ onSpinWait method
-  private val onSpinWaitMethodHandle =
-    try OptionVal.Some(MethodHandles.lookup.findStatic(classOf[Thread], "onSpinWait", methodType(classOf[Void])))
-    catch {
-      case NonFatal(_) => OptionVal.None
-    }
-
   type IdleState = Int
   // IdleState: Initial state
   final val Initial = 0
@@ -85,10 +78,7 @@ private[affinity] object AffinityPool {
           idling = true
           transitionTo(Spinning)
         case Spinning =>
-          onSpinWaitMethodHandle match {
+          OnSpinWait.spinWait()
-            case OptionVal.Some(m) => m.invokeExact()
-            case OptionVal.None    =>
-          }
           turns += 1
           if (turns > maxSpins)
             transitionTo(Yielding)