Simplify clearFastPending() to clarify logic

* clearFastPending() is always called for the current thread so is much simpler.

Author: eregon

truffle/src/com.oracle.truffle.runtime/src/com/oracle/truffle/runtime/hotspot/HotSpotThreadLocalHandshake.java

@@ -92,11 +92,6 @@ static void doHandshake(Object node) {
         SINGLETON.processHandshake((Node) node);
     }
 
-    @Override
-    protected void setFastPending(Thread t) {
-        setVolatile(t, 1);
-    }
-
     @Override
     @TruffleBoundary
     public TruffleSafepointImpl getCurrent() {
@@ -110,21 +105,24 @@ public TruffleSafepointImpl getCurrent() {
 
     @Override
     protected void clearFastPending() {
-        setVolatile(Thread.currentThread(), 0);
+        Thread carrierThread = JAVA_LANG_ACCESS.currentCarrierThread();
+        long eetop = UNSAFE.getLongVolatile(carrierThread, THREAD_EETOP_OFFSET);
+        UNSAFE.putIntVolatile(null, eetop + PENDING_OFFSET, 0);
     }
 
-    private static void setVolatile(Thread thread, int value) {
+    @Override
+    protected void setFastPending(Thread thread) {
         /*
          * The thread will not go away here because the Truffle implementation ensures that this
          * method is no longer used if the thread is no longer active. It only sets this state for
          * contexts that are currently entered on a thread. Being entered implies that the thread is
          * active.
          */
-        assert thread.isAlive() : "thread must remain alive while setting fast pending";
+        assert thread.isAlive() : "thread must remain alive while setting the pending flag";
 
         long eetop = UNSAFE.getLongVolatile(thread, THREAD_EETOP_OFFSET);
         if (eetop != 0) {
-            UNSAFE.putIntVolatile(null, eetop + PENDING_OFFSET, value);
+            UNSAFE.putIntVolatile(null, eetop + PENDING_OFFSET, 1);
         } else { // only the case for VirtualThreads
             Object carrierThread = UNSAFE.getObjectVolatile(thread, THREAD_CARRIER_THREAD_OFFSET);
             if (carrierThread == null) {
@@ -137,7 +135,7 @@ private static void setVolatile(Thread thread, int value) {
                 return;
             }
             eetop = UNSAFE.getLongVolatile(carrierThread, THREAD_EETOP_OFFSET);
-            UNSAFE.putIntVolatile(null, eetop + PENDING_OFFSET, value);
+            UNSAFE.putIntVolatile(null, eetop + PENDING_OFFSET, 1);
             /*
              * If the VirtualThread moves to another carrier thread after this method returns, the
              * pending flag will still be set correctly thanks to setPendingFlagForVirtualThread()