src/java.base/unix/classes/sun/nio/ch/NativeThread.java

@@ -23,10 +23,13 @@
   * questions.
   */
  
  package sun.nio.ch;
  
+ import jdk.internal.access.JavaLangAccess;
+ import jdk.internal.access.SharedSecrets;
+ 
  
  // Signalling operations on native threads
  //
  // On some operating systems (e.g., Linux), closing a channel while another
  // thread is blocked in an I/O operation upon that channel does not cause that

@@ -35,49 +38,83 @@
  // that can be used to release a native thread from a blocking I/O operation.
  // On systems that do not require this type of signalling, the current() method
  // always returns -1 and the signal(long) method has no effect.
  
  public class NativeThread {
+     private static final JavaLangAccess JLA = SharedSecrets.getJavaLangAccess();
      private static final long VIRTUAL_THREAD_ID = -1L;
  
+     private final Thread thread;
+     private final long tid;
+ 
+     private NativeThread(Thread thread, long tid) {
+         this.thread = thread;
+         this.tid = tid;
+     }
+ 
+     Thread thread() {
+         return thread;
+     }
+ 
      /**
-      * Returns the id of the current native thread if the platform can signal
-      * native threads, 0 if the platform can not signal native threads, or
-      * -1L if the current thread is a virtual thread.
+      * Return a NativeThread for the current thread.
       */
-     public static long current() {
-         if (Thread.currentThread().isVirtual()) {
-             return VIRTUAL_THREAD_ID;
+     public static NativeThread current() {
+         Thread t = Thread.currentThread();
+         if (t.isVirtual()) {
+             // return new object for now
+             return new NativeThread(t, VIRTUAL_THREAD_ID);
          } else {
-             return current0();
+             NativeThread nt = JLA.nativeThread(t);
+             if (nt == null) {
+                 nt = new NativeThread(t, current0());
+                 JLA.setNativeThread(nt);
+             }
+             return nt;
          }
      }
  
      /**
-      * Signals the given native thread.
-      *
-      * @throws IllegalArgumentException if tid is not a token to a native thread
+      * Return a NativeThread for the current platform thread. Returns null if called
+      * from a virtual thread.
       */
-     public static void signal(long tid) {
-         if (tid == 0 || tid == VIRTUAL_THREAD_ID)
-             throw new IllegalArgumentException();
-         signal0(tid);
+     public static NativeThread currentNativeThread() {
+         Thread t = Thread.currentThread();
+         if (t.isVirtual()) {
+             return null;
+         } else {
+             NativeThread nt = JLA.nativeThread(t);
+             if (nt == null) {
+                 nt = new NativeThread(t, current0());
+                 JLA.setNativeThread(nt);
+             }
+             return nt;
+         }
      }
  
      /**
-      * Returns true the tid is the id of a native thread.
+      * Return true if the given NativeThread is a platform thread.
       */
-     static boolean isNativeThread(long tid) {
-         return (tid != 0 && tid != VIRTUAL_THREAD_ID);
+     public static boolean isNativeThread(NativeThread nt) {
+         return nt != null && nt.tid != VIRTUAL_THREAD_ID;
      }
  
      /**
-      * Returns true if tid is -1L.
-      * @see #current()
+      * Return true if the given NativeThread is a virtual thread.
       */
-     static boolean isVirtualThread(long tid) {
-         return (tid == VIRTUAL_THREAD_ID);
+     public static boolean isVirtualThread(NativeThread nt) {
+         return nt != null && nt.tid == VIRTUAL_THREAD_ID;
+     }
+ 
+     /**
+      * Signals this native thread.
+      * @throws UnsupportedOperationException if virtual thread
+      */
+     public void signal() {
+         if (tid == VIRTUAL_THREAD_ID)
+             throw new UnsupportedOperationException();
+         signal0(tid);
      }
  
      /**
       * Return true if the operating system supports pending signals. If a signal is sent
       * to a thread but cannot be delivered immediately then it will be delivered when the