8229516: Thread.isInterrupted() always returns false after thread termination

Reviewed-by: dnsimon, sspitsyn, dcubed, alanb

src/java.base/share/classes/java/lang/Thread.java

@@ -154,6 +154,9 @@ class Thread implements Runnable {
     /* Whether or not the thread is a daemon thread. */
     private boolean daemon = false;
 
+    /* Interrupt state of the thread - read/written directly by JVM */
+    private volatile boolean interrupted;
+
     /* Fields reserved for exclusive use by the JVM */
     private boolean stillborn = false;
     private long eetop;
@@ -971,10 +974,14 @@ class Thread implements Runnable {
      *
      * <p> Interrupting a thread that is not alive need not have any effect.
      *
+     * @implNote In the JDK Reference Implementation, interruption of a thread
+     * that is not alive still records that the interrupt request was made and
+     * will report it via {@link #interrupted} and {@link #isInterrupted()}.
+     *
      * @throws  SecurityException
      *          if the current thread cannot modify this thread
      *
-     * @revised 6.0
+     * @revised 6.0, 14
      * @spec JSR-51
      */
     public void interrupt() {
@@ -985,14 +992,15 @@ class Thread implements Runnable {
             synchronized (blockerLock) {
                 Interruptible b = blocker;
                 if (b != null) {
-                    interrupt0();  // set interrupt status
+                    interrupted = true;
+                    interrupt0();  // inform VM of interrupt
                     b.interrupt(this);
                     return;
                 }
             }
         }
-
-        // set interrupt status
+        interrupted = true;
+        // inform VM of interrupt
         interrupt0();
     }
 
@@ -1004,44 +1012,37 @@ class Thread implements Runnable {
      * interrupted again, after the first call had cleared its interrupted
      * status and before the second call had examined it).
      *
-     * <p>A thread interruption ignored because a thread was not alive
-     * at the time of the interrupt will be reflected by this method
-     * returning false.
-     *
      * @return  {@code true} if the current thread has been interrupted;
      *          {@code false} otherwise.
      * @see #isInterrupted()
-     * @revised 6.0
+     * @revised 6.0, 14
      */
     public static boolean interrupted() {
-        return currentThread().isInterrupted(true);
+        Thread t = currentThread();
+        boolean interrupted = t.interrupted;
+        // We may have been interrupted the moment after we read the field,
+        // so only clear the field if we saw that it was set and will return
+        // true; otherwise we could lose an interrupt.
+        if (interrupted) {
+            t.interrupted = false;
+            clearInterruptEvent();
+        }
+        return interrupted;
     }
 
     /**
      * Tests whether this thread has been interrupted.  The <i>interrupted
      * status</i> of the thread is unaffected by this method.
      *
-     * <p>A thread interruption ignored because a thread was not alive
-     * at the time of the interrupt will be reflected by this method
-     * returning false.
-     *
      * @return  {@code true} if this thread has been interrupted;
      *          {@code false} otherwise.
      * @see     #interrupted()
-     * @revised 6.0
+     * @revised 6.0, 14
      */
     public boolean isInterrupted() {
-        return isInterrupted(false);
+        return interrupted;
     }
 
-    /**
-     * Tests if some Thread has been interrupted.  The interrupted state
-     * is reset or not based on the value of ClearInterrupted that is
-     * passed.
-     */
-    @HotSpotIntrinsicCandidate
-    private native boolean isInterrupted(boolean ClearInterrupted);
-
     /**
      * Tests if this thread is alive. A thread is alive if it has
      * been started and has not yet died.
@@ -2080,5 +2081,6 @@ class Thread implements Runnable {
     private native void suspend0();
     private native void resume0();
     private native void interrupt0();
+    private static native void clearInterruptEvent();
     private native void setNativeName(String name);
 }