test/hotspot/jtreg/runtime/handshake/HandshakeWalkSuspendExitTest.java

rev 52283 : [mq]: 8212933
rev 52284 : 8212933: Thread-SMR: requesting a VM operation whilst holding a ThreadsListHandle can cause deadlocks
Reviewed-by: eosterlund, dcubed, sspitsyn

@@ -44,21 +44,23 @@
     static java.util.concurrent.Semaphore _sem = new java.util.concurrent.Semaphore(0);
 
     @Override
     public void run() {
         WhiteBox wb = WhiteBox.getWhiteBox();
-        while(!exit_now) {
+        while (!exit_now) {
             _sem.release();
-            for (int i = 0; i < _threads.length; i+=2) {
-                wb.handshakeWalkStack(null, true);
+            // We only suspend threads on even index and not ourself.
+            // Otherwise we can accidentially suspend all threads.
+            for (int i = 0; i < _threads.length; i += 2) {
+                wb.handshakeWalkStack(null /* ignored */, true /* stackwalk all threads */);
                 if (Thread.currentThread() != _threads[i]) {
                     _threads[i].suspend();
                     _threads[i].resume();
                 }
             }
-            for (int i = 0; i < _threads.length; i+=2) {
-                wb.handshakeWalkStack(_threads[i], false);
+            for (int i = 0; i < _threads.length; i += 2) {
+                wb.handshakeWalkStack(_threads[i] /* thread to stackwalk */, false /* stackwalk one thread */);
                 if (Thread.currentThread() != _threads[i]) {
                     _threads[i].suspend();
                     _threads[i].resume();
                 }
             }

@@ -73,14 +75,19 @@
             _threads[i].start();
         }
         for (int i = 0; i < _test_threads; i++) {
             _sem.acquire();
         }
+        Thread[] exit_threads = new Thread[_test_exit_threads];
         for (int i = 0; i < _test_exit_threads; i++) {
-            new Thread(new Runnable() { public void run() {} }).start();
+            exit_threads[i] = new Thread(new Runnable() { public void run() {} });
+            exit_threads[i].start();
         }
         exit_now = true;
         for (int i = 0; i < _threads.length; i++) {
             _threads[i].join();
         }
+        for (int i = 0; i < exit_threads.length; i++) {
+            exit_threads[i].join();
+        }
     }
 }