undefect. CWE-407 — 63 sites patched across 27 ecosystems

Authors: russell@unturf.com · brackishbert@gmail.com · foxhop.net · TimeHexOn.com

Patches, unit tests, benchmarks, whitepaper, and outreach briefs.
Public domain — no copyright claimed. Use freely.

test/jdk/java/lang/Thread/virtual/YieldQueuing.java

@@ -0,0 +1,133 @@
+/*
+ * Copyright (c) 2022, 2025, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/**
+ * @test
+ * @summary Test Thread.yield submits the virtual thread task to the expected queue
+ * @requires vm.continuations
+ * @run junit/othervm -Djdk.virtualThreadScheduler.maxPoolSize=1 YieldQueuing
+ */
+
+import java.lang.invoke.MethodHandles;
+import java.util.List;
+import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.locks.LockSupport;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.BeforeAll;
+import static org.junit.jupiter.api.Assertions.*;
+
+class YieldQueuing {
+
+    @BeforeAll
+    static void setup() throws Exception {
+        // waiting for LockSupport to be initialized can change the scheduling
+        MethodHandles.lookup().ensureInitialized(LockSupport.class);
+    }
+
+    /**
+     * Test Thread.yield submits the task for the current virtual thread to a scheduler
+     * submission queue when there are no tasks in the local queue.
+     */
+    @Test
+    void testYieldWithEmptyLocalQueue() throws Exception {
+        var list = new CopyOnWriteArrayList<String>();
+
+        var threadsStarted = new AtomicBoolean();
+
+        var threadA = Thread.ofVirtual().unstarted(() -> {
+            // pin thread until task for B is in submission queue
+            while (!threadsStarted.get()) {
+                Thread.onSpinWait();
+            }
+
+            list.add("A");
+            Thread.yield();      // push task for A to submission queue, B should run
+            list.add("A");
+        });
+
+        var threadB = Thread.ofVirtual().unstarted(() -> {
+            list.add("B");
+        });
+
+        // push tasks for A and B to submission queue
+        threadA.start();
+        threadB.start();
+
+        // release A
+        threadsStarted.set(true);
+
+        // wait for result
+        threadA.join();
+        threadB.join();
+        assertEquals(list, List.of("A", "B", "A"));
+    }
+
+    /**
+     * Test Thread.yield submits the task for the current virtual thread to the local
+     * queue when there are tasks in the local queue.
+     */
+    @Test
+    void testYieldWithNonEmptyLocalQueue() throws Exception {
+        var list = new CopyOnWriteArrayList<String>();
+
+        var threadsStarted = new AtomicBoolean();
+
+        var threadA = Thread.ofVirtual().unstarted(() -> {
+            // pin thread until tasks for B and C are in submission queue
+            while (!threadsStarted.get()) {
+                Thread.onSpinWait();
+            }
+
+            list.add("A");
+            LockSupport.park();   // B should run
+            list.add("A");
+        });
+
+        var threadB = Thread.ofVirtual().unstarted(() -> {
+            list.add("B");
+            LockSupport.unpark(threadA);  // push task for A to local queue
+            Thread.yield();               // push task for B to local queue, A should run
+            list.add("B");
+        });
+
+        var threadC = Thread.ofVirtual().unstarted(() -> {
+            list.add("C");
+        });
+
+        // push tasks for A, B and C to submission queue
+        threadA.start();
+        threadB.start();
+        threadC.start();
+
+        // release A
+        threadsStarted.set(true);
+
+        // wait for result
+        threadA.join();
+        threadB.join();
+        threadC.join();
+        assertEquals(list, List.of("A", "B", "A", "B", "C"));
+    }
+}