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/util/concurrent/locks/LockSupport/ParkLoops.java

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+/*
+ * 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.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Martin Buchholz with assistance from members of JCP
+ * JSR-166 Expert Group and released to the public domain, as
+ * explained at http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+/*
+ * @test
+ * @bug 8074773
+ * @summary Stress test looks for lost unparks
+ */
+
+import static java.util.concurrent.TimeUnit.SECONDS;
+
+import java.util.SplittableRandom;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.atomic.AtomicReferenceArray;
+import java.util.concurrent.locks.LockSupport;
+
+public final class ParkLoops {
+    static final int THREADS = 4;
+    static final int ITERS = 30_000;
+
+    static class Parker implements Runnable {
+        static {
+            // Reduce the risk of rare disastrous classloading in first call to
+            // LockSupport.park: https://bugs.openjdk.org/browse/JDK-8074773
+            Class<?> ensureLoaded = LockSupport.class;
+        }
+
+        private final AtomicReferenceArray<Thread> threads;
+        private final CountDownLatch done;
+        private final SplittableRandom rnd;
+
+        Parker(AtomicReferenceArray<Thread> threads,
+                 CountDownLatch done,
+                 SplittableRandom rnd) {
+            this.threads = threads; this.done = done; this.rnd = rnd;
+        }
+
+        public void run() {
+            final Thread current = Thread.currentThread();
+            for (int k = ITERS, j; k > 0; k--) {
+                do {
+                    j = rnd.nextInt(THREADS);
+                } while (!threads.compareAndSet(j, null, current));
+                do {                    // handle spurious wakeups
+                    LockSupport.park();
+                } while (threads.get(j) == current);
+            }
+            done.countDown();
+        }
+    }
+
+    static class Unparker implements Runnable {
+        static {
+            // Reduce the risk of rare disastrous classloading in first call to
+            // LockSupport.park: https://bugs.openjdk.org/browse/JDK-8074773
+            Class<?> ensureLoaded = LockSupport.class;
+        }
+
+        private final AtomicReferenceArray<Thread> threads;
+        private final CountDownLatch done;
+        private final SplittableRandom rnd;
+
+        Unparker(AtomicReferenceArray<Thread> threads,
+                 CountDownLatch done,
+                 SplittableRandom rnd) {
+            this.threads = threads; this.done = done; this.rnd = rnd;
+        }
+
+        public void run() {
+            for (int n = 0; (n++ & 0xff) != 0 || done.getCount() > 0;) {
+                int j = rnd.nextInt(THREADS);
+                Thread parker = threads.get(j);
+                if (parker != null &&
+                    threads.compareAndSet(j, parker, null)) {
+                    LockSupport.unpark(parker);
+                }
+            }
+        }
+    }
+
+    public static void main(String[] args) throws Exception {
+        final SplittableRandom rnd = new SplittableRandom();
+        final ExecutorService pool = Executors.newCachedThreadPool();
+        final AtomicReferenceArray<Thread> threads
+            = new AtomicReferenceArray<>(THREADS);
+        final CountDownLatch done = new CountDownLatch(THREADS);
+        for (int i = 0; i < THREADS; i++) {
+            pool.submit(new Parker(threads, done, rnd.split()));
+            pool.submit(new Unparker(threads, done, rnd.split()));
+        }
+        // Let test harness handle timeout
+        done.await();
+        pool.shutdown();
+        pool.awaitTermination(Long.MAX_VALUE, SECONDS);
+    }
+}