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/StampedLock/ReadersUnlockAfterWriteUnlock.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.
+ */
+
+/*
+ * @test
+ * @bug 8023234
+ * @summary StampedLock serializes readers on writer unlock
+ * @author Dmitry Chyuko
+ * @author Aleksey Shipilev
+ */
+
+import java.util.concurrent.CyclicBarrier;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.concurrent.locks.StampedLock;
+
+public class ReadersUnlockAfterWriteUnlock {
+    public static void main(String[] args) throws InterruptedException {
+        final int RNUM = 2;
+        final int REPS = 128;
+        final StampedLock sl = new StampedLock();
+        final AtomicReference<Throwable> bad = new AtomicReference<>();
+
+        final CyclicBarrier iterationStart = new CyclicBarrier(RNUM + 1);
+        final CyclicBarrier readersHaveLocks = new CyclicBarrier(RNUM);
+        final CyclicBarrier writerHasLock = new CyclicBarrier(RNUM + 1);
+
+        Runnable reader = () -> {
+            try {
+                for (int i = 0; i < REPS; i++) {
+                    iterationStart.await();
+                    writerHasLock.await();
+                    long rs = sl.readLock();
+
+                    // single reader blocks here indefinitely if readers
+                    // are serialized
+                    readersHaveLocks.await();
+
+                    sl.unlockRead(rs);
+                }
+            } catch (Throwable ex) {
+                ex.printStackTrace();
+                bad.set(ex);
+            }
+        };
+
+        Thread[] threads = new Thread[RNUM];
+        for (int i = 0 ; i < RNUM; i++) {
+            Thread thread = new Thread(reader, "Reader");
+            threads[i] = thread;
+            thread.start();
+        }
+        for (int i = 0; i < REPS; i++) {
+            try {
+                iterationStart.await();
+                long ws = sl.writeLock();
+                writerHasLock.await();
+                awaitWaitState(threads);
+                sl.unlockWrite(ws);
+            } catch (Exception e) {
+                throw new IllegalStateException(e);
+            }
+        }
+        for (Thread thread : threads)
+            thread.join();
+        if (bad.get() != null)
+            throw new AssertionError(bad.get());
+    }
+
+    static void awaitWaitState(Thread[] threads) {
+        restart: for (;;) {
+            for (Thread thread : threads) {
+                if (thread.getState() != Thread.State.WAITING) {
+                    Thread.yield();
+                    continue restart;
+                }
+            }
+            break;
+        }
+    }
+}