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/nio/channels/Selector/HelperSlowToDie.java

@@ -0,0 +1,83 @@
+/*
+ * Copyright (c) 2009, 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
+ * @bug 6823609
+ * @summary Selector.select can hangs on Windows for cases where a helper thread
+ *   becomes redudant but a new helper is immediately needed.
+ * @requires (os.family == "windows")
+ */
+
+import java.nio.channels.*;
+import java.io.IOException;
+
+public class HelperSlowToDie {
+    private static final int CHANNELS_PER_THREAD = 1023;
+    private static final int TEST_ITERATIONS = 200;
+    private static volatile boolean done;
+
+    public static void main(String[] args) throws IOException {
+        Selector sel = Selector.open();
+
+        // register channels
+        SocketChannel[] channels = new SocketChannel[CHANNELS_PER_THREAD];
+        for (int i=0; i<CHANNELS_PER_THREAD; i++) {
+            SocketChannel sc = SocketChannel.open();
+            sc.configureBlocking(false);
+            sc.register(sel, SelectionKey.OP_CONNECT);
+            channels[i] = sc;
+        }
+        sel.selectNow();
+
+        // Start threads to swamp all cores but one. This improves the chances
+        // of duplicating the bug.
+        Runnable busy = new Runnable() {
+            public void run() {
+                while (!done) ;  // no nothing
+            }
+        };
+        int ncores = Runtime.getRuntime().availableProcessors();
+        for (int i=0; i<ncores-1; i++)
+            new Thread(busy).start();
+
+        // Loop changing the number of channels from 1023 to 1024 and back.
+        for (int i=0; i<TEST_ITERATIONS; i++) {
+            SocketChannel sc = SocketChannel.open();
+            sc.configureBlocking(false);
+            sc.register(sel, SelectionKey.OP_CONNECT);
+            sel.selectNow();   // cause helper to spin up
+            sc.close();
+            sel.selectNow();  // cause helper to retire
+        }
+
+        // terminate busy threads
+        done = true;
+
+        // clean-up
+        for (int i=0; i<CHANNELS_PER_THREAD; i++) {
+            channels[i].close();
+        }
+        sel.close();
+    }
+}