8145981: (fs) LinuxWatchService can reports events against wrong directory

Fixes wakeup mechanism of LinuxWatchService and introduces a test

Reviewed-by: alanb

jdk/src/java.base/linux/classes/sun/nio/fs/LinuxWatchService.java

@@ -322,19 +322,6 @@ class LinuxWatchService
                         bytesRead = 0;
                     }
 
-                    // process any pending requests
-                    if ((nReady > 1) || (nReady == 1 && bytesRead == 0)) {
-                        try {
-                            read(socketpair[0], address, BUFFER_SIZE);
-                            boolean shutdown = processRequests();
-                            if (shutdown)
-                                break;
-                        } catch (UnixException x) {
-                            if (x.errno() != UnixConstants.EAGAIN)
-                                throw x;
-                        }
-                    }
-
                     // iterate over buffer to decode events
                     int offset = 0;
                     while (offset < bytesRead) {
@@ -369,6 +356,19 @@ class LinuxWatchService
 
                         offset += (SIZEOF_INOTIFY_EVENT + len);
                     }
+
+                    // process any pending requests
+                    if ((nReady > 1) || (nReady == 1 && bytesRead == 0)) {
+                        try {
+                            read(socketpair[0], address, BUFFER_SIZE);
+                            boolean shutdown = processRequests();
+                            if (shutdown)
+                                break;
+                        } catch (UnixException x) {
+                            if (x.errno() != UnixConstants.EAGAIN)
+                                throw x;
+                        }
+                    }
                 }
             } catch (UnixException x) {
                 x.printStackTrace();

jdk/test/java/nio/file/WatchService/UpdateInterference.java

@@ -0,0 +1,107 @@
+/*
+ * Copyright (c) 2015, 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 8145981
+ * @summary LinuxWatchService sometimes reports inotify events against wrong directory
+ * @run main UpdateInterference
+ */
+import java.io.IOException;
+import java.nio.file.*;
+import java.util.List;
+import java.util.concurrent.TimeUnit;
+import static java.nio.file.StandardWatchEventKinds.*;
+
+public class UpdateInterference {
+    public static void main(String[] args) throws IOException, InterruptedException {
+        final Path root = Files.createTempDirectory("test");
+        final Path foo = root.resolve("foo");
+        final Path bar = root.resolve("bar");
+        final Path baz = root.resolve("baz");
+
+        Files.createDirectory(foo);
+        Files.createDirectory(bar);
+        Files.createDirectory(baz);
+
+        final WatchService watcher = root.getFileSystem().newWatchService();
+        final WatchKey fooKey = foo.register(watcher, ENTRY_CREATE);
+        final WatchKey barKey = bar.register(watcher, ENTRY_CREATE);
+
+        new Thread() {
+            { setDaemon(true); }
+
+            @Override
+            public void run() {
+                while (true) {
+                    try {
+                        final Path temp = Files.createTempFile(foo, "temp", ".tmp");
+                        Files.delete(temp);
+                        Thread.sleep(10);
+                    } catch (IOException | InterruptedException e) {
+                        throw new RuntimeException(e);
+                    }
+                }
+            }
+        }.start();
+
+        new Thread() {
+            { setDaemon(true); }
+
+            @Override
+            public void run() {
+                WatchKey bazKeys[] = new WatchKey[32];
+                while (true) {
+                    try {
+                        for( int i = 0; i < bazKeys.length; i++) {
+                            bazKeys[i] = baz.register(watcher, ENTRY_CREATE);
+                        }
+                        for( int i = 0; i < bazKeys.length; i++) {
+                            bazKeys[i].cancel();
+                        }
+                        Thread.sleep(1);
+                    } catch (IOException | InterruptedException e) {
+                        throw new RuntimeException(e);
+                    }
+                }
+            }
+        }.start();
+
+        long time = System.currentTimeMillis();
+        while ((System.currentTimeMillis() - time) < 15000) {
+            final WatchKey key = watcher.poll(60, TimeUnit.SECONDS);
+            if (key == null) continue;
+
+            if (key != fooKey) {
+                List<WatchEvent<?>> pollEvents = key.pollEvents();
+                for (WatchEvent<?> watchEvent : pollEvents) {
+                    System.out.println(watchEvent.count() + " " +
+                                       watchEvent.kind() + " " +
+                                       watchEvent.context());
+                }
+                throw new RuntimeException("Event received for unexpected key");
+            }
+            key.reset();
+        }
+    }
+}
+