From d472c4bc5ff1cb72d6ecb0d691f239b9088378dc Mon Sep 17 00:00:00 2001
Date: Fri, 22 Jan 2021 11:35:09 +0800
Subject: Backport of JDK-8166253

summary: (ch) FileLock object can get GC'd and result in unexpected release of file lock
LLT: jdk/test/java/nio/channels/FileLock/FileLockGC.java

bug link: https://bugs.openjdk.java.net/browse/JDK-8166253
---
 .../classes/sun/nio/ch/FileLockTable.java     |  13 +-
 .../nio/channels/FileLock/FileLockGC.java     | 143 ++++++++++++++++++
 2 files changed, 155 insertions(+), 1 deletion(-)
 create mode 100644 jdk/test/java/nio/channels/FileLock/FileLockGC.java

diff --git a/jdk/src/share/classes/sun/nio/ch/FileLockTable.java b/jdk/src/share/classes/sun/nio/ch/FileLockTable.java
index e77e1c4ce..b0351e566 100644
--- a/jdk/src/share/classes/sun/nio/ch/FileLockTable.java
+++ b/jdk/src/share/classes/sun/nio/ch/FileLockTable.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2005, 2009, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2005, 2018, 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
@@ -115,9 +115,13 @@ class SharedFileLockTable extends FileLockTable {
     // File key for the file that this channel is connected to
     private final FileKey fileKey;
 
+    // Locks obtained for this channel
+    private final Set<FileLock> locks;
+
     SharedFileLockTable(Channel channel, FileDescriptor fd) throws IOException {
         this.channel = channel;
         this.fileKey = FileKey.create(fd);
+        this.locks = new HashSet<FileLock>();
     }
 
     @Override
@@ -135,6 +139,7 @@ class SharedFileLockTable extends FileLockTable {
                     if (prev == null) {
                         // we successfully created the key so we add the file lock
                         list.add(new FileLockReference(fl, queue, fileKey));
+                        locks.add(fl);
                         break;
                     }
                 }
@@ -151,6 +156,7 @@ class SharedFileLockTable extends FileLockTable {
                 if (list == current) {
                     checkList(list, fl.position(), fl.size());
                     list.add(new FileLockReference(fl, queue, fileKey));
+                    locks.add(fl);
                     break;
                 }
                 list = current;
@@ -187,6 +193,7 @@ class SharedFileLockTable extends FileLockTable {
                     assert (lock != null) && (lock.acquiredBy() == channel);
                     ref.clear();
                     list.remove(index);
+                    locks.remove(fl);
                     break;
                 }
                 index++;
@@ -220,6 +227,8 @@ class SharedFileLockTable extends FileLockTable {
 
                 // once the lock list is empty we remove it from the map
                 removeKeyIfEmpty(fileKey, list);
+
+                locks.clear();
             }
         }
         return result;
@@ -238,6 +247,8 @@ class SharedFileLockTable extends FileLockTable {
                 if (lock == fromLock) {
                     ref.clear();
                     list.set(index, new FileLockReference(toLock, queue, fileKey));
+                    locks.remove(fromLock);
+                    locks.add(toLock);
                     break;
                 }
             }
diff --git a/jdk/test/java/nio/channels/FileLock/FileLockGC.java b/jdk/test/java/nio/channels/FileLock/FileLockGC.java
new file mode 100644
index 000000000..fb6618688
--- /dev/null
+++ b/jdk/test/java/nio/channels/FileLock/FileLockGC.java
@@ -0,0 +1,143 @@
+/*
+ * Copyright (c) 2018, 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.
+ */
+
+import java.io.File;
+import java.io.IOException;
+import java.io.RandomAccessFile;
+import java.lang.ref.Reference;
+import java.lang.ref.WeakReference;
+import java.nio.channels.FileLock;
+import java.nio.channels.OverlappingFileLockException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import jdk.testlibrary.FileUtils;
+
+/*
+ * @test
+ * @bug 8166253
+ * @summary Verify that OverlappingFileLockException is thrown when expected.
+ * @library /lib/testlibrary
+ * @build jdk.testlibrary.Utils
+ * @run main/othervm FileLockGC
+ */
+public class FileLockGC {
+    public enum TestType {
+        NO_GC_NO_RELEASE(true),
+        // A hypothetical 'GC_THEN_RELEASE' case is infeasible
+        RELEASE(false),
+        RELEASE_THEN_GC(false),
+        GC(true);
+
+        private final boolean exceptionExpected;
+
+        TestType(boolean exceptionExpected) {
+            this.exceptionExpected = exceptionExpected;
+        }
+
+        boolean exceptionExpected() {
+            return exceptionExpected;
+        }
+    }
+
+    public static void main(String[] args) throws Exception {
+        final File f = new File(System.getProperty("test.dir", ".")
+            + File.separator + "junk.txt");
+        final Path p = f.toPath();
+        int failures = 0;
+
+        for (TestType t : TestType.values()) {
+            try {
+                if (!testFileLockGC(f, t)) {
+                    failures++;
+                }
+            } finally {
+                FileUtils.deleteFileIfExistsWithRetry(p);
+            }
+        }
+
+        if (failures != 0) {
+            throw new RuntimeException("Test had " + failures + " failure(s)");
+        }
+    }
+
+    private static boolean testFileLockGC(File f, TestType type)
+        throws InterruptedException, IOException {
+        System.out.printf("Test %s starting%n", type.toString());
+
+        final RandomAccessFile raf1 = new RandomAccessFile(f, "rw");
+
+        FileLock lock1 = raf1.getChannel().tryLock();
+        WeakReference<FileLock> ref1 = new WeakReference(lock1);
+
+        switch (type) {
+            case GC:
+                lock1 = null;
+                System.gc();
+                break;
+            case RELEASE:
+                lock1.release();
+                break;
+            case RELEASE_THEN_GC:
+                lock1.release();
+                lock1 = null;
+                System.gc();
+                break;
+            default: // NO_GC_NO_RELEASE
+                // lock1 is neither collected nor released
+                break;
+        }
+
+        final RandomAccessFile raf2 = new RandomAccessFile(f, "rw");
+
+        boolean success = true;
+        FileLock lock2 = null;
+        try {
+            lock2 = raf2.getChannel().tryLock();
+            if (type.exceptionExpected()) {
+                System.err.printf
+                    ("No expected OverlappingFileLockException for test %s%n",
+                    type.toString());
+                success = false;
+            }
+        } catch (OverlappingFileLockException ofe) {
+            if (!type.exceptionExpected()) {
+                System.err.printf
+                    ("Unexpected OverlappingFileLockException for test %s%n",
+                    type.toString());
+                success = false;
+            }
+        } finally {
+            if (lock1 != null) {
+                lock1.release();
+            }
+            if (lock2 != null) {
+                lock2.release();
+            }
+            raf2.close();
+            raf1.close();
+            System.out.printf("Test %s finished%n", type.toString());
+        }
+
+        return success;
+    }
+}
-- 
2.19.0