Fix concurrent read / write issue in GitIndex on Windows

GitIndex.write fails if another thread concurrently reads
the index file. The problem is fixed by retrying the rename
operation if it fails.

Bug: 311051
Change-Id: Ib243d2a90adae312712d02521de4834d06804944
Signed-off-by: Jens Baumgart <jens.baumgart@sap.com>

org.eclipse.jgit/src/org/eclipse/jgit/lib/GitIndex.java

@@ -297,10 +297,32 @@ public void write() throws IOException {
 			fc.write(buf);
 			fc.close();
 			fileOutputStream.close();
-			if (cacheFile.exists())
-				if (!cacheFile.delete())
-					throw new IOException(
-						JGitText.get().couldNotRenameDeleteOldIndex);
+			if (cacheFile.exists()) {
+				if (db.getFS().retryFailedLockFileCommit()) {
+					// file deletion fails on windows if another
+					// thread is reading the file concurrently
+					// So let's try 10 times...
+					boolean deleted = false;
+					for (int i = 0; i < 10; i++) {
+						if (cacheFile.delete()) {
+							deleted = true;
+							break;
+						}
+						try {
+							Thread.sleep(100);
+						} catch (InterruptedException e) {
+							// ignore
+						}
+					}
+					if (!deleted)
+						throw new IOException(
+								JGitText.get().couldNotRenameDeleteOldIndex);
+				} else {
+					if (!cacheFile.delete())
+						throw new IOException(
+								JGitText.get().couldNotRenameDeleteOldIndex);
+				}
+			}
 			if (!tmpIndex.renameTo(cacheFile))
 				throw new IOException(
 						JGitText.get().couldNotRenameTemporaryIndexFileToIndex);

org.eclipse.jgit/src/org/eclipse/jgit/util/FS.java

@@ -148,6 +148,13 @@ public File userHome() {
 		return userHome;
 	}
 
+	/**
+	 * Does this file system have problems with atomic renames?
+	 *
+	 * @return true if the caller should retry a failed rename of a lock file.
+	 */
+	public abstract boolean retryFailedLockFileCommit();
+
 	/**
 	 * Determine the user's home directory (location where preferences are).
 	 *

org.eclipse.jgit/src/org/eclipse/jgit/util/FS_POSIX_Java5.java

@@ -57,4 +57,9 @@ public boolean canExecute(final File f) {
 	public boolean setExecute(final File f, final boolean canExec) {
 		return false;
 	}
+
+	@Override
+	public boolean retryFailedLockFileCommit() {
+		return false;
+	}
 }

org.eclipse.jgit/src/org/eclipse/jgit/util/FS_POSIX_Java6.java

@@ -104,4 +104,9 @@ public boolean setExecute(final File f, final boolean canExec) {
 			throw new Error(e);
 		}
 	}
+
+	@Override
+	public boolean retryFailedLockFileCommit() {
+		return false;
+	}
 }

org.eclipse.jgit/src/org/eclipse/jgit/util/FS_Win32.java

@@ -71,4 +71,9 @@ public boolean canExecute(final File f) {
 	public boolean setExecute(final File f, final boolean canExec) {
 		return false;
 	}
+
+	@Override
+	public boolean retryFailedLockFileCommit() {
+		return true;
+	}
 }