Automated rollback of commit 5cca89f.

*** Reason for rollback ***

Break CI Windows nightly build: bazelbuild#3927
https://ci.bazel.io/blue/organizations/jenkins/Global%2Fbazel-tests/detail/bazel-tests/314/pipeline/31

*** Original change description ***

Remove synchronization from FileSystem implementations.

PiperOrigin-RevId: 173243523

src/main/java/com/google/devtools/build/lib/vfs/AbstractFileSystem.java

@@ -90,16 +90,18 @@ protected OutputStream createFileOutputStream(Path path, boolean append)
 
   @Override
   protected OutputStream getOutputStream(Path path, boolean append) throws IOException {
-    try {
-      return createFileOutputStream(path, append);
-    } catch (FileNotFoundException e) {
-      // Why does it throw a *FileNotFoundException* if it can't write?
-      // That does not make any sense! And its in a completely different
-      // format than in other situations, no less!
-      if (e.getMessage().equals(path + ERR_PERMISSION_DENIED)) {
-        throw new FileAccessException(e.getMessage());
+    synchronized (path) {
+      try {
+        return createFileOutputStream(path, append);
+      } catch (FileNotFoundException e) {
+        // Why does it throw a *FileNotFoundException* if it can't write?
+        // That does not make any sense! And its in a completely different
+        // format than in other situations, no less!
+        if (e.getMessage().equals(path + ERR_PERMISSION_DENIED)) {
+          throw new FileAccessException(e.getMessage());
+        }
+        throw e;
       }
-      throw e;
     }
   }
 

src/main/java/com/google/devtools/build/lib/vfs/JavaIoFileSystem.java

@@ -200,24 +200,43 @@ public boolean isFilePathCaseSensitive() {
 
   @Override
   protected boolean createDirectory(Path path) throws IOException {
-    File file = getIoFile(path);
-    if (file.mkdir()) {
-      return true;
-    }
 
-    if (fileIsSymbolicLink(file)) {
-      throw new IOException(path + ERR_FILE_EXISTS);
-    } else if (file.isDirectory()) {
-      return false; // directory already existed
-    } else if (file.exists()) {
-      throw new IOException(path + ERR_FILE_EXISTS);
-    } else if (!file.getParentFile().exists()) {
-      throw new FileNotFoundException(path.getParentDirectory() + ERR_NO_SUCH_FILE_OR_DIR);
-    } else if (!file.getParentFile().canWrite()) {
-      throw new FileAccessException(path + ERR_PERMISSION_DENIED);
-    } else {
-      // Parent exists, is writable, yet we can't create our directory.
-      throw new FileNotFoundException(path.getParentDirectory() + ERR_NOT_A_DIRECTORY);
+    // We always synchronize on the current path before doing it on the parent path and file system
+    // path structure ensures that this locking order will never be reversed.
+    // When refactoring, check that subclasses still work as expected and there can be no
+    // deadlocks.
+    synchronized (path) {
+      File file = getIoFile(path);
+      if (file.mkdir()) {
+        return true;
+      }
+
+      // We will be checking the state of the parent path as well. Synchronize on it before
+      // attempting anything.
+      Path parentDirectory = path.getParentDirectory();
+      synchronized (parentDirectory) {
+        if (fileIsSymbolicLink(file)) {
+          throw new IOException(path + ERR_FILE_EXISTS);
+        }
+        if (file.isDirectory()) {
+          return false; // directory already existed
+        } else if (file.exists()) {
+          throw new IOException(path + ERR_FILE_EXISTS);
+        } else if (!file.getParentFile().exists()) {
+          throw new FileNotFoundException(path.getParentDirectory() + ERR_NO_SUCH_FILE_OR_DIR);
+        }
+        // Parent directory apparently exists - try to create our directory again - protecting
+        // against the case where parent directory would be created right before us obtaining
+        // synchronization lock.
+        if (file.mkdir()) {
+          return true; // Everything is fine finally.
+        } else if (!file.getParentFile().canWrite()) {
+          throw new FileAccessException(path + ERR_PERMISSION_DENIED);
+        } else {
+          // Parent exists, is writable, yet we can't create our directory.
+          throw new FileNotFoundException(path.getParentDirectory() + ERR_NOT_A_DIRECTORY);
+        }
+      }
     }
   }
 
@@ -272,6 +291,7 @@ protected PathFragment readSymbolicLink(Path path) throws IOException {
 
   @Override
   protected void renameTo(Path sourcePath, Path targetPath) throws IOException {
+    synchronized (sourcePath) {
       File sourceFile = getIoFile(sourcePath);
       File targetFile = getIoFile(targetPath);
       if (!sourceFile.renameTo(targetFile)) {
@@ -292,6 +312,7 @@ protected void renameTo(Path sourcePath, Path targetPath) throws IOException {
           throw new FileAccessException(sourcePath + " -> " + targetPath + ERR_PERMISSION_DENIED);
         }
       }
+    }
   }
 
   @Override
@@ -308,6 +329,7 @@ protected long getFileSize(Path path, boolean followSymlinks) throws IOException
   protected boolean delete(Path path) throws IOException {
     File file = getIoFile(path);
     long startTime = Profiler.nanoTimeMaybe();
+    synchronized (path) {
       try {
         if (file.delete()) {
           return true;
@@ -323,6 +345,7 @@ protected boolean delete(Path path) throws IOException {
       } finally {
         profiler.logSimpleTask(startTime, ProfilerTask.VFS_DELETE, file.getPath());
       }
+    }
   }
 
   @Override