Remove synchronization from file system.

After the path refactor we will no longer have path instances to synchronize on.

The underlying OS file systems are already naturally thread safe, that is, their internal data structures cannot be damaged. Any further synchronization (eg. races between directory creation and deletion) has to be managed at the client level.

The last attempt to do this failed because of races in FileUtils#createDirectoryAndParents on Windows. This method is now gone, replaced by a method from the Java framework that knows how to synchronize.

PiperOrigin-RevId: 180290901

1 files changed, 26 insertions, 40 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/unix/UnixFileSystem.java b/src/main/java/com/google/devtools/build/lib/unix/UnixFileSystem.java
index 0af17cfb12..033a6a692d 100644
--- a/src/main/java/com/google/devtools/build/lib/unix/UnixFileSystem.java
+++ b/src/main/java/com/google/devtools/build/lib/unix/UnixFileSystem.java
@@ -257,11 +257,9 @@ public class UnixFileSystem extends AbstractFileSystemWithCustomStat {
    */
   private void modifyPermissionBits(Path path, int permissionBits, boolean add)
     throws IOException {
-    synchronized (path) {
-      int oldMode = statInternal(path, true).getPermissions();
-      int newMode = add ? (oldMode | permissionBits) : (oldMode & ~permissionBits);
-      NativePosixFiles.chmod(path.toString(), newMode);
-    }
+    int oldMode = statInternal(path, true).getPermissions();
+    int newMode = add ? (oldMode | permissionBits) : (oldMode & ~permissionBits);
+    NativePosixFiles.chmod(path.toString(), newMode);
   }
 
   @Override
@@ -281,9 +279,7 @@ public class UnixFileSystem extends AbstractFileSystemWithCustomStat {
 
   @Override
   protected void chmod(Path path, int mode) throws IOException {
-    synchronized (path) {
-      NativePosixFiles.chmod(path.toString(), mode);
-    }
+    NativePosixFiles.chmod(path.toString(), mode);
   }
 
   @Override
@@ -308,19 +304,17 @@ public class UnixFileSystem extends AbstractFileSystemWithCustomStat {
 
   @Override
   public boolean createDirectory(Path path) throws IOException {
-    synchronized (path) {
-      // Note: UNIX mkdir(2), FilesystemUtils.mkdir() and createDirectory all
-      // have different ways of representing failure!
-      if (NativePosixFiles.mkdir(path.toString(), 0777)) {
-        return true; // successfully created
-      }
+    // Note: UNIX mkdir(2), FilesystemUtils.mkdir() and createDirectory all
+    // have different ways of representing failure!
+    if (NativePosixFiles.mkdir(path.toString(), 0777)) {
+      return true; // successfully created
+    }
 
-      // false => EEXIST: something is already in the way (file/dir/symlink)
-      if (isDirectory(path, false)) {
-        return false; // directory already existed
-      } else {
-        throw new IOException(path + " (File exists)");
-      }
+    // false => EEXIST: something is already in the way (file/dir/symlink)
+    if (isDirectory(path, false)) {
+      return false; // directory already existed
+    } else {
+      throw new IOException(path + " (File exists)");
     }
   }
 
@@ -332,9 +326,7 @@ public class UnixFileSystem extends AbstractFileSystemWithCustomStat {
   @Override
   protected void createSymbolicLink(Path linkPath, PathFragment targetFragment)
       throws IOException {
-    synchronized (linkPath) {
-      NativePosixFiles.symlink(targetFragment.toString(), linkPath.toString());
-    }
+    NativePosixFiles.symlink(targetFragment.toString(), linkPath.toString());
   }
 
   @Override
@@ -355,9 +347,7 @@ public class UnixFileSystem extends AbstractFileSystemWithCustomStat {
 
   @Override
   public void renameTo(Path sourcePath, Path targetPath) throws IOException {
-    synchronized (sourcePath) {
-      NativePosixFiles.rename(sourcePath.toString(), targetPath.toString());
-    }
+    NativePosixFiles.rename(sourcePath.toString(), targetPath.toString());
   }
 
   @Override
@@ -369,12 +359,10 @@ public class UnixFileSystem extends AbstractFileSystemWithCustomStat {
   public boolean delete(Path path) throws IOException {
     String name = path.toString();
     long startTime = Profiler.nanoTimeMaybe();
-    synchronized (path) {
-      try {
-        return NativePosixFiles.remove(name);
-      } finally {
-        profiler.logSimpleTask(startTime, ProfilerTask.VFS_DELETE, name);
-      }
+    try {
+      return NativePosixFiles.remove(name);
+    } finally {
+      profiler.logSimpleTask(startTime, ProfilerTask.VFS_DELETE, name);
     }
   }
 
@@ -385,14 +373,12 @@ public class UnixFileSystem extends AbstractFileSystemWithCustomStat {
 
   @Override
   public void setLastModifiedTime(Path path, long newTime) throws IOException {
-    synchronized (path) {
-      if (newTime == -1L) { // "now"
-        NativePosixFiles.utime(path.toString(), true, 0);
-      } else {
-        // newTime > MAX_INT => -ve unixTime
-        int unixTime = (int) (newTime / 1000);
-        NativePosixFiles.utime(path.toString(), false, unixTime);
-      }
+    if (newTime == -1L) { // "now"
+      NativePosixFiles.utime(path.toString(), true, 0);
+    } else {
+      // newTime > MAX_INT => -ve unixTime
+      int unixTime = (int) (newTime / 1000);
+      NativePosixFiles.utime(path.toString(), false, unixTime);
     }
   }