[WIP][FileCollector] FileCollector::Mutex

[jkorous]

Summary

IIUC we should synchronize read and write access to VFSWriter.

It almost feels like we might want to keep FileCollector thread-unsafe and move the responsibility (and the mutex) to client code.

[JDevlieghere]

llvm/include/llvm/Support/FileCollector.h

63

Yep. How about "Synchronizes the file mapping."?

llvm/include/llvm/Support/FileCollector.h

private:
 
   bool getRealPath(StringRef SrcPath, SmallVectorImpl<char> &Result);
 
   void addFileToMapping(StringRef VirtualPath, StringRef RealPath) {
     VFSWriter.addFileMapping(VirtualPath, RealPath);
   }
 
 protected:
+  /// FIXME: Seems more like it synchronizes everything (...accessible via public interface).
   /// Synchronizes adding files.
   std::mutex Mutex;
 
   /// The root directory where files are copied.
   std::string Root;
 
   /// The root directory where the VFS overlay lives.
   std::string OverlayRoot;
 

llvm/lib/Support/FileCollector.cpp

copyAccessAndModificationTime(StringRef Filename,
 
   if (auto EC = sys::Process::SafelyCloseFileDescriptor(FD))
     return EC;
 
   return {};
 }
 
 std::error_code FileCollector::copyFiles(bool StopOnError) {
+  // TODO: We're reading from VFSWriter so we should lock the Mutex, right?
+  std::lock_guard<std::mutex> lock(Mutex);
+
   for (auto &entry : VFSWriter.getMappings()) {
     // Create directory tree.
     if (std::error_code EC =
             sys::fs::create_directories(sys::path::parent_path(entry.RPath),
                                         /*IgnoreExisting=*/true)) {
       if (StopOnError)
         return EC;
     }