[lldb] Multithreading lldb-server works on Windows now; fixed gdb port mapping

Removed fork(). Used threads and the common thread-safe port map for all platform connections.

Updated lldb::FileSystem to use llvm::vfs::createPhysicalFileSystem() with an own virtual working directory per thread.

This patch depends on llvm#100659, llvm#100666.

This patch fixes llvm#97537, llvm#90923, llvm#56346.

lldb-server has been tested on Windows with 50 connections and 100 processes launched simultaneously. Tested also the cross build with Linux x86_64 host and Linux Aarch64 target.

Author: slydiman

lldb/include/lldb/Host/FileSystem.h

@@ -47,6 +47,12 @@ class FileSystem {
 
   static FileSystem &Instance();
 
+  static void InitializePerThread() {
+    lldbassert(!InstancePerThread() && "Already initialized.");
+    InstancePerThread().emplace(llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem>(
+        llvm::vfs::createPhysicalFileSystem().release()));
+  }
+
   template <class... T> static void Initialize(T &&...t) {
     lldbassert(!InstanceImpl() && "Already initialized.");
     InstanceImpl().emplace(std::forward<T>(t)...);
@@ -206,6 +212,7 @@ class FileSystem {
 
 private:
   static std::optional<FileSystem> &InstanceImpl();
+  static std::optional<FileSystem> &InstancePerThread();
   llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> m_fs;
   std::unique_ptr<TildeExpressionResolver> m_tilde_resolver;
   std::string m_home_directory;

lldb/source/Host/common/FileSystem.cpp

@@ -49,7 +49,15 @@ void FileSystem::Terminate() {
   InstanceImpl().reset();
 }
 
+std::optional<FileSystem> &FileSystem::InstancePerThread() {
+  static thread_local std::optional<FileSystem> t_fs;
+  return t_fs;
+}
+
 std::optional<FileSystem> &FileSystem::InstanceImpl() {
+  std::optional<FileSystem> &fs = InstancePerThread();
+  if (fs)
+    return fs;
   static std::optional<FileSystem> g_fs;
   return g_fs;
 }

lldb/source/Host/posix/PipePosix.cpp

@@ -324,6 +324,18 @@ Status PipePosix::ReadWithTimeout(void *buf, size_t size,
         bytes_read += result;
         if (bytes_read == size || result == 0)
           break;
+
+        // This is the workaround for the following bug in Linux multithreading
+        // select() https://bugzilla.kernel.org/show_bug.cgi?id=546
+        // ReadWithTimeout() with a non-zero timeout is used only to
+        // read the port number from the gdbserver pipe
+        // in GDBRemoteCommunication::StartDebugserverProcess().
+        // The port number may be "1024\0".."65535\0".
+        if (timeout.count() > 0 && size == 6 && bytes_read == 5 &&
+            static_cast<char *>(buf)[4] == '\0') {
+          break;
+        }
+
       } else if (errno == EINTR) {
         continue;
       } else {

lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerCommon.cpp

@@ -646,7 +646,9 @@ GDBRemoteCommunicationServerCommon::Handle_vFile_Size(
   packet.GetHexByteString(path);
   if (!path.empty()) {
     uint64_t Size;
-    if (llvm::sys::fs::file_size(path, Size))
+    FileSpec file_spec(path);
+    FileSystem::Instance().Resolve(file_spec);
+    if (llvm::sys::fs::file_size(file_spec.GetPath(), Size))
       return SendErrorResponse(5);
     StreamString response;
     response.PutChar('F');
@@ -725,7 +727,9 @@ GDBRemoteCommunicationServerCommon::Handle_vFile_unlink(
   packet.SetFilePos(::strlen("vFile:unlink:"));
   std::string path;
   packet.GetHexByteString(path);
-  Status error(llvm::sys::fs::remove(path));
+  FileSpec file_spec(path);
+  FileSystem::Instance().Resolve(file_spec);
+  Status error(llvm::sys::fs::remove(file_spec.GetPath()));
   StreamString response;
   response.Printf("F%x,%x", error.GetError(), error.GetError());
   return SendPacketNoLock(response.GetString());
@@ -744,6 +748,13 @@ GDBRemoteCommunicationServerCommon::Handle_qPlatform_shell(
       // uint32_t timeout = packet.GetHexMaxU32(false, 32);
       if (packet.GetChar() == ',')
         packet.GetHexByteString(working_dir);
+      else {
+        auto cwd = FileSystem::Instance()
+                       .GetVirtualFileSystem()
+                       ->getCurrentWorkingDirectory();
+        if (cwd)
+          working_dir = *cwd;
+      }
       int status, signo;
       std::string output;
       FileSpec working_spec(working_dir);