Adopting a different strategy for monitoring pipes and files.

For pipes, we use a monitor thread that performs a zero byte read to detect changes before signaling.

For files, WaitFor{SingleObject,MultipleObjects}() is signaled if the file changes on disk.

Author: ashgti

lldb/include/lldb/Host/File.h

@@ -127,7 +127,6 @@ class File : public IOObject {
   /// \return
   ///     a valid handle or IOObject::kInvalidHandleValue
   WaitableHandle GetWaitableHandle() override;
-  bool HasReadableData() override;
 
   /// Get the file specification for this file, if possible.
   ///
@@ -401,7 +400,6 @@ class NativeFile : public File {
   Status Write(const void *buf, size_t &num_bytes) override;
   Status Close() override;
   WaitableHandle GetWaitableHandle() override;
-  bool HasReadableData() override;
   Status GetFileSpec(FileSpec &file_spec) const override;
   int GetDescriptor() const override;
   FILE *GetStream() override;

lldb/include/lldb/Host/Socket.h

@@ -158,7 +158,6 @@ class Socket : public IOObject {
 
   bool IsValid() const override { return m_socket != kInvalidSocketValue; }
   WaitableHandle GetWaitableHandle() override;
-  bool HasReadableData() override;
 
   static llvm::Expected<HostAndPort>
   DecodeHostAndPort(llvm::StringRef host_and_port);
@@ -186,7 +185,6 @@ class Socket : public IOObject {
 
   SocketProtocol m_protocol;
   NativeSocket m_socket;
-  WaitableHandle m_waitable_handle;
   bool m_should_close_fd;
 };
 

lldb/include/lldb/Host/windows/MainLoopWindows.h

@@ -31,6 +31,18 @@ class MainLoopWindows : public MainLoopBase {
 
   Status Run() override;
 
+  struct FdInfo {
+    FdInfo(intptr_t event, Callback callback)
+        : event(event), callback(callback) {}
+    virtual ~FdInfo() {}
+    virtual void WillPoll() {}
+    virtual void DidPoll() {}
+    virtual void Disarm() {}
+    intptr_t event;
+    Callback callback;
+  };
+  using FdInfoUP = std::unique_ptr<FdInfo>;
+
 protected:
   void UnregisterReadObject(IOObject::WaitableHandle handle) override;
 
@@ -39,11 +51,7 @@ class MainLoopWindows : public MainLoopBase {
 private:
   llvm::Expected<size_t> Poll();
 
-  struct FdInfo {
-    lldb::IOObjectSP object_sp;
-    Callback callback;
-  };
-  llvm::DenseMap<IOObject::WaitableHandle, FdInfo> m_read_fds;
+  llvm::DenseMap<IOObject::WaitableHandle, FdInfoUP> m_read_fds;
   void *m_interrupt_event;
 };
 

lldb/include/lldb/Utility/IOObject.h

@@ -41,7 +41,6 @@ class IOObject {
   FDType GetFdType() const { return m_fd_type; }
 
   virtual WaitableHandle GetWaitableHandle() = 0;
-  virtual bool HasReadableData() = 0;
 
 protected:
   FDType m_fd_type;

lldb/source/Host/common/File.cpp

@@ -118,8 +118,6 @@ IOObject::WaitableHandle File::GetWaitableHandle() {
   return IOObject::kInvalidHandleValue;
 }
 
-bool File::HasReadableData() { return false; }
-
 Status File::GetFileSpec(FileSpec &file_spec) const {
   file_spec.Clear();
   return std::error_code(ENOTSUP, std::system_category());
@@ -283,18 +281,6 @@ IOObject::WaitableHandle NativeFile::GetWaitableHandle() {
 #endif
 }
 
-bool NativeFile::HasReadableData() {
-#ifdef _WIN32
-  DWORD available_bytes = 0;
-  return !PeekNamedPipe((HANDLE)_get_osfhandle(GetDescriptor()), NULL, 0, NULL,
-                        &available_bytes, NULL) ||
-         available_bytes > 0;
-#else
-  size_t buffer_size = 0;
-  return ioctl(GetDescriptor(), FIONREAD, buffer_size) != -1 && buffer_size > 0;
-#endif
-}
-
 FILE *NativeFile::GetStream() {
   ValueGuard stream_guard = StreamIsValid();
   if (!stream_guard) {

lldb/source/Host/common/JSONTransport.cpp

@@ -42,7 +42,7 @@ ReadFull(IOObject &descriptor, size_t length,
   if (timeout && timeout_supported) {
     SelectHelper sh;
     sh.SetTimeout(*timeout);
-    sh.FDSetRead(descriptor.GetWaitableHandle());
+    sh.FDSetRead((lldb::socket_t)descriptor.GetWaitableHandle());
     Status status = sh.Select();
     if (status.Fail()) {
       // Convert timeouts into a specific error.

lldb/source/Host/common/Socket.cpp

@@ -173,7 +173,6 @@ bool Socket::FindProtocolByScheme(const char *scheme,
 Socket::Socket(SocketProtocol protocol, bool should_close)
     : IOObject(eFDTypeSocket), m_protocol(protocol),
       m_socket(kInvalidSocketValue),
-      m_waitable_handle(IOObject::kInvalidHandleValue),
       m_should_close_fd(should_close) {}
 
 Socket::~Socket() { Close(); }
@@ -318,39 +317,7 @@ Socket::DecodeHostAndPort(llvm::StringRef host_and_port) {
 }
 
 IOObject::WaitableHandle Socket::GetWaitableHandle() {
-#ifdef _WIN32
-  if (m_socket == kInvalidSocketValue)
-    return kInvalidHandleValue;
-
-  if (m_waitable_handle == kInvalidHandleValue) {
-    m_waitable_handle = WSACreateEvent();
-    assert(m_waitable_handle != WSA_INVALID_EVENT);
-    if (WSAEventSelect(m_socket, m_waitable_handle,
-                       FD_ACCEPT | FD_READ | FD_WRITE) != 0)
-      return kInvalidHandleValue;
-  }
-
-  return m_waitable_handle;
-#else
-  return m_socket;
-#endif
-}
-
-bool Socket::HasReadableData() {
-#ifdef _WIN32
-  if (!IsValid() || m_waitable_handle == kInvalidHandleValue)
-    return false;
-
-  WSANETWORKEVENTS events;
-  if (WSAEnumNetworkEvents(m_socket, m_waitable_handle, &events) != 0)
-    return false;
-
-  return events.lNetworkEvents & FD_CLOSE ||
-         events.lNetworkEvents & FD_ACCEPT || events.lNetworkEvents & FD_READ;
-#else
-  size_t buffer_size = 0;
-  return ioctl(m_socket, FIONREAD, buffer_size) != -1 && buffer_size > 0;
-#endif
+  return (IOObject::WaitableHandle)m_socket;
 }
 
 Status Socket::Read(void *buf, size_t &num_bytes) {
@@ -416,14 +383,6 @@ Status Socket::Close() {
   Log *log = GetLog(LLDBLog::Connection);
   LLDB_LOGF(log, "%p Socket::Close (fd = %" PRIu64 ")",
             static_cast<void *>(this), static_cast<uint64_t>(m_socket));
-#ifdef _WIN32
-  if (m_waitable_handle != kInvalidHandleValue) {
-    if (WSACloseEvent(m_waitable_handle) == 0)
-      m_waitable_handle = kInvalidHandleValue;
-    else
-      error = GetLastError();
-  }
-#endif
   bool success = CloseSocket(m_socket) == 0;
   // A reference to a FD was passed in, set it to an invalid value
   m_socket = kInvalidSocketValue;