Complete pending write operations before canceling io. (#628)

* Complete pending write operations before canceling io.

* Removed comment, question has been addressed in mr.

* include useful comment from  vthiebaut10

---------

Co-authored-by: Christopher Greene <[email protected]>

Author: cwgreene

contrib/win32/win32compat/termio.c

@@ -263,6 +263,22 @@ int
 syncio_close(struct w32_io* pio)
 {
 	debug4("syncio_close - pio:%p", pio);
+
+	/*
+	* Wait for io write operation that is called by worker thread to terminate
+	* to avoid the write operation being terminated prematurely by CancelIoEx.
+	* If you see any process waiting here indefinitely - its because no one
+	* is draining from other end of the pipe. This is an unfortunate
+	* consequence that should otherwise have very little impact on practical
+	* scenarios.
+	*/
+	if (pio->write_details.pending) {
+		WaitForSingleObject(pio->write_overlapped.hEvent, INFINITE);
+
+		/* drain queued APCs */
+		SleepEx(0, TRUE);
+	}
+
 	CancelIoEx(WINHANDLE(pio), NULL);
 
 	/* If io is pending, let worker threads exit. */
@@ -279,10 +295,10 @@ syncio_close(struct w32_io* pio)
 
 		WaitForSingleObject(pio->read_overlapped.hEvent, INFINITE);
 	}
-	if (pio->write_details.pending)
-		WaitForSingleObject(pio->write_overlapped.hEvent, INFINITE);
+
 	/* drain queued APCs */
 	SleepEx(0, TRUE);
+
 	/* TODO - fix this, closing Console handles is interfering with TTY/PTY rendering */
 	if (FILETYPE(pio) != FILE_TYPE_CHAR)
 		CloseHandle(WINHANDLE(pio));