Hi, I found race conditions between Process (asyncio.subprocess) and Popen (subprocess). Maybe we should drop Process.subprocess attribute to reduce the risk of misuse of the API?
Details: While testing asyncio.subprocess of Trollius with Python 2.6, I found a race condition. If the process exits between the creation of the subprocess transport and the creation of Process object, transport.get_pid() fails in Trollius. It looks like it doesn't occur in Tulip because Tulip creates less futures thanks to "yield from". (It was easy to fix the issue in Trollius, just get the pid from the Popen object.) But there is a second race condition which should also concern Tulip: if Popen.wait() or Popen.poll() is called after the process exited, the return code cannot be retrieved in Popen because asyncio already called os.waitpid(). In Python 3.3, Popen.wait() uses the exit code 0 in this case. In Python 2.7, an error is raised (ESRCH). Victor
