bpo-46364: only use socket for stdin on AIX

Signed-off-by: Christoph Hamsen <hamsen.christoph@posteo.de>

Lib/asyncio/unix_events.py

@@ -788,12 +788,11 @@ class _UnixSubprocessTransport(base_subprocess.BaseSubprocessTransport):
 
  def _start(self, args, shell, stdin, stdout, stderr, bufsize, **kwargs):
  stdin_w = None
- if stdin == subprocess.PIPE:
- # Use a socket pair for stdin, since not all platforms
+ if stdin == subprocess.PIPE and sys.platform.startswith('aix'):
+ # Use a socket pair for stdin on AIX, since it does not
  # support selecting read events on the write end of a
  # socket (which we use in order to detect closing of the
- # other end). Notably this is needed on AIX, and works
- # just fine on other platforms.
+ # other end).
  stdin, stdin_w = socket.socketpair()
  try:
  self._proc = subprocess.Popen(

Misc/NEWS.d/next/Library/2022-01-14-10-49-20.bpo-46364.SzhlU9.rst

@@ -0,0 +1 @@
+Restrict use of sockets instead of pipes for stdin of subprocesses created by :mod:`asyncio` to AIX platform only.