bpo-46364: Use sockets for stdin of asyncio only on AIX (pythonGH-30596)

Signed-off-by: Christoph Hamsen <hamsen.christoph@posteo.de>
Co-authored-by: July Tikhonov <july.tikh@gmail.com>
(cherry picked from commit c9ed032)

Co-authored-by: Christoph Hamsen <37963496+xopham@users.noreply.github.com>

Lib/asyncio/unix_events.py

@@ -800,12 +800,11 @@ 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(

Lib/test/test_asyncio/test_subprocess.py

@@ -427,6 +427,26 @@ async def empty_error():
  self.assertEqual(output, None)
  self.assertEqual(exitcode, 0)
 
+ @unittest.skipIf(sys.platform != 'linux', "Don't have /dev/stdin")
+ def test_devstdin_input(self):
+
+ async def devstdin_input(message):
+ code = 'file = open("/dev/stdin"); data = file.read(); print(len(data))'
+ proc = await asyncio.create_subprocess_exec(
+ sys.executable, '-c', code,
+ stdin=asyncio.subprocess.PIPE,
+ stdout=asyncio.subprocess.PIPE,
+ stderr=asyncio.subprocess.PIPE,
+ close_fds=False,
+ )
+ stdout, stderr = await proc.communicate(message)
+ exitcode = await proc.wait()
+ return (stdout, exitcode)
+
+ output, exitcode = self.loop.run_until_complete(devstdin_input(b'abc'))
+ self.assertEqual(output.rstrip(), b'3')
+ self.assertEqual(exitcode, 0)
+
  def test_cancel_process_wait(self):
  # Issue #23140: cancel Process.wait()
 

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.