Current File : //snap/core20/current/lib/python3.8/multiprocessing/popen_forkserver.py
import io
import os
from .context import reduction, set_spawning_popen
if not reduction.HAVE_SEND_HANDLE:
raise ImportError('No support for sending fds between processes')
from . import forkserver
from . import popen_fork
from . import spawn
from . import util
__all__ = ['Popen']
#
# Wrapper for an fd used while launching a process
#
class _DupFd(object):
def __init__(self, ind):
self.ind = ind
def detach(self):
return forkserver.get_inherited_fds()[self.ind]
#
# Start child process using a server process
#
class Popen(popen_fork.Popen):
method = 'forkserver'
DupFd = _DupFd
def __init__(self, process_obj):
self._fds = []
super().__init__(process_obj)
def duplicate_for_child(self, fd):
self._fds.append(fd)
return len(self._fds) - 1
def _launch(self, process_obj):
prep_data = spawn.get_preparation_data(process_obj._name)
buf = io.BytesIO()
set_spawning_popen(self)
try:
reduction.dump(prep_data, buf)
reduction.dump(process_obj, buf)
finally:
set_spawning_popen(None)
self.sentinel, w = forkserver.connect_to_new_process(self._fds)
# Keep a duplicate of the data pipe's write end as a sentinel of the
# parent process used by the child process.
_parent_w = os.dup(w)
self.finalizer = util.Finalize(self, util.close_fds,
(_parent_w, self.sentinel))
with open(w, 'wb', closefd=True) as f:
f.write(buf.getbuffer())
self.pid = forkserver.read_signed(self.sentinel)
def poll(self, flag=os.WNOHANG):
if self.returncode is None:
from multiprocessing.connection import wait
timeout = 0 if flag == os.WNOHANG else None
if not wait([self.sentinel], timeout):
return None
try:
self.returncode = forkserver.read_signed(self.sentinel)
except (OSError, EOFError):
# This should not happen usually, but perhaps the forkserver
# process itself got killed
self.returncode = 255
return self.returncode
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