[Python-checkins] bpo-36888: Add multiprocessing.parent_process() (GH-13247)
Antoine Pitrou
webhook-mailer at python.org
Mon May 20 15:37:11 EDT 2019
https://github.com/python/cpython/commit/c09a9f56c08d80567454cae6f78f738a89e1ae94
commit: c09a9f56c08d80567454cae6f78f738a89e1ae94
branch: master
author: Thomas Moreau <thomas.moreau.2010 at gmail.com>
committer: Antoine Pitrou <antoine at python.org>
date: 2019-05-20T21:37:05+02:00
summary:
bpo-36888: Add multiprocessing.parent_process() (GH-13247)
files:
A Misc/NEWS.d/next/Library/2019-05-16-18-02-08.bpo-36888.-H2Dkm.rst
M Doc/library/multiprocessing.rst
M Lib/multiprocessing/context.py
M Lib/multiprocessing/forkserver.py
M Lib/multiprocessing/popen_fork.py
M Lib/multiprocessing/popen_forkserver.py
M Lib/multiprocessing/popen_spawn_posix.py
M Lib/multiprocessing/process.py
M Lib/multiprocessing/spawn.py
M Lib/multiprocessing/util.py
M Lib/test/_test_multiprocessing.py
M Modules/_winapi.c
diff --git a/Doc/library/multiprocessing.rst b/Doc/library/multiprocessing.rst
index c6ffb00819c3..cc6dd4e9d702 100644
--- a/Doc/library/multiprocessing.rst
+++ b/Doc/library/multiprocessing.rst
@@ -944,6 +944,14 @@ Miscellaneous
An analogue of :func:`threading.current_thread`.
+.. function:: parent_process()
+
+ Return the :class:`Process` object corresponding to the parent process of
+ the :func:`current_process`. For the main process, ``parent_process`` will
+ be ``None``.
+
+ .. versionadded:: 3.8
+
.. function:: freeze_support()
Add support for when a program which uses :mod:`multiprocessing` has been
diff --git a/Lib/multiprocessing/context.py b/Lib/multiprocessing/context.py
index 871746b1a047..5a4865751c22 100644
--- a/Lib/multiprocessing/context.py
+++ b/Lib/multiprocessing/context.py
@@ -35,6 +35,7 @@ class BaseContext(object):
AuthenticationError = AuthenticationError
current_process = staticmethod(process.current_process)
+ parent_process = staticmethod(process.parent_process)
active_children = staticmethod(process.active_children)
def cpu_count(self):
diff --git a/Lib/multiprocessing/forkserver.py b/Lib/multiprocessing/forkserver.py
index dabf7bcbe6d7..9b6398671dbc 100644
--- a/Lib/multiprocessing/forkserver.py
+++ b/Lib/multiprocessing/forkserver.py
@@ -294,7 +294,8 @@ def _serve_one(child_r, fds, unused_fds, handlers):
*_forkserver._inherited_fds) = fds
# Run process object received over pipe
- code = spawn._main(child_r)
+ parent_sentinel = os.dup(child_r)
+ code = spawn._main(child_r, parent_sentinel)
return code
diff --git a/Lib/multiprocessing/popen_fork.py b/Lib/multiprocessing/popen_fork.py
index 685e8daf77ca..11e216072d09 100644
--- a/Lib/multiprocessing/popen_fork.py
+++ b/Lib/multiprocessing/popen_fork.py
@@ -66,16 +66,20 @@ def kill(self):
def _launch(self, process_obj):
code = 1
parent_r, child_w = os.pipe()
+ child_r, parent_w = os.pipe()
self.pid = os.fork()
if self.pid == 0:
try:
os.close(parent_r)
- code = process_obj._bootstrap()
+ os.close(parent_w)
+ code = process_obj._bootstrap(parent_sentinel=child_r)
finally:
os._exit(code)
else:
os.close(child_w)
- self.finalizer = util.Finalize(self, os.close, (parent_r,))
+ os.close(child_r)
+ self.finalizer = util.Finalize(self, util.close_fds,
+ (parent_r, parent_w,))
self.sentinel = parent_r
def close(self):
diff --git a/Lib/multiprocessing/popen_forkserver.py b/Lib/multiprocessing/popen_forkserver.py
index a51a2771aed8..a56eb9bf1108 100644
--- a/Lib/multiprocessing/popen_forkserver.py
+++ b/Lib/multiprocessing/popen_forkserver.py
@@ -49,7 +49,11 @@ def _launch(self, process_obj):
set_spawning_popen(None)
self.sentinel, w = forkserver.connect_to_new_process(self._fds)
- self.finalizer = util.Finalize(self, os.close, (self.sentinel,))
+ # 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)
diff --git a/Lib/multiprocessing/popen_spawn_posix.py b/Lib/multiprocessing/popen_spawn_posix.py
index 59f8e452cae1..24b8634523e5 100644
--- a/Lib/multiprocessing/popen_spawn_posix.py
+++ b/Lib/multiprocessing/popen_spawn_posix.py
@@ -61,8 +61,12 @@ def _launch(self, process_obj):
with open(parent_w, 'wb', closefd=False) as f:
f.write(fp.getbuffer())
finally:
- if parent_r is not None:
- self.finalizer = util.Finalize(self, os.close, (parent_r,))
- for fd in (child_r, child_w, parent_w):
+ fds_to_close = []
+ for fd in (parent_r, parent_w):
+ if fd is not None:
+ fds_to_close.append(fd)
+ self.finalizer = util.Finalize(self, util.close_fds, fds_to_close)
+
+ for fd in (child_r, child_w):
if fd is not None:
os.close(fd)
diff --git a/Lib/multiprocessing/process.py b/Lib/multiprocessing/process.py
index 780f2d0c2734..c62c826cff95 100644
--- a/Lib/multiprocessing/process.py
+++ b/Lib/multiprocessing/process.py
@@ -7,7 +7,8 @@
# Licensed to PSF under a Contributor Agreement.
#
-__all__ = ['BaseProcess', 'current_process', 'active_children']
+__all__ = ['BaseProcess', 'current_process', 'active_children',
+ 'parent_process']
#
# Imports
@@ -46,6 +47,13 @@ def active_children():
_cleanup()
return list(_children)
+
+def parent_process():
+ '''
+ Return process object representing the parent process
+ '''
+ return _parent_process
+
#
#
#
@@ -76,6 +84,7 @@ def __init__(self, group=None, target=None, name=None, args=(), kwargs={},
self._identity = _current_process._identity + (count,)
self._config = _current_process._config.copy()
self._parent_pid = os.getpid()
+ self._parent_name = _current_process.name
self._popen = None
self._closed = False
self._target = target
@@ -278,9 +287,9 @@ def __repr__(self):
##
- def _bootstrap(self):
+ def _bootstrap(self, parent_sentinel=None):
from . import util, context
- global _current_process, _process_counter, _children
+ global _current_process, _parent_process, _process_counter, _children
try:
if self._start_method is not None:
@@ -290,6 +299,8 @@ def _bootstrap(self):
util._close_stdin()
old_process = _current_process
_current_process = self
+ _parent_process = _ParentProcess(
+ self._parent_name, self._parent_pid, parent_sentinel)
try:
util._finalizer_registry.clear()
util._run_after_forkers()
@@ -337,6 +348,40 @@ def __reduce__(self):
)
return AuthenticationString, (bytes(self),)
+
+#
+# Create object representing the parent process
+#
+
+class _ParentProcess(BaseProcess):
+
+ def __init__(self, name, pid, sentinel):
+ self._identity = ()
+ self._name = name
+ self._pid = pid
+ self._parent_pid = None
+ self._popen = None
+ self._closed = False
+ self._sentinel = sentinel
+ self._config = {}
+
+ def is_alive(self):
+ from multiprocessing.connection import wait
+ return not wait([self._sentinel], timeout=0)
+
+ @property
+ def ident(self):
+ return self._pid
+
+ def join(self, timeout=None):
+ '''
+ Wait until parent process terminates
+ '''
+ from multiprocessing.connection import wait
+ wait([self._sentinel], timeout=timeout)
+
+ pid = ident
+
#
# Create object representing the main process
#
@@ -365,6 +410,7 @@ def close(self):
pass
+_parent_process = None
_current_process = _MainProcess()
_process_counter = itertools.count(1)
_children = set()
diff --git a/Lib/multiprocessing/spawn.py b/Lib/multiprocessing/spawn.py
index f66b5aa9267b..7cc129e26107 100644
--- a/Lib/multiprocessing/spawn.py
+++ b/Lib/multiprocessing/spawn.py
@@ -100,25 +100,24 @@ def spawn_main(pipe_handle, parent_pid=None, tracker_fd=None):
if parent_pid is not None:
source_process = _winapi.OpenProcess(
- _winapi.PROCESS_DUP_HANDLE, False, parent_pid)
+ _winapi.SYNCHRONIZE | _winapi.PROCESS_DUP_HANDLE,
+ False, parent_pid)
else:
source_process = None
- try:
- new_handle = reduction.duplicate(pipe_handle,
- source_process=source_process)
- finally:
- if source_process is not None:
- _winapi.CloseHandle(source_process)
+ new_handle = reduction.duplicate(pipe_handle,
+ source_process=source_process)
fd = msvcrt.open_osfhandle(new_handle, os.O_RDONLY)
+ parent_sentinel = source_process
else:
from . import resource_tracker
resource_tracker._resource_tracker._fd = tracker_fd
fd = pipe_handle
- exitcode = _main(fd)
+ parent_sentinel = os.dup(pipe_handle)
+ exitcode = _main(fd, parent_sentinel)
sys.exit(exitcode)
-def _main(fd):
+def _main(fd, parent_sentinel):
with os.fdopen(fd, 'rb', closefd=True) as from_parent:
process.current_process()._inheriting = True
try:
@@ -127,7 +126,7 @@ def _main(fd):
self = reduction.pickle.load(from_parent)
finally:
del process.current_process()._inheriting
- return self._bootstrap()
+ return self._bootstrap(parent_sentinel)
def _check_not_importing_main():
diff --git a/Lib/multiprocessing/util.py b/Lib/multiprocessing/util.py
index 0c4eb2473273..5674ad773f97 100644
--- a/Lib/multiprocessing/util.py
+++ b/Lib/multiprocessing/util.py
@@ -421,3 +421,9 @@ def spawnv_passfds(path, args, passfds):
finally:
os.close(errpipe_read)
os.close(errpipe_write)
+
+
+def close_fds(*fds):
+ """Close each file descriptor given as an argument"""
+ for fd in fds:
+ os.close(fd)
diff --git a/Lib/test/_test_multiprocessing.py b/Lib/test/_test_multiprocessing.py
index 78ec53beb0f0..071b54a713e2 100644
--- a/Lib/test/_test_multiprocessing.py
+++ b/Lib/test/_test_multiprocessing.py
@@ -269,6 +269,64 @@ def _test(cls, q, *args, **kwds):
q.put(bytes(current.authkey))
q.put(current.pid)
+ def test_parent_process_attributes(self):
+ if self.TYPE == "threads":
+ self.skipTest('test not appropriate for {}'.format(self.TYPE))
+
+ self.assertIsNone(self.parent_process())
+
+ rconn, wconn = self.Pipe(duplex=False)
+ p = self.Process(target=self._test_send_parent_process, args=(wconn,))
+ p.start()
+ p.join()
+ parent_pid, parent_name = rconn.recv()
+ self.assertEqual(parent_pid, self.current_process().pid)
+ self.assertEqual(parent_pid, os.getpid())
+ self.assertEqual(parent_name, self.current_process().name)
+
+ @classmethod
+ def _test_send_parent_process(cls, wconn):
+ from multiprocessing.process import parent_process
+ wconn.send([parent_process().pid, parent_process().name])
+
+ def test_parent_process(self):
+ if self.TYPE == "threads":
+ self.skipTest('test not appropriate for {}'.format(self.TYPE))
+
+ # Launch a child process. Make it launch a grandchild process. Kill the
+ # child process and make sure that the grandchild notices the death of
+ # its parent (a.k.a the child process).
+ rconn, wconn = self.Pipe(duplex=False)
+ p = self.Process(
+ target=self._test_create_grandchild_process, args=(wconn, ))
+ p.start()
+
+ if not rconn.poll(timeout=5):
+ raise AssertionError("Could not communicate with child process")
+ parent_process_status = rconn.recv()
+ self.assertEqual(parent_process_status, "alive")
+
+ p.terminate()
+ p.join()
+
+ if not rconn.poll(timeout=5):
+ raise AssertionError("Could not communicate with child process")
+ parent_process_status = rconn.recv()
+ self.assertEqual(parent_process_status, "not alive")
+
+ @classmethod
+ def _test_create_grandchild_process(cls, wconn):
+ p = cls.Process(target=cls._test_report_parent_status, args=(wconn, ))
+ p.start()
+ time.sleep(100)
+
+ @classmethod
+ def _test_report_parent_status(cls, wconn):
+ from multiprocessing.process import parent_process
+ wconn.send("alive" if parent_process().is_alive() else "not alive")
+ parent_process().join(timeout=5)
+ wconn.send("alive" if parent_process().is_alive() else "not alive")
+
def test_process(self):
q = self.Queue(1)
e = self.Event()
@@ -5398,6 +5456,7 @@ class ProcessesMixin(BaseMixin):
Process = multiprocessing.Process
connection = multiprocessing.connection
current_process = staticmethod(multiprocessing.current_process)
+ parent_process = staticmethod(multiprocessing.parent_process)
active_children = staticmethod(multiprocessing.active_children)
Pool = staticmethod(multiprocessing.Pool)
Pipe = staticmethod(multiprocessing.Pipe)
diff --git a/Misc/NEWS.d/next/Library/2019-05-16-18-02-08.bpo-36888.-H2Dkm.rst b/Misc/NEWS.d/next/Library/2019-05-16-18-02-08.bpo-36888.-H2Dkm.rst
new file mode 100644
index 000000000000..e7b54677280c
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2019-05-16-18-02-08.bpo-36888.-H2Dkm.rst
@@ -0,0 +1,2 @@
+Python child processes can now access the status of their parent process
+using multiprocessing.process.parent_process
diff --git a/Modules/_winapi.c b/Modules/_winapi.c
index 2eb708e9073e..8873519e6ce5 100644
--- a/Modules/_winapi.c
+++ b/Modules/_winapi.c
@@ -1955,6 +1955,7 @@ PyInit__winapi(void)
WINAPI_CONSTANT(F_DWORD, PIPE_UNLIMITED_INSTANCES);
WINAPI_CONSTANT(F_DWORD, PIPE_WAIT);
WINAPI_CONSTANT(F_DWORD, PROCESS_ALL_ACCESS);
+ WINAPI_CONSTANT(F_DWORD, SYNCHRONIZE);
WINAPI_CONSTANT(F_DWORD, PROCESS_DUP_HANDLE);
WINAPI_CONSTANT(F_DWORD, SEC_COMMIT);
WINAPI_CONSTANT(F_DWORD, SEC_IMAGE);
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