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3a7df632c9
`ResourceTracker.__del__` (added in gh-88887 circa Python 3.12) calls os.waitpid(pid, 0) which blocks indefinitely if a process created via os.fork() still holds the tracker pipe's write end. The tracker never sees EOF, never exits, and the parent hangs at interpreter shutdown. Fix with two layers: - **At-fork handler.** An os.register_at_fork(after_in_child=...) handler closes the inherited pipe fd in the child unless a preserve flag is set. popen_fork.Popen._launch() sets the flag before its fork so mp.Process(fork) children keep the fd and reuse the parent's tracker (preserving gh-80849). Raw os.fork() children close the fd, letting the parent reap promptly. - **Timeout safety-net.** _stop_locked() gains a wait_timeout parameter. When called from `__del__`, it polls with WNOHANG using exponential backoff for up to 1 second instead of blocking indefinitely. The at-fork handler makes this unreachable in well-behaved paths; it remains for abnormal shutdowns. Co-authored-by: Itamar Oren <itamarost@gmail.com>
100 lines
3 KiB
Python
100 lines
3 KiB
Python
import atexit
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import os
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import signal
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from . import util
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__all__ = ['Popen']
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#
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# Start child process using fork
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#
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class Popen(object):
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method = 'fork'
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def __init__(self, process_obj):
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util._flush_std_streams()
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self.returncode = None
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self.finalizer = None
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self._launch(process_obj)
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def duplicate_for_child(self, fd):
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return fd
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def poll(self, flag=os.WNOHANG):
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if self.returncode is None:
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try:
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pid, sts = os.waitpid(self.pid, flag)
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except OSError:
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# Child process not yet created. See #1731717
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# e.errno == errno.ECHILD == 10
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return None
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if pid == self.pid:
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self.returncode = os.waitstatus_to_exitcode(sts)
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return self.returncode
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def wait(self, timeout=None):
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if self.returncode is None:
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if timeout is not None:
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from multiprocessing.connection import wait
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if not wait([self.sentinel], timeout):
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return None
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# This shouldn't block if wait() returned successfully.
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return self.poll(os.WNOHANG if timeout == 0.0 else 0)
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return self.returncode
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def _send_signal(self, sig):
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if self.returncode is None:
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try:
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os.kill(self.pid, sig)
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except ProcessLookupError:
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pass
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except OSError:
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if self.wait(timeout=0.1) is None:
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raise
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def interrupt(self):
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self._send_signal(signal.SIGINT)
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def terminate(self):
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self._send_signal(signal.SIGTERM)
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def kill(self):
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self._send_signal(signal.SIGKILL)
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def _launch(self, process_obj):
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code = 1
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parent_r, child_w = os.pipe()
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child_r, parent_w = os.pipe()
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# gh-146313: Tell the resource tracker's at-fork handler to keep
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# the inherited pipe fd so this child reuses the parent's tracker
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# (gh-80849) rather than closing it and launching its own.
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from .resource_tracker import _fork_intent
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_fork_intent.preserve_fd = True
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try:
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self.pid = os.fork()
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finally:
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# Reset in both parent and child so the flag does not leak
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# into a subsequent raw os.fork() or nested Process launch.
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_fork_intent.preserve_fd = False
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if self.pid == 0:
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try:
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atexit._clear()
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atexit.register(util._exit_function)
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os.close(parent_r)
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os.close(parent_w)
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code = process_obj._bootstrap(parent_sentinel=child_r)
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finally:
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atexit._run_exitfuncs()
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os._exit(code)
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else:
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os.close(child_w)
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os.close(child_r)
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self.finalizer = util.Finalize(self, util.close_fds,
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(parent_r, parent_w,))
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self.sentinel = parent_r
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def close(self):
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if self.finalizer is not None:
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self.finalizer()
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