Jan 28, 2026 · Jan 18, 2026 · Jan 18, 2026 · Jan 18, 2026 · Jan 18, 2026 · Jan 18, 2026
diff --git a/Lib/subprocess.py b/Lib/subprocess.py
                    events = kq.control([kev], 1, timeout)  # wait
                except OSError as err:  # should never happen
                    return False
                if not events:
                    raise TimeoutExpired(self.args, timeout)
                else:
                    if not events:
                        raise TimeoutExpired(self.args, timeout)
                return True
            finally:
                kq.close()
                # Try efficient wait first.
                if self._wait_pidfd(timeout) or self._wait_kqueue(timeout):
                    # Process is gone. At this point os.waitpid(pid, 0)
                    # will return immediately, but inveryrare races
                    # the PID may have been reused.
                    # will return immediately, but in rare races (e.g.
                    #long running processes)the PID may have been reused.
                    # os.waitpid(pid, WNOHANG) ensures we attempt a
                    # non-blocking reap without blocking indefinitely.
                    with self._waitpid_lock:
diff --git a/Lib/test/test_subprocess.py b/Lib/test/test_subprocess.py
    CAN_USE_KQUEUE = subprocess._CAN_USE_KQUEUE

    def assert_fast_waitpid_error(self, patch_point):
        # Emulate a case where pidfd_open()(Linux)or kqueue()
        #(BSD/macOS) fails.Busy-poll wait should be used as fallback.
        # Emulate a case where pidfd_open() or kqueue() fails.
        # Busy-poll wait should be used as fallback.
        exc = OSError(errno.EMFILE, os.strerror(errno.EMFILE))
        with mock.patch(patch_point, side_effect=exc) as m:
            p = subprocess.Popen([sys.executable,
Original file line number	Diff line number	Diff line change
Expand Up		@@ -2152,8 +2152,9 @@ def _wait_kqueue(self, timeout):
		events = kq.control([kev], 1, timeout) # wait
		except OSError as err: # should never happen
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		return False
		if not events:
		raise TimeoutExpired(self.args, timeout)
		else:
		if not events:
		raise TimeoutExpired(self.args, timeout)
		return True
		finally:
		kq.close()
Expand All		@@ -2177,8 +2178,8 @@ def _wait(self, timeout):
		# Try efficient wait first.
		if self._wait_pidfd(timeout) or self._wait_kqueue(timeout):
		# Process is gone. At this point os.waitpid(pid, 0)
		# will return immediately, but inveryrare races
		# the PID may have been reused.
		# will return immediately, but in rare races (e.g.
		#long running processes)the PID may have been reused.
		# os.waitpid(pid, WNOHANG) ensures we attempt a
		# non-blocking reap without blocking indefinitely.
		with self._waitpid_lock:
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Original file line number	Diff line number	Diff line change
Expand Up		@@ -4105,8 +4105,8 @@ class FastWaitTestCase(BaseTestCase):
		CAN_USE_KQUEUE = subprocess._CAN_USE_KQUEUE
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		def assert_fast_waitpid_error(self, patch_point):
		# Emulate a case where pidfd_open()(Linux)or kqueue()
		#(BSD/macOS) fails.Busy-poll wait should be used as fallback.
		# Emulate a case where pidfd_open() or kqueue() fails.
		# Busy-poll wait should be used as fallback.
		exc = OSError(errno.EMFILE, os.strerror(errno.EMFILE))
		with mock.patch(patch_point, side_effect=exc) as m:
		p = subprocess.Popen([sys.executable,
Expand Down