lib/_emerge/SubProcess.py

# Copyright 1999-2020 Gentoo Authors
# Distributed under the terms of the GNU General Public License v2

import logging

from portage import os
from portage.util import writemsg_level
from portage.util.futures import asyncio
from _emerge.AbstractPollTask import AbstractPollTask
import signal
import errno


class SubProcess(AbstractPollTask):

    __slots__ = ("pid",) + ("_dummy_pipe_fd", "_files", "_waitpid_id")

    # This is how much time we allow for waitpid to succeed after
    # we've sent a kill signal to our subprocess.
    _cancel_timeout = 1  # seconds

    def _poll(self):
        # Simply rely on _async_waitpid_cb to set the returncode.
        return self.returncode

    def _cancel(self):
        if self.isAlive() and self.pid is not None:
            try:
                os.kill(self.pid, signal.SIGTERM)
            except OSError as e:
                if e.errno == errno.EPERM:
                    # Reported with hardened kernel (bug #358211).
                    writemsg_level(
                        "!!! kill: (%i) - Operation not permitted\n" % (self.pid,),
                        level=logging.ERROR,
                        noiselevel=-1,
                    )
                elif e.errno != errno.ESRCH:
                    raise

    def _async_wait(self):
        if self.returncode is None:
            raise asyncio.InvalidStateError("Result is not ready for %s" % (self,))
        else:
            # This calls _unregister, so don't call it until pid status
            # is available.
            super(SubProcess, self)._async_wait()

    def _async_waitpid(self):
        """
        Wait for exit status of self.pid asynchronously, and then
        set the returncode, and finally notify exit listeners via the
        _async_wait method. Subclasses may override this method in order
        to implement an alternative means to retrieve pid exit status,
        or as a means to delay action until some pending task(s) have
        completed (such as reading data that the subprocess is supposed
        to have written to a pipe).
        """
        if self.returncode is not None:
            self._async_wait()
        elif self._waitpid_id is None:
            self._waitpid_id = self.pid
            self.scheduler._asyncio_child_watcher.add_child_handler(
                self.pid, self._async_waitpid_cb
            )

    def _async_waitpid_cb(self, pid, returncode):
        if pid != self.pid:
            raise AssertionError("expected pid %s, got %s" % (self.pid, pid))
        self.returncode = returncode
        self._async_wait()

    def _orphan_process_warn(self):
        pass

    def _unregister(self):
        """
        Unregister from the scheduler and close open files.
        """

        self._registered = False

        if self._waitpid_id is not None:
            self.scheduler._asyncio_child_watcher.remove_child_handler(self._waitpid_id)
            self._waitpid_id = None

        if self._files is not None:
            for f in self._files.values():
                if isinstance(f, int):
                    os.close(f)
                else:
                    f.close()
            self._files = None