def make_pipes():
			tempdir = tempfile.mkdtemp()
			fifo_path = os.path.join(tempdir, 'fifo')
			os.mkfifo(fifo_path)
			return ((os.open(fifo_path, os.O_NONBLOCK|os.O_RDONLY),
				os.open(fifo_path, os.O_NONBLOCK|os.O_WRONLY)),
				functools.partial(shutil.rmtree, tempdir))

	def _start_post_builddir_lock(self, lock_future=None, start_ipc_daemon=False):
		if lock_future is not None:
			if lock_future is not self._start_future:
				raise AssertionError('lock_future is not self._start_future')
			self._start_future = None
			if lock_future.cancelled():
				self._build_dir = None
				self.cancelled = True
				self._was_cancelled()
				self._async_wait()
				return

			lock_future.result()

		if start_ipc_daemon:
			self.settings['PORTAGE_IPC_DAEMON'] = "1"
			self._start_ipc_daemon()

		if self.fd_pipes is None:
			self.fd_pipes = {}
		null_fd = None
		if 0 not in self.fd_pipes and \
			self.phase not in self._phases_interactive_whitelist and \
			"interactive" not in self.settings.get("PROPERTIES", "").split():
			null_fd = os.open('/dev/null', os.O_RDONLY)
			self.fd_pipes[0] = null_fd

		try:
			SpawnProcess._start(self)
		finally:
			if null_fd is not None:
				os.close(null_fd)

	def testLogfile(self):
		logfile = None
		try:
			fd, logfile = tempfile.mkstemp()
			os.close(fd)
			null_fd = os.open('/dev/null', os.O_RDWR)
			test_string = 2 * "blah blah blah\n"
			task_scheduler = TaskScheduler()
			proc = SpawnProcess(
				args=[BASH_BINARY, "-c",
				"echo -n '%s'" % test_string],
				env={}, fd_pipes={0:sys.stdin.fileno(), 1:null_fd, 2:null_fd},
				scheduler=task_scheduler.sched_iface,
				logfile=logfile)
			task_scheduler.add(proc)
			task_scheduler.run()
			os.close(null_fd)
			f = codecs.open(_unicode_encode(logfile,
				encoding=_encodings['fs'], errors='strict'),
				mode='r', encoding=_encodings['content'], errors='strict')
			log_content = f.read()
			f.close()
			# When logging passes through a pty, this comparison will fail
			# unless the oflag terminal attributes have the termios.OPOST
			# bit disabled. Otherwise, tranformations such as \n -> \r\n
			# may occur.
			self.assertEqual(test_string, log_content)
		finally:
			if logfile:
				try:
					os.unlink(logfile)
				except EnvironmentError as e:
					if e.errno != errno.ENOENT:
						raise
					del e

	def _check_sig_key(self):
		null_fd = os.open('/dev/null', os.O_RDONLY)
		popen_proc = PopenProcess(proc=subprocess.Popen(
			["gpg", "--verify", self._manifest_path],
			stdin=null_fd, stdout=subprocess.PIPE, stderr=subprocess.STDOUT),
			pipe_reader=PipeReader())
		os.close(null_fd)
		popen_proc.pipe_reader.input_files = {
			"producer" : popen_proc.proc.stdout}
		self._start_task(popen_proc, self._check_sig_key_exit)

	def _start(self):
		self._files = self._files_dict()
		input_fd = os.open(self.input_fifo, os.O_RDONLY|os.O_NONBLOCK)
		self._files.pipe_in = os.fdopen(input_fd, 'rb')

		self._reg_id = self.scheduler.register(
			self._files.pipe_in.fileno(),
			self._registered_events, self._input_handler)

		self._registered = True

	def _reopen_input(self):
		"""
		Re-open the input stream, in order to suppress
		POLLHUP events (bug #339976).
		"""
		self.scheduler.unregister(self._reg_id)
		os.close(self._files.pipe_in)
		self._files.pipe_in = \
			os.open(self.input_fifo, os.O_RDONLY|os.O_NONBLOCK)
		self._reg_id = self.scheduler.register(
			self._files.pipe_in,
			self._registered_events, self._input_handler)

	def _start(self):
		self._files = self._files_dict()

		# File streams are in unbuffered mode since we do atomic
		# read and write of whole pickles.
		self._files.pipe_in = \
			os.open(self.input_fifo, os.O_RDONLY|os.O_NONBLOCK)

		self._reg_id = self.scheduler.register(
			self._files.pipe_in,
			self._registered_events, self._input_handler)

		self._registered = True

def hardlink_lockfile(lockfilename, max_wait=14400):
	"""Does the NFS, hardlink shuffle to ensure locking on the disk.
	We create a PRIVATE lockfile, that is just a placeholder on the disk.
	Then we HARDLINK the real lockfile to that private file.
	If our file can 2 references, then we have the lock. :)
	Otherwise we lather, rise, and repeat.
	We default to a 4 hour timeout.
	"""

	start_time = time.time()
	myhardlock = hardlock_name(lockfilename)
	reported_waiting = False
	
	while(time.time() < (start_time + max_wait)):
		# We only need it to exist.
		myfd = os.open(myhardlock, os.O_CREAT|os.O_RDWR,0o660)
		os.close(myfd)
	
		if not os.path.exists(myhardlock):
			raise FileNotFound(
				_("Created lockfile is missing: %(filename)s") % \
				{"filename" : myhardlock})

		try:
			res = os.link(myhardlock, lockfilename)
		except OSError:
			pass

		if hardlink_is_mine(myhardlock, lockfilename):
			# We have the lock.
			if reported_waiting:
				writemsg("\n", noiselevel=-1)
			return True

		if reported_waiting:
			writemsg(".", noiselevel=-1)
		else:
			reported_waiting = True
			from portage.const import PORTAGE_BIN_PATH
			msg = _("\nWaiting on (hardlink) lockfile: (one '.' per 3 seconds)\n"
				"%(bin_path)s/clean_locks can fix stuck locks.\n"
				"Lockfile: %(lockfilename)s\n") % \
				{"bin_path": PORTAGE_BIN_PATH, "lockfilename": lockfilename}
			writemsg(msg, noiselevel=-1)
		time.sleep(3)
	
	os.unlink(myhardlock)
	return False

   def __init__(self, environment):
      self.conf = environment
      pidfile = open(self.conf.get('pid_file'), 'w')

      if (self.conf.get('no_daemon') == False):
         print "forking to background"
         if (os.fork() == 0):
             os.setpgid(0,0);
             pidfile.write(str(os.getpid()));
             pidfile.close();
             fd = os.open("/dev/null", os.O_WRONLY);
             os.dup2(fd,1);
             os.close(fd);
             #self.main_loop()
         else:
            sys.exit()

      else:
           print "Keeping in foreground"
           pidfile.write(str(os.getpid()));
           pidfile.close();

 def testLogfile(self):
     logfile = None
     try:
         fd, logfile = tempfile.mkstemp()
         os.close(fd)
         null_fd = os.open("/dev/null", os.O_RDWR)
         test_string = 2 * "blah blah blah\n"
         scheduler = PollScheduler().sched_iface
         proc = SpawnProcess(
             args=[BASH_BINARY, "-c", "echo -n '%s'" % test_string],
             env={},
             fd_pipes={0: sys.stdin.fileno(), 1: null_fd, 2: null_fd},
             scheduler=scheduler,
             logfile=logfile,
         )
         proc.start()
         os.close(null_fd)
         self.assertEqual(proc.wait(), os.EX_OK)
         f = io.open(
             _unicode_encode(logfile, encoding=_encodings["fs"], errors="strict"),
             mode="r",
             encoding=_encodings["content"],
             errors="strict",
         )
         log_content = f.read()
         f.close()
         # When logging passes through a pty, this comparison will fail
         # unless the oflag terminal attributes have the termios.OPOST
         # bit disabled. Otherwise, tranformations such as \n -> \r\n
         # may occur.
         self.assertEqual(test_string, log_content)
     finally:
         if logfile:
             try:
                 os.unlink(logfile)
             except EnvironmentError as e:
                 if e.errno != errno.ENOENT:
                     raise
                 del e

	def _run(self):

		syncfs_failed = False
		syncfs = self._get_syncfs()

		if syncfs is not None:
			for path in self.paths:
				try:
					fd = os.open(path, os.O_RDONLY)
				except OSError:
					pass
				else:
					try:
						if syncfs(fd) != 0:
							# Happens with PyPy (bug #446610)
							syncfs_failed = True
					finally:
						os.close(fd)

		if syncfs is None or syncfs_failed:
			return 1
		return os.EX_OK

	def _send_reply(self, reply):
		# File streams are in unbuffered mode since we do atomic
		# read and write of whole pickles. Use non-blocking mode so
		# we don't hang if the client is killed before we can send
		# the reply. We rely on the client opening the other side
		# of this fifo before it sends its request, since otherwise
		# we'd have a race condition with this open call raising
		# ENXIO if the client hasn't opened the fifo yet.
		try:
			output_fd = os.open(self.output_fifo,
				os.O_WRONLY | os.O_NONBLOCK)
			try:
				os.write(output_fd, pickle.dumps(reply))
			finally:
				os.close(output_fd)
		except OSError as e:
			# This probably means that the client has been killed,
			# which causes open to fail with ENXIO.
			writemsg_level(
				"!!! EbuildIpcDaemon %s: %s\n" % \
				(_('failed to send reply'), e),
				level=logging.ERROR, noiselevel=-1)

	def testLogfile(self):
		from portage import settings, spawn
		from tempfile import mkstemp
		logfile = None
		try:
			fd, logfile = mkstemp()
			os.close(fd)
			null_fd = os.open('/dev/null', os.O_RDWR)
			test_string = 2 * "blah blah blah\n"
			# Test cases are unique because they run inside src_test() which
			# may or may not already be running within a sandbox. Interaction
			# with SANDBOX_* variables may trigger unwanted sandbox violations
			# that are only reproducible with certain combinations of sandbox,
			# usersandbox, and userpriv FEATURES. Attempts to filter SANDBOX_*
			# variables can interfere with a currently running sandbox
			# instance. Therefore, use free=1 here to avoid potential
			# interactions (see bug #190268).
			spawn("echo -n '%s'" % test_string, settings, logfile=logfile,
				free=1, fd_pipes={0:sys.stdin.fileno(), 1:null_fd, 2:null_fd})
			os.close(null_fd)
			f = codecs.open(_unicode_encode(logfile,
				encoding=_encodings['fs'], errors='strict'),
				mode='r', encoding=_encodings['content'], errors='strict')
			log_content = f.read()
			f.close()
			# When logging passes through a pty, this comparison will fail
			# unless the oflag terminal attributes have the termios.OPOST
			# bit disabled. Otherwise, tranformations such as \n -> \r\n
			# may occur.
			self.assertEqual(test_string, log_content)
		finally:
			if logfile:
				try:
					os.unlink(logfile)
				except EnvironmentError as e:
					if e.errno != errno.ENOENT:
						raise
					del e

	def _reopen_input(self):
		"""
		Re-open the input stream, in order to suppress
		POLLHUP events (bug #339976).
		"""
		self.scheduler.remove_reader(self._files.pipe_in)
		os.close(self._files.pipe_in)
		self._files.pipe_in = \
			os.open(self.input_fifo, os.O_RDONLY|os.O_NONBLOCK)

		# FD_CLOEXEC is enabled by default in Python >=3.4.
		if sys.hexversion < 0x3040000 and fcntl is not None:
			try:
				fcntl.FD_CLOEXEC
			except AttributeError:
				pass
			else:
				fcntl.fcntl(self._files.pipe_in, fcntl.F_SETFD,
					fcntl.fcntl(self._files.pipe_in,
						fcntl.F_GETFD) | fcntl.FD_CLOEXEC)

		self.scheduler.add_reader(
			self._files.pipe_in,
			self._input_handler)

	def _start(self):
		self._files = self._files_dict()

		# File streams are in unbuffered mode since we do atomic
		# read and write of whole pickles.
		self._files.pipe_in = \
			os.open(self.input_fifo, os.O_RDONLY|os.O_NONBLOCK)

		# FD_CLOEXEC is enabled by default in Python >=3.4.
		if sys.hexversion < 0x3040000 and fcntl is not None:
			try:
				fcntl.FD_CLOEXEC
			except AttributeError:
				pass
			else:
				fcntl.fcntl(self._files.pipe_in, fcntl.F_SETFD,
					fcntl.fcntl(self._files.pipe_in,
						fcntl.F_GETFD) | fcntl.FD_CLOEXEC)

		self.scheduler.add_reader(
			self._files.pipe_in,
			self._input_handler)

		self._registered = True

def unlockfile(mytuple):

	#XXX: Compatability hack.
	if len(mytuple) == 3:
		lockfilename, myfd, unlinkfile = mytuple
		locking_method = fcntl.flock
	elif len(mytuple) == 4:
		lockfilename, myfd, unlinkfile, locking_method = mytuple
	else:
		raise InvalidData

	if(myfd == HARDLINK_FD):
		unhardlink_lockfile(lockfilename, unlinkfile=unlinkfile)
		return True
	
	# myfd may be None here due to myfd = mypath in lockfile()
	if isinstance(lockfilename, basestring) and \
		not os.path.exists(lockfilename):
		writemsg(_("lockfile does not exist '%s'\n") % lockfilename, 1)
		if myfd is not None:
			os.close(myfd)
			_open_fds.remove(myfd)
		return False

	try:
		if myfd is None:
			myfd = os.open(lockfilename, os.O_WRONLY, 0o660)
			unlinkfile = 1
		locking_method(myfd, fcntl.LOCK_UN)
	except OSError:
		if isinstance(lockfilename, basestring):
			os.close(myfd)
			_open_fds.remove(myfd)
		raise IOError(_("Failed to unlock file '%s'\n") % lockfilename)

	try:
		# This sleep call was added to allow other processes that are
		# waiting for a lock to be able to grab it before it is deleted.
		# lockfile() already accounts for this situation, however, and
		# the sleep here adds more time than is saved overall, so am
		# commenting until it is proved necessary.
		#time.sleep(0.0001)
		if unlinkfile:
			locking_method(myfd, fcntl.LOCK_EX | fcntl.LOCK_NB)
			# We won the lock, so there isn't competition for it.
			# We can safely delete the file.
			writemsg(_("Got the lockfile...\n"), 1)
			if _fstat_nlink(myfd) == 1:
				os.unlink(lockfilename)
				writemsg(_("Unlinked lockfile...\n"), 1)
				locking_method(myfd, fcntl.LOCK_UN)
			else:
				writemsg(_("lockfile does not exist '%s'\n") % lockfilename, 1)
				os.close(myfd)
				_open_fds.remove(myfd)
				return False
	except SystemExit:
		raise
	except Exception as e:
		writemsg(_("Failed to get lock... someone took it.\n"), 1)
		writemsg(str(e) + "\n", 1)

	# why test lockfilename?  because we may have been handed an
	# fd originally, and the caller might not like having their
	# open fd closed automatically on them.
	if isinstance(lockfilename, basestring):
		os.close(myfd)
		_open_fds.remove(myfd)

	return True

def lockfile(mypath, wantnewlockfile=0, unlinkfile=0,
	waiting_msg=None, flags=0):
	"""
	If wantnewlockfile is True then this creates a lockfile in the parent
	directory as the file: '.' + basename + '.portage_lockfile'.
	"""
	import fcntl

	if not mypath:
		raise InvalidData(_("Empty path given"))

	if isinstance(mypath, basestring) and mypath[-1] == '/':
		mypath = mypath[:-1]

	if hasattr(mypath, 'fileno'):
		mypath = mypath.fileno()
	if isinstance(mypath, int):
		lockfilename    = mypath
		wantnewlockfile = 0
		unlinkfile      = 0
	elif wantnewlockfile:
		base, tail = os.path.split(mypath)
		lockfilename = os.path.join(base, "." + tail + ".portage_lockfile")
		del base, tail
		unlinkfile   = 1
	else:
		lockfilename = mypath

	if isinstance(mypath, basestring):
		if not os.path.exists(os.path.dirname(mypath)):
			raise DirectoryNotFound(os.path.dirname(mypath))
		preexisting = os.path.exists(lockfilename)
		old_mask = os.umask(000)
		try:
			try:
				myfd = os.open(lockfilename, os.O_CREAT|os.O_RDWR, 0o660)
			except OSError as e:
				func_call = "open('%s')" % lockfilename
				if e.errno == OperationNotPermitted.errno:
					raise OperationNotPermitted(func_call)
				elif e.errno == PermissionDenied.errno:
					raise PermissionDenied(func_call)
				else:
					raise

			if not preexisting:
				try:
					if os.stat(lockfilename).st_gid != portage_gid:
						os.chown(lockfilename, -1, portage_gid)
				except OSError as e:
					if e.errno in (errno.ENOENT, errno.ESTALE):
						return lockfile(mypath,
							wantnewlockfile=wantnewlockfile,
							unlinkfile=unlinkfile, waiting_msg=waiting_msg,
							flags=flags)
					else:
						writemsg(_("Cannot chown a lockfile: '%s'\n") % \
							lockfilename, noiselevel=-1)

		finally:
			os.umask(old_mask)

	elif isinstance(mypath, int):
		myfd = mypath

	else:
		raise ValueError(_("Unknown type passed in '%s': '%s'") % \
			(type(mypath), mypath))

	# try for a non-blocking lock, if it's held, throw a message
	# we're waiting on lockfile and use a blocking attempt.
	locking_method = fcntl.lockf
	try:
		fcntl.lockf(myfd,fcntl.LOCK_EX|fcntl.LOCK_NB)
	except IOError as e:
		if "errno" not in dir(e):
			raise
		if e.errno in (errno.EACCES, errno.EAGAIN):
			# resource temp unavailable; eg, someone beat us to the lock.
			if flags & os.O_NONBLOCK:
				raise TryAgain(mypath)

			global _quiet
			out = EOutput()
			out.quiet = _quiet
			if waiting_msg is None:
				if isinstance(mypath, int):
					waiting_msg = _("waiting for lock on fd %i") % myfd
				else:
					waiting_msg = _("waiting for lock on %s\n") % lockfilename
			out.ebegin(waiting_msg)
			# try for the exclusive lock now.
			try:
				fcntl.lockf(myfd, fcntl.LOCK_EX)
			except EnvironmentError as e:
				out.eend(1, str(e))
				raise
			out.eend(os.EX_OK)
		elif e.errno == errno.ENOLCK:
			# We're not allowed to lock on this FS.
#.........这里部分代码省略.........

	def _fetch_uri(self, uri):

		if self.config.options.dry_run:
			# Simply report success.
			logging.info("dry-run: fetch '%s' from '%s'" %
				(self.distfile, uri))
			self._success()
			self.returncode = os.EX_OK
			self.wait()
			return

		if self.config.options.temp_dir:
			self._fetch_tmp_dir_info = 'temp-dir'
			distdir = self.config.options.temp_dir
		else:
			self._fetch_tmp_dir_info = 'distfiles'
			distdir = self.config.options.distfiles

		tmp_basename = self.distfile + '._emirrordist_fetch_.%s' % os.getpid()

		variables = {
			"DISTDIR": distdir,
			"URI":     uri,
			"FILE":    tmp_basename
		}

		self._fetch_tmp_file = os.path.join(distdir, tmp_basename)

		try:
			os.unlink(self._fetch_tmp_file)
		except OSError:
			pass

		args = portage.util.shlex_split(default_fetchcommand)
		args = [portage.util.varexpand(x, mydict=variables)
			for x in args]

		if sys.hexversion < 0x3020000 and sys.hexversion >= 0x3000000 and \
			not os.path.isabs(args[0]):
			# Python 3.1 _execvp throws TypeError for non-absolute executable
			# path passed as bytes (see https://bugs.python.org/issue8513).
			fullname = portage.process.find_binary(args[0])
			if fullname is None:
				raise portage.exception.CommandNotFound(args[0])
			args[0] = fullname

		args = [_unicode_encode(x,
			encoding=_encodings['fs'], errors='strict') for x in args]

		null_fd = os.open(os.devnull, os.O_RDONLY)
		fetcher = PopenProcess(background=self.background,
			proc=subprocess.Popen(args, stdin=null_fd,
			stdout=subprocess.PIPE, stderr=subprocess.STDOUT),
			scheduler=self.scheduler)
		os.close(null_fd)

		fetcher.pipe_reader = PipeLogger(background=self.background,
			input_fd=fetcher.proc.stdout, log_file_path=self._log_path,
			scheduler=self.scheduler)

		self._start_task(fetcher, self._fetcher_exit)

	def _start(self):

		need_builddir = self.phase not in self._phases_without_builddir

		# This can happen if the pre-clean phase triggers
		# die_hooks for some reason, and PORTAGE_BUILDDIR
		# doesn't exist yet.
		if need_builddir and \
			not os.path.isdir(self.settings['PORTAGE_BUILDDIR']):
			msg = _("The ebuild phase '%s' has been aborted "
			"since PORTAGE_BUILDDIR does not exist: '%s'") % \
			(self.phase, self.settings['PORTAGE_BUILDDIR'])
			self._eerror(textwrap.wrap(msg, 72))
			self._set_returncode((self.pid, 1 << 8))
			self._async_wait()
			return

		# Check if the cgroup hierarchy is in place. If it's not, mount it.
		if (os.geteuid() == 0 and platform.system() == 'Linux'
				and 'cgroup' in self.settings.features
				and self.phase not in self._phases_without_cgroup):
			cgroup_root = '/sys/fs/cgroup'
			cgroup_portage = os.path.join(cgroup_root, 'portage')

			try:
				# cgroup tmpfs
				if not os.path.ismount(cgroup_root):
					# we expect /sys/fs to be there already
					if not os.path.isdir(cgroup_root):
						os.mkdir(cgroup_root, 0o755)
					subprocess.check_call(['mount', '-t', 'tmpfs',
						'-o', 'rw,nosuid,nodev,noexec,mode=0755',
						'tmpfs', cgroup_root])

				# portage subsystem
				if not os.path.ismount(cgroup_portage):
					if not os.path.isdir(cgroup_portage):
						os.mkdir(cgroup_portage, 0o755)
					subprocess.check_call(['mount', '-t', 'cgroup',
						'-o', 'rw,nosuid,nodev,noexec,none,name=portage',
						'tmpfs', cgroup_portage])

				cgroup_path = tempfile.mkdtemp(dir=cgroup_portage,
					prefix='%s:%s.' % (self.settings["CATEGORY"],
					self.settings["PF"]))
			except (subprocess.CalledProcessError, OSError):
				pass
			else:
				self.cgroup = cgroup_path

		if self.background:
			# Automatically prevent color codes from showing up in logs,
			# since we're not displaying to a terminal anyway.
			self.settings['NOCOLOR'] = 'true'

		if self._enable_ipc_daemon:
			self.settings.pop('PORTAGE_EBUILD_EXIT_FILE', None)
			if self.phase not in self._phases_without_builddir:
				if 'PORTAGE_BUILDDIR_LOCKED' not in self.settings:
					self._build_dir = EbuildBuildDir(
						scheduler=self.scheduler, settings=self.settings)
					self._build_dir.lock()
				self.settings['PORTAGE_IPC_DAEMON'] = "1"
				self._start_ipc_daemon()
			else:
				self.settings.pop('PORTAGE_IPC_DAEMON', None)
		else:
			# Since the IPC daemon is disabled, use a simple tempfile based
			# approach to detect unexpected exit like in bug #190128.
			self.settings.pop('PORTAGE_IPC_DAEMON', None)
			if self.phase not in self._phases_without_builddir:
				exit_file = os.path.join(
					self.settings['PORTAGE_BUILDDIR'],
					'.exit_status')
				self.settings['PORTAGE_EBUILD_EXIT_FILE'] = exit_file
				try:
					os.unlink(exit_file)
				except OSError:
					if os.path.exists(exit_file):
						# make sure it doesn't exist
						raise
			else:
				self.settings.pop('PORTAGE_EBUILD_EXIT_FILE', None)

		if self.fd_pipes is None:
			self.fd_pipes = {}
		null_fd = None
		if 0 not in self.fd_pipes and \
			self.phase not in self._phases_interactive_whitelist and \
			"interactive" not in self.settings.get("PROPERTIES", "").split():
			null_fd = os.open('/dev/null', os.O_RDONLY)
			self.fd_pipes[0] = null_fd

		try:
			SpawnProcess._start(self)
		finally:
			if null_fd is not None:
				os.close(null_fd)

	def _start(self):

		if self.fd_pipes is None:
			self.fd_pipes = {}
		else:
			self.fd_pipes = self.fd_pipes.copy()
		fd_pipes = self.fd_pipes

		master_fd, slave_fd = self._pipe(fd_pipes)

		can_log = self._can_log(slave_fd)
		if can_log:
			log_file_path = self.logfile
		else:
			log_file_path = None

		null_input = None
		if not self.background or 0 in fd_pipes:
			# Subclasses such as AbstractEbuildProcess may have already passed
			# in a null file descriptor in fd_pipes, so use that when given.
			pass
		else:
			# TODO: Use job control functions like tcsetpgrp() to control
			# access to stdin. Until then, use /dev/null so that any
			# attempts to read from stdin will immediately return EOF
			# instead of blocking indefinitely.
			null_input = os.open('/dev/null', os.O_RDWR)
			fd_pipes[0] = null_input

		fd_pipes.setdefault(0, portage._get_stdin().fileno())
		fd_pipes.setdefault(1, sys.__stdout__.fileno())
		fd_pipes.setdefault(2, sys.__stderr__.fileno())

		# flush any pending output
		stdout_filenos = (sys.__stdout__.fileno(), sys.__stderr__.fileno())
		for fd in fd_pipes.values():
			if fd in stdout_filenos:
				sys.__stdout__.flush()
				sys.__stderr__.flush()
				break

		fd_pipes_orig = fd_pipes.copy()

		if log_file_path is not None or self.background:
			fd_pipes[1] = slave_fd
			fd_pipes[2] = slave_fd

		else:
			# Create a dummy pipe that PipeLogger uses to efficiently
			# monitor for process exit by listening for the EOF event.
			# Re-use of the allocated fd number for the key in fd_pipes
			# guarantees that the keys will not collide for similarly
			# allocated pipes which are used by callers such as
			# FileDigester and MergeProcess. See the _setup_pipes
			# docstring for more benefits of this allocation approach.
			self._dummy_pipe_fd = slave_fd
			fd_pipes[slave_fd] = slave_fd

		kwargs = {}
		for k in self._spawn_kwarg_names:
			v = getattr(self, k)
			if v is not None:
				kwargs[k] = v

		kwargs["fd_pipes"] = fd_pipes
		kwargs["returnpid"] = True
		kwargs.pop("logfile", None)

		retval = self._spawn(self.args, **kwargs)

		os.close(slave_fd)
		if null_input is not None:
			os.close(null_input)

		if isinstance(retval, int):
			# spawn failed
			self._unregister()
			self._set_returncode((self.pid, retval))
			self._async_wait()
			return

		self.pid = retval[0]

		stdout_fd = None
		if can_log and not self.background:
			stdout_fd = os.dup(fd_pipes_orig[1])
			# FD_CLOEXEC is enabled by default in Python >=3.4.
			if sys.hexversion < 0x3040000 and fcntl is not None:
				try:
					fcntl.FD_CLOEXEC
				except AttributeError:
					pass
				else:
					fcntl.fcntl(stdout_fd, fcntl.F_SETFD,
						fcntl.fcntl(stdout_fd,
						fcntl.F_GETFD) | fcntl.FD_CLOEXEC)

		self._pipe_logger = PipeLogger(background=self.background,
			scheduler=self.scheduler, input_fd=master_fd,
			log_file_path=log_file_path,
#.........这里部分代码省略.........