Merge pull request #119 from seebye/orphans

fix process orphans

ueberzug/__main__.py

@@ -1,10 +1,14 @@
 #!/usr/bin/env python3
 """Usage:
- ueberzug MODULE [options]
+ ueberzug layer [options]
+ ueberzug library
+ ueberzug query_windows PIDS ...
 
 Routines:
  layer Display images
  library Prints the path to the bash library
+ query_windows Orders ueberzug to search for windows.
+ Only for internal use.
 
 Layer options:
  -p, --parser <parser> one of json, simple, bash
@@ -26,28 +30,22 @@
  This is free software, and you are welcome to redistribute it
  under certain conditions.
 """
-import sys
-
 import docopt
 
 
 def main():
  options = docopt.docopt(__doc__)
- module_name = options['MODULE']
  module = None
 
- if module_name == 'layer':
+ if options['layer']:
  import ueberzug.layer as layer
  module = layer
- elif module_name == 'library':
+ elif options['library']:
  import ueberzug.library as library
  module = library
-
- if module is None:
- print("Unknown module '{}'"
- .format(module_name),
- file=sys.stderr)
- return
+ elif options['query_windows']:
+ import ueberzug.query_windows as query_windows
+ module = query_windows
 
  module.main(options)
 

ueberzug/layer.py

@@ -116,7 +116,7 @@ def setup_tmux_hooks():
  lock_directory_path = pathlib.PosixPath(tempfile.gettempdir()) / 'ueberzug'
  lock_file_path = lock_directory_path / tmux_util.get_session_id()
  own_pid = str(os.getpid())
- command_template = 'kill -USR1 '
+ command_template = 'ueberzug query_windows '
 
  try:
  lock_directory_path.mkdir()
@@ -216,7 +216,7 @@ def main(options):
  atexit.register(setup_tmux_hooks())
  view.offset = tmux_util.get_offset()
 
- with windows:
+ with windows, image_loader:
  loop.set_default_executor(executor)
 
  for sig in (signal.SIGINT, signal.SIGTERM):

ueberzug/lib/v0/__init__.py

@@ -5,6 +5,8 @@
 import json
 import collections
 import contextlib
+import os
+import signal
 
 import attr
 
@@ -186,7 +188,8 @@ def start(self):
  ['ueberzug', 'layer'] + self.__start_options,
  stdin=subprocess.PIPE,
  bufsize=self.__BUFFER_SIZE_BYTES,
- universal_newlines=True)
+ universal_newlines=True,
+ start_new_session=True)
 
  def stop(self):
  """Sends SIGTERM to the running ueberzug process
@@ -195,17 +198,25 @@ def stop(self):
  SIGKILL will also be send.
  """
  if self.running:
- timer_kill = threading.Timer(
- self.__KILL_TIMEOUT_SECONDS,
- self.__process.kill,
- [])
+ timer_kill = None
 
  try:
+ ueberzug_pgid = os.getpgid(self.__process.pid)
+ own_pgid = os.getpgid(0)
+ assert ueberzug_pgid != own_pgid
+ timer_kill = threading.Timer(
+ self.__KILL_TIMEOUT_SECONDS,
+ os.killpg,
+ [ueberzug_pgid, signal.SIGKILL])
+
  self.__process.terminate()
  timer_kill.start()
  self.__process.communicate()
+ except ProcessLookupError:
+ pass
  finally:
- timer_kill.cancel()
+ if timer_kill is not None:
+ timer_kill.cancel()
 
 
 class CommandTransmitter:

ueberzug/loading.py

@@ -205,6 +205,13 @@ def process_error(self, exception):
  exception is not None):
  self.error_handler(exception)
 
+ def __enter__(self):
+ pass
+
+ def __exit__(self, *_):
+ """Finalises the image loader."""
+ pass
+
 
 class SynchronousImageLoader(ImageLoader):
  """Implementation of ImageLoader
@@ -408,6 +415,10 @@ def __init__(self):
  max_workers=threads_low_priority)
  self.threads = threads + threads_low_priority
 
+ def __exit__(self, *_):
+ self.__executor_low_priority.shutdown()
+ self.__executor.shutdown()
+
  def _schedule(self, function, priority):
  executor = self.__executor
  if priority == self.Priority.LOW:
@@ -437,6 +448,10 @@ def __init__(self):
  .submit(id, id) \
  .result()
 
+ def __exit__(self, *args):
+ super().__exit__(*args)
+ self.__executor_loader.shutdown()
+
  @staticmethod
  def _load_image_extern(path, upper_bound_size, post_load_processor):
  """This function is a wrapper for the image loading function

ueberzug/query_windows.py

@@ -0,0 +1,99 @@
+import os
+import signal
+import errno
+
+
+def get_command(pid):
+ """Figures out the associated command name
+ of a process with the given pid.
+
+ Args:
+ pid (int): the pid of the process of interest
+
+ Returns:
+ str: the associated command name
+ """
+ with open('/proc/{}/comm'.format(pid), 'r') as commfile:
+ return '\n'.join(commfile.readlines())
+
+
+def is_same_command(pid0, pid1):
+ """Checks whether the associated command name
+ of the processes of the given pids equals to each other.
+
+ Args:
+ pid0 (int): the pid of the process of interest
+ pid1 (int): the pid of another process of interest
+
+ Returns:
+ bool: True if both processes have
+ the same associated command name
+ """
+ return get_command(pid0) == get_command(pid1)
+
+
+def send_signal_safe(own_pid, target_pid):
+ """Sends SIGUSR1 to a process if both
+ processes have the same associated command name.
+ (Race condition free)
+
+ Requires:
+ - Python 3.9+
+ - Linux 5.1+
+
+ Args:
+ own_pid (int): the pid of this process
+ target_pid (int):
+ the pid of the process to send the signal to
+ """
+ pidfile = None
+ try:
+ pidfile = os.pidfile_open(target_pid)
+ if is_same_command(own_pid, target_pid):
+ signal.pidfd_send_signal(pidfile, signal.SIGUSR1)
+ except FileNotFoundError:
+ pass
+ except OSError as error:
+ # not sure if errno is really set..
+ # at least the documentation of the used functions says so..
+ # see e.g.: https://github.com/python/cpython/commit/7483451577916e693af6d20cf520b2cc7e2174d2#diff-99fb04b208835118fdca0d54b76a00c450da3eaff09d2b53e8a03d63bbe88e30R1279-R1281
+ # and https://docs.python.org/3/c-api/exceptions.html#c.PyErr_SetFromErrno
+
+ # caused by either pidfile_open or pidfd_send_signal
+ if error.errno != errno.ESRCH:
+ raise
+ # else: the process is death
+ finally:
+ if pidfile is not None:
+ os.close(pidfile)
+
+
+def send_signal_unsafe(own_pid, target_pid):
+ """Sends SIGUSR1 to a process if both
+ processes have the same associated command name.
+ (Race condition if process dies)
+
+ Args:
+ own_pid (int): the pid of this process
+ target_pid (int):
+ the pid of the process to send the signal to
+ """
+ try:
+ if is_same_command(own_pid, target_pid):
+ os.kill(target_pid, signal.SIGUSR1)
+ except (FileNotFoundError, ProcessLookupError):
+ pass
+
+
+def main(options):
+ # assumption:
+ # started by calling the programs name
+ # ueberzug layer and
+ # ueberzug query_windows
+ own_pid = os.getpid()
+
+ for pid in options['PIDS']:
+ try:
+ send_signal_safe(own_pid, int(pid))
+ except AttributeError:
+ send_signal_unsafe(own_pid, int(pid))