1 # 2 # Module providing the `Process` class which emulates `threading.Thread` 3 # 4 # multiprocessing/process.py 5 # 6 # Copyright (c) 2006-2008, R Oudkerk 7 # Licensed to PSF under a Contributor Agreement. 8 # 9 10 __all__ = ['BaseProcess', 'current_process', 'active_children'] 11 12 # 13 # Imports 14 # 15 16 import os 17 import sys 18 import signal 19 import itertools 20 import threading 21 from _weakrefset import WeakSet 22 23 # 24 # 25 # 26 27 try: 28 ORIGINAL_DIR = os.path.abspath(os.getcwd()) 29 except OSError: 30 ORIGINAL_DIR = None 31 32 # 33 # Public functions 34 # 35 36 def current_process(): 37 ''' 38 Return process object representing the current process 39 ''' 40 return _current_process 41 42 def active_children(): 43 ''' 44 Return list of process objects corresponding to live child processes 45 ''' 46 _cleanup() 47 return list(_children) 48 49 # 50 # 51 # 52 53 def _cleanup(): 54 # check for processes which have finished 55 for p in list(_children): 56 if p._popen.poll() is not None: 57 _children.discard(p) 58 59 # 60 # The `Process` class 61 # 62 63 class BaseProcess(object): 64 ''' 65 Process objects represent activity that is run in a separate process 66 67 The class is analogous to `threading.Thread` 68 ''' 69 def _Popen(self): 70 raise NotImplementedError 71 72 def __init__(self, group=None, target=None, name=None, args=(), kwargs={}, 73 *, daemon=None): 74 assert group is None, 'group argument must be None for now' 75 count = next(_process_counter) 76 self._identity = _current_process._identity + (count,) 77 self._config = _current_process._config.copy() 78 self._parent_pid = os.getpid() 79 self._popen = None 80 self._closed = False 81 self._target = target 82 self._args = tuple(args) 83 self._kwargs = dict(kwargs) 84 self._name = name or type(self).__name__ + '-' + \ 85 ':'.join(str(i) for i in self._identity) 86 if daemon is not None: 87 self.daemon = daemon 88 _dangling.add(self) 89 90 def _check_closed(self): 91 if self._closed: 92 raise ValueError("process object is closed") 93 94 def run(self): 95 ''' 96 Method to be run in sub-process; can be overridden in sub-class 97 ''' 98 if self._target: 99 self._target(*self._args, **self._kwargs) 100 101 def start(self): 102 ''' 103 Start child process 104 ''' 105 self._check_closed() 106 assert self._popen is None, 'cannot start a process twice' 107 assert self._parent_pid == os.getpid(), \ 108 'can only start a process object created by current process' 109 assert not _current_process._config.get('daemon'), \ 110 'daemonic processes are not allowed to have children' 111 _cleanup() 112 self._popen = self._Popen(self) 113 self._sentinel = self._popen.sentinel 114 # Avoid a refcycle if the target function holds an indirect 115 # reference to the process object (see bpo-30775) 116 del self._target, self._args, self._kwargs 117 _children.add(self) 118 119 def terminate(self): 120 ''' 121 Terminate process; sends SIGTERM signal or uses TerminateProcess() 122 ''' 123 self._check_closed() 124 self._popen.terminate() 125 126 def kill(self): 127 ''' 128 Terminate process; sends SIGKILL signal or uses TerminateProcess() 129 ''' 130 self._check_closed() 131 self._popen.kill() 132 133 def join(self, timeout=None): 134 ''' 135 Wait until child process terminates 136 ''' 137 self._check_closed() 138 assert self._parent_pid == os.getpid(), 'can only join a child process' 139 assert self._popen is not None, 'can only join a started process' 140 res = self._popen.wait(timeout) 141 if res is not None: 142 _children.discard(self) 143 144 def is_alive(self): 145 ''' 146 Return whether process is alive 147 ''' 148 self._check_closed() 149 if self is _current_process: 150 return True 151 assert self._parent_pid == os.getpid(), 'can only test a child process' 152 153 if self._popen is None: 154 return False 155 156 returncode = self._popen.poll() 157 if returncode is None: 158 return True 159 else: 160 _children.discard(self) 161 return False 162 163 def close(self): 164 ''' 165 Close the Process object. 166 167 This method releases resources held by the Process object. It is 168 an error to call this method if the child process is still running. 169 ''' 170 if self._popen is not None: 171 if self._popen.poll() is None: 172 raise ValueError("Cannot close a process while it is still running. " 173 "You should first call join() or terminate().") 174 self._popen.close() 175 self._popen = None 176 del self._sentinel 177 _children.discard(self) 178 self._closed = True 179 180 @property 181 def name(self): 182 return self._name 183 184 @name.setter 185 def name(self, name): 186 assert isinstance(name, str), 'name must be a string' 187 self._name = name 188 189 @property 190 def daemon(self): 191 ''' 192 Return whether process is a daemon 193 ''' 194 return self._config.get('daemon', False) 195 196 @daemon.setter 197 def daemon(self, daemonic): 198 ''' 199 Set whether process is a daemon 200 ''' 201 assert self._popen is None, 'process has already started' 202 self._config['daemon'] = daemonic 203 204 @property 205 def authkey(self): 206 return self._config['authkey'] 207 208 @authkey.setter 209 def authkey(self, authkey): 210 ''' 211 Set authorization key of process 212 ''' 213 self._config['authkey'] = AuthenticationString(authkey) 214 215 @property 216 def exitcode(self): 217 ''' 218 Return exit code of process or `None` if it has yet to stop 219 ''' 220 self._check_closed() 221 if self._popen is None: 222 return self._popen 223 return self._popen.poll() 224 225 @property 226 def ident(self): 227 ''' 228 Return identifier (PID) of process or `None` if it has yet to start 229 ''' 230 self._check_closed() 231 if self is _current_process: 232 return os.getpid() 233 else: 234 return self._popen and self._popen.pid 235 236 pid = ident 237 238 @property 239 def sentinel(self): 240 ''' 241 Return a file descriptor (Unix) or handle (Windows) suitable for 242 waiting for process termination. 243 ''' 244 self._check_closed() 245 try: 246 return self._sentinel 247 except AttributeError: 248 raise ValueError("process not started") from None 249 250 def __repr__(self): 251 if self is _current_process: 252 status = 'started' 253 elif self._closed: 254 status = 'closed' 255 elif self._parent_pid != os.getpid(): 256 status = 'unknown' 257 elif self._popen is None: 258 status = 'initial' 259 else: 260 if self._popen.poll() is not None: 261 status = self.exitcode 262 else: 263 status = 'started' 264 265 if type(status) is int: 266 if status == 0: 267 status = 'stopped' 268 else: 269 status = 'stopped[%s]' % _exitcode_to_name.get(status, status) 270 271 return '<%s(%s, %s%s)>' % (type(self).__name__, self._name, 272 status, self.daemon and ' daemon' or '') 273 274 ## 275 276 def _bootstrap(self): 277 from . import util, context 278 global _current_process, _process_counter, _children 279 280 try: 281 if self._start_method is not None: 282 context._force_start_method(self._start_method) 283 _process_counter = itertools.count(1) 284 _children = set() 285 util._close_stdin() 286 old_process = _current_process 287 _current_process = self 288 try: 289 util._finalizer_registry.clear() 290 util._run_after_forkers() 291 finally: 292 # delay finalization of the old process object until after 293 # _run_after_forkers() is executed 294 del old_process 295 util.info('child process calling self.run()') 296 try: 297 self.run() 298 exitcode = 0 299 finally: 300 util._exit_function() 301 except SystemExit as e: 302 if not e.args: 303 exitcode = 1 304 elif isinstance(e.args[0], int): 305 exitcode = e.args[0] 306 else: 307 sys.stderr.write(str(e.args[0]) + '\n') 308 exitcode = 1 309 except: 310 exitcode = 1 311 import traceback 312 sys.stderr.write('Process %s:\n' % self.name) 313 traceback.print_exc() 314 finally: 315 threading._shutdown() 316 util.info('process exiting with exitcode %d' % exitcode) 317 util._flush_std_streams() 318 319 return exitcode 320 321 # 322 # We subclass bytes to avoid accidental transmission of auth keys over network 323 # 324 325 class AuthenticationString(bytes): 326 def __reduce__(self): 327 from .context import get_spawning_popen 328 if get_spawning_popen() is None: 329 raise TypeError( 330 'Pickling an AuthenticationString object is ' 331 'disallowed for security reasons' 332 ) 333 return AuthenticationString, (bytes(self),) 334 335 # 336 # Create object representing the main process 337 # 338 339 class _MainProcess(BaseProcess): 340 341 def __init__(self): 342 self._identity = () 343 self._name = 'MainProcess' 344 self._parent_pid = None 345 self._popen = None 346 self._closed = False 347 self._config = {'authkey': AuthenticationString(os.urandom(32)), 348 'semprefix': '/mp'} 349 # Note that some versions of FreeBSD only allow named 350 # semaphores to have names of up to 14 characters. Therefore 351 # we choose a short prefix. 352 # 353 # On MacOSX in a sandbox it may be necessary to use a 354 # different prefix -- see #19478. 355 # 356 # Everything in self._config will be inherited by descendant 357 # processes. 358 359 def close(self): 360 pass 361 362 363 _current_process = _MainProcess() 364 _process_counter = itertools.count(1) 365 _children = set() 366 del _MainProcess 367 368 # 369 # Give names to some return codes 370 # 371 372 _exitcode_to_name = {} 373 374 for name, signum in list(signal.__dict__.items()): 375 if name[:3]=='SIG' and '_' not in name: 376 _exitcode_to_name[-signum] = name 377 378 # For debug and leak testing 379 _dangling = WeakSet() 380
