cpython/Lib/multiprocessing/process.py at main · python/cpython · GitHub

Repository navigation

History

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120

121

122

123

124

125

126

127

128

129

130

131

132

133

134

135

136

137

138

139

140

141

142

143

144

145

146

147

148

149

150

151

152

153

154

155

156

157

158

159

160

161

162

163

164

165

166

167

168

169

170

171

172

173

174

175

176

177

178

179

180

181

182

183

184

185

186

187

188

189

190

191

192

193

194

195

196

197

198

199

200

201

202

203

204

205

206

207

208

209

210

211

212

213

214

215

216

217

218

219

220

221

222

223

224

225

226

227

228

229

230

231

232

233

234

235

236

237

238

239

240

241

242

243

244

245

246

247

248

249

250

251

252

253

254

255

256

257

258

259

260

261

262

263

264

265

266

267

268

269

270

271

272

273

274

275

276

277

278

279

280

281

282

283

284

285

286

287

288

289

290

291

292

293

294

295

296

297

298

299

300

301

302

303

304

305

306

307

308

309

310

311

312

313

314

315

316

317

318

319

320

321

322

323

324

325

326

327

328

329

330

331

332

333

334

335

336

337

338

339

340

341

342

343

344

345

346

347

348

349

350

351

352

353

354

355

356

357

358

359

360

361

362

363

364

365

366

367

368

369

370

371

372

373

374

375

376

377

378

379

380

381

382

383

384

385

386

387

388

389

390

391

392

393

394

395

396

397

398

399

400

401

402

403

404

405

406

407

408

409

410

411

412

413

414

415

416

417

418

419

420

421

422

423

424

425

426

427

428

429

430

431

432

433

434

435

436

437

438

439

440

441

442

443

# Module providing the `Process` class which emulates `threading.Thread`

# multiprocessing/process.py

# Licensed to PSF under a Contributor Agreement.

__all__ = ['BaseProcess', 'current_process', 'active_children',

'parent_process']

# Imports

import os

import sys

import signal

import itertools

import threading

from _weakrefset import WeakSet

try:

ORIGINAL_DIR = os.path.abspath(os.getcwd())

except OSError:

ORIGINAL_DIR = None

# Public functions

def current_process():

'''

Return process object representing the current process

'''

return _current_process

def active_children():

'''

Return list of process objects corresponding to live child processes

'''

_cleanup()

return list(_children)

def parent_process():

'''

Return process object representing the parent process

'''

return _parent_process

def _cleanup():

# check for processes which have finished

for p in list(_children):

if (child_popen := p._popen) and child_popen.poll() is not None:

_children.discard(p)

# The `Process` class

class BaseProcess(object):

'''

Process objects represent activity that is run in a separate process

The class is analogous to `threading.Thread`

'''

def _Popen(self):

raise NotImplementedError

def __init__(self, group=None, target=None, name=None, args=(), kwargs=None,

*, daemon=None):

assert group is None, 'group argument must be None for now'

count = next(_process_counter)

self._identity = _current_process._identity + (count,)

self._config = _current_process._config.copy()

self._parent_pid = os.getpid()

self._parent_name = _current_process.name

self._popen = None

self._closed = False

self._target = target

self._args = tuple(args)

self._kwargs = dict(kwargs) if kwargs else {}

self._name = name or type(self).__name__ + '-' + \

':'.join(str(i) for i in self._identity)

if daemon is not None:

self.daemon = daemon

_dangling.add(self)

def _check_closed(self):

if self._closed:

raise ValueError("process object is closed")

def run(self):

'''

Method to be run in sub-process; can be overridden in sub-class

'''

if self._target:

self._target(*self._args, **self._kwargs)

def start(self):

'''

Start child process

'''

self._check_closed()

assert self._popen is None, 'cannot start a process twice'

assert self._parent_pid == os.getpid(), \

'can only start a process object created by current process'

assert not _current_process._config.get('daemon'), \

'daemonic processes are not allowed to have children'

_cleanup()

self._popen = self._Popen(self)

self._sentinel = self._popen.sentinel

# Avoid a refcycle if the target function holds an indirect

# reference to the process object (see bpo-30775)

del self._target, self._args, self._kwargs

_children.add(self)

def interrupt(self):

'''

Terminate process; sends SIGINT signal

'''

self._check_closed()

self._popen.interrupt()

def terminate(self):

'''

Terminate process; sends SIGTERM signal or uses TerminateProcess()

'''

self._check_closed()

self._popen.terminate()

def kill(self):

'''

Terminate process; sends SIGKILL signal or uses TerminateProcess()

'''

self._check_closed()

self._popen.kill()

def join(self, timeout=None):

'''

Wait until child process terminates

'''

self._check_closed()

assert self._parent_pid == os.getpid(), 'can only join a child process'

assert self._popen is not None, 'can only join a started process'

res = self._popen.wait(timeout)

if res is not None:

_children.discard(self)

def is_alive(self):

'''

Return whether process is alive

'''

self._check_closed()

if self is _current_process:

return True

assert self._parent_pid == os.getpid(), 'can only test a child process'

if self._popen is None:

return False

returncode = self._popen.poll()

if returncode is None:

return True

else:

_children.discard(self)

return False

def close(self):

'''

Close the Process object.

This method releases resources held by the Process object. It is

an error to call this method if the child process is still running.

'''

if self._popen is not None:

if self._popen.poll() is None:

raise ValueError("Cannot close a process while it is still running. "

"You should first call join() or terminate().")

self._popen.close()

self._popen = None

del self._sentinel

_children.discard(self)

self._closed = True

@property

def name(self):

return self._name

@name.setter

def name(self, name):

assert isinstance(name, str), 'name must be a string'

self._name = name

@property

def daemon(self):

'''

Return whether process is a daemon

'''

return self._config.get('daemon', False)

@daemon.setter

def daemon(self, daemonic):

'''

Set whether process is a daemon

'''

assert self._popen is None, 'process has already started'

self._config['daemon'] = daemonic

@property

def authkey(self):

return self._config['authkey']

@authkey.setter

def authkey(self, authkey):

'''

Set authorization key of process

'''

self._config['authkey'] = AuthenticationString(authkey)

@property

def exitcode(self):

'''

Return exit code of process or `None` if it has yet to stop

'''

self._check_closed()

if self._popen is None:

return self._popen

return self._popen.poll()

@property

def ident(self):

'''

Return identifier (PID) of process or `None` if it has yet to start

'''

self._check_closed()

if self is _current_process:

return os.getpid()

else:

return self._popen and self._popen.pid

pid = ident

@property

def sentinel(self):

'''

Return a file descriptor (Unix) or handle (Windows) suitable for

waiting for process termination.

'''

self._check_closed()

try:

return self._sentinel

except AttributeError:

raise ValueError("process not started") from None

def __repr__(self):

exitcode = None

if self is _current_process:

status = 'started'

elif self._closed:

status = 'closed'

elif self._parent_pid != os.getpid():

status = 'unknown'

elif self._popen is None:

status = 'initial'

else:

exitcode = self._popen.poll()

if exitcode is not None:

status = 'stopped'

else:

status = 'started'

info = [type(self).__name__, 'name=%r' % self._name]

if self._popen is not None:

info.append('pid=%s' % self._popen.pid)

info.append('parent=%s' % self._parent_pid)

info.append(status)

if exitcode is not None:

exitcode = _exitcode_to_name.get(exitcode, exitcode)

info.append('exitcode=%s' % exitcode)

if self.daemon:

info.append('daemon')

return '<%s>' % ' '.join(info)

def _bootstrap(self, parent_sentinel=None):

from . import util, context

global _current_process, _parent_process, _process_counter, _children

try:

if self._start_method is not None:

context._force_start_method(self._start_method)

_process_counter = itertools.count(1)

_children = set()

util._close_stdin()

old_process = _current_process

_current_process = self

_parent_process = _ParentProcess(

self._parent_name, self._parent_pid, parent_sentinel)

if threading._HAVE_THREAD_NATIVE_ID:

threading.main_thread()._set_native_id()

try:

self._after_fork()

finally:

# delay finalization of the old process object until after

# _run_after_forkers() is executed

del old_process

util.info('child process calling self.run()')

self.run()

exitcode = 0

except SystemExit as e:

if e.code is None:

exitcode = 0

elif isinstance(e.code, int):

exitcode = e.code

else:

sys.stderr.write(str(e.code) + '\n')

exitcode = 1

except:

exitcode = 1

import traceback

sys.stderr.write('Process %s:\n' % self.name)

traceback.print_exc()

finally:

threading._shutdown()

util.info('process exiting with exitcode %d' % exitcode)

util._flush_std_streams()

return exitcode

@staticmethod

def _after_fork():

from . import util

util._finalizer_registry.clear()

util._run_after_forkers()

# We subclass bytes to avoid accidental transmission of auth keys over network

class AuthenticationString(bytes):

def __reduce__(self):

from .context import get_spawning_popen

if get_spawning_popen() is None:

raise TypeError(

'Pickling an AuthenticationString object is '

'disallowed for security reasons'

)

return AuthenticationString, (bytes(self),)

# Create object representing the parent process

class _ParentProcess(BaseProcess):

def __init__(self, name, pid, sentinel):

self._identity = ()

self._name = name

self._pid = pid

self._parent_pid = None

self._popen = None

self._closed = False

self._sentinel = sentinel

self._config = {}

def is_alive(self):

from multiprocessing.connection import wait

return not wait([self._sentinel], timeout=0)

@property

def ident(self):

return self._pid

def join(self, timeout=None):

'''

Wait until parent process terminates

'''

from multiprocessing.connection import wait

wait([self._sentinel], timeout=timeout)

pid = ident

# Create object representing the main process

class _MainProcess(BaseProcess):

def __init__(self):

self._identity = ()

self._name = 'MainProcess'

self._parent_pid = None

self._popen = None

self._closed = False

self._config = {'authkey': AuthenticationString(os.urandom(32)),

'semprefix': '/mp'}

# Note that some versions of FreeBSD only allow named

# semaphores to have names of up to 14 characters. Therefore

# we choose a short prefix.

# On MacOSX in a sandbox it may be necessary to use a

# different prefix -- see #19478.

# Everything in self._config will be inherited by descendant

# processes.

def close(self):

pass

_parent_process = None

_current_process = _MainProcess()

_process_counter = itertools.count(1)

_children = set()

del _MainProcess

# Give names to some return codes

_exitcode_to_name = {}

for name, signum in list(signal.__dict__.items()):

if name[:3]=='SIG' and '_' not in name:

_exitcode_to_name[-signum] = f'-{name}'

del name, signum

# For debug and leak testing

_dangling = WeakSet()

cpython/Lib/multiprocessing/process.py at main · python/cpython · GitHub

Repository navigation

Expand file tree

Breadcrumbs

process.py

Latest commit

History

Breadcrumbs

process.py

File metadata and controls