Issue #8713: Support alternative start methods in multiprocessing on Unix.

See http://hg.python.org/sandbox/sbt#spawn

Lib/multiprocessing/util.py

@@ -17,13 +17,13 @@ import threading        # we want threading to install it's
                         # cleanup function before multiprocessing does
 from subprocess import _args_from_interpreter_flags
 
-from multiprocessing.process import current_process, active_children
+from . import process
 
 __all__ = [
     'sub_debug', 'debug', 'info', 'sub_warning', 'get_logger',
     'log_to_stderr', 'get_temp_dir', 'register_after_fork',
     'is_exiting', 'Finalize', 'ForkAwareThreadLock', 'ForkAwareLocal',
-    'SUBDEBUG', 'SUBWARNING',
+    'close_all_fds_except', 'SUBDEBUG', 'SUBWARNING',
     ]
 
 #
@@ -71,8 +71,6 @@ def get_logger():
 
             _logger = logging.getLogger(LOGGER_NAME)
             _logger.propagate = 0
-            logging.addLevelName(SUBDEBUG, 'SUBDEBUG')
-            logging.addLevelName(SUBWARNING, 'SUBWARNING')
 
             # XXX multiprocessing should cleanup before logging
             if hasattr(atexit, 'unregister'):
@@ -111,13 +109,14 @@ def log_to_stderr(level=None):
 
 def get_temp_dir():
     # get name of a temp directory which will be automatically cleaned up
-    if current_process()._tempdir is None:
+    tempdir = process.current_process()._config.get('tempdir')
+    if tempdir is None:
         import shutil, tempfile
         tempdir = tempfile.mkdtemp(prefix='pymp-')
         info('created temp directory %s', tempdir)
         Finalize(None, shutil.rmtree, args=[tempdir], exitpriority=-100)
-        current_process()._tempdir = tempdir
-    return current_process()._tempdir
+        process.current_process()._config['tempdir'] = tempdir
+    return tempdir
 
 #
 # Support for reinitialization of objects when bootstrapping a child process
@@ -273,8 +272,8 @@ def is_exiting():
 _exiting = False
 
 def _exit_function(info=info, debug=debug, _run_finalizers=_run_finalizers,
-                   active_children=active_children,
-                   current_process=current_process):
+                   active_children=process.active_children,
+                   current_process=process.current_process):
     # We hold on to references to functions in the arglist due to the
     # situation described below, where this function is called after this
     # module's globals are destroyed.
@@ -303,7 +302,7 @@ def _exit_function(info=info, debug=debug, _run_finalizers=_run_finalizers,
             # #9207.
 
             for p in active_children():
-                if p._daemonic:
+                if p.daemon:
                     info('calling terminate() for daemon %s', p.name)
                     p._popen.terminate()
 
@@ -335,3 +334,54 @@ class ForkAwareLocal(threading.local):
         register_after_fork(self, lambda obj : obj.__dict__.clear())
     def __reduce__(self):
         return type(self), ()
+
+#
+# Close fds except those specified
+#
+
+try:
+    MAXFD = os.sysconf("SC_OPEN_MAX")
+except Exception:
+    MAXFD = 256
+
+def close_all_fds_except(fds):
+    fds = list(fds) + [-1, MAXFD]
+    fds.sort()
+    assert fds[-1] == MAXFD, 'fd too large'
+    for i in range(len(fds) - 1):
+        os.closerange(fds[i]+1, fds[i+1])
+
+#
+# Start a program with only specified fds kept open
+#
+
+def spawnv_passfds(path, args, passfds):
+    import _posixsubprocess, fcntl
+    passfds = sorted(passfds)
+    tmp = []
+    # temporarily unset CLOEXEC on passed fds
+    for fd in passfds:
+        flag = fcntl.fcntl(fd, fcntl.F_GETFD)
+        if flag & fcntl.FD_CLOEXEC:
+            fcntl.fcntl(fd, fcntl.F_SETFD, flag & ~fcntl.FD_CLOEXEC)
+            tmp.append((fd, flag))
+    errpipe_read, errpipe_write = _posixsubprocess.cloexec_pipe()
+    try:
+        return _posixsubprocess.fork_exec(
+            args, [os.fsencode(path)], True, passfds, None, None,
+            -1, -1, -1, -1, -1, -1, errpipe_read, errpipe_write,
+            False, False, None)
+    finally:
+        os.close(errpipe_read)
+        os.close(errpipe_write)
+        # reset CLOEXEC where necessary
+        for fd, flag in tmp:
+            fcntl.fcntl(fd, fcntl.F_SETFD, flag)
+
+#
+# Return pipe with CLOEXEC set on fds
+#
+
+def pipe():
+    import _posixsubprocess
+    return _posixsubprocess.cloexec_pipe()