__all__ = ['ensure_running', 'register', 'unregister']

_HAVE_SIGMASK = hasattr(signal, 'pthread_sigmask')

_IGNORED_SIGNALS = (signal.SIGINT, signal.SIGTERM)

class SemaphoreTracker(object):

with self._lock:

if self._pid is not None:

# semaphore tracker was launched before, is it still running?

pid, status = os.waitpid(self._pid, os.WNOHANG)

if not pid:

# => still alive

return

try:

pid, _ = os.waitpid(self._pid, os.WNOHANG)

except ChildProcessError:

# The process terminated

pass

else:

if not pid:

# => still alive

return

# => dead, launch it again

os.close(self._fd)

self._fd = None

exe = spawn.get_executable()

args = [exe] + util._args_from_interpreter_flags()

args += ['-c', cmd % r]

pid = util.spawnv_passfds(exe, args, fds_to_pass)

# bpo-33613: Register a signal mask that will block the signals.

# This signal mask will be inherited by the child that is going

# to be spawned and will protect the child from a race condition

# that can make the child die before it registers signal handlers

# for SIGINT and SIGTERM. The mask is unregistered after spawning

# the child.

try:

if _HAVE_SIGMASK:

signal.pthread_sigmask(signal.SIG_BLOCK, _IGNORED_SIGNALS)

pid = util.spawnv_passfds(exe, args, fds_to_pass)

finally:

if _HAVE_SIGMASK:

signal.pthread_sigmask(signal.SIG_UNBLOCK, _IGNORED_SIGNALS)

except:

os.close(w)

raise

unregister = _semaphore_tracker.unregister

getfd = _semaphore_tracker.getfd

def main(fd):

'''Run semaphore tracker.'''

# protect the process from ^C and "killall python" etc

signal.signal(signal.SIGINT, signal.SIG_IGN)

signal.signal(signal.SIGTERM, signal.SIG_IGN)

if _HAVE_SIGMASK:

signal.pthread_sigmask(signal.SIG_UNBLOCK, _IGNORED_SIGNALS)

for f in (sys.stdin, sys.stdout):

try: