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bpo-31308: If multiprocessing's forkserver dies, launch it again when necessary (#3246)

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* bpo-31308: If multiprocessing's forkserver dies, launch it again when necessary.

* Fix test on Windows

* Add NEWS entry

* Adopt a different approach: ignore SIGINT and SIGTERM, as in semaphore tracker.

* Fix comment

* Make sure the test doesn't muck with process state

* Also test previously-started processes

* Update 2017-08-30-17-59-36.bpo-31308.KbexyC.rst

* Avoid masking SIGTERM in forkserver.  It's not necessary and causes a race condition in test_many_processes.
This commit is contained in:
Antoine Pitrou 2017-11-03 13:34:22 +01:00 • committed by GitHub
parent 4f57409a2f
commit fc6b348b12
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3 changed files with 66 additions and 5 deletions
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21
Lib/multiprocessing/forkserver.py
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@ -34,6 +34,7 @@ class ForkServer(object):
def __init__(self):
self._forkserver_address = None
self._forkserver_alive_fd = None
self._forkserver_pid = None
self._inherited_fds = None
self._lock = threading.Lock()
self._preload_modules = ['__main__']
@ -90,8 +91,17 @@ class ForkServer(object):
'''
with self._lock:
semaphore_tracker.ensure_running()
if self._forkserver_alive_fd is not None:
return
if self._forkserver_pid is not None:
# forkserver was launched before, is it still running?
pid, status = os.waitpid(self._forkserver_pid, os.WNOHANG)
if not pid:
# still alive
return
# dead, launch it again
os.close(self._forkserver_alive_fd)
self._forkserver_address = None
self._forkserver_alive_fd = None
self._forkserver_pid = None
cmd = ('from multiprocessing.forkserver import main; ' +
'main(%d, %d, %r, **%r)')
@ -127,6 +137,7 @@ class ForkServer(object):
os.close(alive_r)
self._forkserver_address = address
self._forkserver_alive_fd = alive_w
self._forkserver_pid = pid
#
#
@ -157,11 +168,11 @@ def main(listener_fd, alive_r, preload, main_path=None, sys_path=None):
# Dummy signal handler, doesn't do anything
pass
# letting SIGINT through avoids KeyboardInterrupt tracebacks
# unblocking SIGCHLD allows the wakeup fd to notify our event loop
handlers = {
# unblocking SIGCHLD allows the wakeup fd to notify our event loop
signal.SIGCHLD: sigchld_handler,
signal.SIGINT: signal.SIG_DFL,
# protect the process from ^C
signal.SIGINT: signal.SIG_IGN,
}
old_handlers = {sig: signal.signal(sig, val)
for (sig, val) in handlers.items()}