我正在调查一个挂起的python进程问题。我使用gdb附加到程序中并获取它们的回溯记录（如下所示）。
从回溯来看，似乎所有其余线程都是守护进程的（我们可以找到_Thread__daemonic = True）。
可以将一个线程标记为“守护程序线程”。该标志的意义在于，仅保留守护程序线程时，整个Python程序都会退出。” https://docs.python.org/3/library/threading.html#id1
但是该程序即使经过几个小时也永远不会停止。如果程序能够停止，我们将能够恢复。 这里发生了什么程序没有退出？
(gdb) info thread
Id Target Id Frame
3 Thread 0x7fd1a4bc8700 (LWP 57711) "Task Coordinato" 0x00007fd1b3e5a893 in select () at ../sysdeps/unix/syscall-template.S:81
2 Thread 0x7fd19ffff700 (LWP 58424) "Task Coordinato" 0x00007fd1b3e5a893 in select () at ../sysdeps/unix/syscall-template.S:81
* 1 Thread 0x7fd1b4e74700 (LWP 57704) "Task Coordinato" sem_wait () at ../nptl/sysdeps/unix/sysv/linux/x86_64/sem_wait.S:85
Thread 1 (Thread 0x7fd1b4e74700 (LWP 57704)):
Python Exception <type 'exceptions.ImportError'> No module named itertools:
#0 sem_wait () at ../nptl/sysdeps/unix/sysv/linux/x86_64/sem_wait.S:85
#1 0x0000000000573cfc in PyThread_acquire_lock (lock=0x2293ab0, waitflag=1) at ../Python/thread_pthread.h:324
#2 0x000000000062637b in lock_PyThread_acquire_lock (self=0x7fd1a6aa45e0, args=()) at ../Modules/threadmodule.c:52
#3 0x0000000000489909 in PyCFunction_Call (func=<built-in method acquire of thread.lock object at remote 0x7fd1a6aa45e0>, arg=(), kw=0x0) at ../Objects/methodobject.c:81
#4 0x000000000052b7f6 in call_function (pp_stack=0x7fff62112f70, oparg=0) at ../Python/ceval.c:4033
#5 0x00000000005266ca in PyEval_EvalFrameEx (
f=Frame 0x23bff40, for file /usr/lib/python2.7/threading.py, line 340, in wait (self=<_Condition(_Verbose__verbose=False, _Condition__lock=<thread.lock at remote 0x7fd1a70f6d10>, acquire=<built-in method acquire of thread.lock object at remote 0x7fd1a70f6d10>, _Condition__waiters=[<thread.lock at remote 0x7fd1a6aa45e0>], release=<built-in method release of thread.lock object at remote 0x7fd1a70f6d10>) at remote 0x7fd1a710a1b0>, timeout=None, waiter=<thread.lock at remote 0x7fd1a6aa45e0>, saved_state=None), throwflag=0) at ../Python/ceval.c:2679
#6 0x0000000000528f7e in PyEval_EvalCodeEx (co=0x7fd1b3d78ca0,
globals={'current_thread': <function at remote 0x7fd1b3ce03a8>, '_BoundedSemaphore': <type at remote 0x1390980>, 'currentThread': <function at remote 0x7fd1b3ce03a8>, '_Timer': <type at remote 0x1392ae0>, '_format_exc': <function at remote 0x7fd1b4cee1b0>, 'Semaphore': <function at remote 0x7fd1b3cdad80>, '_deque': <type at remote 0x8e4d40>, 'activeCount': <function at remote 0x7fd1b3ce0648>, '_profile_hook': None, '_sleep': <built-in function sleep>, '_trace_hook': None, 'ThreadError': <type at remote 0x137ce30>, '_enumerate': <function at remote 0x7fd1b3ce06f0>, '_start_new_thread': <built-in function start_new_thread>, 'BoundedSemaphore': <function at remote 0x7fd1b3cdd4f8>, '_shutdown': <instancemethod at remote 0x7fd1b4defd60>, '__all__': ['activeCount', 'active_count', 'Condition', 'currentThread', 'current_thread', 'enumerate', 'Event', 'Lock', 'RLock', 'Semaphore', 'BoundedSemaphore', 'Thread', 'Timer', 'setprofile', 'settrace', 'local', 'stack_size'], '_Event': <type at remote 0x1390d70>, 'ac---Type <return> to continue, or q <return> to quit---
tive_count': <fu...(truncated), locals=0x0, args=0x23f5818, argcount=1, kws=0x23f5820, kwcount=0, defs=0x7fd1b3cd4948, defcount=1, closure=0x0) at ../Python/ceval.c:3265
#7 0x000000000052bdc9 in fast_function (func=<function at remote 0x7fd1b3cdd300>, pp_stack=0x7fff62113410, n=1, na=1, nk=0) at ../Python/ceval.c:4129
#8 0x000000000052b9ca in call_function (pp_stack=0x7fff62113410, oparg=0) at ../Python/ceval.c:4054
#9 0x00000000005266ca in PyEval_EvalFrameEx (
f=Frame 0x23f5670, for file /usr/lib/python2.7/threading.py, line 949, in join (self=<Thread(_Thread__ident=140538388711168, _Thread__block=<_Condition(_Verbose__verbose=False, _Condition__lock=<thread.lock at remote 0x7fd1a70f6d10>, acquire=<built-in method acquire of thread.lock object at remote 0x7fd1a70f6d10>, _Condition__waiters=[<thread.lock at remote 0x7fd1a6aa45e0>], release=<built-in method release of thread.lock object at remote 0x7fd1a70f6d10>) at remote 0x7fd1a710a1b0>, _Thread__name='Thread-6', _Thread__daemonic=True, _Thread__started=<_Event(_Verbose__verbose=False, _Event__flag=True, _Event__cond=<_Condition(_Verbose__verbose=False, _Condition__lock=<thread.lock at remote 0x7fd1a70f6c70>, acquire=<built-in method acquire of thread.lock object at remote 0x7fd1a70f6c70>, _Condition__waiters=[], release=<built-in method release of thread.lock object at remote 0x7fd1a70f6c70>) at remote 0x7fd1a710a0d0>) at remote 0x7fd1a710a060>, _Thread__stderr=<file at remote 0x7fd1b4e62280>, _Thread__target=<insta...(truncated), throwflag=0) at ../Python/ceval.c:2679
^^^^^^^^^^^^^^^^^^^^^^
#10 ...
Thread 2 (Thread 0x7fd19ffff700 (LWP 58424)):
Python Exception <type 'exceptions.ImportError'> No module named itertools:
#0 0x00007fd1b3e5a893 in select () at ../sysdeps/unix/syscall-template.S:81
#1 0x0000000000629483 in floatsleep (secs=1) at ../Modules/timemodule.c:948
#2 0x00000000006280f1 in time_sleep (self=0x0, args=(1,)) at ../Modules/timemodule.c:206
#3 0x0000000000489909 in PyCFunction_Call (func=<built-in function sleep>, arg=(1,), kw=0x0) at ../Objects/methodobject.c:81
#4 0x000000000052b7f6 in call_function (pp_stack=0x7fd19fffdd00, oparg=1) at ../Python/ceval.c:4033
#5 0x00000000005266ca in PyEval_EvalFrameEx (
f=Frame 0x7fd194000b70, for file /dependencies/debugenv/local/lib/python2.7/site-packages/ddtrace/writer.py, line 170, in _target (self=<AsyncWorker(_service_queue=<Q(_max_size=1000, _closed=False, _things=[], _lock=<thread.lock at remote 0x7fd1a5686d60>) at remote 0x7fd1a707c7d0>, _priority_sampler=None, _thread=<Thread(_Thread__ident=140538309244672, _Thread__block=<_Condition(_Verbose__verbose=False, _Condition__lock=<thread.lock at remote 0x7fd1a5686a90>, acquire=<built-in method acquire of thread.lock object at remote 0x7fd1a5686a90>, _Condition__waiters=[], release=<built-in method release of thread.lock object at remote 0x7fd1a5686a90>) at remote 0x7fd1a707cbc0>, _Thread__name='Thread-7', _Thread__daemonic=True, _Thread__started=<_Event(_Verbose__verbose=False, _Event__flag=True, _Event__cond=<_Condition(_Verbose__verbose=False, _Condition__lock=<thread.lock at remote 0x7fd1a5686b80>, acquire=<built-in method acquire of thread.lock object at remote 0x7fd1a5686b80>, _Condition__waiters=[], release=<built-...(truncated), throwflag=0) at ../Python/ceval.c:2679
^^^^^^^^^^^^^^^^^^^^^^
#6 0x0000000000528f7e in PyEval_EvalCodeEx (co=0x7fd1b2d40250,
globals={'DEFAULT_TIMEOUT': 5, 'MAX_TRACES': 1000, 'LOG_ERR_INTERVAL': 60, 'logging': <module at remote 0x7fd1b4d31678>, 'log': <Logger(name='ddtrace.writer', parent=<RootLogger(name='root', parent=None, handlers=[<RotatingFileHandler(backupCount=3, stream=<file at remote 0x7fd1a56bd4c0>, encoding=None, lock=<_RLock(_Verbose__verbose=False, _RLock__owner=None, _RLock__block=<thread.lock at remote 0x7fd1a56864a0>, _RLock__count=0) at remote 0x7fd1a7635370>, level=20, _name=None, delay=0, baseFilename='/var/log/pocketgems/task/dd-tasking-daemon.log', mode='a', filters=[<RootOnlyLogFilter(name='', nlen=0) at remote 0x7fd1a56d9840>], formatter=<PGLDJFormatter(info={'runner': 'daemon'}, thread_info={140538659948288: {}, 140538309244672: {}, 140538388711168: {}}, datefmt=None, _fmt='%(message)s') at remote 0x7fd1a578eed0>, maxBytes=10485760) at remote 0x7fd1a56e5bc0>, <RotatingFileHandler(backupCount=3, stream=<file at remote 0x7fd1a56bd640>, encoding=None, lock=<_RLock(_Verbose__verbose=False, _RLock__owner=None, _RLock__...(truncated), locals=0x0, args=0x7fd1a707c788, argcount=1, kws=0x7fd1b4e33088, kwcount=0, defs=0x0, defcount=0, closure=0x0) at ../Python/ceval.c:3265
#7 0x00000000004665d1 in function_call (func=<function at remote 0x7fd1b2d62648>,
arg=(<AsyncWorker(_service_queue=<Q(_max_size=1000, _closed=False, _things=[], _lock=<thread.lock at remote 0x7fd1a5686d60>) at remote 0x7fd1a707c7d0>, _priority_sampler=None, _thread=<Thread(_Thread__ident=140538309244672, _Thread__block=<_Condition(_Verbose__verbose=False, _Condition__lock=<thread.lock at remote 0x7fd1a5686a90>, acquire=<built-in method acquire of thread.lock object at remote 0x7fd1a5686a90>, _Condition__waiters=[], release=<built-in method release of thread.lock object at remote 0x7fd1a5686a90>) at remote 0x7fd1a707cbc0>, _Thread__name='Thread-7', _Thread__daemonic=True, _Thread__started=<_Event(_Verbose__verbose=False, _Event__flag=True, _Event__cond=<_Condition(_Verbose__verbose=False, _Condition__lock=<thread.lock at remote 0x7fd1a5686b80>, acquire=<built-in method acquire of thread.lock object at remote 0x7fd1a5686b80>, _Condition__waiters=[], release=<built-in method release of thread.lock object at remote 0x7fd1a5686b80>) at remote 0x7fd1a707ca70>) at remote 0x7fd1a707c990>, _Thread__std...(truncated), kw={}) at ../Objects/funcobject.c:526
#8 ...
Thread 3 (Thread 0x7fd1a4bc8700 (LWP 57711)):
Python Exception <type 'exceptions.ImportError'> No module named itertools:
#0 0x00007fd1b3e5a893 in select () at ../sysdeps/unix/syscall-template.S:81
#1 0x00000000005fb67f in select_select (self=0x0, args=([<_socketobject at remote 0x7fd1a70df240>, <_socket.socket at remote 0x7fd1a56837f8>], [], [], <float at remote 0x249cb58>))
at ../Modules/selectmodule.c:267
#2 0x0000000000489909 in PyCFunction_Call (func=<built-in function select>,
arg=([<_socketobject at remote 0x7fd1a70df240>, <_socket.socket at remote 0x7fd1a56837f8>], [], [], <float at remote 0x249cb58>), kw={}) at ../Objects/methodobject.c:81
#3 0x000000000052cc79 in ext_do_call (func=<built-in function select>, pp_stack=0x7fd1a4bc5310, flags=3, na=0, nk=0) at ../Python/ceval.c:4343
#4 0x0000000000526982 in PyEval_EvalFrameEx (
f=Frame 0x7fd198003a20, for file /dependencies/debugenv/local/lib/python2.7/site-packages/kazoo/handlers/threading.py, line 192, in _select (self=<SequentialThreadingHandler(_state_change=<thread.lock at remote 0x7fd1a70f68b0>, _workers=[], _running=False, completion_queue=<Queue(unfinished_tasks=0, queue=<collections.deque at remote 0x7fd1a56a67e0>, maxsize=0, all_tasks_done=<_Condition(_Verbose__verbose=False, _Condition__lock=<thread.lock at remote 0x7fd1a5686360>, acquire=<built-in method acquire of thread.lock object at remote 0x7fd1a5686360>, _Condition__waiters=[], release=<built-in method release of thread.lock object at remote 0x7fd1a5686360>) at remote 0x7fd1a56aa0d0>, mutex=<thread.lock at remote 0x7fd1a5686360>, not_full=<_Condition(_Verbose__verbose=False, _Condition__lock=<thread.lock at remote 0x7fd1a5686360>, acquire=<built-in method acquire of thread.lock object at remote 0x7fd1a5686360>, _Condition__waiters=[], release=<built-in method release of thread.lock object at remote 0x7fd1a5686360>) a...(truncated), throwflag=0) at ../Python/ceval.c:2718
#5 0x0000000000528f7e in PyEval_EvalCodeEx (co=0x7fd1a56209e0,
globals={'chain': <type at remote 0x8fde00>, 'utils': <module at remote 0x7fd1a5633268>, 'absolute_import': <_Feature(mandatory=(3, 0, 0, 'alpha', 0), optional=(2, 5, 0, 'alpha', 1), compiler_flag=16384) at remote 0x7fd1b3c74df8>, 'select': <module at remote 0x7fd1b1f39748>, 'AsyncResult': <type at remote 0x207d780>, 'log': <Logger(name='kazoo.handlers.threading', parent=<Logger(name='kazoo', parent=<RootLogger(name='root', parent=None, handlers=[<RotatingFileHandler(backupCount=3, stream=<file at remote 0x7fd1a56bd4c0>, encoding=None, lock=<_RLock(_Verbose__verbose=False, _RLock__owner=None, _RLock__block=<thread.lock at remote 0x7fd1a56864a0>, _RLock__count=0) at remote 0x7fd1a7635370>, level=20, _name=None, delay=0, baseFilename='/var/log/pocketgems/task/dd-tasking-daemon.log', mode='a', filters=[<RootOnlyLogFilter(name='', nlen=0) at remote 0x7fd1a56d9840>], formatter=<PGLDJFormatter(info={'runner': 'daemon'}, thread_info={140538659948288: {}, 140538309244672: {}, 140538388711168: {}}, datefmt=None, _fmt='%(messa...(truncated), locals=0x0, args=0x7fd1a5663598, argcount=5, kws=0x7fd1b4e33088, kwcount=0, defs=0x0, defcount=0, closure=0x0) at ../Python/ceval.c:3265
#6 0x00000000004665d1 in function_call (func=<function at remote 0x7fd1a56305a0>,
arg=(<SequentialThreadingHandler(_state_change=<thread.lock at remote 0x7fd1a70f68b0>, _workers=[], _running=False, completion_queue=<Queue(unfinished_tasks=0, queue=<collections.deque at remote 0x7fd1a56a67e0>, maxsize=0, all_tasks_done=<_Condition(_Verbose__verbose=False, _Condition__lock=<thread.lock at remote 0x7fd1a5686360>, acquire=<built-in method acquire of thread.lock object at remote 0x7fd1a5686360>, _Condition__waiters=[], release=<built-in method release of thread.lock object at remote 0x7fd1a5686360>) at remote 0x7fd1a56aa0d0>, mutex=<thread.lock at remote 0x7fd1a5686360>, not_full=<_Condition(_Verbose__verbose=False, _Condition__lock=<thread.lock at remote 0x7fd1a5686360>, acquire=<built-in method acquire of thread.lock object at remote 0x7fd1a5686360>, _Condition__waiters=[], release=<built-in method release of thread.lock object at remote 0x7fd1a5686360>) at remote 0x7fd1a56aa300>, not_empty=<_Condition(_Verbose__verbose=False, _Condition__lock=<thread.lock at remote 0x7fd1a5686360>, acquire=<buil...(truncated), kw={}) at ../Objects/funcobject.c:526
...
#34 0x0000000000427c3a in PyObject_Call (func=<function at remote 0x7fd1a55a43a8>,
arg=(<ConnectionHandler(retry_sleeper=<KazooRetry(_cur_stoptime=None, max_jitter=80, retry_exceptions=(<type at remote 0x2081990>, <type at remote 0x2083190>, <type at remote 0x20b70a0>, <type at remote 0x2085ce0>), sleep_func=<built-in function sleep>, _attempts=0, max_delay=<float at remote 0x20bb1d8>, delay=<float at remote 0x1dcb600>, deadline=None, _cur_delay=<float at remote 0x1dcb600>, interrupt=<function at remote 0x7fd1a5462a38>, max_tries=None, backoff=2) at remote 0x7fd1a71080d0>, _read_sock=<_socket.socket at remote 0x7fd1a56837f8>, _rw_server=None, _socket=<_socketobject at remote 0x7fd1a70df240>, client=<ZkClient(MultiNonBlockingLease=<functools.partial at remote 0x7fd1a564b280>, SetPartitioner=<functools.partial at remote 0x7fd1a564b858>, _state='CONNECTED', _session_timeout=10000, Semaphore=<functools.partial at remote 0x7fd1a564b8e0>, Party=<functools.partial at remote 0x7fd1a564b6c0>, state_listeners=set([]), ChildrenWatch=<functools.partial at remote 0x7fd1a564b060>, read_only=None, chroot='', ...(truncated), kw={}) at ../Objects/abstract.c:2529
#35 0x000000000052cc98 in ext_do_call (func=<function at remote 0x7fd1a55a43a8>, pp_stack=0x7fd1a4bc71e0, flags=3, na=1, nk=0) at ../Python/ceval.c:4346
#36 0x0000000000526982 in PyEval_EvalFrameEx (
f=Frame 0x7fd1a710b060, for file /usr/lib/python2.7/threading.py, line 763, in run (self=<Thread(_Thread__ident=140538388711168, _Thread__block=<_Condition(_Verbose__verbose=False, _Condition__lock=<thread.lock at remote 0x7fd1a70f6d10>, acquire=<built-in method acquire of thread.lock object at remote 0x7fd1a70f6d10>, _Condition__waiters=[<thread.lock at remote 0x7fd1a6aa45e0>], release=<built-in method release of thread.lock object at remote 0x7fd1a70f6d10>) at remote 0x7fd1a710a1b0>, _Thread__name='Thread-6', _Thread__daemonic=True, _Thread__started=<_Event(_Verbose__verbose=False, _Event__flag=True, _Event__cond=<_Condition(_Verbose__verbose=False, _Condition__lock=<thread.lock at remote 0x7fd1a70f6c70>, acquire=<built-in method acquire of thread.lock object at remote 0x7fd1a70f6c70>, _Condition__waiters=[], release=<built-in method release of thread.lock object at remote 0x7fd1a70f6c70>) at remote 0x7fd1a710a0d0>) at remote 0x7fd1a710a060>, _Thread__stderr=<file at remote 0x7fd1b4e62280>, _Thread__target=<i...(truncated), throwflag=0) at ../Python/ceval.c:2718
^^^^^^^^^^^^^^^^^^^^^^
#37 0x000000000052bcb7 in fast_function (func=<function at remote 0x7fd1b3cde3a8>, pp_stack=0x7fd1a4bc74f0, n=1, na=1, nk=0) at ../Python/ceval.c:4119
#38 ...
如有需要，我很乐意提供更多信息。由于文本限制，Stack Overflow不允许我粘贴整个回溯。