STINNER Victor <vstin...@redhat.com> added the comment:
> At a minimum I think there should be a check trying to reduce arguments via
> incompatible context's process to prevent a SEGV.
I'm not sure that I understand the bug. The reproducer script pass a
multiprocessing.Queue to a child process and then the child crash when
attempting to call multiprocessing.synchronize.Lock.__repr__().
Does the child reuse a copy of the lock of the parent process? Or does the
child create a new SemLock?
I reproduced the bug on Fedora 26. I attached the child process in gdb. The
crash occurs on sem_getvalue() in the child process.
Program received signal SIGSEGV, Segmentation fault.
0x00007f29a5156610 in sem_getvalue@@GLIBC_2.2.5 () from /lib64/libpthread.so.0
(gdb) where
#0 0x00007f29a5156610 in sem_getvalue@@GLIBC_2.2.5 () from
/lib64/libpthread.so.0
#1 0x00007f299c60e7bb in semlock_getvalue (self=0x7f299a95e2b0,
_unused_ignored=0x0)
at /home/haypo/prog/python/master/Modules/_multiprocessing/semaphore.c:541
#2 0x0000000000434537 in _PyMethodDef_RawFastCallKeywords
(method=0x7f299c8102e0 <semlock_methods+192>,
self=<_multiprocessing.SemLock at remote 0x7f299a95e2b0>,
args=0x7f299c5f47e8, nargs=0, kwnames=0x0) at Objects/call.c:629
#3 0x0000000000607aff in _PyMethodDescr_FastCallKeywords
(descrobj=<method_descriptor at remote 0x7f299ca42520>, args=0x7f299c5f47e0,
nargs=1,
kwnames=0x0) at Objects/descrobject.c:288
#4 0x0000000000512f92 in call_function (pp_stack=0x7ffd3591f730, oparg=1,
kwnames=0x0) at Python/ceval.c:4595
(...)
(gdb) py-bt
Traceback (most recent call first):
File "/home/haypo/prog/python/master/Lib/multiprocessing/synchronize.py",
line 170, in __repr__
elif self._semlock._get_value() == 1:
File "/home/haypo/prog/python/master/test_lock_sigsegv.py", line 20, in child
print("Child r_q: %r, %r, %r" % (r_q._rlock, r_q._wlock, r_q._sem),
flush=True)
File "/home/haypo/prog/python/master/Lib/multiprocessing/process.py", line
99, in run
self._target(*self._args, **self._kwargs)
File "/home/haypo/prog/python/master/Lib/multiprocessing/process.py", line
297, in _bootstrap
self.run()
File "/home/haypo/prog/python/master/Lib/multiprocessing/spawn.py", line 130,
in _main
return self._bootstrap()
File "/home/haypo/prog/python/master/Lib/multiprocessing/spawn.py", line 629,
in spawn_main
File "<string>", line 1, in <module>
----------
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Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue33196>
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