[issue22104] test_asyncio unstable in refleak mode
STINNER Victor
report at bugs.python.org
Wed Jul 30 12:08:04 CEST 2014
STINNER Victor added the comment:
> It may be related to the issue #17911.
I checked: it is. The strange reference count can be seen with a single test. Example:
$ ./python -m test -R 3:3: -m test_default_exc_handler_coro test_asyncio
[1/1] test_asyncio
beginning 6 repetitions
123456
......
test_asyncio leaked [53, 53, -106] references, sum=0
test_asyncio leaked [15, 15, -30] memory blocks, sum=0
1 test failed:
test_asyncio
This test uses a coroutine which raises an exception. The exception is stored in a Task object. But the exception contains also a traceback which indirectly creates a reference cycle. For example, the zero_error_coro() coroutine of the test uses the free variable "self".
It's very difficult to find all objects of a reference cycle. We can try to break some cycles, it's already done Task._step() which sets self to None, but it's a waste of time. IMO the correct fix is to not store frame objects in an exception: see the issue #17911.
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<http://bugs.python.org/issue22104>
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