test_threading_local sometimes hangs when run with -R

[pitrou]

BPO	7264
Nosy	@gpshead, @pitrou
Files	threading_local.patch threading_local2.patch

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields: ```python assignee = None closed_at = created_at = labels = ['tests', 'library', 'type-crash'] title = 'test_threading_local sometimes hangs when run with -R' updated_at = user = 'https://github.com/pitrou' ``` bugs.python.org fields: ```python activity = actor = 'pitrou' assignee = 'none' closed = True closed_date = closer = 'pitrou' components = ['Library (Lib)', 'Tests'] creation = creator = 'pitrou' dependencies = [] files = ['15259', '15264'] hgrepos = [] issue_num = 7264 keywords = ['patch'] message_count = 6.0 messages = ['94900', '94901', '94908', '94909', '94922', '94931'] nosy_count = 3.0 nosy_names = ['gregory.p.smith', 'pitrou', 'gps'] pr_nums = [] priority = 'normal' resolution = 'fixed' stage = 'resolved' status = 'closed' superseder = None type = 'crash' url = 'https://bugs.python.org/issue7264' versions = ['Python 2.6', 'Python 3.1', 'Python 2.7', 'Python 3.2'] ```

[pitrou]

If I run something like: ./python -m test.regrtest -R3:2: test_threading_local

Python sometimes hangs and I have to "kill -9" it.

Running through gdb shows it gets stuck at the following point:

/home/antoine/cpython/debug/Lib/threading.py (239): wait /home/antoine/cpython/debug/Lib/threading.py (638): join /home/antoine/cpython/debug/Lib/test/test_threading_local.py (68): test_derived [snip]

That is, it hangs waiting for a thread to join().

[pitrou]

It turns out that the __del method in _threading_local.py tries to call threading.enumerate() which itself takes the _active_limbolock. The problem is that \_del can be called at any point in time (because of the GC), including at a point where the same thread has already taken the lock. The obvious fix is to bypass enumerate().

(an alternate fix would be to use an RLock for _active_limbo_lock, but it could have unforeseen consequences, such as performance ones)

[gpshead]

How about defining this in threading.py:

def _enumerate():
    """Internal use only: enumerate() without the lock."""
    return _active.values() + _limbo.values()

And calling it from _threading_local instead of accessing _active and _limbo directly.

[pitrou]

Good point. Here is a new patch.

[gpshead]

Looks good to me.

typed poorly on a tiny Android phone.

On Nov 4, 2009 3:24 PM, "Antoine Pitrou" \report@bugs.python.org\ wrote:

Antoine Pitrou \pitrou@free.fr\ added the comment:

Good point. Here is a new patch.

---------- Added file: http://bugs.python.org/file15264/threading_local2.patch

___ Python tracker \< report@bugs.python.org> \<http://bugs.python...

[pitrou]

Committed, thanks.