[pypy-dev] FAQ entry

[Maciej Fijalkowski]

On Mon, Apr 6, 2015 at 3:28 PM, Yuriy Taraday <yorik.sar at gmail.com> wrote:
> On Mon, Apr 6, 2015 at 3:48 PM Maciej Fijalkowski <fijall at gmail.com> wrote:
>>
>> maybe we should add something along those lines to FAQ
>>
>> http://emptysqua.re/blog/pypy-garbage-collection-and-a-deadlock/
>
>
> Can't it be fixed? I see 2 possible solutions here:
> 1. We can detect deadlock (any lock contention during GC round will become
> deadlock) and bail out of GC round early to try again later or skip freeing
> this object (and mark all objects referenced by it).
> 2. We can defer all calls to __del__ until after GC round and run them in a
> separate Python thread which would allow them to yield processing to let
> other threads free some lock.
>
> I know that either of these solutions would change semantics a bit, but it
> shouldn't affect user's code.

as you can see from the blog post *any* change does affect user code.
Note that finalizers are not called during GC, but at some later
"safer" stage, where all the internals are in a sane state. Not sure
how you would do 1, really (a global flag on locks?), 2 is something
Java does.

General FAQ entry should say "avoid __del__ doing any substantial job
at any cost" I would think, whacking at locks is like lipstick on a
pig.