> Richard Oudkerk added the comment:
>
>> - now that FDs are non-inheritable by default, fork locks around
>> subprocess and multiprocessing shouldn't be necessary anymore? What
>> other use cases does the fork-lock have?
>
> CLOEXEC fds will still be inherited by forked children.

Hum, right, I was thinking only about subprocess-created children
(where an exec follows immediately).

>> - the current implementation keeps hard-references to the functions
>> passed: so if one isn't careful, you can end up easily with a lot of
>> objects kept alive just because of those references, which can be a
>> problem
>
> True, but you could make the same complaint about atexit.register().

Yeah, but atexit is usually used for process-lifetime resources (I
mean, there's 'exit' in the name).
One of the main use cases for atfork hooks would be the numerous
stdlib objects which have locks (or locks themselves): most of such
objects have arbitrary lifetimes (e.g. logging, events, open files,
etc).

The risk of leak is IMO much greater.