Re: signal handling in plpython

Heikki Linnakangas <hlinnaka(at)iki(dot)fi> writes:
> It would be nice to have a solution for this in plpython itself, so that
> the query cancel was turned into a Python exception. Patches for that
> would be welcome. I think you could use Py_AddPendingCall() from
> PostgreSQL's signal handler, to schedule a call to a function that in
> turn throws a Python exception.

Py_AddPendingCall is safe to call from a signal handler? That would
be ... quite remarkable. I should think it'd at least need to do a
malloc(). Also, seeing that it's documented as part of Python threading,
I wonder whether we can call it at all without the backend becoming
multithreaded.

> That'll need some changes to
> PostgreSQL's normal signal handlers, like die() and
> StatementCancelHandler() in postgres.c, but it seems doable.

I'm not in principle averse to letting extensions get control in
the signal handlers, but I'm afraid that any such feature would
mostly act as a magnet for unsafe coding.

regards, tom lane