Re: Leader backend hang on IPC/ParallelFinish when LWLock held at parallel query start

On Thu, Nov 07, 2024 at 02:29:19PM -0500, Tom Lane wrote:
> Noah Misch <noah@leadboat.com> writes:
> > This thread's previous commit just forced a serial plan.
> 
> My concern is that the previous commit forced new plans to be serial,
> but did nothing about re-use of an existing plan.

I agree.  It solved one way of reaching the problem, leaving at least one
unsolved.

> > The executor
> > counterpart would look like having the executor do what it does when there are
> > no free worker slots.
> 
> Ah, that could be a way out.  Stick an INTERRUPTS_CAN_BE_PROCESSED()
> call somewhere in there?

Exactly.  If !INTERRUPTS_CAN_BE_PROCESSED(), proceed as though no workers can
be launched.

> That could even allow us to revert the
> planner change, which would simplify testing of the executor change.

True.