Re: injection_points: canceled or terminated waiters leak their wait slots

> I think that I'd rather use a PG_TRY/PG_FINALLY and avoid the
> refactoring with the extra routine required, keeping the cleanup
> action local to injection_wait()

Wouldn't that miss FATAL? (pg_terminate_backend in the testcase)

> Thanks for that. I'm always OK to deal with a backpatch as required.
> Posting versions saves some time, of course, just don't feel obliged
> if you feel that this is extra work on your side.

I don't always consistently do this (sometimes it's interesting to
check that its different in back branches, sometimes I completely
forgot about it)

In this case, I started the testing / debugging on pg19, and only
checked that the code is different on master after I already had the
fix. Verifying that the code is the same on earlier branches wasn't
much extra work after that.

> Another thought: the addition of a SQL
> function that provides the list of waiters that we reuse here.

I can implement that if you think it is better, my initial logic was
to keep the fix smaller and strictly a bugfix.