BUG #6123: DELETE fails if before trigger causes another trigger to UPDATE

The following bug has been logged online:

Bug reference:      6123
Logged by:          Kevin Grittner
Email address:      Kevin.Grittner@wicourts.gov
PostgreSQL version: HEAD and 9.0.4
Operating system:   Linux (probably doesn't matter)
Description:        DELETE fails if before trigger causes another trigger to
UPDATE
Details:

create table a (aid int not null primary key,
                bcnt int not null default 0);
create table b (bid int not null primary key,
                aid int not null);

create function a_del_func()
  returns trigger language plpgsql as
  $$begin delete from b where aid = old.aid;
          return old; end;$$;
create trigger a_del_trig before delete On a
  for each row execute procedure a_del_func();

create function b_ins_func()
  returns trigger language plpgsql as
  $$begin update a set bcnt = bcnt + 1
            where aid = new.aid; return new; end;$$;
create trigger b_ins_trig after insert on b
  for each row execute procedure b_ins_func();

create function b_del_func()
  returns trigger language plpgsql as
  $$begin update a set bcnt = bcnt - 1
            where aid = old.aid; return old; end;$$;
create trigger b_del_trig after delete on b
  for each row execute procedure b_del_func();

insert into a values (1, 0);
insert into b values (10, 1);
select * from a; select * from b;
delete from a where aid = 1;
select * from a; select * from b;

I expect the DELETE from a to delete related b record(s) and then succeed.
Instead the UPDATE in b_del_trig causes delete of a to silently fail.

-Kevin