If I create a large table with "CREATE TABLE ... AS SELECT ... from generate_series(1,3e7)" with no explicit transactions, then once it is done I wait for autovac to kick in, then when I try to build an index on that table (or drop the table) the autovac doesn't go away on its own.
After a bit more poking at this, I think we are checking if we ourselves are an autovac process, not doing the intended check of whether the other guy is one.
Where would be a good spot to add a regression test for this? "isolation_regression" ?