I have just found a bug in _bt_getstackbuf that I think explains Joe
Conway's recent reports of PANICs under heavy concurrent insertions.
We're gonna have to re-wrap 7.4.4 or relabel it 7.4.5, your choice.
Fortunately the bug is not present in 7.3 and earlier, so those
packagings can forge ahead.
regards, tom lane