>
> > Please consider the following fix to the problem, patching function
> > cancel-change-group.
>
> Thanks.
>
> If this problem could be solved locally in the atomic groups code, I'd
> prefer that.


The patch is local to the atomic groups code: it only changes
the function cancel-change-group, whose purpose is to abort an atomic group.

  If not, then let's postpone changes in the low-level
> undo machinery


There is no intention to change there anything.

 I'd like to
> avoid adding more changes in such deep innards.
>

That is perfectly understandable.

>