> However, there's still a problem: GetUndoRecPtr also gets SInvalLock
> while its caller holds WALInsertLock, and therefore this routine
> could create the second leg of the deadlock too. Removing the
> SInvalLock lock there creates the problem that backends might be
> added to or deleted from the PROC array while GetUndoRecPtr runs.
> I think it might be possible to survive that, by adding an assumption
> that logRec.xrecoff can be set to zero atomically, but it
> seems tricky.
Checkpoint' undo is not used currently so just comment out GetUndoRecPtr
call in CreateCheckPoint - we'll find solution later.
Vadim