[Tarantool-patches] [PATCH v19 2/3] qsync: order access to the limbo terms

[Cyrill Gorcunov]

On Tue, Oct 05, 2021 at 04:25:21PM +0300, Serge Petrenko wrote:
> 
> Here's what can happen. You're the old leader, and you've received a
> promote from someone else already, it's being written now.
> Now some replica sends you an ack. You enter txn_limbo_ack
> (it doesn't check the latch). txn_limbo_ack() may result in writing a
> CONFIRM.
> 
> The PROMOTE is already in progress, so you'll end up writing CONFIRM for
> a wrong leader id (your own) after PROMOTE is written.

This sounds like we need more general lock for limbo operations. And
as we have been discussing already for box change params as well. I'm
starting to doubt that promote latch is a good name. Anyway I'll prepare
a draft version and send it out.