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

[Serge Petrenko]

01.10.2021 15:31, Cyrill Gorcunov пишет:
> On Fri, Oct 01, 2021 at 03:14:52PM +0300, Serge Petrenko wrote:
> ...
>>> +/** Process a synchronous replication request. */
>>>    void
>>>    txn_limbo_process(struct txn_limbo *limbo, const struct synchro_request *req);
>> Thanks for the patch!
>>
>> Mostly ok with one question:
>>
>> What about txn_limbo_write_confirm/txn_limbo_read_confirm pairs issued
>> inside txn_limbo_ack() and txn_limbo_on_parameters_change() ?
>>
>> Shouldn't they take the latch as well? I mean, txn_limbo_ack() and
>> txn_limbo_on_parameters_change() as a whole.
> Wait, Serge, currently we guard promote_map/max_term, so it won't be
> read while there is its update on the fly. Thus If only I'm not missing
> something obvious txn_limbo_on_parameters_change() can't interfere with
> promote data or race with it anyhow. If you mean some other race then
> it seems I don't see it yet, but I suspect I might be simply wrong :)
Shouldn't we guard limbo->owner as well?
Otherwise you may start writing confirm for an old leader once promote 
for a new
one is already in progress.

I don't remember us discussing this before, so, maybe I'm just confused.

-- 
Serge Petrenko