Tarantool development patches archive
 help / color / mirror / Atom feed
From: Serge Petrenko via Tarantool-patches <tarantool-patches@dev.tarantool.org>
To: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>,
	Cyrill Gorcunov <gorcunov@gmail.com>
Cc: tml <tarantool-patches@dev.tarantool.org>
Subject: Re: [Tarantool-patches] [PATCH v27 2/3] qsync: order access to the limbo terms
Date: Thu, 13 Jan 2022 13:13:07 +0300	[thread overview]
Message-ID: <5cc5a52d-e6a7-b4cc-d2a1-23a9b1758288@tarantool.org> (raw)
In-Reply-To: <63f0bdcc-4ab1-6fa9-411f-ddce6e0aa215@tarantool.org>

13.01.2022 00:30, Vladislav Shpilevoy пишет:
> Hi!
> On 12.01.2022 15:01, Serge Petrenko wrote:
>> 11.01.2022 23:39, Cyrill Gorcunov пишет:
>>> On Mon, Jan 10, 2022 at 05:28:43PM +0300, Serge Petrenko wrote:
>>>>      Hi! Thanks for the patch!
>>>>           box_issue_promote() and box_issue_demote() need fine-grained locking
>>>>      anyway.
>>>>      Otherwise it’s possible that promote() is already issued, but not yet
>>>>      written to WAL, and some
>>>>      outdated request is applied by applier at that exact moment.
>>> True. And in previous series Vlad has asked to not move in code which is
>>> not covered by tests. So I think this is a task for the next part. Currently
>>> we cover only the race between appliers.
>> Let's ask Vlad, then.
>> I feel like we should fix this now, not waiting for a full fine-grained locking
>> patch.
>> First of all, this is a known bug (and fine-grained locking was meant to
>> cover everything we don't know of, just in case).
> I am not sure I understand what you both are talking about here. Sergey, do
> you mean 'fine-grained locking' as big critical sections covering a lot of
> code at once or as many small critical sections?

I mean "locking every limbo function", like Cyrill tried to do that in the
previous patch version.
> I am confused because of this sentence. "Cover everything we don't know" is
> rather opposite to fine-grained locking. I voted for big locks because
> apparently it was too hard to implement smaller more precise locks.
>> Besides, simply locking issue_promote/issue_demote should be
>> much easier than implementing the fine-grained locking patch.
> Yes. I remember the proposal was to lock entire promote/demote and other
> qsync/raft functions from beginning to end. Because it should be relatively
> easy. I didn't look at the code in this patch though, can't comment it.

This particular patch only locks applier_apply_synchro_request(), 
and txn_limbo_is_replica_outdated(), so that applier cannot apply a 
request from an
already stale term.

My proposal is to lock box_issue_promote() and box_issue_demote()
(not whole promote/demote) to get rid of another race: when promote is 
to WAL, but not yed processed.

What you're talking about is what I call "fine grained locking", and it 
out rather hard to implement, so Cyrill abandoned this idea for now.

Serge Petrenko

  reply	other threads:[~2022-01-13 10:13 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-30 20:23 [Tarantool-patches] [PATCH v27 0/3] qsync: implement packet filtering (part 1) Cyrill Gorcunov via Tarantool-patches
2021-12-30 20:23 ` [Tarantool-patches] [PATCH v27 1/3] latch: add latch_is_locked helper Cyrill Gorcunov via Tarantool-patches
2021-12-30 20:23 ` [Tarantool-patches] [PATCH v27 2/3] qsync: order access to the limbo terms Cyrill Gorcunov via Tarantool-patches
2022-01-10 14:28   ` Serge Petrenko via Tarantool-patches
2022-01-11 20:39     ` Cyrill Gorcunov via Tarantool-patches
2022-01-12 14:01       ` Serge Petrenko via Tarantool-patches
2022-01-12 21:30         ` Vladislav Shpilevoy via Tarantool-patches
2022-01-13 10:13           ` Serge Petrenko via Tarantool-patches [this message]
2022-01-13 23:32             ` Vladislav Shpilevoy via Tarantool-patches
2022-01-14 10:20               ` Serge Petrenko via Tarantool-patches
2022-01-14 10:33                 ` Cyrill Gorcunov via Tarantool-patches
2021-12-30 20:23 ` [Tarantool-patches] [PATCH v27 3/3] test: add gh-6036-qsync-order test Cyrill Gorcunov via Tarantool-patches
2022-01-10 14:29   ` Serge Petrenko via Tarantool-patches
2022-01-11 20:41     ` Cyrill Gorcunov via Tarantool-patches

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=5cc5a52d-e6a7-b4cc-d2a1-23a9b1758288@tarantool.org \
    --to=tarantool-patches@dev.tarantool.org \
    --cc=gorcunov@gmail.com \
    --cc=sergepetrenko@tarantool.org \
    --cc=v.shpilevoy@tarantool.org \
    --subject='Re: [Tarantool-patches] [PATCH v27 2/3] qsync: order access to the limbo terms' \


* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox