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From: Vladislav Shpilevoy via Tarantool-patches <tarantool-patches@dev.tarantool.org>
To: Serge Petrenko <sergepetrenko@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: Wed, 12 Jan 2022 22:30:14 +0100	[thread overview]
Message-ID: <63f0bdcc-4ab1-6fa9-411f-ddce6e0aa215@tarantool.org> (raw)
In-Reply-To: <77b533c1-0c2f-c11d-0aa6-4109674a7025@tarantool.org>


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     outdated request is applied by applier at that exact moment.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 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.

  reply	other threads:[~2022-01-12 21:30 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 [this message]
2022-01-13 10:13           ` Serge Petrenko via Tarantool-patches
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

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