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 Fri, 13 Nov 2020 12:48:00 +0300 (MSK)
References: <20201112195121.191366-1-gorcunov@gmail.com>
 <20201112195121.191366-8-gorcunov@gmail.com>
From: Serge Petrenko <sergepetrenko@tarantool.org>
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Date: Fri, 13 Nov 2020 12:47:59 +0300
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Subject: Re: [Tarantool-patches] [PATCH 07/11] qsync: move limbo owner
 transition into separate helper
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To: Cyrill Gorcunov <gorcunov@gmail.com>, tml <tarantool-patches@dev.tarantool.org>
Cc: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>


12.11.2020 22:51, Cyrill Gorcunov пишет:
> This makes transition more explicit since owner_id persistence
> while processing limbo queue is a key moment. Same time we
> don't need to check for owner_id == REPLICA_ID_NIL since
> it can't be nil with nonempty queue.
>
> Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
> ---
>   src/box/txn_limbo.c | 29 +++++++++++++++++++++--------
>   1 file changed, 21 insertions(+), 8 deletions(-)
>
> diff --git a/src/box/txn_limbo.c b/src/box/txn_limbo.c
> index 674dcad28..b58b9647d 100644
> --- a/src/box/txn_limbo.c
> +++ b/src/box/txn_limbo.c
> @@ -48,6 +48,24 @@ txn_limbo_create(struct txn_limbo *limbo)
>   	limbo->is_in_rollback = false;
>   }
>   
> +static bool
> +txn_limbo_change_owner(struct txn_limbo *limbo, uint32_t owner_id)
> +{
> +	/*
> +	 * Owner transition is allowed for empty txn queue only
> +	 * since different nodes have own vclocks and LSNs won't
> +	 * be ordered in limbo context.
> +	 */
> +	if (rlist_empty(&limbo->queue)) {
> +		limbo->owner_id = owner_id;
> +		limbo->confirmed_lsn = 0;
> +		return true;
> +	}
> +
> +	diag_set(ClientError, ER_UNCOMMITTED_FOREIGN_SYNC_TXNS, limbo->owner_id);
> +	return false;
> +}
> +


AFAIK we use `return 0/-1` for such functions. bool is only used for 
something that
really returns true or false, like `field_mp_type_is_compatible()`.

Other than that the patch looks good.


>   struct txn_limbo_entry *
>   txn_limbo_append(struct txn_limbo *limbo, uint32_t owner_id, struct txn *txn)
>   {
> @@ -77,17 +95,12 @@ txn_limbo_append(struct txn_limbo *limbo, uint32_t owner_id, struct txn *txn)
>   		 */
>   		owner_id = instance_id;
>   	}
> +
>   	if (limbo->owner_id != owner_id) {
> -		if (limbo->owner_id == REPLICA_ID_NIL ||
> -		    rlist_empty(&limbo->queue)) {
> -			limbo->owner_id = owner_id;
> -			limbo->confirmed_lsn = 0;
> -		} else {
> -			diag_set(ClientError, ER_UNCOMMITTED_FOREIGN_SYNC_TXNS,
> -				 limbo->owner_id);
> +		if (!txn_limbo_change_owner(limbo, owner_id))
>   			return NULL;
> -		}
>   	}
> +
>   	size_t size;
>   	struct txn_limbo_entry *e = region_alloc_object(&txn->region,
>   							typeof(*e), &size);

-- 
Serge Petrenko