Re: [Tarantool-patches] [PATCH 11/16] tx: introduce conflict tracker

[Vladislav Shpilevoy <v.shpilevoy@tarantool.org>]

Thanks for the patch!

See 1 comment below.

On 08.07.2020 17:14, Aleksandr Lyapunov wrote:
> ---
>  src/box/txn.c | 98 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  src/box/txn.h |  5 +++
>  2 files changed, 103 insertions(+)
> 
> diff --git a/src/box/txn.c b/src/box/txn.c
> index 2bd44a3..b9f1737 100644
> --- a/src/box/txn.c
> +++ b/src/box/txn.c
> @@ -998,3 +1053,46 @@ void
>  tx_manager_free()
>  {
>  }
> +
> +int
> +txm_cause_conflict(struct txn *wreaker, struct txn *victim)
> +{
> +	struct tx_conflict_tracker *tracker = NULL;
> +	struct rlist *r1 = wreaker->conflict_list.next;
> +	struct rlist *r2 = wreaker->conflicted_by_list.next;
> +	while (r1 != &wreaker->conflict_list &&
> +	       r2 != &wreaker->conflicted_by_list) {
> +		tracker = rlist_entry(r1, struct tx_conflict_tracker,
> +				      in_conflict_list);
> +		if (tracker->wreaker == wreaker && tracker->victim == victim)
> +			break;
> +		tracker = rlist_entry(r2, struct tx_conflict_tracker,
> +				      in_conflicted_by_list);
> +		if (tracker->wreaker == wreaker && tracker->victim == victim)
> +			break;
> +		tracker = NULL;
> +		r1 = r1->next;
> +		r2 = r2->next;
> +	}
> +	if (tracker != NULL) {
> +		/* Move to the beginning of a list
> +		 * for a case of subsequent lookups */
> +		rlist_del(&tracker->in_conflict_list);
> +		rlist_del(&tracker->in_conflicted_by_list);
> +	} else {
> +		size_t size;
> +		tracker = region_alloc_object(&victim->region,
> +					      struct tx_conflict_tracker,
> +					      &size);
> +		if (tracker == NULL) {
> +			diag_set(OutOfMemory, size, "tx region",
> +				 "conflict_tracker");
> +			return -1;
> +		}
> +	}
> +	tracker->wreaker = wreaker;
> +	tracker->victim = victim;

Why don't you save anything into the victim? How will it be
removed from the lists if it will commit earlier than 'wreaker'?