[dpdk-dev] [PATCH] lib: change rte_ring dequeue to guarantee ordering before tail update
Ananyev, Konstantin
konstantin.ananyev at intel.com
Fri Jul 15 14:22:29 CEST 2016
>
> Consumer queue dequeuing must be guaranteed to be done fully before the tail is updated. This is not guaranteed with a read barrier,
> changed to a write barrier just before tail update which in practice guarantees correct order of reads and writes.
>
> Signed-off-by: Juhamatti Kuusisaari <juhamatti.kuusisaari at coriant.com>
> ---
> lib/librte_ring/rte_ring.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/lib/librte_ring/rte_ring.h b/lib/librte_ring/rte_ring.h index eb45e41..14920af 100644
> --- a/lib/librte_ring/rte_ring.h
> +++ b/lib/librte_ring/rte_ring.h
> @@ -748,7 +748,7 @@ __rte_ring_sc_do_dequeue(struct rte_ring *r, void **obj_table,
>
> /* copy in table */
> DEQUEUE_PTRS();
> - rte_smp_rmb();
> + rte_smp_wmb();
>
> __RING_STAT_ADD(r, deq_success, n);
> r->cons.tail = cons_next;
> --
Acked-by: Konstantin Ananyev <konstantin.ananyev at intel.com>
> 2.9.0
>
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