From: Steven Lariau Date: Fri, 25 Sep 2020 17:43:37 +0000 (+0100) Subject: stack: remove redundant orderings on pop X-Git-Url: http://git.droids-corp.org/?a=commitdiff_plain;h=2cdfe4e57765e46eed03e42c7c3f78cf22d7dc61;p=dpdk.git stack: remove redundant orderings on pop The load-acquire of list->len on pop function is redundant. Only the CAS success needs to be load-acquire. It synchronizes with the store release in push, to ensure that the updated head is visible when the new length is visible. Without this, one thread in pop could see the increased length but the old list, which doesn't have enough items yet for pop to succeed. Signed-off-by: Steven Lariau Reviewed-by: Dharmik Thakkar Reviewed-by: Ruifeng Wang Acked-by: Gage Eads --- diff --git a/lib/librte_stack/rte_stack_lf_c11.h b/lib/librte_stack/rte_stack_lf_c11.h index 82b7287f19..2bc6394194 100644 --- a/lib/librte_stack/rte_stack_lf_c11.h +++ b/lib/librte_stack/rte_stack_lf_c11.h @@ -80,7 +80,7 @@ __rte_stack_lf_pop_elems(struct rte_stack_lf_list *list, int success; /* Reserve num elements, if available */ - len = __atomic_load_n(&list->len, __ATOMIC_ACQUIRE); + len = __atomic_load_n(&list->len, __ATOMIC_RELAXED); while (1) { /* Does the list contain enough elements? */ @@ -91,7 +91,7 @@ __rte_stack_lf_pop_elems(struct rte_stack_lf_list *list, if (__atomic_compare_exchange_n(&list->len, &len, len - num, 1, __ATOMIC_ACQUIRE, - __ATOMIC_ACQUIRE)) + __ATOMIC_RELAXED)) break; }