From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from dpdk.org (dpdk.org [92.243.14.124]) by inbox.dpdk.org (Postfix) with ESMTP id 1AE48A04BB; Fri, 11 Sep 2020 17:31:36 +0200 (CEST) Received: from [92.243.14.124] (localhost [127.0.0.1]) by dpdk.org (Postfix) with ESMTP id 45B8E1C10A; Fri, 11 Sep 2020 17:31:26 +0200 (CEST) Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by dpdk.org (Postfix) with ESMTP id 2C6E61C10A for ; Fri, 11 Sep 2020 17:31:25 +0200 (CEST) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id B32B81063; Fri, 11 Sep 2020 08:31:24 -0700 (PDT) Received: from localhost.localdomain (unknown [10.57.10.210]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 545393F73C; Fri, 11 Sep 2020 08:31:23 -0700 (PDT) From: Steven Lariau To: Gage Eads , Olivier Matz Cc: dev@dpdk.org, nd@arm.com, dharmik.thakkar@arm.com, Steven Lariau Date: Fri, 11 Sep 2020 16:29:36 +0100 Message-Id: <20200911152938.8019-4-steven.lariau@arm.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20200911152938.8019-1-steven.lariau@arm.com> References: <20200911152938.8019-1-steven.lariau@arm.com> Subject: [dpdk-dev] [PATCH 3/5] lib/stack: remove redundant orderings for list->len X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" 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 --- lib/librte_stack/rte_stack_lf_c11.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/lib/librte_stack/rte_stack_lf_c11.h b/lib/librte_stack/rte_stack_lf_c11.h index 82b7287f1..2bc639419 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; } -- 2.17.1