From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from foss.arm.com (foss.arm.com [217.140.101.70]) by dpdk.org (Postfix) with ESMTP id 42D832BE5; Mon, 17 Sep 2018 10:11:32 +0200 (CEST) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 9A15FED1; Mon, 17 Sep 2018 01:11:31 -0700 (PDT) Received: from net-arm-thunderx2.shanghai.arm.com (net-arm-thunderx2.shanghai.arm.com [10.169.40.70]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 33DB13F5C0; Mon, 17 Sep 2018 01:11:30 -0700 (PDT) From: Gavin Hu To: dev@dpdk.org Cc: gavin.hu@arm.com, Honnappa.Nagarahalli@arm.com, steve.capper@arm.com, Ola.Liljedahl@arm.com, jerin.jacob@caviumnetworks.com, nd@arm.com, stable@dpdk.org Date: Mon, 17 Sep 2018 16:11:17 +0800 Message-Id: <1537171879-64390-2-git-send-email-gavin.hu@arm.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1537171879-64390-1-git-send-email-gavin.hu@arm.com> References: <20180917074735.28161-1-gavin.hu@arm.com> <1537171879-64390-1-git-send-email-gavin.hu@arm.com> Subject: [dpdk-dev] [PATCH v4 2/4] ring: read tail using atomic load 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: , X-List-Received-Date: Mon, 17 Sep 2018 08:11:32 -0000 In update_tail, read ht->tail using __atomic_load.Although the compiler currently seems to be doing the right thing even without _atomic_load, we don't want to give the compiler freedom to optimise what should be an atomic load, it should not be arbitarily moved around. Fixes: 39368ebfc6 ("ring: introduce C11 memory model barrier option") Cc: stable@dpdk.org Signed-off-by: Gavin Hu Reviewed-by: Honnappa Nagarahalli Reviewed-by: Steve Capper Reviewed-by: Ola Liljedahl --- lib/librte_ring/rte_ring_c11_mem.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/lib/librte_ring/rte_ring_c11_mem.h b/lib/librte_ring/rte_ring_c11_mem.h index 94df3c4..234fea0 100644 --- a/lib/librte_ring/rte_ring_c11_mem.h +++ b/lib/librte_ring/rte_ring_c11_mem.h @@ -21,7 +21,8 @@ update_tail(struct rte_ring_headtail *ht, uint32_t old_val, uint32_t new_val, * we need to wait for them to complete */ if (!single) - while (unlikely(ht->tail != old_val)) + while (unlikely(old_val != __atomic_load_n(&ht->tail, + __ATOMIC_RELAXED))) rte_pause(); __atomic_store_n(&ht->tail, new_val, __ATOMIC_RELEASE); -- 2.7.4