From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rasesh Mody Subject: [net-next 07/12] bna: CQ Read Fix Date: Tue, 17 Dec 2013 17:07:37 -0800 Message-ID: <1387328862-27213-8-git-send-email-rmody@brocade.com> References: <1387328862-27213-1-git-send-email-rmody@brocade.com> Mime-Version: 1.0 Content-Type: text/plain Cc: , , Rasesh Mody To: Return-path: Received: from mx0a-000f0801.pphosted.com ([67.231.144.122]:42885 "EHLO mx0a-000f0801.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752286Ab3LRBIk (ORCPT ); Tue, 17 Dec 2013 20:08:40 -0500 In-Reply-To: <1387328862-27213-1-git-send-email-rmody@brocade.com> Sender: netdev-owner@vger.kernel.org List-ID: Valid bit check for completion needs read fence, so that it does not get reordered with other loads. Signed-off-by: Rasesh Mody --- drivers/net/ethernet/brocade/bna/bnad.c | 23 ++++++++++++++++++++++- 1 file changed, 22 insertions(+), 1 deletion(-) diff --git a/drivers/net/ethernet/brocade/bna/bnad.c b/drivers/net/ethernet/brocade/bna/bnad.c index 03fa4a6..7394d46 100644 --- a/drivers/net/ethernet/brocade/bna/bnad.c +++ b/drivers/net/ethernet/brocade/bna/bnad.c @@ -601,7 +601,18 @@ bnad_cq_process(struct bnad *bnad, struct bna_ccb *ccb, int budget) cq = ccb->sw_q; cmpl = &cq[ccb->producer_index]; - while (cmpl->valid && (packets < budget)) { + while (packets < budget) { + if (!cmpl->valid) + break; + /* The 'valid' field is set by the adapter, only after writing + * the other fields of completion entry. Hence, do not load + * other fields of completion entry *before* the 'valid' is + * loaded. Adding the rmb() here prevents the compiler and/or + * CPU from reordering the reads which would potentially result + * in reading stale values in completion entry. + */ + rmb(); + BNA_UPDATE_PKT_CNT(pkt_rt, ntohs(cmpl->length)); if (bna_is_small_rxq(cmpl->rxq_id)) @@ -641,6 +652,16 @@ bnad_cq_process(struct bnad *bnad, struct bna_ccb *ccb, int budget) if (!next_cmpl->valid) break; + /* The 'valid' field is set by the adapter, only + * after writing the other fields of completion + * entry. Hence, do not load other fields of + * completion entry *before* the 'valid' is + * loaded. Adding the rmb() here prevents the + * compiler and/or CPU from reordering the reads + * which would potentially result in reading + * stale values in completion entry. + */ + rmb(); len = ntohs(next_cmpl->length); flags = ntohl(next_cmpl->flags); -- 1.8.2.3