From patchwork Tue Apr 10 17:35:58 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Daniel Mack X-Patchwork-Id: 10333551 X-Patchwork-Delegate: kvalo@adurom.com Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id ABE0E6053C for ; Tue, 10 Apr 2018 17:36:25 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 96A861FE8B for ; Tue, 10 Apr 2018 17:36:25 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 8A5DC205AD; Tue, 10 Apr 2018 17:36:25 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00, MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 005471FE8B for ; Tue, 10 Apr 2018 17:36:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751611AbeDJRgW (ORCPT ); Tue, 10 Apr 2018 13:36:22 -0400 Received: from mail.bugwerft.de ([46.23.86.59]:34498 "EHLO mail.bugwerft.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751504AbeDJRgW (ORCPT ); Tue, 10 Apr 2018 13:36:22 -0400 Received: from localhost.localdomain (pD95EF508.dip0.t-ipconnect.de [217.94.245.8]) by mail.bugwerft.de (Postfix) with ESMTPSA id BB2EC286DD2; Tue, 10 Apr 2018 17:34:33 +0000 (UTC) From: Daniel Mack To: linux-wireless@vger.kernel.org Cc: wcn36xx@lists.infradead.org, kvalo@codeaurora.org, rfried@codeaurora.org, bjorn.andersson@linaro.org, Daniel Mack Subject: [PATCH] wcn36xx: use READ_ONCE() to access desc->ctrl Date: Tue, 10 Apr 2018 19:35:58 +0200 Message-Id: <20180410173558.32425-1-daniel@zonque.org> X-Mailer: git-send-email 2.14.3 Sender: linux-wireless-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP When accessing shared memory to check for the stat of submitted descriptors, make sure to use READ_ONCE(). This will guarantee the compiler treats these memory locations as volatile and doesn't apply any caching. While this doesn't fix any particular problem I ran into, it's best practice to do it this way. Note that this patch also removes the superflous extra condition check in the do-while loop in reap_tx_dxes(), as the loop will break instantly anyway in that case. Signed-off-by: Daniel Mack --- drivers/net/wireless/ath/wcn36xx/dxe.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/drivers/net/wireless/ath/wcn36xx/dxe.c b/drivers/net/wireless/ath/wcn36xx/dxe.c index 26e6c42f886a..c52f1c21ece9 100644 --- a/drivers/net/wireless/ath/wcn36xx/dxe.c +++ b/drivers/net/wireless/ath/wcn36xx/dxe.c @@ -363,7 +363,7 @@ static void reap_tx_dxes(struct wcn36xx *wcn, struct wcn36xx_dxe_ch *ch) spin_lock_irqsave(&ch->lock, flags); ctl = ch->tail_blk_ctl; do { - if (ctl->desc->ctrl & WCN36xx_DXE_CTRL_VLD) + if (READ_ONCE(ctl->desc->ctrl) & WCN36xx_DXE_CTRL_VLD) break; if (ctl->skb) { dma_unmap_single(wcn->dev, ctl->desc->src_addr_l, @@ -382,8 +382,7 @@ static void reap_tx_dxes(struct wcn36xx *wcn, struct wcn36xx_dxe_ch *ch) ctl->skb = NULL; } ctl = ctl->next; - } while (ctl != ch->head_blk_ctl && - !(ctl->desc->ctrl & WCN36xx_DXE_CTRL_VLD)); + } while (ctl != ch->head_blk_ctl); ch->tail_blk_ctl = ctl; spin_unlock_irqrestore(&ch->lock, flags); @@ -525,7 +524,7 @@ static int wcn36xx_rx_handle_packets(struct wcn36xx *wcn, int_mask = WCN36XX_DXE_INT_CH3_MASK; } - while (!(dxe->ctrl & WCN36xx_DXE_CTRL_VLD)) { + while (!(READ_ONCE(dxe->ctrl) & WCN36xx_DXE_CTRL_VLD)) { skb = ctl->skb; dma_addr = dxe->dst_addr_l; ret = wcn36xx_dxe_fill_skb(wcn->dev, ctl, GFP_ATOMIC);