Return-path: 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 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> (sfid-20180410_193628_094566_6F340BC2) Sender: linux-wireless-owner@vger.kernel.org List-ID: 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); -- 2.14.3