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Commit 9ff6fde8 authored by Daniel Mack's avatar Daniel Mack Committed by Kalle Valo
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wcn36xx: use READ_ONCE() to access desc->ctrl 



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: default avatarDaniel Mack <daniel@zonque.org>
Signed-off-by: default avatarKalle Valo <kvalo@codeaurora.org>
parent 6da2b2d4

drivers/net/wireless/ath/wcn36xx/dxe.c

+3 −4
Original line number Diff line number Diff line
@@ -368,7 +368,7 @@ 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,
@@ -387,8 +387,7 @@ 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);
@@ -530,7 +529,7 @@ 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);