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Date: Sun, 15 May 2016 20:07:34 +0200 From: Francois Romieu <romieu@...zoreil.com> To: Shuyu Wei <wsy2220@...il.com> Cc: wxt@...k-chips.com, davem@...emloft.net, heiko@...ech.de, linux-rockchip@...ts.infradead.org, netdev@...r.kernel.org Subject: Re: [PATCH] ethernet:arc: Fix racing of TX ring buffer Shuyu Wei <wsy2220@...il.com> : [...] > I still have a question, is it possible that tx_clean() run > between priv->tx_buff[*txbd_curr].skb = skb and dma_wmb()? A (previous) run can take place after priv->tx_buff[*txbd_curr].skb and before *info = cpu_to_le32(FOR_EMAC | FIRST_OR_LAST_MASK | len). So, yes, the driver must check in arc_emac_tx_clean() that 1) either txbd_dirty != txbd_curr or 2) "info" is not consistent with a still-not-used status word. Please be patient with me and get rid of the useless "i" diff --git a/drivers/net/ethernet/arc/emac_main.c b/drivers/net/ethernet/arc/emac_main.c index a3a9392..337ea3b 100644 --- a/drivers/net/ethernet/arc/emac_main.c +++ b/drivers/net/ethernet/arc/emac_main.c @@ -153,9 +153,8 @@ static void arc_emac_tx_clean(struct net_device *ndev) { struct arc_emac_priv *priv = netdev_priv(ndev); struct net_device_stats *stats = &ndev->stats; - unsigned int i; - for (i = 0; i < TX_BD_NUM; i++) { + while (priv->txbd_dirty != priv->txbd_curr) { unsigned int *txbd_dirty = &priv->txbd_dirty; struct arc_emac_bd *txbd = &priv->txbd[*txbd_dirty]; struct buffer_state *tx_buff = &priv->tx_buff[*txbd_dirty]; -- Ueimor
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