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Message-ID: <20100114101445.GA7210@ff.dom.local>
Date: Thu, 14 Jan 2010 10:14:45 +0000
From: Jarek Poplawski <jarkao2@...il.com>
To: Stephen Hemminger <shemminger@...tta.com>
Cc: Michael Breuer <mbreuer@...jas.com>,
David Miller <davem@...emloft.net>, mikem@...g3k.org,
flyboy@...il.com, rjw@...k.pl, netdev@...r.kernel.org
Subject: Re: [PATCH] sky2: safer transmit ring cleaning (v4)
On Wed, Jan 13, 2010 at 07:41:48PM -0800, Stephen Hemminger wrote:
> Subject: sky2: safer transmit cleanup
>
> This code makes transmit path and transmit reset safer by:
> * adding memory barrier before checking available ring slots
> * reseting state of tx ring elements after free
> * seperate cleanup function from ring done function
> * removing mostly unused tx_next element
> * ignoring transmit completion if device is offline
>
> Signed-off-by: Stephen Hemminger <shemminger@...tta.com>
>
> ---
> This patch is against the current net-next-2.6 tree.
> This version handles the case of dual port shared transmit status
> and other cases where it is possible for tx_done to be called when
> device is being changed.
>
> --- a/drivers/net/sky2.c 2010-01-13 08:32:51.360161158 -0800
> +++ b/drivers/net/sky2.c 2010-01-13 08:35:37.685531490 -0800
> @@ -1596,6 +1596,9 @@ static inline int tx_inuse(const struct
> /* Number of list elements available for next tx */
> static inline int tx_avail(const struct sky2_port *sky2)
> {
> + /* Makes sure update of tx_prod from start_xmit and
> + tx_cons from tx_done are seen. */
> + smp_mb();
> return sky2->tx_pending - tx_inuse(sky2);
> }
>
> @@ -1618,8 +1621,7 @@ static unsigned tx_le_req(const struct s
> return count;
> }
>
> -static void sky2_tx_unmap(struct pci_dev *pdev,
> - const struct tx_ring_info *re)
> +static void sky2_tx_unmap(struct pci_dev *pdev, struct tx_ring_info *re)
> {
> if (re->flags & TX_MAP_SINGLE)
> pci_unmap_single(pdev, pci_unmap_addr(re, mapaddr),
> @@ -1629,6 +1631,7 @@ static void sky2_tx_unmap(struct pci_dev
> pci_unmap_page(pdev, pci_unmap_addr(re, mapaddr),
> pci_unmap_len(re, maplen),
> PCI_DMA_TODEVICE);
> + re->flags = 0;
> }
>
> /*
> @@ -1804,7 +1807,8 @@ mapping_error:
> }
>
> /*
> - * Free ring elements from starting at tx_cons until "done"
> + * Transmit complete processing
> + * Free ring elements from starting at tx_cons until done index
> *
> * NB:
> * 1. The hardware will tell us about partial completion of multi-part
> @@ -1813,11 +1817,14 @@ mapping_error:
> * looks at the tail of the queue of FIFO (tx_cons), not
> * the head (tx_prod)
> */
> -static void sky2_tx_complete(struct sky2_port *sky2, u16 done)
> +static void sky2_tx_done(struct net_device *dev, u16 done)
> {
> - struct net_device *dev = sky2->netdev;
> + struct sky2_port *sky2 = netdev_priv(dev);
> unsigned idx;
>
> + if (!(netif_running(dev) & netif_device_present(dev)))
This makes it safe, but it still resembles the "short term fix"
according do David's opinion.
This change seems to affect dev->stats too. Since they are not
updated in sky2_tx_clean(). Btw, I hope "&" is some optimization
because it's less readable than "&&".
Jarek P.
> + return;
> +
> BUG_ON(done >= sky2->tx_ring_size);
>
> for (idx = sky2->tx_cons; idx != done;
> @@ -1828,6 +1835,8 @@ static void sky2_tx_complete(struct sky2
> sky2_tx_unmap(sky2->hw->pdev, re);
>
> if (skb) {
> + re->skb = NULL;
> +
> if (unlikely(netif_msg_tx_done(sky2)))
> printk(KERN_DEBUG "%s: tx done %u\n",
> dev->name, idx);
> @@ -1836,16 +1845,12 @@ static void sky2_tx_complete(struct sky2
> dev->stats.tx_bytes += skb->len;
>
> dev_kfree_skb_any(skb);
> -
> - sky2->tx_next = RING_NEXT(idx, sky2->tx_ring_size);
> }
> }
>
> sky2->tx_cons = idx;
> - smp_mb();
>
> - /* Wake unless it's detached, and called e.g. from sky2_down() */
> - if (tx_avail(sky2) > MAX_SKB_TX_LE + 4 && netif_device_present(dev))
> + if (tx_avail(sky2) > MAX_SKB_TX_LE + 4)
> netif_wake_queue(dev);
> }
>
> @@ -1871,6 +1876,21 @@ static void sky2_tx_reset(struct sky2_hw
> sky2_write8(hw, SK_REG(port, TX_GMF_CTRL_T), GMF_RST_SET);
> }
>
> +static void sky2_tx_clean(struct sky2_port *sky2)
> +{
> + u16 idx;
> +
> + for (idx = 0; idx < sky2->tx_ring_size; idx++) {
> + struct tx_ring_info *re = sky2->tx_ring + idx;
> +
> + sky2_tx_unmap(sky2->hw->pdev, re);
> + if (re->skb) {
> + dev_kfree_skb_any(re->skb);
> + re->skb = NULL;
> + }
> + }
> +}
> +
> /* Network shutdown */
> static int sky2_down(struct net_device *dev)
> {
> @@ -1934,8 +1954,7 @@ static int sky2_down(struct net_device *
> sky2_tx_reset(hw, port);
>
> /* Free any pending frames stuck in HW queue */
> - sky2_tx_complete(sky2, sky2->tx_prod);
> -
> + sky2_tx_clean(sky2);
> sky2_rx_clean(sky2);
>
> sky2_free_buffers(sky2);
> @@ -2412,15 +2431,6 @@ error:
> goto resubmit;
> }
>
> -/* Transmit complete */
> -static inline void sky2_tx_done(struct net_device *dev, u16 last)
> -{
> - struct sky2_port *sky2 = netdev_priv(dev);
> -
> - if (netif_running(dev))
> - sky2_tx_complete(sky2, last);
> -}
> -
> static inline void sky2_skb_rx(const struct sky2_port *sky2,
> u32 status, struct sk_buff *skb)
> {
> @@ -3177,9 +3187,9 @@ static void sky2_reset(struct sky2_hw *h
> static void sky2_detach(struct net_device *dev)
> {
> if (netif_running(dev)) {
> - netif_tx_lock(dev);
> + netif_tx_lock_bh(dev);
> netif_device_detach(dev); /* stop txq */
> - netif_tx_unlock(dev);
> + netif_tx_unlock_bh(dev);
> sky2_down(dev);
> }
> }
> @@ -4202,7 +4212,7 @@ static int sky2_debug_show(struct seq_fi
>
> /* Dump contents of tx ring */
> sop = 1;
> - for (idx = sky2->tx_next; idx != sky2->tx_prod && idx < sky2->tx_ring_size;
> + for (idx = sky2->tx_cons; idx != sky2->tx_prod && idx < sky2->tx_ring_size;
> idx = RING_NEXT(idx, sky2->tx_ring_size)) {
> const struct sky2_tx_le *le = sky2->tx_le + idx;
> u32 a = le32_to_cpu(le->addr);
> --- a/drivers/net/sky2.h 2010-01-13 08:32:27.919849429 -0800
> +++ b/drivers/net/sky2.h 2010-01-13 08:33:03.410162026 -0800
> @@ -2187,7 +2187,6 @@ struct sky2_port {
> u16 tx_ring_size;
> u16 tx_cons; /* next le to check */
> u16 tx_prod; /* next le to use */
> - u16 tx_next; /* debug only */
>
> u16 tx_pending;
> u16 tx_last_mss;
--
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