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Date: Wed, 7 Dec 2016 22:37:57 +0100
From: Pavel Machek <pavel@....cz>
To: Lino Sanfilippo <LinoSanfilippo@....de>
Cc: bh74.an@...sung.com, ks.giri@...sung.com, vipul.pandya@...sung.com,
peppe.cavallaro@...com, alexandre.torgue@...com,
davem@...emloft.net, linux-kernel@...r.kernel.org,
netdev@...r.kernel.org
Subject: Re: [PATCH 2/2] net: ethernet: stmmac: remove private tx queue lock
On Wed 2016-12-07 21:05:38, Lino Sanfilippo wrote:
> The driver uses a private lock for synchronization between the xmit
> function and the xmit completion handler, but since the NETIF_F_LLTX flag
> is not set, the xmit function is also called with the xmit_lock held.
>
> On the other hand the xmit completion handler first takes the private lock
> and (in case that the tx queue has been stopped) the xmit_lock, leading to
> a reverse locking order and the potential danger of a deadlock.
>
> Fix this by removing the private lock completely and synchronizing the xmit
> function and completion handler solely by means of the xmit_lock. By doing
> this remove also the now unnecessary double check for a stopped tx queue.
>
FYI, here's modified version. I believe _bh versions are needed, and
I'm testing that version now. (Oh and I also ported it to net-next).
It survived 30 minutes of testing so far...
Best regards,
Pavel
Signed-off-by: Lino Sanfilippo <LinoSanfilippo@....de>
Signed-off-by: Pavel Machek <pavel@...x.de>
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac.h b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
index dbacb80..eab04ae 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac.h
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
@@ -64,7 +64,6 @@ struct stmmac_priv {
dma_addr_t dma_tx_phy;
int tx_coalesce;
int hwts_tx_en;
- spinlock_t tx_lock;
bool tx_path_in_lpi_mode;
struct timer_list txtimer;
bool tso;
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 982c952..7415bc2 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -1308,7 +1308,7 @@ static void stmmac_tx_clean(struct stmmac_priv *priv)
unsigned int bytes_compl = 0, pkts_compl = 0;
unsigned int entry = priv->dirty_tx;
- spin_lock(&priv->tx_lock);
+ netif_tx_lock_bh(priv->dev);
priv->xstats.tx_clean++;
@@ -1378,23 +1378,18 @@ static void stmmac_tx_clean(struct stmmac_priv *priv)
netdev_completed_queue(priv->dev, pkts_compl, bytes_compl);
- if (unlikely(netif_queue_stopped(priv->dev) &&
- stmmac_tx_avail(priv) > STMMAC_TX_THRESH)) {
- netif_tx_lock(priv->dev);
- if (netif_queue_stopped(priv->dev) &&
- stmmac_tx_avail(priv) > STMMAC_TX_THRESH) {
- netif_dbg(priv, tx_done, priv->dev,
- "%s: restart transmit\n", __func__);
- netif_wake_queue(priv->dev);
- }
- netif_tx_unlock(priv->dev);
+ if (netif_queue_stopped(priv->dev) &&
+ stmmac_tx_avail(priv) > STMMAC_TX_THRESH) {
+ netif_dbg(priv, tx_done, priv->dev,
+ "%s: restart transmit\n", __func__);
+ netif_wake_queue(priv->dev);
}
if ((priv->eee_enabled) && (!priv->tx_path_in_lpi_mode)) {
stmmac_enable_eee_mode(priv);
mod_timer(&priv->eee_ctrl_timer, STMMAC_LPI_T(eee_timer));
}
- spin_unlock(&priv->tx_lock);
+ netif_tx_unlock_bh(priv->dev);
}
static inline void stmmac_enable_dma_irq(struct stmmac_priv *priv)
@@ -2006,8 +2001,6 @@ static netdev_tx_t stmmac_tso_xmit(struct sk_buff *skb, struct net_device *dev)
u8 proto_hdr_len;
int i;
- spin_lock(&priv->tx_lock);
-
/* Compute header lengths */
proto_hdr_len = skb_transport_offset(skb) + tcp_hdrlen(skb);
@@ -2021,7 +2014,6 @@ static netdev_tx_t stmmac_tso_xmit(struct sk_buff *skb, struct net_device *dev)
"%s: Tx Ring full when queue awake\n",
__func__);
}
- spin_unlock(&priv->tx_lock);
return NETDEV_TX_BUSY;
}
@@ -2156,11 +2148,9 @@ static netdev_tx_t stmmac_tso_xmit(struct sk_buff *skb, struct net_device *dev)
priv->hw->dma->set_tx_tail_ptr(priv->ioaddr, priv->tx_tail_addr,
STMMAC_CHAN0);
- spin_unlock(&priv->tx_lock);
return NETDEV_TX_OK;
dma_map_err:
- spin_unlock(&priv->tx_lock);
dev_err(priv->device, "Tx dma map failed\n");
dev_kfree_skb(skb);
priv->dev->stats.tx_dropped++;
@@ -2192,10 +2182,7 @@ static netdev_tx_t stmmac_xmit(struct sk_buff *skb, struct net_device *dev)
return stmmac_tso_xmit(skb, dev);
}
- spin_lock(&priv->tx_lock);
-
if (unlikely(stmmac_tx_avail(priv) < nfrags + 1)) {
- spin_unlock(&priv->tx_lock);
if (!netif_queue_stopped(dev)) {
netif_stop_queue(dev);
/* This is a hard error, log it. */
@@ -2366,11 +2353,9 @@ static netdev_tx_t stmmac_xmit(struct sk_buff *skb, struct net_device *dev)
priv->hw->dma->set_tx_tail_ptr(priv->ioaddr, priv->tx_tail_addr,
STMMAC_CHAN0);
- spin_unlock(&priv->tx_lock);
return NETDEV_TX_OK;
dma_map_err:
- spin_unlock(&priv->tx_lock);
netdev_err(priv->dev, "Tx DMA map failed\n");
dev_kfree_skb(skb);
priv->dev->stats.tx_dropped++;
@@ -3357,7 +3342,6 @@ int stmmac_dvr_probe(struct device *device,
netif_napi_add(ndev, &priv->napi, stmmac_poll, 64);
spin_lock_init(&priv->lock);
- spin_lock_init(&priv->tx_lock);
ret = register_netdev(ndev);
if (ret) {
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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