[PATCH net-next 0/6] net: core: remove TX_LOCKED support

[PATCH net-next 0/6] net: core: remove TX_LOCKED support

[Florian Westphal]

 Not that many users left, lets kill it.

 TX_LOCKED was meant to be used by LLTX drivers when spin_trylock()
 failed.  Stack then re-queued if collisions happened on different
 cpus or free'd the skb to prevent deadlocks.

 Most of the driver removal patches fall into one of three categories:
 1. remove the driver-private tx lock (and LLTX flag), or...
 2. convert spin_trylock to plain spin_lock, or...
 3. convert TX_LOCKED to free+TX_OK

 Patches are grouped by these categories, last patch is the actual removal.
 All driver changes were compile tested only with exception of atl1e.

 Documentation/networking/netdev-features.txt         |   10 ++---
 Documentation/networking/netdevices.txt              |    9 +----
 drivers/infiniband/hw/nes/nes_nic.c                  |   13 ++-----
 drivers/net/ethernet/amd/7990.c                      |    8 ++--
 drivers/net/ethernet/amd/a2065.c                     |    7 +---
 drivers/net/ethernet/atheros/atl1c/atl1c.h           |    3 -
 drivers/net/ethernet/atheros/atl1c/atl1c_main.c      |   11 ------
 drivers/net/ethernet/atheros/atl1e/atl1e.h           |    1 
 drivers/net/ethernet/atheros/atl1e/atl1e_main.c      |   12 -------
 drivers/net/ethernet/chelsio/cxgb/sge.c              |    3 -
 drivers/net/ethernet/dec/tulip/de4x5.c               |    7 ++--
 drivers/net/ethernet/neterion/s2io.c                 |    9 -----
 drivers/net/ethernet/oki-semi/pch_gbe/pch_gbe_main.c |    6 +--
 drivers/net/ethernet/tehuti/tehuti.c                 |    8 ----
 drivers/net/hamradio/baycom_epp.c                    |    6 ++-
 drivers/net/hamradio/hdlcdrv.c                       |    6 ++-
 drivers/net/rionet.c                                 |    6 ---
 include/linux/netdevice.h                            |    3 -
 net/core/net-procfs.c                                |    3 +
 net/core/pktgen.c                                    |    1 
 net/sched/sch_generic.c                              |   32 -------------------
 21 files changed, 43 insertions(+), 121 deletions(-)

[PATCH net-next 1/6] RDMA/nes: remove use of NETDEV_TX_LOCKED

[Florian Westphal]

ndo_start_xmit never returns it to stack, but nes_nic_send helper used it if
skb could not be queued to hardware.  Switch to bool instead.

Cc: <linux-rdma@vger.kernel.org>
Signed-off-by: Florian Westphal <fw@strlen.de>
---
 drivers/infiniband/hw/nes/nes_nic.c | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/drivers/infiniband/hw/nes/nes_nic.c b/drivers/infiniband/hw/nes/nes_nic.c
index 3ea9e05..b09a6db 100644
--- a/drivers/infiniband/hw/nes/nes_nic.c
+++ b/drivers/infiniband/hw/nes/nes_nic.c
@@ -356,7 +356,7 @@ static int nes_netdev_stop(struct net_device *netdev)
 /**
  * nes_nic_send
  */
-static int nes_nic_send(struct sk_buff *skb, struct net_device *netdev)
+static bool nes_nic_send(struct sk_buff *skb, struct net_device *netdev)
 {
 	struct nes_vnic *nesvnic = netdev_priv(netdev);
 	struct nes_device *nesdev = nesvnic->nesdev;
@@ -413,7 +413,7 @@ static int nes_nic_send(struct sk_buff *skb, struct net_device *netdev)
 					netdev->name, skb_shinfo(skb)->nr_frags + 2, skb_headlen(skb));
 			kfree_skb(skb);
 			nesvnic->tx_sw_dropped++;
-			return NETDEV_TX_LOCKED;
+			return false;
 		}
 		set_bit(nesnic->sq_head, nesnic->first_frag_overflow);
 		bus_address = pci_map_single(nesdev->pcidev, skb->data + NES_FIRST_FRAG_SIZE,
@@ -454,8 +454,7 @@ static int nes_nic_send(struct sk_buff *skb, struct net_device *netdev)
 	set_wqe_32bit_value(nic_sqe->wqe_words, NES_NIC_SQ_WQE_MISC_IDX, wqe_misc);
 	nesnic->sq_head++;
 	nesnic->sq_head &= nesnic->sq_size - 1;
-
-	return NETDEV_TX_OK;
+	return true;
 }
 
 
@@ -673,13 +672,11 @@ tso_sq_no_longer_full:
 			skb_linearize(skb);
 			skb_set_transport_header(skb, hoffset);
 			skb_set_network_header(skb, nhoffset);
-			send_rc = nes_nic_send(skb, netdev);
-			if (send_rc != NETDEV_TX_OK)
+			if (!nes_nic_send(skb, netdev))
 				return NETDEV_TX_OK;
 		}
 	} else {
-		send_rc = nes_nic_send(skb, netdev);
-		if (send_rc != NETDEV_TX_OK)
+		if (!nes_nic_send(skb, netdev))
 			return NETDEV_TX_OK;
 	}
 
-- 
2.7.3

[PATCH net-next 2/6] atl1c: remove private tx lock

[Florian Westphal]

AFAICS this is safe: the lock is only used in the .ndo_start_xmit
function and this driver does not set LLTX.

Gets rid of TX_LOCKED return value, followup patches will remove it.

Cc: Jay Cliburn <jcliburn@gmail.com>
Cc: Chris Snook <chris.snook@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
---
 drivers/net/ethernet/atheros/atl1c/atl1c.h      |  3 +--
 drivers/net/ethernet/atheros/atl1c/atl1c_main.c | 11 -----------
 2 files changed, 1 insertion(+), 13 deletions(-)

diff --git a/drivers/net/ethernet/atheros/atl1c/atl1c.h b/drivers/net/ethernet/atheros/atl1c/atl1c.h
index b9203d9..c46b489 100644
--- a/drivers/net/ethernet/atheros/atl1c/atl1c.h
+++ b/drivers/net/ethernet/atheros/atl1c/atl1c.h
@@ -488,7 +488,7 @@ struct atl1c_tpd_ring {
 	dma_addr_t dma;		/* descriptor ring physical address */
 	u16 size;		/* descriptor ring length in bytes */
 	u16 count;		/* number of descriptors in the ring */
-	u16 next_to_use; 	/* this is protectd by adapter->tx_lock */
+	u16 next_to_use;
 	atomic_t next_to_clean;
 	struct atl1c_buffer *buffer_info;
 };
@@ -542,7 +542,6 @@ struct atl1c_adapter {
 	u16 link_duplex;
 
 	spinlock_t mdio_lock;
-	spinlock_t tx_lock;
 	atomic_t irq_sem;
 
 	struct work_struct common_task;
diff --git a/drivers/net/ethernet/atheros/atl1c/atl1c_main.c b/drivers/net/ethernet/atheros/atl1c/atl1c_main.c
index d0084d4..a3200ea 100644
--- a/drivers/net/ethernet/atheros/atl1c/atl1c_main.c
+++ b/drivers/net/ethernet/atheros/atl1c/atl1c_main.c
@@ -821,7 +821,6 @@ static int atl1c_sw_init(struct atl1c_adapter *adapter)
 	atl1c_set_rxbufsize(adapter, adapter->netdev);
 	atomic_set(&adapter->irq_sem, 1);
 	spin_lock_init(&adapter->mdio_lock);
-	spin_lock_init(&adapter->tx_lock);
 	set_bit(__AT_DOWN, &adapter->flags);
 
 	return 0;
@@ -2206,7 +2205,6 @@ static netdev_tx_t atl1c_xmit_frame(struct sk_buff *skb,
 					  struct net_device *netdev)
 {
 	struct atl1c_adapter *adapter = netdev_priv(netdev);
-	unsigned long flags;
 	u16 tpd_req = 1;
 	struct atl1c_tpd_desc *tpd;
 	enum atl1c_trans_queue type = atl1c_trans_normal;
@@ -2217,16 +2215,10 @@ static netdev_tx_t atl1c_xmit_frame(struct sk_buff *skb,
 	}
 
 	tpd_req = atl1c_cal_tpd_req(skb);
-	if (!spin_trylock_irqsave(&adapter->tx_lock, flags)) {
-		if (netif_msg_pktdata(adapter))
-			dev_info(&adapter->pdev->dev, "tx locked\n");
-		return NETDEV_TX_LOCKED;
-	}
 
 	if (atl1c_tpd_avail(adapter, type) < tpd_req) {
 		/* no enough descriptor, just stop queue */
 		netif_stop_queue(netdev);
-		spin_unlock_irqrestore(&adapter->tx_lock, flags);
 		return NETDEV_TX_BUSY;
 	}
 
@@ -2234,7 +2226,6 @@ static netdev_tx_t atl1c_xmit_frame(struct sk_buff *skb,
 
 	/* do TSO and check sum */
 	if (atl1c_tso_csum(adapter, skb, &tpd, type) != 0) {
-		spin_unlock_irqrestore(&adapter->tx_lock, flags);
 		dev_kfree_skb_any(skb);
 		return NETDEV_TX_OK;
 	}
@@ -2257,12 +2248,10 @@ static netdev_tx_t atl1c_xmit_frame(struct sk_buff *skb,
 			   "tx-skb droppted due to dma error\n");
 		/* roll back tpd/buffer */
 		atl1c_tx_rollback(adapter, tpd, type);
-		spin_unlock_irqrestore(&adapter->tx_lock, flags);
 		dev_kfree_skb_any(skb);
 	} else {
 		netdev_sent_queue(adapter->netdev, skb->len);
 		atl1c_tx_queue(adapter, skb, tpd, type);
-		spin_unlock_irqrestore(&adapter->tx_lock, flags);
 	}
 
 	return NETDEV_TX_OK;
-- 
2.7.3

Re: [PATCH net-next 2/6] atl1c: remove private tx lock

[Francois Romieu]

Florian Westphal <fw@strlen.de> :
[...]
> diff --git a/drivers/net/ethernet/atheros/atl1c/atl1c_main.c b/drivers/net/ethernet/atheros/atl1c/atl1c_main.c
> index d0084d4..a3200ea 100644
> --- a/drivers/net/ethernet/atheros/atl1c/atl1c_main.c
> +++ b/drivers/net/ethernet/atheros/atl1c/atl1c_main.c
[...]
> @@ -2217,16 +2215,10 @@ static netdev_tx_t atl1c_xmit_frame(struct sk_buff *skb,
>  	}
>  
>  	tpd_req = atl1c_cal_tpd_req(skb);
> -	if (!spin_trylock_irqsave(&adapter->tx_lock, flags)) {
> -		if (netif_msg_pktdata(adapter))
> -			dev_info(&adapter->pdev->dev, "tx locked\n");
> -		return NETDEV_TX_LOCKED;
> -	}
>  
>  	if (atl1c_tpd_avail(adapter, type) < tpd_req) {
>  		/* no enough descriptor, just stop queue */
>  		netif_stop_queue(netdev);
> -		spin_unlock_irqrestore(&adapter->tx_lock, flags);
>  		return NETDEV_TX_BUSY;
>  	}
>

Play it safe and keep the implicit local_irq_{save / restore} call ?

It may not be needed but it will help avoiding any unexpected regression
report pointing at the NETDEV_TX_LOCKED removal change.

-- 
Ueimor

Re: [PATCH net-next 2/6] atl1c: remove private tx lock

[Francois Romieu]

Florian Westphal <fw@strlen.de> :
[...]
> diff --git a/drivers/net/ethernet/atheros/atl1c/atl1c_main.c b/drivers/net/ethernet/atheros/atl1c/atl1c_main.c
> index d0084d4..a3200ea 100644
> --- a/drivers/net/ethernet/atheros/atl1c/atl1c_main.c
> +++ b/drivers/net/ethernet/atheros/atl1c/atl1c_main.c
[...]
> @@ -2217,16 +2215,10 @@ static netdev_tx_t atl1c_xmit_frame(struct sk_buff *skb,
>  	}
>  
>  	tpd_req = atl1c_cal_tpd_req(skb);
> -	if (!spin_trylock_irqsave(&adapter->tx_lock, flags)) {
> -		if (netif_msg_pktdata(adapter))
> -			dev_info(&adapter->pdev->dev, "tx locked\n");
> -		return NETDEV_TX_LOCKED;
> -	}
>  
>  	if (atl1c_tpd_avail(adapter, type) < tpd_req) {
>  		/* no enough descriptor, just stop queue */
>  		netif_stop_queue(netdev);
> -		spin_unlock_irqrestore(&adapter->tx_lock, flags);
>  		return NETDEV_TX_BUSY;
>  	}
>

Play it safe and keep the implicit local_irq_{save / restore} call ?

It may not be needed but it will help avoiding any unexpected regression
report pointing at the NETDEV_TX_LOCKED removal change.

-- 
Ueimor

Re: [PATCH net-next 2/6] atl1c: remove private tx lock

[Florian Westphal]

Francois Romieu <romieu@fr.zoreil.com> wrote:
> Florian Westphal <fw@strlen.de> :
> [...]
> > diff --git a/drivers/net/ethernet/atheros/atl1c/atl1c_main.c b/drivers/net/ethernet/atheros/atl1c/atl1c_main.c
> > index d0084d4..a3200ea 100644
> > --- a/drivers/net/ethernet/atheros/atl1c/atl1c_main.c
> > +++ b/drivers/net/ethernet/atheros/atl1c/atl1c_main.c
> [...]
> > @@ -2217,16 +2215,10 @@ static netdev_tx_t atl1c_xmit_frame(struct sk_buff *skb,
> >  	}
> >  
> >  	tpd_req = atl1c_cal_tpd_req(skb);
> > -	if (!spin_trylock_irqsave(&adapter->tx_lock, flags)) {
> > -		if (netif_msg_pktdata(adapter))
> > -			dev_info(&adapter->pdev->dev, "tx locked\n");
> > -		return NETDEV_TX_LOCKED;
> > -	}
> >  
> >  	if (atl1c_tpd_avail(adapter, type) < tpd_req) {
> >  		/* no enough descriptor, just stop queue */
> >  		netif_stop_queue(netdev);
> > -		spin_unlock_irqrestore(&adapter->tx_lock, flags);
> >  		return NETDEV_TX_BUSY;
> >  	}
> >
> 
> Play it safe and keep the implicit local_irq_{save / restore} call ?
> 
> It may not be needed but it will help avoiding any unexpected regression
> report pointing at the NETDEV_TX_LOCKED removal change.

I thought about that but it doesn't prevent the irq handler from
running on another CPU, so leaving it around seemed like cargo culting
to me...

I don't have an atl1c, but the atl1e in my laptop seems to work fine
with the (similar) change.

If you disagree I can respin with local_irq_save of course, but, if
'playing it safe' is main goal then its simpler to convert
spin_trylock_irqsave to spin_lock_irqsave.

Re: [PATCH net-next 2/6] atl1c: remove private tx lock

[Francois Romieu]

Florian Westphal <fw@strlen.de> :
> Francois Romieu <romieu@fr.zoreil.com> wrote:
[...]
> > Play it safe and keep the implicit local_irq_{save / restore} call ?
> > 
> > It may not be needed but it will help avoiding any unexpected regression
> > report pointing at the NETDEV_TX_LOCKED removal change.
> 
> I thought about that but it doesn't prevent the irq handler from
> running on another CPU, so leaving it around seemed like cargo culting
> to me...

I don't mind removing it in a different patch at all. I'd rather see
the commit history underline that it's unrelated to whatever
NETDEV_TX_LOCKED / LLTX change.

> I don't have an atl1c, but the atl1e in my laptop seems to work fine
> with the (similar) change.
> 
> If you disagree I can respin with local_irq_save of course, but, if
> 'playing it safe' is main goal then its simpler to convert
> spin_trylock_irqsave to spin_lock_irqsave.

Your call, really.

-- 
Ueimor

[PATCH net-next 3/6] atle1: remove LLTX support and TX_UNLOCKED

[Florian Westphal]

similar to atl1c: lock is only used in ndo_start_xmit, but we also
advertised LLTX, so remove that as well and let core stack handle
tx locking.

Allows to remove the TX_LOCKED return value from the driver.

Cc: Jay Cliburn <jcliburn@gmail.com>
Cc: Chris Snook <chris.snook@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
---
 drivers/net/ethernet/atheros/atl1e/atl1e.h      |  1 -
 drivers/net/ethernet/atheros/atl1e/atl1e_main.c | 12 +-----------
 2 files changed, 1 insertion(+), 12 deletions(-)

diff --git a/drivers/net/ethernet/atheros/atl1e/atl1e.h b/drivers/net/ethernet/atheros/atl1e/atl1e.h
index 0212dac..632bb84 100644
--- a/drivers/net/ethernet/atheros/atl1e/atl1e.h
+++ b/drivers/net/ethernet/atheros/atl1e/atl1e.h
@@ -442,7 +442,6 @@ struct atl1e_adapter {
 	u16 link_duplex;
 
 	spinlock_t mdio_lock;
-	spinlock_t tx_lock;
 	atomic_t irq_sem;
 
 	struct work_struct reset_task;
diff --git a/drivers/net/ethernet/atheros/atl1e/atl1e_main.c b/drivers/net/ethernet/atheros/atl1e/atl1e_main.c
index 59a03a1..974713b 100644
--- a/drivers/net/ethernet/atheros/atl1e/atl1e_main.c
+++ b/drivers/net/ethernet/atheros/atl1e/atl1e_main.c
@@ -648,7 +648,6 @@ static int atl1e_sw_init(struct atl1e_adapter *adapter)
 
 	atomic_set(&adapter->irq_sem, 1);
 	spin_lock_init(&adapter->mdio_lock);
-	spin_lock_init(&adapter->tx_lock);
 
 	set_bit(__AT_DOWN, &adapter->flags);
 
@@ -1866,7 +1865,6 @@ static netdev_tx_t atl1e_xmit_frame(struct sk_buff *skb,
 					  struct net_device *netdev)
 {
 	struct atl1e_adapter *adapter = netdev_priv(netdev);
-	unsigned long flags;
 	u16 tpd_req = 1;
 	struct atl1e_tpd_desc *tpd;
 
@@ -1880,13 +1878,10 @@ static netdev_tx_t atl1e_xmit_frame(struct sk_buff *skb,
 		return NETDEV_TX_OK;
 	}
 	tpd_req = atl1e_cal_tdp_req(skb);
-	if (!spin_trylock_irqsave(&adapter->tx_lock, flags))
-		return NETDEV_TX_LOCKED;
 
 	if (atl1e_tpd_avail(adapter) < tpd_req) {
 		/* no enough descriptor, just stop queue */
 		netif_stop_queue(netdev);
-		spin_unlock_irqrestore(&adapter->tx_lock, flags);
 		return NETDEV_TX_BUSY;
 	}
 
@@ -1910,7 +1905,6 @@ static netdev_tx_t atl1e_xmit_frame(struct sk_buff *skb,
 
 	/* do TSO and check sum */
 	if (atl1e_tso_csum(adapter, skb, tpd) != 0) {
-		spin_unlock_irqrestore(&adapter->tx_lock, flags);
 		dev_kfree_skb_any(skb);
 		return NETDEV_TX_OK;
 	}
@@ -1921,10 +1915,7 @@ static netdev_tx_t atl1e_xmit_frame(struct sk_buff *skb,
 	}
 
 	atl1e_tx_queue(adapter, tpd_req, tpd);
-
-	netdev->trans_start = jiffies; /* NETIF_F_LLTX driver :( */
 out:
-	spin_unlock_irqrestore(&adapter->tx_lock, flags);
 	return NETDEV_TX_OK;
 }
 
@@ -2285,8 +2276,7 @@ static int atl1e_init_netdev(struct net_device *netdev, struct pci_dev *pdev)
 
 	netdev->hw_features = NETIF_F_SG | NETIF_F_HW_CSUM | NETIF_F_TSO |
 			      NETIF_F_HW_VLAN_CTAG_RX;
-	netdev->features = netdev->hw_features | NETIF_F_LLTX |
-			   NETIF_F_HW_VLAN_CTAG_TX;
+	netdev->features = netdev->hw_features | NETIF_F_HW_VLAN_CTAG_TX;
 	/* not enabled by default */
 	netdev->hw_features |= NETIF_F_RXALL | NETIF_F_RXFCS;
 	return 0;
-- 
2.7.3

[PATCH net-next 4/6] drivers: net: use NETDEV_TX_OK instead of NETDEV_TX_LOCKED

[Florian Westphal]

These drivers already call netif_stop_queue() so we should not be called
unless tx space is available.  Just free the skb and return TX_OK.

Followup patch will remove NETDEV_TX_LOCKED from the kernel.

Cc: linux-parisc@vger.kernel.org
Cc: linux-hams@vger.kernel.org
Cc: Thomas Sailer <t.sailer@alumni.ethz.ch>
Signed-off-by: Florian Westphal <fw@strlen.de>
---
 checkpatch chokes on this one, tulip uses spaces, not tabs...

 drivers/net/ethernet/amd/7990.c        | 8 +++++---
 drivers/net/ethernet/amd/a2065.c       | 7 +++----
 drivers/net/ethernet/dec/tulip/de4x5.c | 7 +++++--
 drivers/net/hamradio/baycom_epp.c      | 6 ++++--
 drivers/net/hamradio/hdlcdrv.c         | 6 ++++--
 5 files changed, 21 insertions(+), 13 deletions(-)

diff --git a/drivers/net/ethernet/amd/7990.c b/drivers/net/ethernet/amd/7990.c
index 66d0b73c..8e75755 100644
--- a/drivers/net/ethernet/amd/7990.c
+++ b/drivers/net/ethernet/amd/7990.c
@@ -543,11 +543,13 @@ int lance_start_xmit(struct sk_buff *skb, struct net_device *dev)
 	static int outs;
 	unsigned long flags;
 
-	if (!TX_BUFFS_AVAIL)
-		return NETDEV_TX_LOCKED;
-
 	netif_stop_queue(dev);
 
+	if (!TX_BUFFS_AVAIL) {
+		dev_consume_skb_any(skb);
+		return NETDEV_TX_OK;
+	}
+
 	skblen = skb->len;
 
 #ifdef DEBUG_DRIVER
diff --git a/drivers/net/ethernet/amd/a2065.c b/drivers/net/ethernet/amd/a2065.c
index 5613918..2a18d34 100644
--- a/drivers/net/ethernet/amd/a2065.c
+++ b/drivers/net/ethernet/amd/a2065.c
@@ -547,10 +547,8 @@ static netdev_tx_t lance_start_xmit(struct sk_buff *skb,
 
 	local_irq_save(flags);
 
-	if (!lance_tx_buffs_avail(lp)) {
-		local_irq_restore(flags);
-		return NETDEV_TX_LOCKED;
-	}
+	if (!lance_tx_buffs_avail(lp))
+		goto out_free;
 
 #ifdef DEBUG
 	/* dump the packet */
@@ -573,6 +571,7 @@ static netdev_tx_t lance_start_xmit(struct sk_buff *skb,
 
 	/* Kick the lance: transmit now */
 	ll->rdp = LE_C0_INEA | LE_C0_TDMD;
+ out_free:
 	dev_kfree_skb(skb);
 
 	local_irq_restore(flags);
diff --git a/drivers/net/ethernet/dec/tulip/de4x5.c b/drivers/net/ethernet/dec/tulip/de4x5.c
index 3acde3b..d88fbab 100644
--- a/drivers/net/ethernet/dec/tulip/de4x5.c
+++ b/drivers/net/ethernet/dec/tulip/de4x5.c
@@ -1465,7 +1465,7 @@ de4x5_queue_pkt(struct sk_buff *skb, struct net_device *dev)
 
     netif_stop_queue(dev);
     if (!lp->tx_enable)                   /* Cannot send for now */
-	return NETDEV_TX_LOCKED;
+		goto tx_err;
 
     /*
     ** Clean out the TX ring asynchronously to interrupts - sometimes the
@@ -1478,7 +1478,7 @@ de4x5_queue_pkt(struct sk_buff *skb, struct net_device *dev)
 
     /* Test if cache is already locked - requeue skb if so */
     if (test_and_set_bit(0, (void *)&lp->cache.lock) && !lp->interrupt)
-	return NETDEV_TX_LOCKED;
+		goto tx_err;
 
     /* Transmit descriptor ring full or stale skb */
     if (netif_queue_stopped(dev) || (u_long) lp->tx_skb[lp->tx_new] > 1) {
@@ -1519,6 +1519,9 @@ de4x5_queue_pkt(struct sk_buff *skb, struct net_device *dev)
     lp->cache.lock = 0;
 
     return NETDEV_TX_OK;
+tx_err:
+	dev_kfree_skb_any(skb);
+	return NETDEV_TX_OK;
 }
 
 /*
diff --git a/drivers/net/hamradio/baycom_epp.c b/drivers/net/hamradio/baycom_epp.c
index 72c9f1f..eb66638 100644
--- a/drivers/net/hamradio/baycom_epp.c
+++ b/drivers/net/hamradio/baycom_epp.c
@@ -780,8 +780,10 @@ static int baycom_send_packet(struct sk_buff *skb, struct net_device *dev)
 		dev_kfree_skb(skb);
 		return NETDEV_TX_OK;
 	}
-	if (bc->skb)
-		return NETDEV_TX_LOCKED;
+	if (bc->skb) {
+		dev_kfree_skb(skb);
+		return NETDEV_TX_OK;
+	}
 	/* strip KISS byte */
 	if (skb->len >= HDLCDRV_MAXFLEN+1 || skb->len < 3) {
 		dev_kfree_skb(skb);
diff --git a/drivers/net/hamradio/hdlcdrv.c b/drivers/net/hamradio/hdlcdrv.c
index 49fe59b..4bad0b8 100644
--- a/drivers/net/hamradio/hdlcdrv.c
+++ b/drivers/net/hamradio/hdlcdrv.c
@@ -412,8 +412,10 @@ static netdev_tx_t hdlcdrv_send_packet(struct sk_buff *skb,
 		dev_kfree_skb(skb);
 		return NETDEV_TX_OK;
 	}
-	if (sm->skb)
-		return NETDEV_TX_LOCKED;
+	if (sm->skb) {
+		dev_kfree_skb(skb);
+		return NETDEV_TX_OK;
+	}
 	netif_stop_queue(dev);
 	sm->skb = skb;
 	return NETDEV_TX_OK;
-- 
2.7.3

[PATCH net-next 5/6] drivers: net: remove NETDEV_TX_LOCKED

[Florian Westphal]

replace the trylock by a full spin_lock and remove TX_LOCKED return value.
Followup patch will remove TX_LOCKED from the kernel.

Cc: Jon Mason <jdmason@kudzu.us>
Cc: Andy Gospodarek <andy@greyhouse.net>
Signed-off-by: Florian Westphal <fw@strlen.de>
---
 drivers/net/ethernet/chelsio/cxgb/sge.c              | 3 +--
 drivers/net/ethernet/neterion/s2io.c                 | 9 +--------
 drivers/net/ethernet/oki-semi/pch_gbe/pch_gbe_main.c | 6 ++----
 drivers/net/ethernet/tehuti/tehuti.c                 | 8 +-------
 drivers/net/rionet.c                                 | 6 +-----
 5 files changed, 6 insertions(+), 26 deletions(-)

diff --git a/drivers/net/ethernet/chelsio/cxgb/sge.c b/drivers/net/ethernet/chelsio/cxgb/sge.c
index 526ea74..86f467a 100644
--- a/drivers/net/ethernet/chelsio/cxgb/sge.c
+++ b/drivers/net/ethernet/chelsio/cxgb/sge.c
@@ -1664,8 +1664,7 @@ static int t1_sge_tx(struct sk_buff *skb, struct adapter *adapter,
 	struct cmdQ *q = &sge->cmdQ[qid];
 	unsigned int credits, pidx, genbit, count, use_sched_skb = 0;
 
-	if (!spin_trylock(&q->lock))
-		return NETDEV_TX_LOCKED;
+	spin_lock(&q->lock);
 
 	reclaim_completed_tx(sge, q);
 
diff --git a/drivers/net/ethernet/neterion/s2io.c b/drivers/net/ethernet/neterion/s2io.c
index 9ba9758..2874dff 100644
--- a/drivers/net/ethernet/neterion/s2io.c
+++ b/drivers/net/ethernet/neterion/s2io.c
@@ -4021,7 +4021,6 @@ static netdev_tx_t s2io_xmit(struct sk_buff *skb, struct net_device *dev)
 	unsigned long flags = 0;
 	u16 vlan_tag = 0;
 	struct fifo_info *fifo = NULL;
-	int do_spin_lock = 1;
 	int offload_type;
 	int enable_per_list_interrupt = 0;
 	struct config_param *config = &sp->config;
@@ -4074,7 +4073,6 @@ static netdev_tx_t s2io_xmit(struct sk_buff *skb, struct net_device *dev)
 					queue += sp->udp_fifo_idx;
 					if (skb->len > 1024)
 						enable_per_list_interrupt = 1;
-					do_spin_lock = 0;
 				}
 			}
 		}
@@ -4084,12 +4082,7 @@ static netdev_tx_t s2io_xmit(struct sk_buff *skb, struct net_device *dev)
 			[skb->priority & (MAX_TX_FIFOS - 1)];
 	fifo = &mac_control->fifos[queue];
 
-	if (do_spin_lock)
-		spin_lock_irqsave(&fifo->tx_lock, flags);
-	else {
-		if (unlikely(!spin_trylock_irqsave(&fifo->tx_lock, flags)))
-			return NETDEV_TX_LOCKED;
-	}
+	spin_lock_irqsave(&fifo->tx_lock, flags);
 
 	if (sp->config.multiq) {
 		if (__netif_subqueue_stopped(dev, fifo->fifo_no)) {
diff --git a/drivers/net/ethernet/oki-semi/pch_gbe/pch_gbe_main.c b/drivers/net/ethernet/oki-semi/pch_gbe/pch_gbe_main.c
index 3b98b263b..4475dcc 100644
--- a/drivers/net/ethernet/oki-semi/pch_gbe/pch_gbe_main.c
+++ b/drivers/net/ethernet/oki-semi/pch_gbe/pch_gbe_main.c
@@ -2137,10 +2137,8 @@ static int pch_gbe_xmit_frame(struct sk_buff *skb, struct net_device *netdev)
 	struct pch_gbe_tx_ring *tx_ring = adapter->tx_ring;
 	unsigned long flags;
 
-	if (!spin_trylock_irqsave(&tx_ring->tx_lock, flags)) {
-		/* Collision - tell upper layer to requeue */
-		return NETDEV_TX_LOCKED;
-	}
+	spin_trylock_irqsave(&tx_ring->tx_lock, flags);
+
 	if (unlikely(!PCH_GBE_DESC_UNUSED(tx_ring))) {
 		netif_stop_queue(netdev);
 		spin_unlock_irqrestore(&tx_ring->tx_lock, flags);
diff --git a/drivers/net/ethernet/tehuti/tehuti.c b/drivers/net/ethernet/tehuti/tehuti.c
index 14c9d1b..2524a69 100644
--- a/drivers/net/ethernet/tehuti/tehuti.c
+++ b/drivers/net/ethernet/tehuti/tehuti.c
@@ -1610,7 +1610,6 @@ static inline int bdx_tx_space(struct bdx_priv *priv)
  * o NETDEV_TX_BUSY Cannot transmit packet, try later
  *   Usually a bug, means queue start/stop flow control is broken in
  *   the driver. Note: the driver must NOT put the skb in its DMA ring.
- * o NETDEV_TX_LOCKED Locking failed, please retry quickly.
  */
 static netdev_tx_t bdx_tx_transmit(struct sk_buff *skb,
 				   struct net_device *ndev)
@@ -1630,12 +1629,7 @@ static netdev_tx_t bdx_tx_transmit(struct sk_buff *skb,
 
 	ENTER;
 	local_irq_save(flags);
-	if (!spin_trylock(&priv->tx_lock)) {
-		local_irq_restore(flags);
-		DBG("%s[%s]: TX locked, returning NETDEV_TX_LOCKED\n",
-		    BDX_DRV_NAME, ndev->name);
-		return NETDEV_TX_LOCKED;
-	}
+	spin_lock(&priv->tx_lock);
 
 	/* build tx descriptor */
 	BDX_ASSERT(f->m.wptr >= f->m.memsz);	/* started with valid wptr */
diff --git a/drivers/net/rionet.c b/drivers/net/rionet.c
index 9cfe6ae..a31f461 100644
--- a/drivers/net/rionet.c
+++ b/drivers/net/rionet.c
@@ -179,11 +179,7 @@ static int rionet_start_xmit(struct sk_buff *skb, struct net_device *ndev)
 	unsigned long flags;
 	int add_num = 1;
 
-	local_irq_save(flags);
-	if (!spin_trylock(&rnet->tx_lock)) {
-		local_irq_restore(flags);
-		return NETDEV_TX_LOCKED;
-	}
+	spin_lock_irqsave(&rnet->tx_lock, flags);
 
 	if (is_multicast_ether_addr(eth->h_dest))
 		add_num = nets[rnet->mport->id].nact;
-- 
2.7.3

[PATCH net-next 6/6] net: remove NETDEV_TX_LOCKED support

[Florian Westphal]

No more users in the tree, remove NETDEV_TX_LOCKED support.
Adds another hole in softnet_stats struct, but better than keeping
the unused collision counter around.

Signed-off-by: Florian Westphal <fw@strlen.de>
---
 Documentation/networking/netdev-features.txt | 10 ++++-----
 Documentation/networking/netdevices.txt      |  9 +++-----
 include/linux/netdevice.h                    |  3 ---
 net/core/net-procfs.c                        |  3 ++-
 net/core/pktgen.c                            |  1 -
 net/sched/sch_generic.c                      | 32 ----------------------------
 6 files changed, 9 insertions(+), 49 deletions(-)

diff --git a/Documentation/networking/netdev-features.txt b/Documentation/networking/netdev-features.txt
index f310ede..7413eb0 100644
--- a/Documentation/networking/netdev-features.txt
+++ b/Documentation/networking/netdev-features.txt
@@ -131,13 +131,11 @@ stack. Driver should not change behaviour based on them.
 
  * LLTX driver (deprecated for hardware drivers)
 
-NETIF_F_LLTX should be set in drivers that implement their own locking in
-transmit path or don't need locking at all (e.g. software tunnels).
-In ndo_start_xmit, it is recommended to use a try_lock and return
-NETDEV_TX_LOCKED when the spin lock fails.  The locking should also properly
-protect against other callbacks (the rules you need to find out).
+NETIF_F_LLTX is meant to be used by drivers that don't need locking at all,
+e.g. software tunnels.
 
-Don't use it for new drivers.
+This is also used in a few legacy drivers that implement their
+own locking, don't use it for new (hardware) drivers.
 
  * netns-local device
 
diff --git a/Documentation/networking/netdevices.txt b/Documentation/networking/netdevices.txt
index 0b1cf6b..7fec206 100644
--- a/Documentation/networking/netdevices.txt
+++ b/Documentation/networking/netdevices.txt
@@ -69,10 +69,9 @@ ndo_start_xmit:
 
 	When the driver sets NETIF_F_LLTX in dev->features this will be
 	called without holding netif_tx_lock. In this case the driver
-	has to lock by itself when needed. It is recommended to use a try lock
-	for this and return NETDEV_TX_LOCKED when the spin lock fails.
-	The locking there should also properly protect against 
-	set_rx_mode. Note that the use of NETIF_F_LLTX is deprecated.
+	has to lock by itself when needed.
+	The locking there should also properly protect against
+	set_rx_mode. WARNING: use of NETIF_F_LLTX is deprecated.
 	Don't use it for new drivers.
 
 	Context: Process with BHs disabled or BH (timer),
@@ -83,8 +82,6 @@ ndo_start_xmit:
 	o NETDEV_TX_BUSY Cannot transmit packet, try later 
 	  Usually a bug, means queue start/stop flow control is broken in
 	  the driver. Note: the driver must NOT put the skb in its DMA ring.
-	o NETDEV_TX_LOCKED Locking failed, please retry quickly.
-	  Only valid when NETIF_F_LLTX is set.
 
 ndo_tx_timeout:
 	Synchronization: netif_tx_lock spinlock; all TX queues frozen.
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 1f6d5db..18d8394 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -106,7 +106,6 @@ enum netdev_tx {
 	__NETDEV_TX_MIN	 = INT_MIN,	/* make sure enum is signed */
 	NETDEV_TX_OK	 = 0x00,	/* driver took care of packet */
 	NETDEV_TX_BUSY	 = 0x10,	/* driver tx path was busy*/
-	NETDEV_TX_LOCKED = 0x20,	/* driver tx lock was already taken */
 };
 typedef enum netdev_tx netdev_tx_t;
 
@@ -831,7 +830,6 @@ struct tc_to_netdev {
  *	the queue before that can happen; it's for obsolete devices and weird
  *	corner cases, but the stack really does a non-trivial amount
  *	of useless work if you return NETDEV_TX_BUSY.
- *        (can also return NETDEV_TX_LOCKED iff NETIF_F_LLTX)
  *	Required; cannot be NULL.
  *
  * netdev_features_t (*ndo_fix_features)(struct net_device *dev,
@@ -2737,7 +2735,6 @@ struct softnet_data {
 	/* stats */
 	unsigned int		processed;
 	unsigned int		time_squeeze;
-	unsigned int		cpu_collision;
 	unsigned int		received_rps;
 #ifdef CONFIG_RPS
 	struct softnet_data	*rps_ipi_list;
diff --git a/net/core/net-procfs.c b/net/core/net-procfs.c
index 2bf8329..14d0934 100644
--- a/net/core/net-procfs.c
+++ b/net/core/net-procfs.c
@@ -162,7 +162,8 @@ static int softnet_seq_show(struct seq_file *seq, void *v)
 		   "%08x %08x %08x %08x %08x %08x %08x %08x %08x %08x %08x\n",
 		   sd->processed, sd->dropped, sd->time_squeeze, 0,
 		   0, 0, 0, 0, /* was fastroute */
-		   sd->cpu_collision, sd->received_rps, flow_limit_count);
+		   0,	/* was cpu_collision */
+		   sd->received_rps, flow_limit_count);
 	return 0;
 }
 
diff --git a/net/core/pktgen.c b/net/core/pktgen.c
index 20999aa..8604ae2 100644
--- a/net/core/pktgen.c
+++ b/net/core/pktgen.c
@@ -3472,7 +3472,6 @@ xmit_more:
 				     pkt_dev->odevname, ret);
 		pkt_dev->errors++;
 		/* fallthru */
-	case NETDEV_TX_LOCKED:
 	case NETDEV_TX_BUSY:
 		/* Retry it next time */
 		atomic_dec(&(pkt_dev->skb->users));
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 80742ed..9c77562 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -108,35 +108,6 @@ static struct sk_buff *dequeue_skb(struct Qdisc *q, bool *validate,
 	return skb;
 }
 
-static inline int handle_dev_cpu_collision(struct sk_buff *skb,
-					   struct netdev_queue *dev_queue,
-					   struct Qdisc *q)
-{
-	int ret;
-
-	if (unlikely(dev_queue->xmit_lock_owner == smp_processor_id())) {
-		/*
-		 * Same CPU holding the lock. It may be a transient
-		 * configuration error, when hard_start_xmit() recurses. We
-		 * detect it by checking xmit owner and drop the packet when
-		 * deadloop is detected. Return OK to try the next skb.
-		 */
-		kfree_skb_list(skb);
-		net_warn_ratelimited("Dead loop on netdevice %s, fix it urgently!\n",
-				     dev_queue->dev->name);
-		ret = qdisc_qlen(q);
-	} else {
-		/*
-		 * Another cpu is holding lock, requeue & delay xmits for
-		 * some time.
-		 */
-		__this_cpu_inc(softnet_data.cpu_collision);
-		ret = dev_requeue_skb(skb, q);
-	}
-
-	return ret;
-}
-
 /*
  * Transmit possibly several skbs, and handle the return status as
  * required. Holding the __QDISC___STATE_RUNNING bit guarantees that
@@ -174,9 +145,6 @@ int sch_direct_xmit(struct sk_buff *skb, struct Qdisc *q,
 	if (dev_xmit_complete(ret)) {
 		/* Driver sent out skb successfully or skb was consumed */
 		ret = qdisc_qlen(q);
-	} else if (ret == NETDEV_TX_LOCKED) {
-		/* Driver try lock failed */
-		ret = handle_dev_cpu_collision(skb, txq, q);
 	} else {
 		/* Driver returned NETDEV_TX_BUSY - requeue skb */
 		if (unlikely(ret != NETDEV_TX_BUSY))
-- 
2.7.3

Re: [PATCH net-next 0/6] net: core: remove TX_LOCKED support

[David Miller]

From: Florian Westphal <fw@strlen.de>
Date: Sun, 24 Apr 2016 21:38:08 +0200

>  Not that many users left, lets kill it.
> 
>  TX_LOCKED was meant to be used by LLTX drivers when spin_trylock()
>  failed.  Stack then re-queued if collisions happened on different
>  cpus or free'd the skb to prevent deadlocks.
> 
>  Most of the driver removal patches fall into one of three categories:
>  1. remove the driver-private tx lock (and LLTX flag), or...
>  2. convert spin_trylock to plain spin_lock, or...
>  3. convert TX_LOCKED to free+TX_OK
> 
>  Patches are grouped by these categories, last patch is the actual removal.
>  All driver changes were compile tested only with exception of atl1e.

This looks good to me, series applied, thanks Florian.