Discussion:
[PATCHv5 net-next 4/4] sunvnet: Remove irqsave/irqrestore on vio.lock
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Sowmini Varadhan
2014-10-22 22:12:52 UTC
Permalink
After the NAPIfication of sunvnet, we no longer need to
synchronize by doing irqsave/restore on vio.lock in the
I/O fastpath.

NAPI ->poll() is non-reentrant, so all RX processing occurs
strictly in a serialized environment. TX reclaim is done in NAPI
context, so the netif_tx_lock can be used to serialize
critical sections between Tx and Rx paths.

Signed-off-by: Sowmini Varadhan <***@oracle.com>
---
drivers/net/ethernet/sun/sunvnet.c | 30 +++++-------------------------
1 file changed, 5 insertions(+), 25 deletions(-)

diff --git a/drivers/net/ethernet/sun/sunvnet.c b/drivers/net/ethernet/sun/sunvnet.c
index 097ea5f..ac5cfc0 100644
--- a/drivers/net/ethernet/sun/sunvnet.c
+++ b/drivers/net/ethernet/sun/sunvnet.c
@@ -844,18 +844,6 @@ struct vnet_port *__tx_port_find(struct vnet *vp, struct sk_buff *skb)
return NULL;
}

-struct vnet_port *tx_port_find(struct vnet *vp, struct sk_buff *skb)
-{
- struct vnet_port *ret;
- unsigned long flags;
-
- spin_lock_irqsave(&vp->lock, flags);
- ret = __tx_port_find(vp, skb);
- spin_unlock_irqrestore(&vp->lock, flags);
-
- return ret;
-}
-
static struct sk_buff *vnet_clean_tx_ring(struct vnet_port *port,
unsigned *pending)
{
@@ -916,11 +904,10 @@ static void vnet_clean_timer_expire(unsigned long port0)
struct vnet_port *port = (struct vnet_port *)port0;
struct sk_buff *freeskbs;
unsigned pending;
- unsigned long flags;

- spin_lock_irqsave(&port->vio.lock, flags);
+ netif_tx_lock(port->vp->dev);
freeskbs = vnet_clean_tx_ring(port, &pending);
- spin_unlock_irqrestore(&port->vio.lock, flags);
+ netif_tx_unlock(port->vp->dev);

vnet_free_skbs(freeskbs);

@@ -973,7 +960,6 @@ static int vnet_start_xmit(struct sk_buff *skb, struct net_device *dev)
struct vnet_port *port = NULL;
struct vio_dring_state *dr;
struct vio_net_desc *d;
- unsigned long flags;
unsigned int len;
struct sk_buff *freeskbs = NULL;
int i, err, txi;
@@ -986,7 +972,7 @@ static int vnet_start_xmit(struct sk_buff *skb, struct net_device *dev)
goto out_dropped;

rcu_read_lock();
- port = tx_port_find(vp, skb);
+ port = __tx_port_find(vp, skb);
if (unlikely(!port))
goto out_dropped;

@@ -1022,8 +1008,6 @@ static int vnet_start_xmit(struct sk_buff *skb, struct net_device *dev)
goto out_dropped;
}

- spin_lock_irqsave(&port->vio.lock, flags);
-
dr = &port->vio.drings[VIO_DRIVER_TX_RING];
if (unlikely(vnet_tx_dring_avail(dr) < 1)) {
if (!netif_queue_stopped(dev)) {
@@ -1057,7 +1041,7 @@ static int vnet_start_xmit(struct sk_buff *skb, struct net_device *dev)
(LDC_MAP_SHADOW | LDC_MAP_DIRECT | LDC_MAP_RW));
if (err < 0) {
netdev_info(dev, "tx buffer map error %d\n", err);
- goto out_dropped_unlock;
+ goto out_dropped;
}
port->tx_bufs[txi].ncookies = err;

@@ -1110,7 +1094,7 @@ static int vnet_start_xmit(struct sk_buff *skb, struct net_device *dev)
netdev_info(dev, "TX trigger error %d\n", err);
d->hdr.state = VIO_DESC_FREE;
dev->stats.tx_carrier_errors++;
- goto out_dropped_unlock;
+ goto out_dropped;
}

ldc_start_done:
@@ -1126,7 +1110,6 @@ ldc_start_done:
netif_wake_queue(dev);
}

- spin_unlock_irqrestore(&port->vio.lock, flags);
(void)mod_timer(&port->clean_timer, jiffies + VNET_CLEAN_TIMEOUT);
rcu_read_unlock();

@@ -1134,9 +1117,6 @@ ldc_start_done:

return NETDEV_TX_OK;

-out_dropped_unlock:
- spin_unlock_irqrestore(&port->vio.lock, flags);
-
out_dropped:
if (pending)
(void)mod_timer(&port->clean_timer,
--
1.8.4.2
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