xen/netfront: add netconsole support.

add polling interface to xen-netfront device to support netconsole

This patch also alters the spin_lock usage to use irqsave variant.
Documentation/networking/netdevices.txt states that start_xmit
can be called with interrupts disabled by netconsole and therefore using
the irqsave/restore locking in this function is looks correct.

Signed-off-by: Tina.Yang <tina.yang@oracle.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: Zhenzhong.Duan <zhenzhong.duan@oracle.com>
Tested-by: gurudas.pai <gurudas.pai@oracle.com>
[v1: Copy-n-pasted Ian Campbell comments]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index fa679057630f9152f418e9e2f9b60f549dded7e3..db638b4454e34b3b066dd24f82567be9b7432338 100644 (file)
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -489,6 +489,7 @@ static int xennet_start_xmit(struct sk_buff *skb, struct net_device *dev)
        int frags = skb_shinfo(skb)->nr_frags;
        unsigned int offset = offset_in_page(data);
        unsigned int len = skb_headlen(skb);
+       unsigned long flags;
 
        frags += DIV_ROUND_UP(offset + len, PAGE_SIZE);
        if (unlikely(frags > MAX_SKB_FRAGS + 1)) {
@@ -498,12 +499,12 @@ static int xennet_start_xmit(struct sk_buff *skb, struct net_device *dev)
                goto drop;
        }
 
-       spin_lock_irq(&np->tx_lock);
+       spin_lock_irqsave(&np->tx_lock, flags);
 
        if (unlikely(!netif_carrier_ok(dev) ||
                     (frags > 1 && !xennet_can_sg(dev)) ||
                     netif_needs_gso(skb, netif_skb_features(skb)))) {
-               spin_unlock_irq(&np->tx_lock);
+               spin_unlock_irqrestore(&np->tx_lock, flags);
                goto drop;
        }
 
@@ -574,7 +575,7 @@ static int xennet_start_xmit(struct sk_buff *skb, struct net_device *dev)
        if (!netfront_tx_slot_available(np))
                netif_stop_queue(dev);
 
-       spin_unlock_irq(&np->tx_lock);
+       spin_unlock_irqrestore(&np->tx_lock, flags);
 
        return NETDEV_TX_OK;
 
@@ -1228,6 +1229,33 @@ static int xennet_set_features(struct net_device *dev,
        return 0;
 }
 
+static irqreturn_t xennet_interrupt(int irq, void *dev_id)
+{
+       struct net_device *dev = dev_id;
+       struct netfront_info *np = netdev_priv(dev);
+       unsigned long flags;
+
+       spin_lock_irqsave(&np->tx_lock, flags);
+
+       if (likely(netif_carrier_ok(dev))) {
+               xennet_tx_buf_gc(dev);
+               /* Under tx_lock: protects access to rx shared-ring indexes. */
+               if (RING_HAS_UNCONSUMED_RESPONSES(&np->rx))
+                       napi_schedule(&np->napi);
+       }
+
+       spin_unlock_irqrestore(&np->tx_lock, flags);
+
+       return IRQ_HANDLED;
+}
+
+#ifdef CONFIG_NET_POLL_CONTROLLER
+static void xennet_poll_controller(struct net_device *dev)
+{
+       xennet_interrupt(0, dev);
+}
+#endif
+
 static const struct net_device_ops xennet_netdev_ops = {
        .ndo_open            = xennet_open,
        .ndo_uninit          = xennet_uninit,
@@ -1239,6 +1267,9 @@ static const struct net_device_ops xennet_netdev_ops = {
        .ndo_validate_addr   = eth_validate_addr,
        .ndo_fix_features    = xennet_fix_features,
        .ndo_set_features    = xennet_set_features,
+#ifdef CONFIG_NET_POLL_CONTROLLER
+       .ndo_poll_controller = xennet_poll_controller,
+#endif
 };
 
 static struct net_device * __devinit xennet_create_dev(struct xenbus_device *dev)
@@ -1448,26 +1479,6 @@ static int xen_net_read_mac(struct xenbus_device *dev, u8 mac[])
        return 0;
 }
 
-static irqreturn_t xennet_interrupt(int irq, void *dev_id)
-{
-       struct net_device *dev = dev_id;
-       struct netfront_info *np = netdev_priv(dev);
-       unsigned long flags;
-
-       spin_lock_irqsave(&np->tx_lock, flags);
-
-       if (likely(netif_carrier_ok(dev))) {
-               xennet_tx_buf_gc(dev);
-               /* Under tx_lock: protects access to rx shared-ring indexes. */
-               if (RING_HAS_UNCONSUMED_RESPONSES(&np->rx))
-                       napi_schedule(&np->napi);
-       }
-
-       spin_unlock_irqrestore(&np->tx_lock, flags);
-
-       return IRQ_HANDLED;
-}
-
 static int setup_netfront(struct xenbus_device *dev, struct netfront_info *info)
 {
        struct xen_netif_tx_sring *txs;