[NETPOLL]: add retry timeout

Add limited retry logic to netpoll_send_skb

Each time we attempt to send, decrement our per-device retry counter.
On every successful send, we reset the counter.

We delay 50us between attempts with up to 20000 retries for a total of
1 second. After we've exhausted our retries, subsequent failed
attempts will try only once until reset by success.

Signed-off-by: Matt Mackall <mpm@selenic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/netpoll.h b/include/linux/netpoll.h
index bcd0ac3..be68d94 100644 (file)
--- a/include/linux/netpoll.h
+++ b/include/linux/netpoll.h
@@ -26,6 +26,7 @@ struct netpoll {
 struct netpoll_info {
        spinlock_t poll_lock;
        int poll_owner;
+       int tries;
        int rx_flags;
        spinlock_t rx_lock;
        struct netpoll *rx_np; /* netpoll that registered an rx_hook */

diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index 59ed186..d09affd 100644 (file)
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -33,6 +33,7 @@
 #define MAX_UDP_CHUNK 1460
 #define MAX_SKBS 32
 #define MAX_QUEUE_DEPTH (MAX_SKBS / 2)
+#define MAX_RETRIES 20000
 
 static DEFINE_SPINLOCK(skb_list_lock);
 static int nr_skbs;
@@ -265,7 +266,8 @@ static void netpoll_send_skb(struct netpoll *np, struct sk_buff *skb)
                return;
        }
 
-       while (1) {
+       do {
+               npinfo->tries--;
                spin_lock(&np->dev->xmit_lock);
                np->dev->xmit_lock_owner = smp_processor_id();
 
@@ -277,6 +279,7 @@ static void netpoll_send_skb(struct netpoll *np, struct sk_buff *skb)
                        np->dev->xmit_lock_owner = -1;
                        spin_unlock(&np->dev->xmit_lock);
                        netpoll_poll(np);
+                       udelay(50);
                        continue;
                }
 
@@ -285,12 +288,15 @@ static void netpoll_send_skb(struct netpoll *np, struct sk_buff *skb)
                spin_unlock(&np->dev->xmit_lock);
 
                /* success */
-               if(!status)
+               if(!status) {
+                       npinfo->tries = MAX_RETRIES; /* reset */
                        return;
+               }
 
                /* transmit busy */
                netpoll_poll(np);
-       }
+               udelay(50);
+       } while (npinfo->tries > 0);
 }
 
 void netpoll_send_udp(struct netpoll *np, const char *msg, int len)
@@ -642,6 +648,7 @@ int netpoll_setup(struct netpoll *np)
                npinfo->rx_np = NULL;
                npinfo->poll_lock = SPIN_LOCK_UNLOCKED;
                npinfo->poll_owner = -1;
+               npinfo->tries = MAX_RETRIES;
                npinfo->rx_lock = SPIN_LOCK_UNLOCKED;
        } else
                npinfo = ndev->npinfo;