[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>

2 files changed, 11 insertions, 3 deletions

diff --git a/include/linux/netpoll.h b/include/linux/netpoll.h
index bcd0ac33f592..be68d94b03d5 100644
--- 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 59ed186e4f46..d09affdbad3c 100644
--- 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;