[Xen-changelog] If netfront fails to allocate a receive skbuff, push all pending

[Xen patchbot -unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User kaf24@xxxxxxxxxxxxxxxxxxxx
# Node ID 8b74b9603d5e1b8e4f2a0b970f1425b2840b17cc
# Parent  7c1f2e20123a61341c0355f97437f916e1b54095
If netfront fails to allocate a receive skbuff, push all pending
skbuffs out onto the shared ring. If there are no skbuffs to push,
schedule a timer to try again later. This will avoid interface
lockups in low-memory conditions.

Signed-off-by: Keir Fraser <keir@xxxxxxxxxxxxx>

diff -r 7c1f2e20123a -r 8b74b9603d5e 
linux-2.6-xen-sparse/drivers/xen/netfront/netfront.c
--- a/linux-2.6-xen-sparse/drivers/xen/netfront/netfront.c      Tue Dec 27 
10:40:33 2005
+++ b/linux-2.6-xen-sparse/drivers/xen/netfront/netfront.c      Wed Dec 28 
11:29:15 2005
@@ -116,6 +116,8 @@
 #define RX_MAX_TARGET NET_RX_RING_SIZE
        int rx_min_target, rx_max_target, rx_target;
        struct sk_buff_head rx_batch;
+
+       struct timer_list rx_refill_timer;
 
        /*
         * {tx,rx}_skbs store outstanding skbuffs. The first entry in each
@@ -517,6 +519,13 @@
 }
 
 
+static void rx_refill_timeout(unsigned long data)
+{
+       struct net_device *dev = (struct net_device *)data;
+       netif_rx_schedule(dev);
+}
+
+
 static void network_alloc_rx_buffers(struct net_device *dev)
 {
        unsigned short id;
@@ -534,7 +543,7 @@
         * Allocate skbuffs greedily, even though we batch updates to the
         * receive ring. This creates a less bursty demand on the memory
         * allocator, so should reduce the chance of failed allocation requests
-        *  both for ourself and for other kernel subsystems.
+        * both for ourself and for other kernel subsystems.
         */
        batch_target = np->rx_target - (req_prod - np->rx.rsp_cons);
        for (i = skb_queue_len(&np->rx_batch); i < batch_target; i++) {
@@ -545,8 +554,15 @@
                skb = alloc_xen_skb(
                        ((PAGE_SIZE - sizeof(struct skb_shared_info)) &
                         (-SKB_DATA_ALIGN(1))) - 16);
-               if (skb == NULL)
-                       break;
+               if (skb == NULL) {
+                       /* Any skbuffs queued for refill? Force them out. */
+                       if (i != 0)
+                               goto refill;
+                       /* Could not allocate any skbuffs. Try again later. */
+                       mod_timer(&np->rx_refill_timer,
+                                 jiffies + (HZ/10));
+                       return;
+               }
                __skb_queue_tail(&np->rx_batch, skb);
        }
 
@@ -554,6 +570,12 @@
        if (i < (np->rx_target/2))
                return;
 
+       /* Adjust our fill target if we risked running out of buffers. */
+       if (((req_prod - np->rx.sring->rsp_prod) < (np->rx_target / 4)) &&
+           ((np->rx_target *= 2) > np->rx_max_target))
+               np->rx_target = np->rx_max_target;
+
+ refill:
        for (i = 0; ; i++) {
                if ((skb = __skb_dequeue(&np->rx_batch)) == NULL)
                        break;
@@ -608,11 +630,6 @@
        /* Above is a suitable barrier to ensure backend will see requests. */
        np->rx.req_prod_pvt = req_prod + i;
        RING_PUSH_REQUESTS(&np->rx);
-
-       /* Adjust our fill target if we risked running out of buffers. */
-       if (((req_prod - np->rx.sring->rsp_prod) < (np->rx_target / 4)) &&
-           ((np->rx_target *= 2) > np->rx_max_target))
-               np->rx_target = np->rx_max_target;
 }
 
 
@@ -1077,6 +1094,10 @@
        np->rx_min_target = RX_MIN_TARGET;
        np->rx_max_target = RX_MAX_TARGET;
 
+       init_timer(&np->rx_refill_timer);
+       np->rx_refill_timer.data = (unsigned long)netdev;
+       np->rx_refill_timer.function = rx_refill_timeout;
+
        /* Initialise {tx,rx}_skbs as a free chain containing every entry. */
        for (i = 0; i <= NET_TX_RING_SIZE; i++) {
                np->tx_skbs[i] = (void *)((unsigned long) i+1);
@@ -1223,7 +1244,7 @@
        /* info->backend_state = BEST_DISCONNECTED; */
        spin_unlock(&info->rx_lock);
        spin_unlock_irq(&info->tx_lock);
-    
+
        end_access(info->tx_ring_ref, info->tx.sring);
        end_access(info->rx_ring_ref, info->rx.sring);
        info->tx_ring_ref = GRANT_INVALID_REF;
@@ -1234,6 +1255,8 @@
        if (info->irq)
                unbind_from_irqhandler(info->irq, info->netdev);
        info->evtchn = info->irq = 0;
+
+       del_timer_sync(&info->rx_refill_timer);
 }
 
 

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