Staging: octeon-ethernet: Fix race freeing transmit buffers.

[pandora-kernel.git] / drivers / staging / octeon / ethernet-tx.c

diff --git a/drivers/staging/octeon/ethernet-tx.c b/drivers/staging/octeon/ethernet-tx.c
index bfd3dd2..81a8513 100644 (file)
--- a/drivers/staging/octeon/ethernet-tx.c
+++ b/drivers/staging/octeon/ethernet-tx.c
@@ -47,6 +47,7 @@
 
 #include "ethernet-defines.h"
 #include "octeon-ethernet.h"
+#include "ethernet-tx.h"
 #include "ethernet-util.h"
 
 #include "cvmx-wqe.h"
@@ -82,8 +83,10 @@ int cvm_oct_xmit(struct sk_buff *skb, struct net_device *dev)
        uint64_t old_scratch2;
        int dropped;
        int qos;
+       int queue_it_up;
        struct octeon_ethernet *priv = netdev_priv(dev);
-       int32_t in_use;
+       int32_t skb_to_free;
+       int32_t undo;
        int32_t buffers_to_free;
 #if REUSE_SKBUFFS_WITHOUT_FREE
        unsigned char *fpa_head;
@@ -120,15 +123,15 @@ int cvm_oct_xmit(struct sk_buff *skb, struct net_device *dev)
                old_scratch2 = cvmx_scratch_read64(CVMX_SCR_SCRATCH + 8);
 
                /*
-                * Assume we're going to be able t osend this
-                * packet. Fetch and increment the number of pending
-                * packets for output.
+                * Fetch and increment the number of packets to be
+                * freed.
                 */
                cvmx_fau_async_fetch_and_add32(CVMX_SCR_SCRATCH + 8,
                                               FAU_NUM_PACKET_BUFFERS_TO_FREE,
                                               0);
                cvmx_fau_async_fetch_and_add32(CVMX_SCR_SCRATCH,
-                                              priv->fau + qos * 4, 1);
+                                              priv->fau + qos * 4,
+                                              MAX_SKB_TO_FREE);
        }
 
        /*
@@ -286,15 +289,29 @@ dont_put_skbuff_in_hw:
        if (USE_ASYNC_IOBDMA) {
                /* Get the number of skbuffs in use by the hardware */
                CVMX_SYNCIOBDMA;
-               in_use = cvmx_scratch_read64(CVMX_SCR_SCRATCH);
+               skb_to_free = cvmx_scratch_read64(CVMX_SCR_SCRATCH);
                buffers_to_free = cvmx_scratch_read64(CVMX_SCR_SCRATCH + 8);
        } else {
                /* Get the number of skbuffs in use by the hardware */
-               in_use = cvmx_fau_fetch_and_add32(priv->fau + qos * 4, 1);
+               skb_to_free = cvmx_fau_fetch_and_add32(priv->fau + qos * 4,
+                                                      MAX_SKB_TO_FREE);
                buffers_to_free =
                    cvmx_fau_fetch_and_add32(FAU_NUM_PACKET_BUFFERS_TO_FREE, 0);
        }
 
+       /*
+        * We try to claim MAX_SKB_TO_FREE buffers.  If there were not
+        * that many available, we have to un-claim (undo) any that
+        * were in excess.  If skb_to_free is positive we will free
+        * that many buffers.
+        */
+       undo = skb_to_free > 0 ?
+               MAX_SKB_TO_FREE : skb_to_free + MAX_SKB_TO_FREE;
+       if (undo > 0)
+               cvmx_fau_atomic_add32(priv->fau+qos*4, -undo);
+       skb_to_free = -skb_to_free > MAX_SKB_TO_FREE ?
+               MAX_SKB_TO_FREE : -skb_to_free;
+
        /*
         * If we're sending faster than the receive can free them then
         * don't do the HW free.
@@ -330,38 +347,31 @@ dont_put_skbuff_in_hw:
                cvmx_scratch_write64(CVMX_SCR_SCRATCH + 8, old_scratch2);
        }
 
+       queue_it_up = 0;
        if (unlikely(dropped)) {
                dev_kfree_skb_any(skb);
-               cvmx_fau_atomic_add32(priv->fau + qos * 4, -1);
                priv->stats.tx_dropped++;
        } else {
                if (USE_SKBUFFS_IN_HW) {
                        /* Put this packet on the queue to be freed later */
                        if (pko_command.s.dontfree)
-                               skb_queue_tail(&priv->tx_free_list[qos], skb);
-                       else {
+                               queue_it_up = 1;
+                       else
                                cvmx_fau_atomic_add32
                                    (FAU_NUM_PACKET_BUFFERS_TO_FREE, -1);
-                               cvmx_fau_atomic_add32(priv->fau + qos * 4, -1);
-                       }
                } else {
                        /* Put this packet on the queue to be freed later */
-                       skb_queue_tail(&priv->tx_free_list[qos], skb);
+                       queue_it_up = 1;
                }
        }
 
-       /* Free skbuffs not in use by the hardware, possibly two at a time */
-       if (skb_queue_len(&priv->tx_free_list[qos]) > in_use) {
+       if (queue_it_up) {
                spin_lock(&priv->tx_free_list[qos].lock);
-               /*
-                * Check again now that we have the lock. It might
-                * have changed.
-                */
-               if (skb_queue_len(&priv->tx_free_list[qos]) > in_use)
-                       dev_kfree_skb(__skb_dequeue(&priv->tx_free_list[qos]));
-               if (skb_queue_len(&priv->tx_free_list[qos]) > in_use)
-                       dev_kfree_skb(__skb_dequeue(&priv->tx_free_list[qos]));
+               __skb_queue_tail(&priv->tx_free_list[qos], skb);
+               cvm_oct_free_tx_skbs(priv, skb_to_free, qos, 0);
                spin_unlock(&priv->tx_free_list[qos].lock);
+       } else {
+               cvm_oct_free_tx_skbs(priv, skb_to_free, qos, 1);
        }
 
        return 0;