[PATCH] iseries_veth: Replace lock-protected atomic with an ordinary variable

The iseries_veth driver uses atomic ops to manipulate the in_use field of
one of its per-connection structures. However all references to the
flag occur while the connection's lock is held, so the atomic ops aren't
necessary.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>

1 files changed, 7 insertions, 6 deletions

diff --git a/drivers/net/iseries_veth.c b/drivers/net/iseries_veth.c
index 231b2d2d3264..427ac8cc56be 100644
--- a/drivers/net/iseries_veth.c
+++ b/drivers/net/iseries_veth.c
@@ -117,7 +117,7 @@ struct veth_msg {
         struct veth_msg *next;
         struct VethFramesData data;
         int token;
-        unsigned long in_use;
+        int in_use;
         struct sk_buff *skb;
         struct device *dev;
 };
@@ -957,6 +957,8 @@ static int veth_transmit_to_one(struct sk_buff *skb, HvLpIndex rlp,
                 goto drop;
         }
 
+        msg->in_use = 1;
+
         dma_length = skb->len;
         dma_address = dma_map_single(port->dev, skb->data,
                                      dma_length, DMA_TO_DEVICE);
@@ -971,7 +973,6 @@ static int veth_transmit_to_one(struct sk_buff *skb, HvLpIndex rlp,
         msg->data.addr[0] = dma_address;
         msg->data.len[0] = dma_length;
         msg->data.eofmask = 1 << VETH_EOF_SHIFT;
-        set_bit(0, &(msg->in_use));
         rc = veth_signaldata(cnx, VethEventTypeFrames, msg->token, &msg->data);
 
         if (rc != HvLpEvent_Rc_Good)
@@ -981,10 +982,8 @@ static int veth_transmit_to_one(struct sk_buff *skb, HvLpIndex rlp,
         return 0;
 
  recycle_and_drop:
+        /* we free the skb below, so tell veth_recycle_msg() not to. */
         msg->skb = NULL;
-        /* need to set in use to make veth_recycle_msg in case this
-         * was a mapping failure */
-        set_bit(0, &msg->in_use);
         veth_recycle_msg(cnx, msg);
  drop:
         port->stats.tx_errors++;
@@ -1066,12 +1065,14 @@ static int veth_start_xmit(struct sk_buff *skb, struct net_device *dev)
         return 0;
 }
 
+/* You must hold the connection's lock when you call this function. */
 static void veth_recycle_msg(struct veth_lpar_connection *cnx,
                              struct veth_msg *msg)
 {
         u32 dma_address, dma_length;
 
-        if (test_and_clear_bit(0, &msg->in_use)) {
+        if (msg->in_use) {
+                msg->in_use = 0;
                 dma_address = msg->data.addr[0];
                 dma_length = msg->data.len[0];