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Subject[PATCH 8/12] 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.


---
drivers/net/iseries_veth.c | 13 +++++++------
1 files changed, 7 insertions(+), 6 deletions(-)
Index: veth-dev/drivers/net/iseries_veth.c
===================================================================
--- veth-dev.orig/drivers/net/iseries_veth.c
+++ veth-dev/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;
};
@@ -959,6 +959,8 @@ static int veth_transmit_to_one(struct s
goto drop;
}

+ msg->in_use = 1;
+
dma_length = skb->len;
dma_address = dma_map_single(port->dev, skb->data,
dma_length, DMA_TO_DEVICE);
@@ -973,7 +975,6 @@ static int veth_transmit_to_one(struct s
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)
@@ -983,10 +984,8 @@ static int veth_transmit_to_one(struct s
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++;
@@ -1068,12 +1067,14 @@ static int veth_start_xmit(struct sk_buf
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];

-
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