On May 2, 2007, at 2:57 PM, Scott Wood wrote:
The hardware must not see that is given ownership of a buffer until
it is
completely written, and when the driver receives ownership of a
buffer,
it must ensure that any other reads to the buffer reflect its final
state. Thus, I/O barriers are added where required.
Without this patch, I have observed GCC reordering the setting of
bdp->length and bdp->status in gfar_new_skb.
Signed-off-by: Scott Wood <[EMAIL PROTECTED]>
---
This is version 2 of this patch. I was told that eieio doesn't order
loads from main memory, so a sync is used instead. Also, due to
objectons that iobarrier_* shouldn't be used for main memory, I used
eieio() instead (a wmb() would be unnecessarily heavy).
I'd rather see a wmb() instead of eieio() to keep this code non-ppc
specific. (also, we implement wmb as eieio, so I don't keep the
comment about it being too heavy, unless you mean generically).
- k
drivers/net/gianfar.c | 3 +++
1 files changed, 3 insertions(+), 0 deletions(-)
diff --git a/drivers/net/gianfar.c b/drivers/net/gianfar.c
index b666a0c..b014d27 100644
--- a/drivers/net/gianfar.c
+++ b/drivers/net/gianfar.c
@@ -1025,6 +1025,7 @@ static int gfar_start_xmit(struct sk_buff
*skb, struct net_device *dev)
dev->trans_start = jiffies;
+ eieio();
txbdp->status = status;
/* If this was the last BD in the ring, the next one */
@@ -1301,6 +1302,7 @@ struct sk_buff * gfar_new_skb(struct
net_device *dev, struct rxbd8 *bdp)
bdp->length = 0;
/* Mark the buffer empty */
+ eieio();
bdp->status |= (RXBD_EMPTY | RXBD_INTERRUPT);
return skb;
@@ -1484,6 +1486,7 @@ int gfar_clean_rx_ring(struct net_device
*dev, int rx_work_limit)
bdp = priv->cur_rx;
while (!((bdp->status & RXBD_EMPTY) || (--rx_work_limit < 0))) {
+ rmb();
skb = priv->rx_skbuff[priv->skb_currx];
if (!(bdp->status &
--
1.5.0.3
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