bnx2x: Prevent load reordering in tx completion processing

[ Upstream commit ea811b795df24644a8eb760b493c43fba4450677 ]

This patch fixes an issue seen on Power systems with bnx2x which results
in the skb is NULL WARN_ON in bnx2x_free_tx_pkt firing due to the skb
pointer getting loaded in bnx2x_free_tx_pkt prior to the hw_cons
load in bnx2x_tx_int. Adding a read memory barrier resolves the issue.

Signed-off-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/net/ethernet/broadcom/bnx2x/bnx2x_cmn.c b/drivers/net/ethernet/broadcom/bnx2x/bnx2x_cmn.c
index 78a01880931c0853ff4a2dedfcb35034c5e690f6..9f07b85091f376a678dbd0c67e2388ffcabd6715 100644 (file)
--- a/drivers/net/ethernet/broadcom/bnx2x/bnx2x_cmn.c
+++ b/drivers/net/ethernet/broadcom/bnx2x/bnx2x_cmn.c
@@ -285,6 +285,9 @@ int bnx2x_tx_int(struct bnx2x *bp, struct bnx2x_fp_txdata *txdata)
        hw_cons = le16_to_cpu(*txdata->tx_cons_sb);
        sw_cons = txdata->tx_pkt_cons;
 
+       /* Ensure subsequent loads occur after hw_cons */
+       smp_rmb();
+
        while (sw_cons != hw_cons) {
                u16 pkt_cons;