netdev - [PATCH] bnx2x: Prevent load reordering in tx completion processing

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Message-Id: <1563226910-21660-1-git-send-email-brking@linux.vnet.ibm.com>
Date:   Mon, 15 Jul 2019 16:41:50 -0500
From:   Brian King <brking@...ux.vnet.ibm.com>
To:     GR-everest-linux-l2@...vell.com
Cc:     skalluru@...vell.com, aelior@...vell.com, netdev@...r.kernel.org,
        Brian King <brking@...ux.vnet.ibm.com>
Subject: [PATCH] bnx2x: Prevent load reordering in tx completion processing

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@...ux.vnet.ibm.com>
---
 drivers/net/ethernet/broadcom/bnx2x/bnx2x_cmn.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/net/ethernet/broadcom/bnx2x/bnx2x_cmn.c b/drivers/net/ethernet/broadcom/bnx2x/bnx2x_cmn.c
index 656ed80..e2be5a6 100644
--- 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;
 
-- 
1.8.3.1