debug prints to track bnx2x_tx_free_pkts panic

drivers/net/ethernet/broadcom/bnx2x/bnx2x_cmn.c

@@ -218,6 +218,11 @@ static u16 bnx2x_free_tx_pkt(struct bnx2x *bp, struct bnx2x_fp_txdata *txdata,
 	int nbd;
 	u16 split_bd_len = 0;
 
+#if CONFIG_XEN_SME
+  int orig_nbd;
+  u16 orig_first_bd_idx;
+#endif
+
 	/* prefetch skb end pointer to speedup dev_kfree_skb() */
 	prefetch(&skb->end);
 
@@ -227,6 +232,10 @@ static u16 bnx2x_free_tx_pkt(struct bnx2x *bp, struct bnx2x_fp_txdata *txdata,
 	tx_start_bd = &txdata->tx_desc_ring[bd_idx].start_bd;
 
 	nbd = le16_to_cpu(tx_start_bd->nbd) - 1;
+#if CONFIG_XEN_SME
+  orig_nbd = nbd;
+  orig_first_bd_idx = bd_idx;
+#endif
 #ifdef BNX2X_STOP_ON_ERROR
 	if ((nbd - 1) > (MAX_SKB_FRAGS + 2)) {
 		BNX2X_ERR("BAD nbd!\n");
@@ -272,6 +281,16 @@ static u16 bnx2x_free_tx_pkt(struct bnx2x *bp, struct bnx2x_fp_txdata *txdata,
 	}
 
 	/* release skb */
+#if CONFIG_XEN_SME
+  if (!skb) {
+    BNX2X_ERR("NULL SKB TXQ[%d] idx %d nbd %d => %d bd_idx %d => %d\n"
+        "bd_prod %u pkt_prod %u bd_cons %u pkt_cons %u hw_cons %u"
+        , txdata->txq_index, idx, orig_nbd, nbd, orig_first_bd_idx, bd_idx
+        , txdata->tx_bd_prod, txdata->tx_pkt_prod, txdata->tx_bd_cons
+        , txdata->tx_pkt_cons, le16_to_cpu(*txdata->tx_cons_sb)
+        );
+  }
+#endif
 	WARN_ON(!skb);
 	if (likely(skb)) {
 		(*pkts_compl)++;