netdev - [PATCH 1/5 net-next] ibmvnic: Fix TX descriptor tracking again

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Date:   Mon, 26 Feb 2018 18:10:55 -0600
From:   Thomas Falcon <tlfalcon@...ux.vnet.ibm.com>
To:     netdev@...r.kernel.org
Cc:     jallen@...ux.vnet.ibm.com, nfont@...ux.vnet.ibm.com,
        Thomas Falcon <tlfalcon@...ux.vnet.ibm.com>
Subject: [PATCH 1/5 net-next] ibmvnic: Fix TX descriptor tracking again

Sorry, the previous change introduced a race condition between
transmit completion processing and tracking TX descriptors. If a
completion is received before the number of descriptors is logged,
the number of descriptors will be add but not removed. After enough
times, this could halt the transmit queue forever.

Log the number of descriptors used by a transmit before sending.
I stress tested the fix on two different systems running over the
weekend without any issues.

Signed-off-by: Thomas Falcon <tlfalcon@...ux.vnet.ibm.com>
---
 drivers/net/ethernet/ibm/ibmvnic.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/ibm/ibmvnic.c b/drivers/net/ethernet/ibm/ibmvnic.c
index 5a86a916492c..32ee202de13a 100644
--- a/drivers/net/ethernet/ibm/ibmvnic.c
+++ b/drivers/net/ethernet/ibm/ibmvnic.c
@@ -1482,6 +1482,7 @@ static int ibmvnic_xmit(struct sk_buff *skb, struct net_device *netdev)
 	if ((*hdrs >> 7) & 1) {
 		build_hdr_descs_arr(tx_buff, &num_entries, *hdrs);
 		tx_crq.v1.n_crq_elem = num_entries;
+		tx_buff->num_entries = num_entries;
 		tx_buff->indir_arr[0] = tx_crq;
 		tx_buff->indir_dma = dma_map_single(dev, tx_buff->indir_arr,
 						    sizeof(tx_buff->indir_arr),
@@ -1500,6 +1501,7 @@ static int ibmvnic_xmit(struct sk_buff *skb, struct net_device *netdev)
 					       (u64)tx_buff->indir_dma,
 					       (u64)num_entries);
 	} else {
+		tx_buff->num_entries = num_entries;
 		lpar_rc = send_subcrq(adapter, handle_array[queue_num],
 				      &tx_crq);
 	}
@@ -1536,7 +1538,6 @@ static int ibmvnic_xmit(struct sk_buff *skb, struct net_device *netdev)
 		netif_stop_subqueue(netdev, queue_num);
 	}
 
-	tx_buff->num_entries = num_entries;
 	tx_packets++;
 	tx_bytes += skb->len;
 	txq->trans_start = jiffies;
-- 
2.15.0