netdev - [PATCH net-next 5/7] ibmvnic: Fixup atomic API usage

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Message-Id: <20170409041157.47642.96627.stgit@ltcalpine2-lp14.aus.stglabs.ibm.com>
Date:   Sun, 09 Apr 2017 00:11:57 -0400
From:   Nathan Fontenot <nfont@...ux.vnet.ibm.com>
To:     netdev@...r.kernel.org, tlfalcon@...ux.vnet.ibm.com,
        jallen@...ux.vnet.ibm.com
Cc:     brking@...ux.vnet.ibm.com, muvic@...ux.vnet.ibm.com
Subject: [PATCH net-next 5/7] ibmvnic: Fixup atomic API usage

From: Brian King <brking@...ux.vnet.ibm.com>

Replace a couple of modifications of an atomic followed
by a read of the atomic, which is no longer atomic, to
use atomic_XX_return variants to avoid race conditions.

Signed-off-by: Brian King <brking@...ux.vnet.ibm.com>
Signed-off-by: Nathan Fontenot <nfont@...ux.vnet.ibm.com>
---
 drivers/net/ethernet/ibm/ibmvnic.c |   10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/ibm/ibmvnic.c b/drivers/net/ethernet/ibm/ibmvnic.c
index 5f9aad8..4e27518 100644
--- a/drivers/net/ethernet/ibm/ibmvnic.c
+++ b/drivers/net/ethernet/ibm/ibmvnic.c
@@ -964,9 +964,8 @@ static int ibmvnic_xmit(struct sk_buff *skb, struct net_device *netdev)
 		goto out;
 	}
 
-	atomic_inc(&tx_scrq->used);
-
-	if (atomic_read(&tx_scrq->used) >= adapter->req_tx_entries_per_subcrq) {
+	if (atomic_inc_return(&tx_scrq->used) 
+					>= adapter->req_tx_entries_per_subcrq) {
 		netdev_info(netdev, "Stopping queue %d\n", queue_num);
 		netif_stop_subqueue(netdev, queue_num);
 	}
@@ -1501,9 +1500,8 @@ static int ibmvnic_complete_tx(struct ibmvnic_adapter *adapter,
 			}
 
 			if (txbuff->last_frag) {
-				atomic_dec(&scrq->used);
-
-				if (atomic_read(&scrq->used) <=
+				if (atomic_sub_return(next->tx_comp.num_comps,
+						      &scrq->used) <=
 				    (adapter->req_tx_entries_per_subcrq / 2) &&
 				    netif_subqueue_stopped(adapter->netdev,
 							   txbuff->skb)) {