netdev - [PATCH net-next 2/2] pfifo_fast: drop unneeded additional lock on dequeue

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Message-Id: <8a1740148995663939837bedb14f29716c7cf6f5.1526392746.git.pabeni@redhat.com>
Date:   Tue, 15 May 2018 16:24:37 +0200
From:   Paolo Abeni <pabeni@...hat.com>
To:     netdev@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        John Fastabend <john.fastabend@...il.com>,
        "Michael S. Tsirkin" <mst@...hat.com>
Subject: [PATCH net-next 2/2] pfifo_fast: drop unneeded additional lock on dequeue

After the previous patch, for NOLOCK qdiscs, q->seqlock is
always held when the dequeue() is invoked, we can drop
any additional locking to protect such operation.

Signed-off-by: Paolo Abeni <pabeni@...hat.com>
---
 include/linux/skb_array.h | 5 +++++
 net/sched/sch_generic.c   | 4 ++--
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/include/linux/skb_array.h b/include/linux/skb_array.h
index a6b6e8bb3d7b..62d9b0a6329f 100644
--- a/include/linux/skb_array.h
+++ b/include/linux/skb_array.h
@@ -97,6 +97,11 @@ static inline bool skb_array_empty_any(struct skb_array *a)
 	return ptr_ring_empty_any(&a->ring);
 }
 
+static inline struct sk_buff *__skb_array_consume(struct skb_array *a)
+{
+	return __ptr_ring_consume(&a->ring);
+}
+
 static inline struct sk_buff *skb_array_consume(struct skb_array *a)
 {
 	return ptr_ring_consume(&a->ring);
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index a126f16bc30b..760ab1b09f8b 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -656,7 +656,7 @@ static struct sk_buff *pfifo_fast_dequeue(struct Qdisc *qdisc)
 		if (__skb_array_empty(q))
 			continue;
 
-		skb = skb_array_consume_bh(q);
+		skb = __skb_array_consume(q);
 	}
 	if (likely(skb)) {
 		qdisc_qstats_cpu_backlog_dec(qdisc, skb);
@@ -697,7 +697,7 @@ static void pfifo_fast_reset(struct Qdisc *qdisc)
 		if (!q->ring.queue)
 			continue;
 
-		while ((skb = skb_array_consume_bh(q)) != NULL)
+		while ((skb = __skb_array_consume(q)) != NULL)
 			kfree_skb(skb);
 	}
 
-- 
2.14.3