netdev - [Patch net-next] net_sched: remove the unsafe __skb_array

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Date:   Thu, 21 Dec 2017 16:03:30 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     netdev@...r.kernel.org
Cc:     jakub.kicinski@...ronome.com, Cong Wang <xiyou.wangcong@...il.com>,
        John Fastabend <john.fastabend@...il.com>
Subject: [Patch net-next] net_sched: remove the unsafe __skb_array_empty()

__skb_array_empty() is only safe if array is never resized.
pfifo_fast_dequeue() is called in TX BH context and without
qdisc lock, so even after we disable BH on ->reset() path
we can still race with other CPU's.

Fixes: c5ad119fb6c0 ("net: sched: pfifo_fast use skb_array")
Reported-by: Jakub Kicinski <jakub.kicinski@...ronome.com>
Cc: John Fastabend <john.fastabend@...il.com>
Signed-off-by: Cong Wang <xiyou.wangcong@...il.com>
---
 net/sched/sch_generic.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 00ddb5f8f430..9279258ce060 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -622,9 +622,6 @@ static struct sk_buff *pfifo_fast_dequeue(struct Qdisc *qdisc)
 	for (band = 0; band < PFIFO_FAST_BANDS && !skb; band++) {
 		struct skb_array *q = band2list(priv, band);
 
-		if (__skb_array_empty(q))
-			continue;
-
 		skb = skb_array_consume_bh(q);
 	}
 	if (likely(skb)) {
-- 
2.13.0