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| author | John Fastabend <john.fastabend@gmail.com> | 2017-12-07 09:55:45 -0800 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2017-12-08 13:32:25 -0500 |
| commit | a53851e2c3218aa30b77abd6e68cf1c371f15afe (patch) | |
| tree | 7003db6a43cb7a0853a497ce33e64333756e4b87 /include/net/sch_generic.h | |
| parent | d59f5ffa59d80ff3a2f3b56a9acea4310974c6d1 (diff) | |
| download | lwn-a53851e2c3218aa30b77abd6e68cf1c371f15afe.tar.gz lwn-a53851e2c3218aa30b77abd6e68cf1c371f15afe.zip | |
net: sched: explicit locking in gso_cpu fallback
This work is preparing the qdisc layer to support egress lockless
qdiscs. If we are running the egress qdisc lockless in the case we
overrun the netdev, for whatever reason, the netdev returns a busy
error code and the skb is parked on the gso_skb pointer. With many
cores all hitting this case at once its possible to have multiple
sk_buffs here so we turn gso_skb into a queue.
This should be the edge case and if we see this frequently then
the netdev/qdisc layer needs to back off.
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/net/sch_generic.h')
| -rw-r--r-- | include/net/sch_generic.h | 20 |
1 files changed, 12 insertions, 8 deletions
diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h index 6fd9a4e70066..9b9e4feda127 100644 --- a/include/net/sch_generic.h +++ b/include/net/sch_generic.h @@ -88,7 +88,7 @@ struct Qdisc { /* * For performance sake on SMP, we put highly modified fields at the end */ - struct sk_buff *gso_skb ____cacheline_aligned_in_smp; + struct sk_buff_head gso_skb ____cacheline_aligned_in_smp; struct qdisc_skb_head q; struct gnet_stats_basic_packed bstats; seqcount_t running; @@ -796,26 +796,30 @@ static inline struct sk_buff *qdisc_peek_head(struct Qdisc *sch) /* generic pseudo peek method for non-work-conserving qdisc */ static inline struct sk_buff *qdisc_peek_dequeued(struct Qdisc *sch) { + struct sk_buff *skb = skb_peek(&sch->gso_skb); + /* we can reuse ->gso_skb because peek isn't called for root qdiscs */ - if (!sch->gso_skb) { - sch->gso_skb = sch->dequeue(sch); - if (sch->gso_skb) { + if (!skb) { + skb = sch->dequeue(sch); + + if (skb) { + __skb_queue_head(&sch->gso_skb, skb); /* it's still part of the queue */ - qdisc_qstats_backlog_inc(sch, sch->gso_skb); + qdisc_qstats_backlog_inc(sch, skb); sch->q.qlen++; } } - return sch->gso_skb; + return skb; } /* use instead of qdisc->dequeue() for all qdiscs queried with ->peek() */ static inline struct sk_buff *qdisc_dequeue_peeked(struct Qdisc *sch) { - struct sk_buff *skb = sch->gso_skb; + struct sk_buff *skb = skb_peek(&sch->gso_skb); if (skb) { - sch->gso_skb = NULL; + skb = __skb_dequeue(&sch->gso_skb); qdisc_qstats_backlog_dec(sch, skb); sch->q.qlen--; } else { |