From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH net-next 2/2] pfifo_fast: drop unneeded additional lock on dequeue Date: Tue, 15 May 2018 23:17:32 +0300 Message-ID: <20180515221013-mutt-send-email-mst@kernel.org> References: <8a1740148995663939837bedb14f29716c7cf6f5.1526392746.git.pabeni@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netdev@vger.kernel.org, "David S. Miller" , Jamal Hadi Salim , Cong Wang , Jiri Pirko , John Fastabend To: Paolo Abeni Return-path: Received: from mx3-rdu2.redhat.com ([66.187.233.73]:43704 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752419AbeEOURe (ORCPT ); Tue, 15 May 2018 16:17:34 -0400 Content-Disposition: inline In-Reply-To: <8a1740148995663939837bedb14f29716c7cf6f5.1526392746.git.pabeni@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: On Tue, May 15, 2018 at 04:24:37PM +0200, Paolo Abeni wrote: > 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 > --- > include/linux/skb_array.h | 5 +++++ > net/sched/sch_generic.c | 4 ++-- > 2 files changed, 7 insertions(+), 2 deletions(-) Is the seqlock taken during qdisc_change_tx_queue_len? We need to prevent that racing with dequeue. > 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