From: Jakub Kicinski <kuba@kernel.org>
To: Yunsheng Lin <linyunsheng@huawei.com>
Cc: <davem@davemloft.net>, <olteanv@gmail.com>, <ast@kernel.org>,
<daniel@iogearbox.net>, <andriin@fb.com>, <edumazet@google.com>,
<weiwan@google.com>, <cong.wang@bytedance.com>,
<ap420073@gmail.com>, <netdev@vger.kernel.org>,
<linux-kernel@vger.kernel.org>, <linuxarm@openeuler.org>,
<mkl@pengutronix.de>, <linux-can@vger.kernel.org>
Subject: Re: [RFC v2] net: sched: implement TCQ_F_CAN_BYPASS for lockless qdisc
Date: Mon, 15 Mar 2021 11:53:32 -0700 [thread overview]
Message-ID: <20210315115332.1647e92b@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> (raw)
In-Reply-To: <1615777818-13969-1-git-send-email-linyunsheng@huawei.com>
On Mon, 15 Mar 2021 11:10:18 +0800 Yunsheng Lin wrote:
> @@ -606,6 +623,11 @@ static const u8 prio2band[TC_PRIO_MAX + 1] = {
> */
> struct pfifo_fast_priv {
> struct skb_array q[PFIFO_FAST_BANDS];
> +
> + /* protect against data race between enqueue/dequeue and
> + * qdisc->empty setting
> + */
> + spinlock_t lock;
> };
>
> static inline struct skb_array *band2list(struct pfifo_fast_priv *priv,
> @@ -623,7 +645,10 @@ static int pfifo_fast_enqueue(struct sk_buff *skb, struct Qdisc *qdisc,
> unsigned int pkt_len = qdisc_pkt_len(skb);
> int err;
>
> - err = skb_array_produce(q, skb);
> + spin_lock(&priv->lock);
> + err = __ptr_ring_produce(&q->ring, skb);
> + WRITE_ONCE(qdisc->empty, false);
> + spin_unlock(&priv->lock);
>
> if (unlikely(err)) {
> if (qdisc_is_percpu_stats(qdisc))
> @@ -642,6 +667,7 @@ static struct sk_buff *pfifo_fast_dequeue(struct Qdisc *qdisc)
> struct sk_buff *skb = NULL;
> int band;
>
> + spin_lock(&priv->lock);
> for (band = 0; band < PFIFO_FAST_BANDS && !skb; band++) {
> struct skb_array *q = band2list(priv, band);
>
> @@ -655,6 +681,7 @@ static struct sk_buff *pfifo_fast_dequeue(struct Qdisc *qdisc)
> } else {
> WRITE_ONCE(qdisc->empty, true);
> }
> + spin_unlock(&priv->lock);
>
> return skb;
> }
I thought pfifo was supposed to be "lockless" and this change
re-introduces a lock between producer and consumer, no?
next prev parent reply other threads:[~2021-03-15 18:54 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-13 2:47 [PATCH RFC] net: sched: implement TCQ_F_CAN_BYPASS for lockless qdisc Yunsheng Lin
2021-03-14 0:03 ` Vladimir Oltean
2021-03-14 10:15 ` Marc Kleine-Budde
2021-03-15 0:50 ` Yunsheng Lin
2021-03-15 3:10 ` [RFC v2] " Yunsheng Lin
2021-03-15 12:29 ` Vladimir Oltean
2021-03-15 13:09 ` Marc Kleine-Budde
2021-03-15 18:53 ` Jakub Kicinski [this message]
2021-03-16 0:35 ` Yunsheng Lin
2021-03-16 3:47 ` [Linuxarm] " Yunsheng Lin
2021-03-16 8:15 ` Eric Dumazet
2021-03-16 12:36 ` Yunsheng Lin
2021-03-16 22:48 ` Cong Wang
2021-03-17 1:14 ` Yunsheng Lin
2021-03-17 13:35 ` Toke Høiland-Jørgensen
2021-03-17 13:45 ` Jason A. Donenfeld
2021-03-18 7:33 ` [Linuxarm] " Yunsheng Lin
2021-03-19 18:15 ` Cong Wang
2021-03-22 0:55 ` Yunsheng Lin
2021-03-24 1:49 ` Cong Wang
2021-03-24 2:36 ` Yunsheng Lin
2021-03-19 19:03 ` Jason A. Donenfeld
2021-03-22 1:05 ` Yunsheng Lin
2021-03-18 7:10 ` Ahmad Fatoum
2021-03-18 7:46 ` Yunsheng Lin
2021-03-18 9:09 ` Ahmad Fatoum
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