Commit c45bd26c authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

net_sched: sch_codel: implement lockless codel_dump() 



Instead of relying on RTNL, codel_dump() can use READ_ONCE()
annotations, paired with WRITE_ONCE() ones in codel_change().

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Reviewed-by: default avatarSimon Horman <horms@kernel.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 7253c1d1

net/sched/sch_codel.c

+18 −11
Original line number Diff line number Diff line
@@ -118,26 +118,31 @@ static int codel_change(struct Qdisc *sch, struct nlattr *opt, 
	if (tb[TCA_CODEL_TARGET]) {

		u32 target = nla_get_u32(tb[TCA_CODEL_TARGET]);



		q->params.target = ((u64)target * NSEC_PER_USEC) >> CODEL_SHIFT;

		WRITE_ONCE(q->params.target,

			   ((u64)target * NSEC_PER_USEC) >> CODEL_SHIFT);

	}



	if (tb[TCA_CODEL_CE_THRESHOLD]) {

		u64 val = nla_get_u32(tb[TCA_CODEL_CE_THRESHOLD]);



		q->params.ce_threshold = (val * NSEC_PER_USEC) >> CODEL_SHIFT;

		WRITE_ONCE(q->params.ce_threshold,

			   (val * NSEC_PER_USEC) >> CODEL_SHIFT);

	}



	if (tb[TCA_CODEL_INTERVAL]) {

		u32 interval = nla_get_u32(tb[TCA_CODEL_INTERVAL]);



		q->params.interval = ((u64)interval * NSEC_PER_USEC) >> CODEL_SHIFT;

		WRITE_ONCE(q->params.interval,

			   ((u64)interval * NSEC_PER_USEC) >> CODEL_SHIFT);

	}



	if (tb[TCA_CODEL_LIMIT])

		sch->limit = nla_get_u32(tb[TCA_CODEL_LIMIT]);

		WRITE_ONCE(sch->limit,

			   nla_get_u32(tb[TCA_CODEL_LIMIT]));



	if (tb[TCA_CODEL_ECN])

		q->params.ecn = !!nla_get_u32(tb[TCA_CODEL_ECN]);

		WRITE_ONCE(q->params.ecn,

			   !!nla_get_u32(tb[TCA_CODEL_ECN]));



	qlen = sch->q.qlen;

	while (sch->q.qlen > sch->limit) {
@@ -183,6 +188,7 @@ static int codel_init(struct Qdisc *sch, struct nlattr *opt, 
static int codel_dump(struct Qdisc *sch, struct sk_buff *skb)

{

	struct codel_sched_data *q = qdisc_priv(sch);

	codel_time_t ce_threshold;

	struct nlattr *opts;



	opts = nla_nest_start_noflag(skb, TCA_OPTIONS);
@@ -190,17 +196,18 @@ static int codel_dump(struct Qdisc *sch, struct sk_buff *skb) 
		goto nla_put_failure;



	if (nla_put_u32(skb, TCA_CODEL_TARGET,

			codel_time_to_us(q->params.target)) ||

			codel_time_to_us(READ_ONCE(q->params.target))) ||

	    nla_put_u32(skb, TCA_CODEL_LIMIT,

			sch->limit) ||

			READ_ONCE(sch->limit)) ||

	    nla_put_u32(skb, TCA_CODEL_INTERVAL,

			codel_time_to_us(q->params.interval)) ||

			codel_time_to_us(READ_ONCE(q->params.interval))) ||

	    nla_put_u32(skb, TCA_CODEL_ECN,

			q->params.ecn))

			READ_ONCE(q->params.ecn)))

		goto nla_put_failure;

	if (q->params.ce_threshold != CODEL_DISABLED_THRESHOLD &&

	ce_threshold = READ_ONCE(q->params.ce_threshold);

	if (ce_threshold != CODEL_DISABLED_THRESHOLD &&

	    nla_put_u32(skb, TCA_CODEL_CE_THRESHOLD,

			codel_time_to_us(q->params.ce_threshold)))

			codel_time_to_us(ce_threshold)))

		goto nla_put_failure;

	return nla_nest_end(skb, opts);