Commit 6c00dc4f authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

net_sched: sch_pie: implement lockless pie_dump() 



Instead of relying on RTNL, pie_dump() can use READ_ONCE()
annotations, paired with WRITE_ONCE() ones in pie_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 293c7e2b

net/sched/sch_pie.c

+21 −18
Original line number Diff line number Diff line
@@ -156,36 +156,38 @@ static int pie_change(struct Qdisc *sch, struct nlattr *opt, 
		u32 target = nla_get_u32(tb[TCA_PIE_TARGET]);



		/* convert to pschedtime */

		q->params.target = PSCHED_NS2TICKS((u64)target * NSEC_PER_USEC);

		WRITE_ONCE(q->params.target,

			   PSCHED_NS2TICKS((u64)target * NSEC_PER_USEC));

	}



	/* tupdate is in jiffies */

	if (tb[TCA_PIE_TUPDATE])

		q->params.tupdate =

			usecs_to_jiffies(nla_get_u32(tb[TCA_PIE_TUPDATE]));

		WRITE_ONCE(q->params.tupdate,

			   usecs_to_jiffies(nla_get_u32(tb[TCA_PIE_TUPDATE])));



	if (tb[TCA_PIE_LIMIT]) {

		u32 limit = nla_get_u32(tb[TCA_PIE_LIMIT]);



		q->params.limit = limit;

		sch->limit = limit;

		WRITE_ONCE(q->params.limit, limit);

		WRITE_ONCE(sch->limit, limit);

	}



	if (tb[TCA_PIE_ALPHA])

		q->params.alpha = nla_get_u32(tb[TCA_PIE_ALPHA]);

		WRITE_ONCE(q->params.alpha, nla_get_u32(tb[TCA_PIE_ALPHA]));



	if (tb[TCA_PIE_BETA])

		q->params.beta = nla_get_u32(tb[TCA_PIE_BETA]);

		WRITE_ONCE(q->params.beta, nla_get_u32(tb[TCA_PIE_BETA]));



	if (tb[TCA_PIE_ECN])

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

		WRITE_ONCE(q->params.ecn, nla_get_u32(tb[TCA_PIE_ECN]));



	if (tb[TCA_PIE_BYTEMODE])

		q->params.bytemode = nla_get_u32(tb[TCA_PIE_BYTEMODE]);

		WRITE_ONCE(q->params.bytemode,

			   nla_get_u32(tb[TCA_PIE_BYTEMODE]));



	if (tb[TCA_PIE_DQ_RATE_ESTIMATOR])

		q->params.dq_rate_estimator =

				nla_get_u32(tb[TCA_PIE_DQ_RATE_ESTIMATOR]);

		WRITE_ONCE(q->params.dq_rate_estimator,

			   nla_get_u32(tb[TCA_PIE_DQ_RATE_ESTIMATOR]));



	/* Drop excess packets if new limit is lower */

	qlen = sch->q.qlen;
@@ -469,17 +471,18 @@ static int pie_dump(struct Qdisc *sch, struct sk_buff *skb) 


	/* convert target from pschedtime to us */

	if (nla_put_u32(skb, TCA_PIE_TARGET,

			((u32)PSCHED_TICKS2NS(q->params.target)) /

			((u32)PSCHED_TICKS2NS(READ_ONCE(q->params.target))) /

			NSEC_PER_USEC) ||

	    nla_put_u32(skb, TCA_PIE_LIMIT, sch->limit) ||

	    nla_put_u32(skb, TCA_PIE_LIMIT, READ_ONCE(sch->limit)) ||

	    nla_put_u32(skb, TCA_PIE_TUPDATE,

			jiffies_to_usecs(q->params.tupdate)) ||

	    nla_put_u32(skb, TCA_PIE_ALPHA, q->params.alpha) ||

	    nla_put_u32(skb, TCA_PIE_BETA, q->params.beta) ||

			jiffies_to_usecs(READ_ONCE(q->params.tupdate))) ||

	    nla_put_u32(skb, TCA_PIE_ALPHA, READ_ONCE(q->params.alpha)) ||

	    nla_put_u32(skb, TCA_PIE_BETA, READ_ONCE(q->params.beta)) ||

	    nla_put_u32(skb, TCA_PIE_ECN, q->params.ecn) ||

	    nla_put_u32(skb, TCA_PIE_BYTEMODE, q->params.bytemode) ||

	    nla_put_u32(skb, TCA_PIE_BYTEMODE,

			READ_ONCE(q->params.bytemode)) ||

	    nla_put_u32(skb, TCA_PIE_DQ_RATE_ESTIMATOR,

			q->params.dq_rate_estimator))

			READ_ONCE(q->params.dq_rate_estimator)))

		goto nla_put_failure;



	return nla_nest_end(skb, opts);