Commit 6f542efc authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

net_sched: htb: do not acquire qdisc lock in dump operations 



htb_dump() and htb_dump_class() do not strictly need to acquire
qdisc lock to fetch qdisc and/or class parameters.

We hold RTNL and no changes can occur.

This reduces by 50% qdisc lock pressure while doing tc qdisc|class dump
operations.

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent e86800f9

net/sched/sch_htb.c

+8 −12
Original line number Diff line number Diff line
@@ -1062,12 +1062,13 @@ static int htb_init(struct Qdisc *sch, struct nlattr *opt) 


static int htb_dump(struct Qdisc *sch, struct sk_buff *skb)

{

	spinlock_t *root_lock = qdisc_root_sleeping_lock(sch);

	struct htb_sched *q = qdisc_priv(sch);

	struct nlattr *nest;

	struct tc_htb_glob gopt;



	spin_lock_bh(root_lock);

	/* Its safe to not acquire qdisc lock. As we hold RTNL,

	 * no change can happen on the qdisc parameters.

	 */



	gopt.direct_pkts = q->direct_pkts;

	gopt.version = HTB_VER;
@@ -1081,13 +1082,10 @@ static int htb_dump(struct Qdisc *sch, struct sk_buff *skb) 
	if (nla_put(skb, TCA_HTB_INIT, sizeof(gopt), &gopt) ||

	    nla_put_u32(skb, TCA_HTB_DIRECT_QLEN, q->direct_qlen))

		goto nla_put_failure;

	nla_nest_end(skb, nest);



	spin_unlock_bh(root_lock);

	return skb->len;

	return nla_nest_end(skb, nest);



nla_put_failure:

	spin_unlock_bh(root_lock);

	nla_nest_cancel(skb, nest);

	return -1;

}
@@ -1096,11 +1094,12 @@ static int htb_dump_class(struct Qdisc *sch, unsigned long arg, 
			  struct sk_buff *skb, struct tcmsg *tcm)

{

	struct htb_class *cl = (struct htb_class *)arg;

	spinlock_t *root_lock = qdisc_root_sleeping_lock(sch);

	struct nlattr *nest;

	struct tc_htb_opt opt;



	spin_lock_bh(root_lock);

	/* Its safe to not acquire qdisc lock. As we hold RTNL,

	 * no change can happen on the class parameters.

	 */

	tcm->tcm_parent = cl->parent ? cl->parent->common.classid : TC_H_ROOT;

	tcm->tcm_handle = cl->common.classid;

	if (!cl->level && cl->un.leaf.q)
@@ -1128,12 +1127,9 @@ static int htb_dump_class(struct Qdisc *sch, unsigned long arg, 
	    nla_put_u64(skb, TCA_HTB_CEIL64, cl->ceil.rate_bytes_ps))

		goto nla_put_failure;



	nla_nest_end(skb, nest);

	spin_unlock_bh(root_lock);

	return skb->len;

	return nla_nest_end(skb, nest);



nla_put_failure:

	spin_unlock_bh(root_lock);

	nla_nest_cancel(skb, nest);

	return -1;

}

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