Commit 49e8ae53 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

net_sched: sch_hfsc: implement lockless accesses to q->defcls 



Instead of relying on RTNL, hfsc_dump_qdisc() can use READ_ONCE()
annotation, paired with WRITE_ONCE() one in hfsc_change_qdisc().

Use READ_ONCE(q->defcls) in hfsc_classify() to
no longer acquire qdisc lock from hfsc_change_qdisc().

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 13a9965d

net/sched/sch_hfsc.c

+4 −5
Original line number Diff line number Diff line
@@ -1174,7 +1174,8 @@ hfsc_classify(struct sk_buff *skb, struct Qdisc *sch, int *qerr) 
	}



	/* classification failed, try default class */

	cl = hfsc_find_class(TC_H_MAKE(TC_H_MAJ(sch->handle), q->defcls), sch);

	cl = hfsc_find_class(TC_H_MAKE(TC_H_MAJ(sch->handle),

				       READ_ONCE(q->defcls)), sch);

	if (cl == NULL || cl->level > 0)

		return NULL;
@@ -1443,9 +1444,7 @@ hfsc_change_qdisc(struct Qdisc *sch, struct nlattr *opt, 
		return -EINVAL;

	qopt = nla_data(opt);



	sch_tree_lock(sch);

	q->defcls = qopt->defcls;

	sch_tree_unlock(sch);

	WRITE_ONCE(q->defcls, qopt->defcls);



	return 0;

}
@@ -1525,7 +1524,7 @@ hfsc_dump_qdisc(struct Qdisc *sch, struct sk_buff *skb) 
	unsigned char *b = skb_tail_pointer(skb);

	struct tc_hfsc_qopt qopt;



	qopt.defcls = q->defcls;

	qopt.defcls = READ_ONCE(q->defcls);

	if (nla_put(skb, TCA_OPTIONS, sizeof(qopt), &qopt))

		goto nla_put_failure;

	return skb->len;