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

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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: Eric Dumazet <edumazet@google.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2024-04-18 07:32:45 +00:00 committed by David S. Miller
parent 13a9965de3
commit 49e8ae5370
1 changed files with 4 additions and 5 deletions
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9
net/sched/sch_hfsc.c
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@ -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;