Commit 74030603 authored Jun 13, 2017 by WANG Cong Committed by David S. Miller Jun 14, 2017

net_sched: move tcf_lock down after gen_replace_estimator()



Laura reported a sleep-in-atomic kernel warning inside
tcf_act_police_init() which calls gen_replace_estimator() with
spinlock protection.

It is not necessary in this case, we already have RTNL lock here
so it is enough to protect concurrent writers. For the reader,
i.e. tcf_act_police(), it needs to make decision based on this
rate estimator, in the worst case we drop more/less packets than
necessary while changing the rate in parallel, it is still acceptable.

Reported-by: Laura Abbott <labbott@redhat.com>
Reported-by: Nick Huber <nicholashuber@gmail.com>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 20a3d5bf

net/sched/act_police.c

+3 −5

Original line number	Diff line number	Diff line
		@@ -132,21 +132,21 @@ static int tcf_act_police_init(struct net net, struct nlattr nla,
		}
		}

		spin_lock_bh(&police->tcf_lock);
		if (est) {
		err = gen_replace_estimator(&police->tcf_bstats, NULL,
		&police->tcf_rate_est,
		&police->tcf_lock,
		NULL, est);
		if (err)
		goto failure_unlock;
		goto failure;
		} else if (tb[TCA_POLICE_AVRATE] &&
		(ret == ACT_P_CREATED \|\|
		!gen_estimator_active(&police->tcf_rate_est))) {
		err = -EINVAL;
		goto failure_unlock;
		goto failure;
		}

		spin_lock_bh(&police->tcf_lock);
		/* No failure allowed after this point */
		police->tcfp_mtu = parm->mtu;
		if (police->tcfp_mtu == 0) {
		@@ -192,8 +192,6 @@ static int tcf_act_police_init(struct net net, struct nlattr nla,

		return ret;

		failure_unlock:
		spin_unlock_bh(&police->tcf_lock);
		failure:
		qdisc_put_rtab(P_tab);
		qdisc_put_rtab(R_tab);