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Commit 2d550dba authored by Davide Caratti's avatar Davide Caratti Committed by David S. Miller
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net/sched: act_police: don't use spinlock in the data path 



use RCU instead of spinlocks, to protect concurrent read/write on
act_police configuration. This reduces the effects of contention in the
data path, in case multiple readers are present.

Signed-off-by: default avatarDavide Caratti <dcaratti@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 93be42f9

net/sched/act_police.c

+92 −64
Original line number Diff line number Diff line
@@ -22,8 +22,7 @@ 
#include <net/act_api.h>

#include <net/netlink.h>



struct tcf_police {

	struct tc_action	common;

struct tcf_police_params {

	int			tcfp_result;

	u32			tcfp_ewma_rate;

	s64			tcfp_burst;
@@ -36,6 +35,12 @@ struct tcf_police { 
	bool			rate_present;

	struct psched_ratecfg	peak;

	bool			peak_present;

	struct rcu_head rcu;

};



struct tcf_police {

	struct tc_action	common;

	struct tcf_police_params __rcu *params;

};



#define to_police(pc) ((struct tcf_police *)pc)
@@ -84,6 +89,7 @@ static int tcf_police_init(struct net *net, struct nlattr *nla, 
	struct tcf_police *police;

	struct qdisc_rate_table *R_tab = NULL, *P_tab = NULL;

	struct tc_action_net *tn = net_generic(net, police_net_id);

	struct tcf_police_params *new;

	bool exists = false;

	int size;
@@ -151,50 +157,60 @@ static int tcf_police_init(struct net *net, struct nlattr *nla, 
		goto failure;

	}



	spin_lock_bh(&police->tcf_lock);

	new = kzalloc(sizeof(*new), GFP_KERNEL);

	if (unlikely(!new)) {

		err = -ENOMEM;

		goto failure;

	}



	/* No failure allowed after this point */

	police->tcfp_mtu = parm->mtu;

	if (police->tcfp_mtu == 0) {

		police->tcfp_mtu = ~0;

	new->tcfp_mtu = parm->mtu;

	if (!new->tcfp_mtu) {

		new->tcfp_mtu = ~0;

		if (R_tab)

			police->tcfp_mtu = 255 << R_tab->rate.cell_log;

			new->tcfp_mtu = 255 << R_tab->rate.cell_log;

	}

	if (R_tab) {

		police->rate_present = true;

		psched_ratecfg_precompute(&police->rate, &R_tab->rate, 0);

		new->rate_present = true;

		psched_ratecfg_precompute(&new->rate, &R_tab->rate, 0);

		qdisc_put_rtab(R_tab);

	} else {

		police->rate_present = false;

		new->rate_present = false;

	}

	if (P_tab) {

		police->peak_present = true;

		psched_ratecfg_precompute(&police->peak, &P_tab->rate, 0);

		new->peak_present = true;

		psched_ratecfg_precompute(&new->peak, &P_tab->rate, 0);

		qdisc_put_rtab(P_tab);

	} else {

		police->peak_present = false;

		new->peak_present = false;

	}



	if (tb[TCA_POLICE_RESULT])

		police->tcfp_result = nla_get_u32(tb[TCA_POLICE_RESULT]);

	police->tcfp_burst = PSCHED_TICKS2NS(parm->burst);

	police->tcfp_toks = police->tcfp_burst;

	if (police->peak_present) {

		police->tcfp_mtu_ptoks = (s64) psched_l2t_ns(&police->peak,

							     police->tcfp_mtu);

		police->tcfp_ptoks = police->tcfp_mtu_ptoks;

		new->tcfp_result = nla_get_u32(tb[TCA_POLICE_RESULT]);

	new->tcfp_burst = PSCHED_TICKS2NS(parm->burst);

	new->tcfp_toks = new->tcfp_burst;

	if (new->peak_present) {

		new->tcfp_mtu_ptoks = (s64)psched_l2t_ns(&new->peak,

							 new->tcfp_mtu);

		new->tcfp_ptoks = new->tcfp_mtu_ptoks;

	}

	police->tcf_action = parm->action;



	if (tb[TCA_POLICE_AVRATE])

		police->tcfp_ewma_rate = nla_get_u32(tb[TCA_POLICE_AVRATE]);

		new->tcfp_ewma_rate = nla_get_u32(tb[TCA_POLICE_AVRATE]);



	spin_lock_bh(&police->tcf_lock);

	new->tcfp_t_c = ktime_get_ns();

	police->tcf_action = parm->action;

	rcu_swap_protected(police->params,

			   new,

			   lockdep_is_held(&police->tcf_lock));

	spin_unlock_bh(&police->tcf_lock);

	if (ret != ACT_P_CREATED)

		return ret;



	police->tcfp_t_c = ktime_get_ns();

	tcf_idr_insert(tn, *a);

	if (new)

		kfree_rcu(new, rcu);



	if (ret == ACT_P_CREATED)

		tcf_idr_insert(tn, *a);

	return ret;



failure:
@@ -208,68 +224,77 @@ static int tcf_police_act(struct sk_buff *skb, const struct tc_action *a, 
			  struct tcf_result *res)

{

	struct tcf_police *police = to_police(a);

	struct tcf_police_params *p;

	s64 now, toks, ptoks = 0;

	int ret;



	tcf_lastuse_update(&police->tcf_tm);

	bstats_cpu_update(this_cpu_ptr(police->common.cpu_bstats), skb);



	spin_lock(&police->tcf_lock);

	if (police->tcfp_ewma_rate) {

	ret = READ_ONCE(police->tcf_action);

	p = rcu_dereference_bh(police->params);



	if (p->tcfp_ewma_rate) {

		struct gnet_stats_rate_est64 sample;



		if (!gen_estimator_read(&police->tcf_rate_est, &sample) ||

		    sample.bps >= police->tcfp_ewma_rate) {

			ret = police->tcf_action;

		    sample.bps >= p->tcfp_ewma_rate)

			goto inc_overlimits;

	}

	}



	if (qdisc_pkt_len(skb) <= police->tcfp_mtu) {

		if (!police->rate_present) {

			ret = police->tcfp_result;

			goto unlock;

	if (qdisc_pkt_len(skb) <= p->tcfp_mtu) {

		if (!p->rate_present) {

			ret = p->tcfp_result;

			goto end;

		}



		now = ktime_get_ns();

		toks = min_t(s64, now - police->tcfp_t_c,

			     police->tcfp_burst);

		if (police->peak_present) {

			ptoks = toks + police->tcfp_ptoks;

			if (ptoks > police->tcfp_mtu_ptoks)

				ptoks = police->tcfp_mtu_ptoks;

			ptoks -= (s64) psched_l2t_ns(&police->peak,

		toks = min_t(s64, now - p->tcfp_t_c, p->tcfp_burst);

		if (p->peak_present) {

			ptoks = toks + p->tcfp_ptoks;

			if (ptoks > p->tcfp_mtu_ptoks)

				ptoks = p->tcfp_mtu_ptoks;

			ptoks -= (s64)psched_l2t_ns(&p->peak,

						    qdisc_pkt_len(skb));

		}

		toks += police->tcfp_toks;

		if (toks > police->tcfp_burst)

			toks = police->tcfp_burst;

		toks -= (s64) psched_l2t_ns(&police->rate, qdisc_pkt_len(skb));

		toks += p->tcfp_toks;

		if (toks > p->tcfp_burst)

			toks = p->tcfp_burst;

		toks -= (s64)psched_l2t_ns(&p->rate, qdisc_pkt_len(skb));

		if ((toks|ptoks) >= 0) {

			police->tcfp_t_c = now;

			police->tcfp_toks = toks;

			police->tcfp_ptoks = ptoks;

			ret = police->tcfp_result;

			p->tcfp_t_c = now;

			p->tcfp_toks = toks;

			p->tcfp_ptoks = ptoks;

			ret = p->tcfp_result;

			goto inc_drops;

		}

	}

	ret = police->tcf_action;



inc_overlimits:

	qstats_overlimit_inc(this_cpu_ptr(police->common.cpu_qstats));

inc_drops:

	if (ret == TC_ACT_SHOT)

		qstats_drop_inc(this_cpu_ptr(police->common.cpu_qstats));

unlock:

	spin_unlock(&police->tcf_lock);

end:

	return ret;

}



static void tcf_police_cleanup(struct tc_action *a)

{

	struct tcf_police *police = to_police(a);

	struct tcf_police_params *p;



	p = rcu_dereference_protected(police->params, 1);

	if (p)

		kfree_rcu(p, rcu);

}



static int tcf_police_dump(struct sk_buff *skb, struct tc_action *a,

			       int bind, int ref)

{

	unsigned char *b = skb_tail_pointer(skb);

	struct tcf_police *police = to_police(a);

	struct tcf_police_params *p;

	struct tc_police opt = {

		.index = police->tcf_index,

		.refcnt = refcount_read(&police->tcf_refcnt) - ref,
@@ -279,19 +304,21 @@ static int tcf_police_dump(struct sk_buff *skb, struct tc_action *a, 


	spin_lock_bh(&police->tcf_lock);

	opt.action = police->tcf_action;

	opt.mtu = police->tcfp_mtu;

	opt.burst = PSCHED_NS2TICKS(police->tcfp_burst);

	if (police->rate_present)

		psched_ratecfg_getrate(&opt.rate, &police->rate);

	if (police->peak_present)

		psched_ratecfg_getrate(&opt.peakrate, &police->peak);

	p = rcu_dereference_protected(police->params,

				      lockdep_is_held(&police->tcf_lock));

	opt.mtu = p->tcfp_mtu;

	opt.burst = PSCHED_NS2TICKS(p->tcfp_burst);

	if (p->rate_present)

		psched_ratecfg_getrate(&opt.rate, &p->rate);

	if (p->peak_present)

		psched_ratecfg_getrate(&opt.peakrate, &p->peak);

	if (nla_put(skb, TCA_POLICE_TBF, sizeof(opt), &opt))

		goto nla_put_failure;

	if (police->tcfp_result &&

	    nla_put_u32(skb, TCA_POLICE_RESULT, police->tcfp_result))

	if (p->tcfp_result &&

	    nla_put_u32(skb, TCA_POLICE_RESULT, p->tcfp_result))

		goto nla_put_failure;

	if (police->tcfp_ewma_rate &&

	    nla_put_u32(skb, TCA_POLICE_AVRATE, police->tcfp_ewma_rate))

	if (p->tcfp_ewma_rate &&

	    nla_put_u32(skb, TCA_POLICE_AVRATE, p->tcfp_ewma_rate))

		goto nla_put_failure;



	t.install = jiffies_to_clock_t(jiffies - police->tcf_tm.install);
@@ -330,6 +357,7 @@ static struct tc_action_ops act_police_ops = { 
	.init		=	tcf_police_init,

	.walk		=	tcf_police_walker,

	.lookup		=	tcf_police_search,

	.cleanup	=	tcf_police_cleanup,

	.size		=	sizeof(struct tcf_police),

};