Commit fabf3a85 authored by Eric Dumazet's avatar Eric Dumazet Committed by Patrick McHardy
Browse files

netfilter: xt_statistic: remove nth_lock spinlock 



Use atomic_cmpxchg() to avoid dirtying a shared location.

xt_statistic_priv smp aligned to avoid sharing same cache line with
other stuff.

Signed-off-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: default avatarPatrick McHardy <kaber@trash.net>
parent a8b56389

net/netfilter/xt_statistic.c

+9 −10
Original line number Diff line number Diff line
@@ -18,8 +18,8 @@ 
#include <linux/netfilter/x_tables.h>



struct xt_statistic_priv {

	uint32_t count;

};

	atomic_t count;

} ____cacheline_aligned_in_smp;



MODULE_LICENSE("GPL");

MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
@@ -27,13 +27,12 @@ MODULE_DESCRIPTION("Xtables: statistics-based matching (\"Nth\", random)"); 
MODULE_ALIAS("ipt_statistic");

MODULE_ALIAS("ip6t_statistic");



static DEFINE_SPINLOCK(nth_lock);



static bool

statistic_mt(const struct sk_buff *skb, struct xt_action_param *par)

{

	const struct xt_statistic_info *info = par->matchinfo;

	bool ret = info->flags & XT_STATISTIC_INVERT;

	int nval, oval;



	switch (info->mode) {

	case XT_STATISTIC_MODE_RANDOM:
@@ -41,12 +40,12 @@ statistic_mt(const struct sk_buff *skb, struct xt_action_param *par) 
			ret = !ret;

		break;

	case XT_STATISTIC_MODE_NTH:

		spin_lock_bh(&nth_lock);

		if (info->master->count++ == info->u.nth.every) {

			info->master->count = 0;

		do {

			oval = atomic_read(&info->master->count);

			nval = (oval == info->u.nth.every) ? 0 : oval + 1;

		} while (atomic_cmpxchg(&info->master->count, oval, nval) != oval);

		if (nval == 0)

			ret = !ret;

		}

		spin_unlock_bh(&nth_lock);

		break;

	}
@@ -64,7 +63,7 @@ static int statistic_mt_check(const struct xt_mtchk_param *par) 
	info->master = kzalloc(sizeof(*info->master), GFP_KERNEL);

	if (info->master == NULL)

		return -ENOMEM;

	info->master->count = info->u.nth.count;

	atomic_set(&info->master->count, info->u.nth.count);



	return 0;

}