Le mercredi 26 mai 2010 à 20:07 +0800, Changli Gao a écrit :
> On Wed, May 26, 2010 at 7:54 PM, Eric Dumazet <eric.dumazet@xxxxxxxxx> wrote:
> >
> > Signed-off-by: Eric Dumazet <eric.dumazet@xxxxxxxxx>
> > ---
> > diff --git a/net/netfilter/xt_statistic.c b/net/netfilter/xt_statistic.c
> > index 96e62b8..0114d2b 100644
> > --- a/net/netfilter/xt_statistic.c
> > +++ b/net/netfilter/xt_statistic.c
> > @@ -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@xxxxxxxxx>");
> > @@ -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 +40,14 @@ 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 + 1;
> > + if (nval == info->u.nth.every)
> > + nval = 0;
>
> these lines should be:
> if (oval == info->u.nth.every)
> nval = 0;
> else
> nval = oval + 1;
Good catch, this "every" counter is off by one...
Thanks
[PATCH v2] 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: Eric Dumazet <eric.dumazet@xxxxxxxxx>
---
net/netfilter/xt_statistic.c | 19 +++++++++----------
1 file changed, 9 insertions(+), 10 deletions(-)
diff --git a/net/netfilter/xt_statistic.c b/net/netfilter/xt_statistic.c
index 96e62b8..42ecb71 100644
--- a/net/netfilter/xt_statistic.c
+++ b/net/netfilter/xt_statistic.c
@@ -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@xxxxxxxxx>");
@@ -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;
}
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