* [PATCH nf 1/2] netfilter: flowtable: avoid possible false sharing
@ 2021-07-17 8:28 Pablo Neira Ayuso
2021-07-17 8:28 ` [PATCH nf 2/2] netfilter: nft_last: " Pablo Neira Ayuso
0 siblings, 1 reply; 2+ messages in thread
From: Pablo Neira Ayuso @ 2021-07-17 8:28 UTC (permalink / raw)
To: netfilter-devel
The flowtable follows the same timeout approach as conntrack, use the
same idiom as in cc16921351d8 ("netfilter: conntrack: avoid same-timeout
update") but also include the fix provided by e37542ba111f ("netfilter:
conntrack: avoid possible false sharing").
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
net/netfilter/nf_flow_table_core.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/net/netfilter/nf_flow_table_core.c b/net/netfilter/nf_flow_table_core.c
index 1e50908b1b7e..551976e4284c 100644
--- a/net/netfilter/nf_flow_table_core.c
+++ b/net/netfilter/nf_flow_table_core.c
@@ -331,7 +331,11 @@ EXPORT_SYMBOL_GPL(flow_offload_add);
void flow_offload_refresh(struct nf_flowtable *flow_table,
struct flow_offload *flow)
{
- flow->timeout = nf_flowtable_time_stamp + flow_offload_get_timeout(flow);
+ u32 timeout;
+
+ timeout = nf_flowtable_time_stamp + flow_offload_get_timeout(flow);
+ if (READ_ONCE(flow->timeout) != timeout)
+ WRITE_ONCE(flow->timeout, timeout);
if (likely(!nf_flowtable_hw_offload(flow_table)))
return;
--
2.30.2
^ permalink raw reply related [flat|nested] 2+ messages in thread
* [PATCH nf 2/2] netfilter: nft_last: avoid possible false sharing
2021-07-17 8:28 [PATCH nf 1/2] netfilter: flowtable: avoid possible false sharing Pablo Neira Ayuso
@ 2021-07-17 8:28 ` Pablo Neira Ayuso
0 siblings, 0 replies; 2+ messages in thread
From: Pablo Neira Ayuso @ 2021-07-17 8:28 UTC (permalink / raw)
To: netfilter-devel
Use the idiom described in:
https://github.com/google/ktsan/wiki/READ_ONCE-and-WRITE_ONCE#it-may-improve-performance
Moreover, prevent a compiler optimization.
Fixes: 836382dc2471 ("netfilter: nf_tables: add last expression")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
net/netfilter/nft_last.c | 20 +++++++++++++-------
1 file changed, 13 insertions(+), 7 deletions(-)
diff --git a/net/netfilter/nft_last.c b/net/netfilter/nft_last.c
index 8088b99f2ee3..f29f205e9992 100644
--- a/net/netfilter/nft_last.c
+++ b/net/netfilter/nft_last.c
@@ -48,24 +48,30 @@ static void nft_last_eval(const struct nft_expr *expr,
{
struct nft_last_priv *priv = nft_expr_priv(expr);
- priv->last_jiffies = jiffies;
- priv->last_set = 1;
+ if (READ_ONCE(priv->last_set) == 0)
+ WRITE_ONCE(priv->last_set, 1);
+ if (READ_ONCE(priv->last_jiffies) != jiffies)
+ WRITE_ONCE(priv->last_jiffies, jiffies);
}
static int nft_last_dump(struct sk_buff *skb, const struct nft_expr *expr)
{
struct nft_last_priv *priv = nft_expr_priv(expr);
+ unsigned long last_jiffies = READ_ONCE(priv->last_jiffies);
+ u32 last_set = READ_ONCE(priv->last_set);
__be64 msecs;
- if (time_before(jiffies, priv->last_jiffies))
- priv->last_set = 0;
+ if (time_before(jiffies, last_jiffies)) {
+ WRITE_ONCE(priv->last_set, 0);
+ last_set = 0;
+ }
- if (priv->last_set)
- msecs = nf_jiffies64_to_msecs(jiffies - priv->last_jiffies);
+ if (last_set)
+ msecs = nf_jiffies64_to_msecs(jiffies - last_jiffies);
else
msecs = 0;
- if (nla_put_be32(skb, NFTA_LAST_SET, htonl(priv->last_set)) ||
+ if (nla_put_be32(skb, NFTA_LAST_SET, htonl(last_set)) ||
nla_put_be64(skb, NFTA_LAST_MSECS, msecs, NFTA_LAST_PAD))
goto nla_put_failure;
--
2.30.2
^ permalink raw reply related [flat|nested] 2+ messages in thread
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