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   1 From: Pablo Neira Ayuso <pablo@netfilter.org>
   2 Date: Sat, 17 Jul 2021 10:10:29 +0200
   3 Subject: [PATCH] netfilter: flowtable: avoid possible false sharing
   4
   5 The flowtable follows the same timeout approach as conntrack, use the
   6 same idiom as in cc16921351d8 ("netfilter: conntrack: avoid same-timeout
   7 update") but also include the fix provided by e37542ba111f ("netfilter:
   8 conntrack: avoid possible false sharing").
   9
  10 Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
  11 ---
  12
  13 --- a/net/netfilter/nf_flow_table_core.c
  14 +++ b/net/netfilter/nf_flow_table_core.c
  15 @@ -328,7 +328,11 @@ EXPORT_SYMBOL_GPL(flow_offload_add);
  16  void flow_offload_refresh(struct nf_flowtable *flow_table,
  17                           struct flow_offload *flow)
  18  {
  19 -       flow->timeout = nf_flowtable_time_stamp + flow_offload_get_timeout(flow);
  20 +       u32 timeout;
  21 +
  22 +       timeout = nf_flowtable_time_stamp + flow_offload_get_timeout(flow);
  23 +       if (READ_ONCE(flow->timeout) != timeout)
  24 +               WRITE_ONCE(flow->timeout, timeout);
  25
  26         if (likely(!nf_flowtable_hw_offload(flow_table)))
  27                 return;