[0/3] Don't use RCU for x_tables synchronization
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Message ID 20210304013116.8420-1-mark.tomlinson@alliedtelesis.co.nz
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  • Don't use RCU for x_tables synchronization
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Mark Tomlinson March 4, 2021, 1:31 a.m. UTC
The patches to change to using RCU synchronization in x_tables cause
updating tables to be slowed down by an order of magnitude. This has
been tried before, see https://lore.kernel.org/patchwork/patch/151796/
and ultimately was rejected. As mentioned in the patch description, a
different method can be used to ensure ordering of reads/writes. This
can simply be done by changing from smp_wmb() to smp_mb().

Mark Tomlinson (3):
  Revert "netfilter: x_tables: Update remaining dereference to RCU"
  Revert "netfilter: x_tables: Switch synchronization to RCU"
  netfilter: x_tables: Use correct memory barriers.

 include/linux/netfilter/x_tables.h |  7 ++---
 net/ipv4/netfilter/arp_tables.c    | 16 +++++-----
 net/ipv4/netfilter/ip_tables.c     | 16 +++++-----
 net/ipv6/netfilter/ip6_tables.c    | 16 +++++-----
 net/netfilter/x_tables.c           | 49 +++++++++++++++++++++---------
 5 files changed, 60 insertions(+), 44 deletions(-)