Subject: Re: [PATCH] netfilter: use per-cpu spinlock rather than RCU (v3)

From: Stephen Hemminger <[email-masked]>
Date: Wed, 15 Apr 2009 09:31:44 -0700

On Wed, 15 Apr 2009 12:59:03 +0200
Patrick McHardy <[email-masked]> wrote:

> Eric Dumazet wrote:
> > Stephen Hemminger a écrit :
> >> This is an alternative version of ip/ip6/arp tables locking using
> >> per-cpu locks.  This avoids the overhead of synchronize_net() during
> >> update but still removes the expensive rwlock in earlier versions.
> >>
> >> The idea for this came from an earlier version done by Eric Dumazet.
> >> Locking is done per-cpu, the fast path locks on the current cpu
> >> and updates counters.  The slow case involves acquiring the locks on
> >> all cpu's.
> >>
> >> The mutex that was added for 2.6.30 in xt_table is unnecessary since
> >> there already is a mutex for xt[af].mutex that is held.
> >>
> >> Signed-off-by: Stephen Hemminger <[email-masked]>
> >>
> >> ---
> >>  include/linux/netfilter/x_tables.h |    5 -
> >>  net/ipv4/netfilter/arp_tables.c    |  112 +++++++++------------------------
> >>  net/ipv4/netfilter/ip_tables.c     |  123 +++++++++++--------------------------
> >>  net/ipv6/netfilter/ip6_tables.c    |  119 +++++++++++------------------------
> >>  net/netfilter/x_tables.c           |   28 --------
> >>  5 files changed, 110 insertions(+), 277 deletions(-)
> >>
> > 
> > Tested successfuly on my dev machine, thanks Stephen.
> > 
> > Signed-off-by: Eric Dumazet <[email-masked]>
> 
> Applied, thanks everyone. I'll give it some testing myself and
> will send it upstream tonight.

I am running it with LOCKDEP now to check for any issues.
It also needs to be validated with SMP configured kernel running on UP.
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