Re: [PATCH] netfilter: use per-CPU recursive lock {XIV}

Eric Dumazet
2009-04-24T05:04:11Z

Stephen Hemminger a écrit :
> In days of old in 2.6.29, netfilter did locketh using a
> lock of the reader kind when doing its table business, and do
> a writer when with pen in hand like a overworked accountant
> did replace the tables. This sucketh and caused the single
> lock to fly back and forth like a poor errant boy.
>
> But then netfilter was blessed with RCU and the performance
> was divine, but alas there were those that suffered for
> trying to replace their many rules one at a time.
>
> So now RCU must be vanquished from the scene, and better
> chastity belts be placed upon this valuable asset most dear.
> The locks that were but one are now replaced by one per suitor.
>
> The repair was made after much discussion involving
> Eric the wise, and Linus the foul. With flowers springing
> up amid the thorns some peace has finally prevailed and
> all is soothed. This patch and purple prose was penned by
> in honor of "Talk like Shakespeare" day.
>
> Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>

Philip Davis of the university’s School of English said :

"Shakespeare surprises the brain and catches it off guard in
a manner that produces a sudden burst of activity - a sense
of drama created out of the simplest of things."

http://www.physorg.com/news85664210.html

>
> ---
> What hath changed over the last two setting suns:
> * more words, mostly correct...
>
> * no need to locketh for writeh on current cpu tis
> always so
>
> * the locking of all cpu's on replace is always done as
> part of the get_counters cycle, so the sychronize swip
> in replace tables is gone with only a comment remaing
>
> include/linux/netfilter/x_tables.h | 55 ++++++++++++++--
> net/ipv4/netfilter/arp_tables.c | 125 ++++++++++--------------------------
> net/ipv4/netfilter/ip_tables.c | 126 ++++++++++---------------------------
> net/ipv6/netfilter/ip6_tables.c | 123 ++++++++++--------------------------
> net/netfilter/x_tables.c | 55 ++++++++--------
> 5 files changed, 188 insertions(+), 296 deletions(-)
>

>
> static int __init xt_init(void)
> {
> - int i, rv;
> + unsigned int i;
> + int rv;
> + static struct lock_class_key xt_lock_key[NR_CPUS];

Could we avoid this [NR_CPUS] thing ?

> +
> + for_each_possible_cpu(i) {
> + rwlock_t *lock = &per_cpu(xt_info_locks, i);
> +
> + rwlock_init(lock);
> + lockdep_set_class(lock, xt_lock_key+i);
> + }

Did you tried :

static DECLARE_PER_CPU(struct lock_class_key, xt_locks_key);

static int __init xt_init(void)
{
unsigned int i;
int rv;

for_each_possible_cpu(i) {
rwlock_t *lock = &per_cpu(xt_info_locks, i);

rwlock_init(lock);
lockdep_set_class(lock, &per_cpu(&xt_locks_key, i));
}
...

Thanks