Re: [PATCH 08/14] netfilter: ipset: Introduce RCU locking instead of rwlock per set in the core

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Sun, Nov 30, 2014 at 07:56:59PM +0100, Jozsef Kadlecsik wrote:
> Signed-off-by: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>
> ---
>  include/linux/netfilter/ipset/ip_set.h         |  6 ++++-
>  include/linux/netfilter/ipset/ip_set_timeout.h | 27 ++++++++------------
>  net/netfilter/ipset/ip_set_core.c              | 35 +++++++++++++-------------
>  3 files changed, 34 insertions(+), 34 deletions(-)
> 
> diff --git a/include/linux/netfilter/ipset/ip_set.h b/include/linux/netfilter/ipset/ip_set.h
> index f1606fa..d5d5bcd 100644
> --- a/include/linux/netfilter/ipset/ip_set.h
> +++ b/include/linux/netfilter/ipset/ip_set.h
> @@ -223,7 +223,7 @@ struct ip_set {
>  	/* The name of the set */
>  	char name[IPSET_MAXNAMELEN];
>  	/* Lock protecting the set data */
> -	rwlock_t lock;
> +	spinlock_t lock;
>  	/* References to the set */
>  	u32 ref;
>  	/* The core set type */
> @@ -322,6 +322,10 @@ ip_set_update_counter(struct ip_set_counter *counter,
>  	}
>  }
>  
> +#define ip_set_rcu_deref(t)		\
> +	rcu_dereference_index_check(t,	\
> +		rcu_read_lock_held() || rcu_read_lock_bh_held())
> +

This is not used from this patch itself?

>  static inline void
>  ip_set_get_skbinfo(struct ip_set_skbinfo *skbinfo,
>  		      const struct ip_set_ext *ext,
> diff --git a/include/linux/netfilter/ipset/ip_set_timeout.h b/include/linux/netfilter/ipset/ip_set_timeout.h
> index 83c2f9e..1d6a935 100644
> --- a/include/linux/netfilter/ipset/ip_set_timeout.h
> +++ b/include/linux/netfilter/ipset/ip_set_timeout.h
> @@ -40,38 +40,33 @@ ip_set_timeout_uget(struct nlattr *tb)
>  }
>  
>  static inline bool
> -ip_set_timeout_test(unsigned long timeout)
> +ip_set_timeout_expired(unsigned long *t)
>  {
> -	return timeout == IPSET_ELEM_PERMANENT ||
> -	       time_is_after_jiffies(timeout);
> -}
> -
> -static inline bool
> -ip_set_timeout_expired(unsigned long *timeout)
> -{
> -	return *timeout != IPSET_ELEM_PERMANENT &&
> -	       time_is_before_jiffies(*timeout);
> +	return *t != IPSET_ELEM_PERMANENT && time_is_before_jiffies(*t);
>  }
>  
>  static inline void
> -ip_set_timeout_set(unsigned long *timeout, u32 t)
> +ip_set_timeout_set(unsigned long *timeout, u32 value)
>  {
> -	if (!t) {
> +	unsigned long t;
> +
> +	if (!value) {
>  		*timeout = IPSET_ELEM_PERMANENT;
>  		return;
>  	}
>  
> -	*timeout = msecs_to_jiffies(t * 1000) + jiffies;
> -	if (*timeout == IPSET_ELEM_PERMANENT)
> +	t = msecs_to_jiffies(value * MSEC_PER_SEC) + jiffies;
> +	if (t == IPSET_ELEM_PERMANENT)
>  		/* Bingo! :-) */
> -		(*timeout)--;
> +		t--;
> +	*timeout = t;
>  }
>  
>  static inline u32
>  ip_set_timeout_get(unsigned long *timeout)
>  {
>  	return *timeout == IPSET_ELEM_PERMANENT ? 0 :
> -		jiffies_to_msecs(*timeout - jiffies)/1000;
> +		jiffies_to_msecs(*timeout - jiffies)/MSEC_PER_SEC;
>  }
>  
>  #endif	/* __KERNEL__ */
> diff --git a/net/netfilter/ipset/ip_set_core.c b/net/netfilter/ipset/ip_set_core.c
> index 912e5a0..9fb2610 100644
> --- a/net/netfilter/ipset/ip_set_core.c
> +++ b/net/netfilter/ipset/ip_set_core.c
> @@ -217,6 +217,7 @@ ip_set_type_register(struct ip_set_type *type)
>  		 type->revision_min, type->revision_max);
>  unlock:
>  	ip_set_type_unlock();
> +	synchronize_rcu();

Why this synchronize_rcu()?

ip_set_type_register() didn't publish any new object in the unlock
path.