On Fri, 2017-04-28 at 10:04 -0700, Cong Wang wrote:
> After commit 1215e51edad1 ("ipv4: fix a deadlock in ip_ra_control")
> we always take RTNL lock for ip_ra_control() which is the only place
> we update the list ip_ra_chain, so the ip_ra_lock is no longer needed.
>
> As Eric points out, BH does not need to disable either, RCU readers
> don't care.
>
> Signed-off-by: Cong Wang <[email protected]>
> ---
> net/ipv4/ip_sockglue.c | 9 +--------
> 1 file changed, 1 insertion(+), 8 deletions(-)
>
> diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
> index 1d46d05..4c25458 100644
> --- a/net/ipv4/ip_sockglue.c
> +++ b/net/ipv4/ip_sockglue.c
> @@ -330,7 +330,6 @@ int ip_cmsg_send(struct sock *sk, struct msghdr *msg,
> struct ipcm_cookie *ipc,
> sent to multicast group to reach destination designated router.
> */
> struct ip_ra_chain __rcu *ip_ra_chain;
> -static DEFINE_SPINLOCK(ip_ra_lock);
>
>
> static void ip_ra_destroy_rcu(struct rcu_head *head)
> @@ -352,21 +351,17 @@ int ip_ra_control(struct sock *sk, unsigned char on,
>
> new_ra = on ? kmalloc(sizeof(*new_ra), GFP_KERNEL) : NULL;
>
> - spin_lock_bh(&ip_ra_lock);
> for (rap = &ip_ra_chain;
> - (ra = rcu_dereference_protected(*rap,
> - lockdep_is_held(&ip_ra_lock))) != NULL;
> + (ra = rtnl_dereference(*rap)) != NULL;
> rap = &ra->next) {
> if (ra->sk == sk) {
> if (on) {
> - spin_unlock_bh(&ip_ra_lock);
> kfree(new_ra);
> return -EADDRINUSE;
> }
> /* dont let ip_call_ra_chain() use sk again */
> ra->sk = NULL;
> RCU_INIT_POINTER(*rap, ra->next);
> - spin_unlock_bh(&ip_ra_lock);
>
> if (ra->destructor)
> ra->destructor(sk);
> @@ -381,7 +376,6 @@ int ip_ra_control(struct sock *sk, unsigned char on,
> }
> }
> if (!new_ra) {
> - spin_unlock_bh(&ip_ra_lock);
> return -ENOBUFS;
> }
Minor point : You could have removed the {}
Acked-by: Eric Dumazet <[email protected]>
Thanks !
