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Commit a4298e45 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

net: add SOCK_RCU_FREE socket flag 



We want a generic way to insert an RCU grace period before socket
freeing for cases where RCU_SLAB_DESTROY_BY_RCU is adding too
much overhead.

SLAB_DESTROY_BY_RCU strict rules force us to take a reference
on the socket sk_refcnt, and it is a performance problem for UDP
encapsulation, or TCP synflood behavior, as many CPUs might
attempt the atomic operations on a shared sk_refcnt

UDP sockets and TCP listeners can set SOCK_RCU_FREE so that their
lookup can use traditional RCU rules, without refcount changes.
They can set the flag only once hashed and visible by other cpus.

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Cc: Tom Herbert <tom@herbertland.com>
Tested-by: default avatarTom Herbert <tom@herbertland.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 43e2dfb2

include/net/sock.h

+2 −0
Original line number Diff line number Diff line
@@ -438,6 +438,7 @@ struct sock { 
						  struct sk_buff *skb);

	void                    (*sk_destruct)(struct sock *sk);

	struct sock_reuseport __rcu	*sk_reuseport_cb;

	struct rcu_head		sk_rcu;

};



#define __sk_user_data(sk) ((*((void __rcu **)&(sk)->sk_user_data)))
@@ -720,6 +721,7 @@ enum sock_flags { 
		     */

	SOCK_FILTER_LOCKED, /* Filter cannot be changed anymore */

	SOCK_SELECT_ERR_QUEUE, /* Wake select on error queue */

	SOCK_RCU_FREE, /* wait rcu grace period in sk_destruct() */

};



#define SK_FLAGS_TIMESTAMP ((1UL << SOCK_TIMESTAMP) | (1UL << SOCK_TIMESTAMPING_RX_SOFTWARE))

net/core/sock.c

+13 −1
Original line number Diff line number Diff line
@@ -1419,8 +1419,12 @@ struct sock *sk_alloc(struct net *net, int family, gfp_t priority, 
}

EXPORT_SYMBOL(sk_alloc);



void sk_destruct(struct sock *sk)

/* Sockets having SOCK_RCU_FREE will call this function after one RCU

 * grace period. This is the case for UDP sockets and TCP listeners.

 */

static void __sk_destruct(struct rcu_head *head)

{

	struct sock *sk = container_of(head, struct sock, sk_rcu);

	struct sk_filter *filter;



	if (sk->sk_destruct)
@@ -1449,6 +1453,14 @@ void sk_destruct(struct sock *sk) 
	sk_prot_free(sk->sk_prot_creator, sk);

}



void sk_destruct(struct sock *sk)

{

	if (sock_flag(sk, SOCK_RCU_FREE))

		call_rcu(&sk->sk_rcu, __sk_destruct);

	else

		__sk_destruct(&sk->sk_rcu);

}



static void __sk_free(struct sock *sk)

{

	if (unlikely(sock_diag_has_destroy_listeners(sk) && sk->sk_net_refcnt))