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net: Convert TCP/DCCP listening hash tables to use RCU

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This is the last step to be able to perform full RCU lookups
in __inet_lookup() : After established/timewait tables, we
add RCU lookups to listening hash table.

The only trick here is that a socket of a given type (TCP ipv4,
TCP ipv6, ...) can now flight between two different tables
(established and listening) during a RCU grace period, so we
must use different 'nulls' end-of-chain values for two tables.

We define a large value :

#define LISTENING_NULLS_BASE (1U << 29)

So that slots in listening table are guaranteed to have different
end-of-chain values than slots in established table. A reader can
still detect it finished its lookup in the right chain.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2008-11-23 17:22:55 -08:00 • committed by David S. Miller
parent 8c862c23e2
commit c25eb3bfb9
5 changed files with 145 additions and 114 deletions
Download patch file Download diff file Expand all files Collapse all files

92
net/ipv6/inet6_hashtables.c
View file

@ -33,7 +33,7 @@ void __inet6_hash(struct sock *sk)
ilb = &hashinfo->listening_hash[inet_sk_listen_hashfn(sk)];
spin_lock(&ilb->lock);
__sk_add_node(sk, &ilb->head);
__sk_nulls_add_node_rcu(sk, &ilb->head);
spin_unlock(&ilb->lock);
} else {
unsigned int hash;
@ -118,47 +118,71 @@ out:
}
EXPORT_SYMBOL(__inet6_lookup_established);
static int inline compute_score(struct sock *sk, struct net *net,
const unsigned short hnum,
const struct in6_addr *daddr,
const int dif)
{
int score = -1;
if (net_eq(sock_net(sk), net) && inet_sk(sk)->num == hnum &&
sk->sk_family == PF_INET6) {
const struct ipv6_pinfo *np = inet6_sk(sk);
score = 1;
if (!ipv6_addr_any(&np->rcv_saddr)) {
if (!ipv6_addr_equal(&np->rcv_saddr, daddr))
return -1;
score++;
}
if (sk->sk_bound_dev_if) {
if (sk->sk_bound_dev_if != dif)
return -1;
score++;
}
}
return score;
}
struct sock *inet6_lookup_listener(struct net *net,
struct inet_hashinfo *hashinfo, const struct in6_addr *daddr,
const unsigned short hnum, const int dif)
{
struct sock *sk;
const struct hlist_node *node;
struct sock *result = NULL;
int score, hiscore = 0;
struct inet_listen_hashbucket *ilb;
const struct hlist_nulls_node *node;
struct sock *result;
int score, hiscore;
unsigned int hash = inet_lhashfn(net, hnum);
struct inet_listen_hashbucket *ilb = &hashinfo->listening_hash[hash];
ilb = &hashinfo->listening_hash[inet_lhashfn(net, hnum)];
spin_lock(&ilb->lock);
sk_for_each(sk, node, &ilb->head) {
if (net_eq(sock_net(sk), net) && inet_sk(sk)->num == hnum &&
sk->sk_family == PF_INET6) {
const struct ipv6_pinfo *np = inet6_sk(sk);
score = 1;
if (!ipv6_addr_any(&np->rcv_saddr)) {
if (!ipv6_addr_equal(&np->rcv_saddr, daddr))
continue;
score++;
}
if (sk->sk_bound_dev_if) {
if (sk->sk_bound_dev_if != dif)
continue;
score++;
}
if (score == 3) {
result = sk;
break;
}
if (score > hiscore) {
hiscore = score;
result = sk;
}
rcu_read_lock();
begin:
result = NULL;
hiscore = -1;
sk_nulls_for_each(sk, node, &ilb->head) {
score = compute_score(sk, net, hnum, daddr, dif);
if (score > hiscore) {
hiscore = score;
result = sk;
}
}
if (result)
sock_hold(result);
spin_unlock(&ilb->lock);
/*
* if the nulls value we got at the end of this lookup is
* not the expected one, we must restart lookup.
* We probably met an item that was moved to another chain.
*/
if (get_nulls_value(node) != hash + LISTENING_NULLS_BASE)
goto begin;
if (result) {
if (unlikely(!atomic_inc_not_zero(&result->sk_refcnt)))
result = NULL;
else if (unlikely(compute_score(result, net, hnum, daddr,
dif) < hiscore)) {
sock_put(result);
goto begin;
}
}
rcu_read_unlock();
return result;
}