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udp: Use hlist_nulls in UDP RCU code
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This is a straightforward patch, using hlist_nulls infrastructure.

RCUification already done on UDP two weeks ago.

Using hlist_nulls permits us to avoid some memory barriers, both
at lookup time and delete time.

Patch is large because it adds new macros to include/net/sock.h.
These macros will be used by TCP & DCCP in next patch.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Eric Dumazet authored and David S. Miller committed Nov 17, 2008
1 parent bbaffac commit 88ab193
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Showing 5 changed files with 83 additions and 66 deletions.
17 changes: 0 additions & 17 deletions include/linux/rculist.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -383,22 +383,5 @@ static inline void hlist_add_after_rcu(struct hlist_node *prev,
({ tpos = hlist_entry(pos, typeof(*tpos), member); 1; }); \
pos = rcu_dereference(pos->next))

/**
* hlist_for_each_entry_rcu_safenext - iterate over rcu list of given type
* @tpos: the type * to use as a loop cursor.
* @pos: the &struct hlist_node to use as a loop cursor.
* @head: the head for your list.
* @member: the name of the hlist_node within the struct.
* @next: the &struct hlist_node to use as a next cursor
*
* Special version of hlist_for_each_entry_rcu that make sure
* each next pointer is fetched before each iteration.
*/
#define hlist_for_each_entry_rcu_safenext(tpos, pos, head, member, next) \
for (pos = rcu_dereference((head)->first); \
pos && ({ next = pos->next; smp_rmb(); prefetch(next); 1; }) && \
({ tpos = hlist_entry(pos, typeof(*tpos), member); 1; }); \
pos = rcu_dereference(next))

#endif /* __KERNEL__ */
#endif
57 changes: 46 additions & 11 deletions include/net/sock.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -42,6 +42,7 @@

#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/list_nulls.h>
#include <linux/timer.h>
#include <linux/cache.h>
#include <linux/module.h>
Expand All @@ -52,6 +53,7 @@
#include <linux/security.h>

#include <linux/filter.h>
#include <linux/rculist_nulls.h>

#include <asm/atomic.h>
#include <net/dst.h>
Expand Down Expand Up @@ -106,6 +108,7 @@ struct net;
* @skc_reuse: %SO_REUSEADDR setting
* @skc_bound_dev_if: bound device index if != 0
* @skc_node: main hash linkage for various protocol lookup tables
* @skc_nulls_node: main hash linkage for UDP/UDP-Lite protocol
* @skc_bind_node: bind hash linkage for various protocol lookup tables
* @skc_refcnt: reference count
* @skc_hash: hash value used with various protocol lookup tables
Expand All @@ -120,7 +123,10 @@ struct sock_common {
volatile unsigned char skc_state;
unsigned char skc_reuse;
int skc_bound_dev_if;
struct hlist_node skc_node;
union {
struct hlist_node skc_node;
struct hlist_nulls_node skc_nulls_node;
};
struct hlist_node skc_bind_node;
atomic_t skc_refcnt;
unsigned int skc_hash;
Expand Down Expand Up @@ -206,6 +212,7 @@ struct sock {
#define sk_reuse __sk_common.skc_reuse
#define sk_bound_dev_if __sk_common.skc_bound_dev_if
#define sk_node __sk_common.skc_node
#define sk_nulls_node __sk_common.skc_nulls_node
#define sk_bind_node __sk_common.skc_bind_node
#define sk_refcnt __sk_common.skc_refcnt
#define sk_hash __sk_common.skc_hash
Expand Down Expand Up @@ -300,12 +307,30 @@ static inline struct sock *sk_head(const struct hlist_head *head)
return hlist_empty(head) ? NULL : __sk_head(head);
}

static inline struct sock *__sk_nulls_head(const struct hlist_nulls_head *head)
{
return hlist_nulls_entry(head->first, struct sock, sk_nulls_node);
}

static inline struct sock *sk_nulls_head(const struct hlist_nulls_head *head)
{
return hlist_nulls_empty(head) ? NULL : __sk_nulls_head(head);
}

static inline struct sock *sk_next(const struct sock *sk)
{
return sk->sk_node.next ?
hlist_entry(sk->sk_node.next, struct sock, sk_node) : NULL;
}

static inline struct sock *sk_nulls_next(const struct sock *sk)
{
return (!is_a_nulls(sk->sk_nulls_node.next)) ?
hlist_nulls_entry(sk->sk_nulls_node.next,
struct sock, sk_nulls_node) :
NULL;
}

static inline int sk_unhashed(const struct sock *sk)
{
return hlist_unhashed(&sk->sk_node);
Expand All @@ -321,6 +346,11 @@ static __inline__ void sk_node_init(struct hlist_node *node)
node->pprev = NULL;
}

static __inline__ void sk_nulls_node_init(struct hlist_nulls_node *node)
{
node->pprev = NULL;
}

static __inline__ void __sk_del_node(struct sock *sk)
{
__hlist_del(&sk->sk_node);
Expand Down Expand Up @@ -367,18 +397,18 @@ static __inline__ int sk_del_node_init(struct sock *sk)
return rc;
}

static __inline__ int __sk_del_node_init_rcu(struct sock *sk)
static __inline__ int __sk_nulls_del_node_init_rcu(struct sock *sk)
{
if (sk_hashed(sk)) {
hlist_del_init_rcu(&sk->sk_node);
hlist_nulls_del_init_rcu(&sk->sk_nulls_node);
return 1;
}
return 0;
}

static __inline__ int sk_del_node_init_rcu(struct sock *sk)
static __inline__ int sk_nulls_del_node_init_rcu(struct sock *sk)
{
int rc = __sk_del_node_init_rcu(sk);
int rc = __sk_nulls_del_node_init_rcu(sk);

if (rc) {
/* paranoid for a while -acme */
Expand All @@ -399,15 +429,15 @@ static __inline__ void sk_add_node(struct sock *sk, struct hlist_head *list)
__sk_add_node(sk, list);
}

static __inline__ void __sk_add_node_rcu(struct sock *sk, struct hlist_head *list)
static __inline__ void __sk_nulls_add_node_rcu(struct sock *sk, struct hlist_nulls_head *list)
{
hlist_add_head_rcu(&sk->sk_node, list);
hlist_nulls_add_head_rcu(&sk->sk_nulls_node, list);
}

static __inline__ void sk_add_node_rcu(struct sock *sk, struct hlist_head *list)
static __inline__ void sk_nulls_add_node_rcu(struct sock *sk, struct hlist_nulls_head *list)
{
sock_hold(sk);
__sk_add_node_rcu(sk, list);
__sk_nulls_add_node_rcu(sk, list);
}

static __inline__ void __sk_del_bind_node(struct sock *sk)
Expand All @@ -423,11 +453,16 @@ static __inline__ void sk_add_bind_node(struct sock *sk,

#define sk_for_each(__sk, node, list) \
hlist_for_each_entry(__sk, node, list, sk_node)
#define sk_for_each_rcu_safenext(__sk, node, list, next) \
hlist_for_each_entry_rcu_safenext(__sk, node, list, sk_node, next)
#define sk_nulls_for_each(__sk, node, list) \
hlist_nulls_for_each_entry(__sk, node, list, sk_nulls_node)
#define sk_nulls_for_each_rcu(__sk, node, list) \
hlist_nulls_for_each_entry_rcu(__sk, node, list, sk_nulls_node)
#define sk_for_each_from(__sk, node) \
if (__sk && ({ node = &(__sk)->sk_node; 1; })) \
hlist_for_each_entry_from(__sk, node, sk_node)
#define sk_nulls_for_each_from(__sk, node) \
if (__sk && ({ node = &(__sk)->sk_nulls_node; 1; })) \
hlist_nulls_for_each_entry_from(__sk, node, sk_nulls_node)
#define sk_for_each_continue(__sk, node) \
if (__sk && ({ node = &(__sk)->sk_node; 1; })) \
hlist_for_each_entry_continue(__sk, node, sk_node)
Expand Down
2 changes: 1 addition & 1 deletion include/net/udp.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -51,7 +51,7 @@ struct udp_skb_cb {
#define UDP_SKB_CB(__skb) ((struct udp_skb_cb *)((__skb)->cb))

struct udp_hslot {
struct hlist_head head;
struct hlist_nulls_head head;
spinlock_t lock;
} __attribute__((aligned(2 * sizeof(long))));
struct udp_table {
Expand Down
47 changes: 22 additions & 25 deletions net/ipv4/udp.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -127,9 +127,9 @@ static int udp_lib_lport_inuse(struct net *net, __u16 num,
const struct sock *sk2))
{
struct sock *sk2;
struct hlist_node *node;
struct hlist_nulls_node *node;

sk_for_each(sk2, node, &hslot->head)
sk_nulls_for_each(sk2, node, &hslot->head)
if (net_eq(sock_net(sk2), net) &&
sk2 != sk &&
sk2->sk_hash == num &&
Expand Down Expand Up @@ -189,12 +189,7 @@ int udp_lib_get_port(struct sock *sk, unsigned short snum,
inet_sk(sk)->num = snum;
sk->sk_hash = snum;
if (sk_unhashed(sk)) {
/*
* We need that previous write to sk->sk_hash committed
* before write to sk->next done in following add_node() variant
*/
smp_wmb();
sk_add_node_rcu(sk, &hslot->head);
sk_nulls_add_node_rcu(sk, &hslot->head);
sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
}
error = 0;
Expand Down Expand Up @@ -261,7 +256,7 @@ static struct sock *__udp4_lib_lookup(struct net *net, __be32 saddr,
int dif, struct udp_table *udptable)
{
struct sock *sk, *result;
struct hlist_node *node, *next;
struct hlist_nulls_node *node;
unsigned short hnum = ntohs(dport);
unsigned int hash = udp_hashfn(net, hnum);
struct udp_hslot *hslot = &udptable->hash[hash];
Expand All @@ -271,20 +266,22 @@ static struct sock *__udp4_lib_lookup(struct net *net, __be32 saddr,
begin:
result = NULL;
badness = -1;
sk_for_each_rcu_safenext(sk, node, &hslot->head, next) {
/*
* lockless reader, and SLAB_DESTROY_BY_RCU items:
* We must check this item was not moved to another chain
*/
if (udp_hashfn(net, sk->sk_hash) != hash)
goto begin;
sk_nulls_for_each_rcu(sk, node, &hslot->head) {
score = compute_score(sk, net, saddr, hnum, sport,
daddr, dport, dif);
if (score > badness) {
result = sk;
badness = score;
}
}
/*
* 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)
goto begin;

if (result) {
if (unlikely(!atomic_inc_not_zero(&result->sk_refcnt)))
result = NULL;
Expand Down Expand Up @@ -325,11 +322,11 @@ static inline struct sock *udp_v4_mcast_next(struct net *net, struct sock *sk,
__be16 rmt_port, __be32 rmt_addr,
int dif)
{
struct hlist_node *node;
struct hlist_nulls_node *node;
struct sock *s = sk;
unsigned short hnum = ntohs(loc_port);

sk_for_each_from(s, node) {
sk_nulls_for_each_from(s, node) {
struct inet_sock *inet = inet_sk(s);

if (!net_eq(sock_net(s), net) ||
Expand Down Expand Up @@ -977,7 +974,7 @@ void udp_lib_unhash(struct sock *sk)
struct udp_hslot *hslot = &udptable->hash[hash];

spin_lock_bh(&hslot->lock);
if (sk_del_node_init_rcu(sk)) {
if (sk_nulls_del_node_init_rcu(sk)) {
inet_sk(sk)->num = 0;
sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
}
Expand Down Expand Up @@ -1130,7 +1127,7 @@ static int __udp4_lib_mcast_deliver(struct net *net, struct sk_buff *skb,
int dif;

spin_lock(&hslot->lock);
sk = sk_head(&hslot->head);
sk = sk_nulls_head(&hslot->head);
dif = skb->dev->ifindex;
sk = udp_v4_mcast_next(net, sk, uh->dest, daddr, uh->source, saddr, dif);
if (sk) {
Expand All @@ -1139,7 +1136,7 @@ static int __udp4_lib_mcast_deliver(struct net *net, struct sk_buff *skb,
do {
struct sk_buff *skb1 = skb;

sknext = udp_v4_mcast_next(net, sk_next(sk), uh->dest,
sknext = udp_v4_mcast_next(net, sk_nulls_next(sk), uh->dest,
daddr, uh->source, saddr,
dif);
if (sknext)
Expand Down Expand Up @@ -1560,10 +1557,10 @@ static struct sock *udp_get_first(struct seq_file *seq, int start)
struct net *net = seq_file_net(seq);

for (state->bucket = start; state->bucket < UDP_HTABLE_SIZE; ++state->bucket) {
struct hlist_node *node;
struct hlist_nulls_node *node;
struct udp_hslot *hslot = &state->udp_table->hash[state->bucket];
spin_lock_bh(&hslot->lock);
sk_for_each(sk, node, &hslot->head) {
sk_nulls_for_each(sk, node, &hslot->head) {
if (!net_eq(sock_net(sk), net))
continue;
if (sk->sk_family == state->family)
Expand All @@ -1582,7 +1579,7 @@ static struct sock *udp_get_next(struct seq_file *seq, struct sock *sk)
struct net *net = seq_file_net(seq);

do {
sk = sk_next(sk);
sk = sk_nulls_next(sk);
} while (sk && (!net_eq(sock_net(sk), net) || sk->sk_family != state->family));

if (!sk) {
Expand Down Expand Up @@ -1753,7 +1750,7 @@ void __init udp_table_init(struct udp_table *table)
int i;

for (i = 0; i < UDP_HTABLE_SIZE; i++) {
INIT_HLIST_HEAD(&table->hash[i].head);
INIT_HLIST_NULLS_HEAD(&table->hash[i].head, i);
spin_lock_init(&table->hash[i].lock);
}
}
Expand Down
26 changes: 14 additions & 12 deletions net/ipv6/udp.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -98,7 +98,7 @@ static struct sock *__udp6_lib_lookup(struct net *net,
int dif, struct udp_table *udptable)
{
struct sock *sk, *result;
struct hlist_node *node, *next;
struct hlist_nulls_node *node;
unsigned short hnum = ntohs(dport);
unsigned int hash = udp_hashfn(net, hnum);
struct udp_hslot *hslot = &udptable->hash[hash];
Expand All @@ -108,19 +108,21 @@ static struct sock *__udp6_lib_lookup(struct net *net,
begin:
result = NULL;
badness = -1;
sk_for_each_rcu_safenext(sk, node, &hslot->head, next) {
/*
* lockless reader, and SLAB_DESTROY_BY_RCU items:
* We must check this item was not moved to another chain
*/
if (udp_hashfn(net, sk->sk_hash) != hash)
goto begin;
sk_nulls_for_each_rcu(sk, node, &hslot->head) {
score = compute_score(sk, net, hnum, saddr, sport, daddr, dport, dif);
if (score > badness) {
result = sk;
badness = score;
}
}
/*
* 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)
goto begin;

if (result) {
if (unlikely(!atomic_inc_not_zero(&result->sk_refcnt)))
result = NULL;
Expand Down Expand Up @@ -374,11 +376,11 @@ static struct sock *udp_v6_mcast_next(struct net *net, struct sock *sk,
__be16 rmt_port, struct in6_addr *rmt_addr,
int dif)
{
struct hlist_node *node;
struct hlist_nulls_node *node;
struct sock *s = sk;
unsigned short num = ntohs(loc_port);

sk_for_each_from(s, node) {
sk_nulls_for_each_from(s, node) {
struct inet_sock *inet = inet_sk(s);

if (!net_eq(sock_net(s), net))
Expand Down Expand Up @@ -423,7 +425,7 @@ static int __udp6_lib_mcast_deliver(struct net *net, struct sk_buff *skb,
int dif;

spin_lock(&hslot->lock);
sk = sk_head(&hslot->head);
sk = sk_nulls_head(&hslot->head);
dif = inet6_iif(skb);
sk = udp_v6_mcast_next(net, sk, uh->dest, daddr, uh->source, saddr, dif);
if (!sk) {
Expand All @@ -432,7 +434,7 @@ static int __udp6_lib_mcast_deliver(struct net *net, struct sk_buff *skb,
}

sk2 = sk;
while ((sk2 = udp_v6_mcast_next(net, sk_next(sk2), uh->dest, daddr,
while ((sk2 = udp_v6_mcast_next(net, sk_nulls_next(sk2), uh->dest, daddr,
uh->source, saddr, dif))) {
struct sk_buff *buff = skb_clone(skb, GFP_ATOMIC);
if (buff) {
Expand Down

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