On Tue, 2013-05-21 at 19:01 -0700, Eric Dumazet wrote:
> Please use ACCESS_ONCE(), which is the standard way to deal with this,
> and remove the rcu_dereference_raw() in
> hlist_nulls_for_each_entry_rcu()
>
> something like : (for the nulls part only)
Thinking a bit more about this, I am a bit worried by other uses of
ACCESS_ONCE(ptr->field)
rcu_dereference(ptr->field) intent is to reload ptr->field every time
from memory.
Do we really need a
#define ACCESS_FIELD_ONCE(PTR, FIELD) (((volatile typeof(*PTR) *)PTR)->FIELD)
#define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x))
and change all rcu_dererence(ptr->field) occurrences ?
I probably miss something obvious.
Anyway, following patch seems to also solve the problem, I need a sleep to
understand why.
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 0bf5d39..10b5c54 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -410,7 +410,7 @@ static inline int compute_score2(struct sock *sk, struct
net *net,
static struct sock *udp4_lib_lookup2(struct net *net,
__be32 saddr, __be16 sport,
__be32 daddr, unsigned int hnum, int dif,
- struct udp_hslot *hslot2, unsigned int slot2)
+ struct hlist_nulls_head *head, unsigned int slot2)
{
struct sock *sk, *result;
struct hlist_nulls_node *node;
@@ -420,7 +420,7 @@ static struct sock *udp4_lib_lookup2(struct net *net,
begin:
result = NULL;
badness = 0;
- udp_portaddr_for_each_entry_rcu(sk, node, &hslot2->head) {
+ udp_portaddr_for_each_entry_rcu(sk, node, head) {
score = compute_score2(sk, net, saddr, sport,
daddr, hnum, dif);
if (score > badness) {
@@ -483,7 +483,7 @@ struct sock *__udp4_lib_lookup(struct net *net, __be32
saddr,
result = udp4_lib_lookup2(net, saddr, sport,
daddr, hnum, dif,
- hslot2, slot2);
+ &hslot2->head, slot2);
if (!result) {
hash2 = udp4_portaddr_hash(net, htonl(INADDR_ANY),
hnum);
slot2 = hash2 & udptable->mask;
@@ -493,7 +493,7 @@ struct sock *__udp4_lib_lookup(struct net *net, __be32
saddr,
result = udp4_lib_lookup2(net, saddr, sport,
htonl(INADDR_ANY), hnum, dif,
- hslot2, slot2);
+ &hslot2->head, slot2);
}
rcu_read_unlock();
return result;
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 42923b1..b5bc667 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -200,7 +200,7 @@ static inline int compute_score2(struct sock *sk, struct
net *net,
static struct sock *udp6_lib_lookup2(struct net *net,
const struct in6_addr *saddr, __be16 sport,
const struct in6_addr *daddr, unsigned int hnum, int dif,
- struct udp_hslot *hslot2, unsigned int slot2)
+ struct hlist_nulls_head *head, unsigned int slot2)
{
struct sock *sk, *result;
struct hlist_nulls_node *node;
@@ -210,7 +210,7 @@ static struct sock *udp6_lib_lookup2(struct net *net,
begin:
result = NULL;
badness = -1;
- udp_portaddr_for_each_entry_rcu(sk, node, &hslot2->head) {
+ udp_portaddr_for_each_entry_rcu(sk, node, head) {
score = compute_score2(sk, net, saddr, sport,
daddr, hnum, dif);
if (score > badness) {
@@ -274,7 +274,7 @@ struct sock *__udp6_lib_lookup(struct net *net,
result = udp6_lib_lookup2(net, saddr, sport,
daddr, hnum, dif,
- hslot2, slot2);
+ &hslot2->head, slot2);
if (!result) {
hash2 = udp6_portaddr_hash(net, &in6addr_any, hnum);
slot2 = hash2 & udptable->mask;
@@ -284,7 +284,7 @@ struct sock *__udp6_lib_lookup(struct net *net,
result = udp6_lib_lookup2(net, saddr, sport,
&in6addr_any, hnum, dif,
- hslot2, slot2);
+ &hslot2->head, slot2);
}
rcu_read_unlock();
return result;
--
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