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net: avoid potential false sharing in neighbor related code

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There are common instances of the following construct :

	if (n->confirmed != now)
		n->confirmed = now;

A C compiler could legally remove the conditional.

Use READ_ONCE()/WRITE_ONCE() to avoid this problem.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2019-11-05 14:11:51 -08:00 committed by David S. Miller
parent 3828a93f5c
commit 25c7a6d1f9
3 changed files with 12 additions and 12 deletions
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4
include/net/arp.h
View File

@ -57,8 +57,8 @@ static inline void __ipv4_confirm_neigh(struct net_device *dev, u32 key)
unsigned long now = jiffies; unsigned long now = jiffies;
/* avoid dirtying neighbour */ /* avoid dirtying neighbour */
if (n->confirmed != now) if (READ_ONCE(n->confirmed) != now)
n->confirmed = now; WRITE_ONCE(n->confirmed, now);
} }
rcu_read_unlock_bh(); rcu_read_unlock_bh();
} }

8
include/net/ndisc.h
View File

@ -414,8 +414,8 @@ static inline void __ipv6_confirm_neigh(struct net_device *dev,
unsigned long now = jiffies; unsigned long now = jiffies;
/* avoid dirtying neighbour */ /* avoid dirtying neighbour */
if (n->confirmed != now) if (READ_ONCE(n->confirmed) != now)
n->confirmed = now; WRITE_ONCE(n->confirmed, now);
} }
rcu_read_unlock_bh(); rcu_read_unlock_bh();
} }
@ -431,8 +431,8 @@ static inline void __ipv6_confirm_neigh_stub(struct net_device *dev,
unsigned long now = jiffies; unsigned long now = jiffies;
/* avoid dirtying neighbour */ /* avoid dirtying neighbour */
if (n->confirmed != now) if (READ_ONCE(n->confirmed) != now)
n->confirmed = now; WRITE_ONCE(n->confirmed, now);
} }
rcu_read_unlock_bh(); rcu_read_unlock_bh();
} }

12
include/net/sock.h
View File

@ -1939,8 +1939,8 @@ struct dst_entry *sk_dst_check(struct sock *sk, u32 cookie);
static inline void sk_dst_confirm(struct sock *sk) static inline void sk_dst_confirm(struct sock *sk)
{ {
if (!sk->sk_dst_pending_confirm) if (!READ_ONCE(sk->sk_dst_pending_confirm))
sk->sk_dst_pending_confirm = 1; WRITE_ONCE(sk->sk_dst_pending_confirm, 1);
} }
static inline void sock_confirm_neigh(struct sk_buff *skb, struct neighbour *n) static inline void sock_confirm_neigh(struct sk_buff *skb, struct neighbour *n)
@ -1950,10 +1950,10 @@ static inline void sock_confirm_neigh(struct sk_buff *skb, struct neighbour *n)
unsigned long now = jiffies; unsigned long now = jiffies;
/* avoid dirtying neighbour */ /* avoid dirtying neighbour */
if (n->confirmed != now) if (READ_ONCE(n->confirmed) != now)
n->confirmed = now; WRITE_ONCE(n->confirmed, now);
if (sk && sk->sk_dst_pending_confirm) if (sk && READ_ONCE(sk->sk_dst_pending_confirm))
sk->sk_dst_pending_confirm = 0; WRITE_ONCE(sk->sk_dst_pending_confirm, 0);
} }
} }