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