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tcp: ensure proper barriers in lockless contexts

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Some functions access TCP sockets without holding a lock and
might output non consistent data, depending on compiler and or
architecture.

tcp_diag_get_info(), tcp_get_info(), tcp_poll(), get_tcp4_sock() ...

Introduce sk_state_load() and sk_state_store() to fix the issues,
and more clearly document where this lack of locking is happening.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet
2015-11-12 08:43:18 -08:00
committed by David S. Miller
parent 5883d9c6d7
commit 00fd38d938
6 changed files with 62 additions and 23 deletions
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25
include/net/sock.h
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@@ -2226,6 +2226,31 @@ static inline bool sk_listener(const struct sock *sk)
return (1 << sk->sk_state) & (TCPF_LISTEN | TCPF_NEW_SYN_RECV);
}
/**
* sk_state_load - read sk->sk_state for lockless contexts
* @sk: socket pointer
*
* Paired with sk_state_store(). Used in places we do not hold socket lock :
* tcp_diag_get_info(), tcp_get_info(), tcp_poll(), get_tcp4_sock() ...
*/
static inline int sk_state_load(const struct sock *sk)
{
return smp_load_acquire(&sk->sk_state);
}
/**
* sk_state_store - update sk->sk_state
* @sk: socket pointer
* @newstate: new state
*
* Paired with sk_state_load(). Should be used in contexts where
* state change might impact lockless readers.
*/
static inline void sk_state_store(struct sock *sk, int newstate)
{
smp_store_release(&sk->sk_state, newstate);
}
void sock_enable_timestamp(struct sock *sk, int flag);
int sock_get_timestamp(struct sock *, struct timeval __user *);
int sock_get_timestampns(struct sock *, struct timespec __user *);