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authorEric Dumazet <edumazet@google.com>2015-11-12 08:43:18 -0800
committerDavid S. Miller <davem@davemloft.net>2015-11-15 18:36:38 -0500
commit00fd38d938db3f1ab1c486549afc450cb7e751b1 (patch)
tree484653a166b88da8777c900a01b2b8e0d5455147 /include/net
parent5883d9c6d7e680bcdc7a8a9ed2509cd10dd98206 (diff)
tcp: ensure proper barriers in lockless contexts
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>
Diffstat (limited to 'include/net')
-rw-r--r--include/net/sock.h25
1 files changed, 25 insertions, 0 deletions
diff --git a/include/net/sock.h b/include/net/sock.h
index bbf7c2cf15b4..7f89e4ba18d1 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -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 *);

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