tcp: add memory barriers to write space paths
Ensure that we either see that the buffer has write space in tcp_poll() or that we perform a wakeup from the input side. Did not run into any actual problem here, but thought that we should make things explicit. Signed-off-by: Jason Baron <jbaron@akamai.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -520,8 +520,10 @@ unsigned int tcp_poll(struct file *file, struct socket *sock, poll_table *wait)
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/* Race breaker. If space is freed after
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* wspace test but before the flags are set,
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* IO signal will be lost.
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* IO signal will be lost. Memory barrier
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* pairs with the input side.
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*/
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smp_mb__after_atomic();
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if (sk_stream_is_writeable(sk))
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mask |= POLLOUT | POLLWRNORM;
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}
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@ -4845,6 +4845,8 @@ static void tcp_check_space(struct sock *sk)
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{
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if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) {
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sock_reset_flag(sk, SOCK_QUEUE_SHRUNK);
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/* pairs with tcp_poll() */
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smp_mb__after_atomic();
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if (sk->sk_socket &&
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test_bit(SOCK_NOSPACE, &sk->sk_socket->flags))
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tcp_new_space(sk);
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