diff options
| author | jbaron@akamai.com <jbaron@akamai.com> | 2015-04-20 20:05:07 +0000 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2015-04-21 15:57:34 -0400 |
| commit | 3c7151275c0c9a80c3375f9874b1c7129a105eea (patch) | |
| tree | d1c703725e11d908f2d027dd62c22f83bc1e0c19 | |
| parent | 71cd26e76a9514715df7880db0a8f7c37c17149a (diff) | |
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>
| -rw-r--r-- | net/ipv4/tcp.c | 4 | ||||
| -rw-r--r-- | net/ipv4/tcp_input.c | 2 |
2 files changed, 5 insertions, 1 deletions
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 59c8a027721b..8c5cd9efebbc 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -520,8 +520,10 @@ unsigned int tcp_poll(struct file *file, struct socket *sock, poll_table *wait) /* Race breaker. If space is freed after * wspace test but before the flags are set, - * IO signal will be lost. + * IO signal will be lost. Memory barrier + * pairs with the input side. */ + smp_mb__after_atomic(); if (sk_stream_is_writeable(sk)) mask |= POLLOUT | POLLWRNORM; } diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index a7ef679dd3ea..3a4d9b34bed4 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -4845,6 +4845,8 @@ static void tcp_check_space(struct sock *sk) { if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) { sock_reset_flag(sk, SOCK_QUEUE_SHRUNK); + /* pairs with tcp_poll() */ + smp_mb__after_atomic(); if (sk->sk_socket && test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) tcp_new_space(sk); |