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authorjbaron@akamai.com <jbaron@akamai.com>2015-04-20 20:05:07 +0000
committerDavid S. Miller <davem@davemloft.net>2015-04-21 15:57:34 -0400
commit3c7151275c0c9a80c3375f9874b1c7129a105eea (patch)
treed1c703725e11d908f2d027dd62c22f83bc1e0c19 /net
parent71cd26e76a9514715df7880db0a8f7c37c17149a (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>
Diffstat (limited to 'net')
-rw-r--r--net/ipv4/tcp.c4
-rw-r--r--net/ipv4/tcp_input.c2
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);