From bd7c5f983f3185b75cc23bdd5dbc3a676aef3d1e Mon Sep 17 00:00:00 2001 From: Sowmini Varadhan Date: Mon, 2 May 2016 11:24:52 -0700 Subject: RDS: TCP: Synchronize accept() and connect() paths on t_conn_lock. An arbitration scheme for duelling SYNs is implemented as part of commit 241b271952eb ("RDS-TCP: Reset tcp callbacks if re-using an outgoing socket in rds_tcp_accept_one()") which ensures that both nodes involved will arrive at the same arbitration decision. However, this needs to be synchronized with an outgoing SYN to be generated by rds_tcp_conn_connect(). This commit achieves the synchronization through the t_conn_lock mutex in struct rds_tcp_connection. The rds_conn_state is checked in rds_tcp_conn_connect() after acquiring the t_conn_lock mutex. A SYN is sent out only if the RDS connection is not already UP (an UP would indicate that rds_tcp_accept_one() has completed 3WH, so no SYN needs to be generated). Similarly, the rds_conn_state is checked in rds_tcp_accept_one() after acquiring the t_conn_lock mutex. The only acceptable states (to allow continuation of the arbitration logic) are UP (i.e., outgoing SYN was SYN-ACKed by peer after it sent us the SYN) or CONNECTING (we sent outgoing SYN before we saw incoming SYN). Signed-off-by: Sowmini Varadhan Acked-by: Santosh Shilimkar Signed-off-by: David S. Miller --- net/rds/tcp_connect.c | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'net/rds/tcp_connect.c') diff --git a/net/rds/tcp_connect.c b/net/rds/tcp_connect.c index 5cb16875c460..49a3fcfed360 100644 --- a/net/rds/tcp_connect.c +++ b/net/rds/tcp_connect.c @@ -78,7 +78,14 @@ int rds_tcp_conn_connect(struct rds_connection *conn) struct socket *sock = NULL; struct sockaddr_in src, dest; int ret; + struct rds_tcp_connection *tc = conn->c_transport_data; + + mutex_lock(&tc->t_conn_lock); + if (rds_conn_up(conn)) { + mutex_unlock(&tc->t_conn_lock); + return 0; + } ret = sock_create_kern(rds_conn_net(conn), PF_INET, SOCK_STREAM, IPPROTO_TCP, &sock); if (ret < 0) @@ -120,6 +127,7 @@ int rds_tcp_conn_connect(struct rds_connection *conn) } out: + mutex_unlock(&tc->t_conn_lock); if (sock) sock_release(sock); return ret; -- cgit v1.2.3