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.h | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'net/rds/tcp.h') diff --git a/net/rds/tcp.h b/net/rds/tcp.h index 64f873c0c6b6..41c228300525 100644 --- a/net/rds/tcp.h +++ b/net/rds/tcp.h @@ -12,6 +12,10 @@ struct rds_tcp_connection { struct list_head t_tcp_node; struct rds_connection *conn; + /* t_conn_lock synchronizes the connection establishment between + * rds_tcp_accept_one and rds_tcp_conn_connect + */ + struct mutex t_conn_lock; struct socket *t_sock; void *t_orig_write_space; void *t_orig_data_ready; -- cgit v1.2.3