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author | Sowmini Varadhan <sowmini.varadhan@oracle.com> | 2016-05-02 18:24:52 (GMT) |
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committer | David S. Miller <davem@davemloft.net> | 2016-05-03 20:03:44 (GMT) |
commit | bd7c5f983f3185b75cc23bdd5dbc3a676aef3d1e (patch) | |
tree | 42b348d05eaf5e948bd694bdbe390ebb6a9c354f /net/rds/tcp_connect.c | |
parent | eb192840266fab3e3da644018121eed30153355d (diff) | |
download | linux-bd7c5f983f3185b75cc23bdd5dbc3a676aef3d1e.tar.xz |
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 <sowmini.varadhan@oracle.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/rds/tcp_connect.c')
-rw-r--r-- | net/rds/tcp_connect.c | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/net/rds/tcp_connect.c b/net/rds/tcp_connect.c index 5cb1687..49a3fcf 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; |