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authorSowmini Varadhan <sowmini.varadhan@oracle.com>2016-05-02 11:24:52 -0700
committerDavid S. Miller <davem@davemloft.net>2016-05-03 16:03:44 -0400
commitbd7c5f983f3185b75cc23bdd5dbc3a676aef3d1e (patch)
tree42b348d05eaf5e948bd694bdbe390ebb6a9c354f /net/rds/tcp.h
parenteb192840266fab3e3da644018121eed30153355d (diff)
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.h')
-rw-r--r--net/rds/tcp.h4
1 files changed, 4 insertions, 0 deletions
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;