RDS: Change send lock from a mutex to a spinlock
This change allows us to call rds_send_xmit() from a tasklet,
which is crucial to our new operating model.
* Change c_send_lock to a spinlock
* Update stats fields "sem_" to "_lock"
* Remove unneeded rds_conn_is_sending()
About locking between shutdown and send -- send checks if the
connection is up. Shutdown puts the connection into
DISCONNECTING. After this, all threads entering send will exit
immediately. However, a thread could be *in* send_xmit(), so
shutdown acquires the c_send_lock to ensure everyone is out
before proceeding with connection shutdown.
Signed-off-by: Andy Grover <andy.grover@oracle.com>
diff --git a/net/rds/stats.c b/net/rds/stats.c
index c66d95d..b77be8b 100644
--- a/net/rds/stats.c
+++ b/net/rds/stats.c
@@ -57,8 +57,8 @@
"recv_ping",
"send_queue_empty",
"send_queue_full",
- "send_sem_contention",
- "send_sem_queue_raced",
+ "send_lock_contention",
+ "send_lock_queue_raced",
"send_immediate_retry",
"send_delayed_retry",
"send_drop_acked",