From 049ee3f500954176a87f22e6ee3e98aecb1b8958 Mon Sep 17 00:00:00 2001 From: Andy Grover Date: Tue, 23 Mar 2010 17:39:07 -0700 Subject: 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 --- net/rds/send.c | 15 +++++++-------- 1 file changed, 7 insertions(+), 8 deletions(-) (limited to 'net/rds/send.c') diff --git a/net/rds/send.c b/net/rds/send.c index 8a0647af5d95..d4feec6ad09c 100644 --- a/net/rds/send.c +++ b/net/rds/send.c @@ -116,19 +116,18 @@ int rds_send_xmit(struct rds_connection *conn) int was_empty = 0; LIST_HEAD(to_be_dropped); + if (!rds_conn_up(conn)) + goto out; + /* * sendmsg calls here after having queued its message on the send * queue. We only have one task feeding the connection at a time. If * another thread is already feeding the queue then we back off. This * avoids blocking the caller and trading per-connection data between * caches per message. - * - * The sem holder will issue a retry if they notice that someone queued - * a message after they stopped walking the send queue but before they - * dropped the sem. */ - if (!mutex_trylock(&conn->c_send_lock)) { - rds_stats_inc(s_send_sem_contention); + if (!spin_trylock_irqsave(&conn->c_send_lock, flags)) { + rds_stats_inc(s_send_lock_contention); ret = -ENOMEM; goto out; } @@ -346,7 +345,7 @@ int rds_send_xmit(struct rds_connection *conn) * stop processing the loop when the transport hasn't taken * responsibility for forward progress. */ - mutex_unlock(&conn->c_send_lock); + spin_unlock_irqrestore(&conn->c_send_lock, flags); if (send_quota == 0 && !was_empty) { /* We exhausted the send quota, but there's work left to @@ -360,7 +359,7 @@ int rds_send_xmit(struct rds_connection *conn) * spin lock */ spin_lock_irqsave(&conn->c_lock, flags); if (!list_empty(&conn->c_send_queue)) { - rds_stats_inc(s_send_sem_queue_raced); + rds_stats_inc(s_send_lock_queue_raced); ret = -EAGAIN; } spin_unlock_irqrestore(&conn->c_lock, flags); -- cgit v1.2.3