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RDS: Change send lock from a mutex to a spinlock

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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>
This commit is contained in:
Andy Grover
2010-03-23 17:39:07 -07:00
parent f17a1a55fb
commit 049ee3f500
4 changed files with 18 additions and 29 deletions
Download Patch File Download Diff File Expand all files Collapse all files
net/rds/connection.c
+6 -16
View File
@@ -62,18 +62,6 @@ static struct hlist_head *rds_conn_bucket(__be32 laddr, __be32 faddr)
var |= RDS_INFO_CONNECTION_FLAG_##suffix; \
} while (0)
static inline int rds_conn_is_sending(struct rds_connection *conn)
{
int ret = 0;
if (!mutex_trylock(&conn->c_send_lock))
ret = 1;
else
mutex_unlock(&conn->c_send_lock);
return ret;
}
static struct rds_connection *rds_conn_lookup(struct hlist_head *head,
__be32 laddr, __be32 faddr,
struct rds_transport *trans)
@@ -158,7 +146,7 @@ static struct rds_connection *__rds_conn_create(__be32 laddr, __be32 faddr,
spin_lock_init(&conn->c_lock);
conn->c_next_tx_seq = 1;
mutex_init(&conn->c_send_lock);
spin_lock_init(&conn->c_send_lock);
INIT_LIST_HEAD(&conn->c_send_queue);
INIT_LIST_HEAD(&conn->c_retrans);
@@ -283,10 +271,12 @@ void rds_conn_shutdown(struct rds_connection *conn)
}
mutex_unlock(&conn->c_cm_lock);
mutex_lock(&conn->c_send_lock);
/* verify everybody's out of rds_send_xmit() */
spin_lock_irq(&conn->c_send_lock);
spin_unlock_irq(&conn->c_send_lock);
conn->c_trans->conn_shutdown(conn);
rds_conn_reset(conn);
mutex_unlock(&conn->c_send_lock);
if (!rds_conn_transition(conn, RDS_CONN_DISCONNECTING, RDS_CONN_DOWN)) {
/* This can happen - eg when we're in the middle of tearing
@@ -476,7 +466,7 @@ static int rds_conn_info_visitor(struct rds_connection *conn,
cinfo->flags = 0;
rds_conn_info_set(cinfo->flags,
rds_conn_is_sending(conn), SENDING);
spin_is_locked(&conn->c_send_lock), SENDING);
/* XXX Future: return the state rather than these funky bits */
rds_conn_info_set(cinfo->flags,
atomic_read(&conn->c_state) == RDS_CONN_CONNECTING,