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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
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6
net/rds/rds.h
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@@ -91,7 +91,7 @@ struct rds_connection {
struct rds_cong_map *c_lcong;
struct rds_cong_map *c_fcong;
struct mutex c_send_lock; /* protect send ring */
spinlock_t c_send_lock; /* protect send ring */
struct rds_message *c_xmit_rm;
unsigned long c_xmit_sg;
unsigned int c_xmit_hdr_off;
@@ -548,8 +548,8 @@ struct rds_statistics {
uint64_t s_recv_ping;
uint64_t s_send_queue_empty;
uint64_t s_send_queue_full;
uint64_t s_send_sem_contention;
uint64_t s_send_sem_queue_raced;
uint64_t s_send_lock_contention;
uint64_t s_send_lock_queue_raced;
uint64_t s_send_immediate_retry;
uint64_t s_send_delayed_retry;
uint64_t s_send_drop_acked;