[PATCH 09/10] SUNRPC: discard sp_lock

[NeilBrown <neilb@suse.de>]

sp_lock is now only used to protect sp_all_threads.  This isn't needed
as sp_all_threads is only manipulated through svc_set_num_threads(),
which must be locked.  Read-acccess only requires rcu_read_lock().  So
no more locking is needed.

Signed-off-by: NeilBrown <neilb@suse.de>
---
 include/linux/sunrpc/svc.h |  1 -
 net/sunrpc/svc.c           | 10 +++++-----
 2 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index c972561f5ab8..b80b698b09c5 100644
--- a/include/linux/sunrpc/svc.h
+++ b/include/linux/sunrpc/svc.h
@@ -34,7 +34,6 @@
  */
 struct svc_pool {
 	unsigned int		sp_id;	    	/* pool id; also node id on NUMA */
-	spinlock_t		sp_lock;	/* protects all fields */
 	struct lwq		sp_xprts;	/* pending transports */
 	atomic_t		sp_nrthreads;	/* # of threads in pool */
 	struct list_head	sp_all_threads;	/* all server threads */
diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
index 9524af33ace9..61ea8ce7975f 100644
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c
@@ -511,7 +511,6 @@ __svc_create(struct svc_program *prog, unsigned int bufsize, int npools,
 		lwq_init(&pool->sp_xprts);
 		INIT_LIST_HEAD(&pool->sp_all_threads);
 		init_llist_head(&pool->sp_idle_threads);
-		spin_lock_init(&pool->sp_lock);
 
 		percpu_counter_init(&pool->sp_messages_arrived, 0, GFP_KERNEL);
 		percpu_counter_init(&pool->sp_sockets_queued, 0, GFP_KERNEL);
@@ -682,9 +681,12 @@ svc_prepare_thread(struct svc_serv *serv, struct svc_pool *pool, int node)
 	spin_unlock_bh(&serv->sv_lock);
 
 	atomic_inc(&pool->sp_nrthreads);
-	spin_lock_bh(&pool->sp_lock);
+
+	/* Protected by whatever lock the service uses when calling
+	 * svc_set_num_threads()
+	 */
 	list_add_rcu(&rqstp->rq_all, &pool->sp_all_threads);
-	spin_unlock_bh(&pool->sp_lock);
+
 	return rqstp;
 }
 
@@ -922,9 +924,7 @@ svc_exit_thread(struct svc_rqst *rqstp)
 	struct svc_serv	*serv = rqstp->rq_server;
 	struct svc_pool	*pool = rqstp->rq_pool;
 
-	spin_lock_bh(&pool->sp_lock);
 	list_del_rcu(&rqstp->rq_all);
-	spin_unlock_bh(&pool->sp_lock);
 
 	atomic_dec(&pool->sp_nrthreads);
 
-- 
2.40.1