SUNRPC: Optimise rpciod_up()
Instead of taking the mutex every time we just need to increment/decrement
rpciod_users, we can optmise by using atomic_inc_not_zero and
atomic_dec_and_test.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
index d95fe4e..f6eed4d 100644
--- a/net/sunrpc/sched.c
+++ b/net/sunrpc/sched.c
@@ -58,7 +58,7 @@
* rpciod-related stuff
*/
static DEFINE_MUTEX(rpciod_mutex);
-static unsigned int rpciod_users;
+static atomic_t rpciod_users = ATOMIC_INIT(0);
struct workqueue_struct *rpciod_workqueue;
/*
@@ -1047,28 +1047,27 @@
struct workqueue_struct *wq;
int error = 0;
+ if (atomic_inc_not_zero(&rpciod_users))
+ return 0;
+
mutex_lock(&rpciod_mutex);
- dprintk("RPC: rpciod_up: users %u\n", rpciod_users);
- rpciod_users++;
- if (rpciod_workqueue)
- goto out;
- /*
- * If there's no pid, we should be the first user.
- */
- if (rpciod_users > 1)
- printk(KERN_WARNING "rpciod_up: no workqueue, %u users??\n", rpciod_users);
+
+ /* Guard against races with rpciod_down() */
+ if (rpciod_workqueue != NULL)
+ goto out_ok;
/*
* Create the rpciod thread and wait for it to start.
*/
+ dprintk("RPC: creating workqueue rpciod\n");
error = -ENOMEM;
wq = create_workqueue("rpciod");
- if (wq == NULL) {
- printk(KERN_WARNING "rpciod_up: create workqueue failed, error=%d\n", error);
- rpciod_users--;
+ if (wq == NULL)
goto out;
- }
+
rpciod_workqueue = wq;
error = 0;
+out_ok:
+ atomic_inc(&rpciod_users);
out:
mutex_unlock(&rpciod_mutex);
return error;
@@ -1077,23 +1076,17 @@
void
rpciod_down(void)
{
+ if (!atomic_dec_and_test(&rpciod_users))
+ return;
+
mutex_lock(&rpciod_mutex);
- dprintk("RPC: rpciod_down sema %u\n", rpciod_users);
- if (rpciod_users) {
- if (--rpciod_users)
- goto out;
- } else
- printk(KERN_WARNING "rpciod_down: no users??\n");
+ dprintk("RPC: destroying workqueue rpciod\n");
- if (!rpciod_workqueue) {
- dprintk("RPC: rpciod_down: Nothing to do!\n");
- goto out;
+ if (atomic_read(&rpciod_users) == 0 && rpciod_workqueue != NULL) {
+ rpciod_killall();
+ destroy_workqueue(rpciod_workqueue);
+ rpciod_workqueue = NULL;
}
- rpciod_killall();
-
- destroy_workqueue(rpciod_workqueue);
- rpciod_workqueue = NULL;
- out:
mutex_unlock(&rpciod_mutex);
}