[rfc] IPVS: convert scheduler management to RCU

[Simon Horman <horms@xxxxxxxxxxxx>]

Signed-off-by: Simon Horman <horms@xxxxxxxxxxxx>

--- 

I'm still getting my head around RCU, so review would be greatly appreciated.

It occurs to me that this code is not performance critical, so
perhaps simply replacing the rwlock with a spinlock would be better?

Index: nf-next-2.6/net/netfilter/ipvs/ip_vs_sched.c
===================================================================
--- nf-next-2.6.orig/net/netfilter/ipvs/ip_vs_sched.c   2010-08-20 
22:21:01.000000000 +0900
+++ nf-next-2.6/net/netfilter/ipvs/ip_vs_sched.c        2010-08-20 
22:21:51.000000000 +0900
@@ -35,7 +35,7 @@
 static LIST_HEAD(ip_vs_schedulers);
 
 /* lock for service table */
-static DEFINE_RWLOCK(__ip_vs_sched_lock);
+static DEFINE_SPINLOCK(ip_vs_sched_mutex);
 
 
 /*
@@ -91,9 +91,9 @@ static struct ip_vs_scheduler *ip_vs_sch
 
        IP_VS_DBG(2, "%s(): sched_name \"%s\"\n", __func__, sched_name);
 
-       read_lock_bh(&__ip_vs_sched_lock);
+       rcu_read_lock_bh();
 
-       list_for_each_entry(sched, &ip_vs_schedulers, n_list) {
+       list_for_each_entry_rcu(sched, &ip_vs_schedulers, n_list) {
                /*
                 * Test and get the modules atomically
                 */
@@ -105,14 +105,14 @@ static struct ip_vs_scheduler *ip_vs_sch
                }
                if (strcmp(sched_name, sched->name)==0) {
                        /* HIT */
-                       read_unlock_bh(&__ip_vs_sched_lock);
+                       rcu_read_unlock_bh();
                        return sched;
                }
                if (sched->module)
                        module_put(sched->module);
        }
 
-       read_unlock_bh(&__ip_vs_sched_lock);
+       rcu_read_unlock_bh();
        return NULL;
 }
 
@@ -167,10 +167,10 @@ int register_ip_vs_scheduler(struct ip_v
        /* increase the module use count */
        ip_vs_use_count_inc();
 
-       write_lock_bh(&__ip_vs_sched_lock);
+       spin_lock_bh(&ip_vs_sched_mutex);
 
        if (!list_empty(&scheduler->n_list)) {
-               write_unlock_bh(&__ip_vs_sched_lock);
+               spin_unlock_bh(&ip_vs_sched_mutex);
                ip_vs_use_count_dec();
                pr_err("%s(): [%s] scheduler already linked\n",
                       __func__, scheduler->name);
@@ -181,9 +181,9 @@ int register_ip_vs_scheduler(struct ip_v
         *  Make sure that the scheduler with this name doesn't exist
         *  in the scheduler list.
         */
-       list_for_each_entry(sched, &ip_vs_schedulers, n_list) {
+       list_for_each_entry_rcu(sched, &ip_vs_schedulers, n_list) {
                if (strcmp(scheduler->name, sched->name) == 0) {
-                       write_unlock_bh(&__ip_vs_sched_lock);
+                       spin_unlock_bh(&ip_vs_sched_mutex);
                        ip_vs_use_count_dec();
                        pr_err("%s(): [%s] scheduler already existed "
                               "in the system\n", __func__, scheduler->name);
@@ -193,8 +193,8 @@ int register_ip_vs_scheduler(struct ip_v
        /*
         *      Add it into the d-linked scheduler list
         */
-       list_add(&scheduler->n_list, &ip_vs_schedulers);
-       write_unlock_bh(&__ip_vs_sched_lock);
+       list_add_rcu(&scheduler->n_list, &ip_vs_schedulers);
+       spin_unlock_bh(&ip_vs_sched_mutex);
 
        pr_info("[%s] scheduler registered.\n", scheduler->name);
 
@@ -212,9 +212,9 @@ int unregister_ip_vs_scheduler(struct ip
                return -EINVAL;
        }
 
-       write_lock_bh(&__ip_vs_sched_lock);
+       spin_lock_bh(&ip_vs_sched_mutex);
        if (list_empty(&scheduler->n_list)) {
-               write_unlock_bh(&__ip_vs_sched_lock);
+               spin_unlock_bh(&ip_vs_sched_mutex);
                pr_err("%s(): [%s] scheduler is not in the list. failed\n",
                       __func__, scheduler->name);
                return -EINVAL;
@@ -223,8 +223,8 @@ int unregister_ip_vs_scheduler(struct ip
        /*
         *      Remove it from the d-linked scheduler list
         */
-       list_del(&scheduler->n_list);
-       write_unlock_bh(&__ip_vs_sched_lock);
+       list_del_rcu(&scheduler->n_list);
+       spin_unlock_bh(&ip_vs_sched_mutex);
 
        /* decrease the module use count */
        ip_vs_use_count_dec();
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