From 0982d8debd9d67d80f3862f8b31ff6558f281de3 Mon Sep 17 00:00:00 2001
From: Rostislav Lisovy <lisovy@gmail.com>
Date: Thu, 1 Sep 2011 13:44:35 +0200
Subject: [PATCH] Reading and changing struct canprio_rules protected by RCU.

---
 net/sched/cls_canprio.c | 41 ++++++++++++++++++++++++++++++-----------
 1 file changed, 30 insertions(+), 11 deletions(-)

diff --git a/net/sched/cls_canprio.c b/net/sched/cls_canprio.c
index bba0f4dd4fa..7efed62009f 100644
--- a/net/sched/cls_canprio.c
+++ b/net/sched/cls_canprio.c
@@ -70,6 +70,8 @@ struct canprio_rules {
 	int rules_count;
 	int eff_rules_count;
 	int sff_rules_count;
+
+	struct rcu_head rcu;
 };
 
 struct canprio_head {
@@ -136,40 +138,46 @@ static int canprio_classify(struct sk_buff *skb, struct tcf_proto *tp,
 {
 	struct canprio_head *head = (struct canprio_head *)tp->root;
 	struct canprio_filter *f;
+	struct canprio_rules *r;
 	u32 can_id;
 	int i;
 
 	printk(" canprio_classify() invoked\n");
 	can_id = (u32)canprio_get_id(skb);
 
+	rcu_read_lock();
 	list_for_each_entry(f, &head->flist, link) {
 		bool match = false;
+		r = rcu_dereference(f->rules);
+		
 
 		if (can_id & CAN_EFF_FLAG) {
 			can_id &= CAN_EFF_MASK;
 			
-			for (i = 0; i < f->rules->eff_rules_count; i++) {
-				if ((f->rules->rules_raw[i].can_id & f->rules->rules_raw[i].can_mask & CAN_EFF_MASK) ==
-					(can_id & f->rules->rules_raw[i].can_mask & CAN_EFF_MASK)) {
+			for (i = 0; i < r->eff_rules_count; i++) {
+				if ((r->rules_raw[i].can_id & r->rules_raw[i].can_mask & CAN_EFF_MASK) ==
+					(can_id & r->rules_raw[i].can_mask & CAN_EFF_MASK)) {
 
 					match = true;
 					break;
 				}
 			}
 		} else {
-			match = test_bit(can_id, f->rules->match_sff);
+			match = test_bit(can_id, r->match_sff);
 		}
 
-		//if (f->rules->inv_match_en)
+		//if (r->inv_match_en)
 		//	match = !match;
 
 		if (match) {
 			*res = f->res;
 			printk( "   canprio_classify() match ok: ID 0x%x\n", can_id);
+			rcu_read_unlock();
 			return TC_POLICE_OK;
 		}
 	}
 
+	rcu_read_unlock();
 	return TC_POLICE_UNSPEC;
 }
 
@@ -231,6 +239,11 @@ static unsigned int canprio_gen_handle(struct tcf_proto *tp)
 }
 
 
+static void canprio_rules_free_rcu(struct rcu_head *rcu)
+{
+	kfree(container_of(rcu, struct canprio_rules, rcu));
+}
+
 static int canprio_set_parms(struct tcf_proto *tp, struct canprio_filter *f,
 				unsigned long base, struct nlattr **tb,
 				struct nlattr *est)
@@ -301,13 +314,12 @@ static int canprio_set_parms(struct tcf_proto *tp, struct canprio_filter *f,
 		rules_tmp->inv_match_en = nla_get_u32(tb[TCA_CANPRIO_INV_EN]);
 
 	if (f->rules == NULL) { // Setting parameters for newly created filter
-		f->rules = rules_tmp;
+		rcu_assign_pointer(f->rules, rules_tmp);
 	} else { // Changing existing filter
 		struct canprio_rules *rules_old;
 
-		rules_old = f->rules;
-		f->rules = rules_tmp;
-		kfree(rules_old);		
+		rules_old = xchg(&f->rules, rules_tmp);
+		call_rcu(&rules_old->rcu, canprio_rules_free_rcu);
 	}
 
 	return 0;
@@ -408,6 +420,8 @@ errout:
 static void canprio_delete_filter(struct tcf_proto *tp, struct canprio_filter *f)
 {
 	tcf_unbind_filter(tp, &f->res);
+
+	rcu_barrier();
 	kfree(f->rules->rules_raw);
 	kfree(f->rules);
         kfree(f);
@@ -503,11 +517,14 @@ static int canprio_dump(struct tcf_proto *tp, unsigned long fh,
 {
 	struct canprio_filter *f = (struct canprio_filter *) fh;
 	struct nlattr *nest;
+	struct canprio_rules *r;
 	printk("%s() invoked\n", __FUNCTION__);
 
 	if (f == NULL)
 		return skb->len;
 
+	rcu_read_lock();
+	r = rcu_dereference(f->rules);
 	t->tcm_handle = f->handle;
 
 	nest = nla_nest_start(skb, TCA_OPTIONS);
@@ -517,16 +534,18 @@ static int canprio_dump(struct tcf_proto *tp, unsigned long fh,
 	if (f->res.classid)
 		NLA_PUT_U32(skb, TCA_CANPRIO_CLASSID, f->res.classid);
 
-	NLA_PUT(skb, TCA_CANPRIO_RULES, f->rules->rules_count * 
-		sizeof(struct can_filter), f->rules->rules_raw);
+	NLA_PUT(skb, TCA_CANPRIO_RULES, r->rules_count * 
+		sizeof(struct can_filter), r->rules_raw);
 
 
 	nla_nest_end(skb, nest);
 
+	rcu_read_unlock();
 	return skb->len;
 
 nla_put_failure:
 	nla_nest_cancel(skb, nest);
+	rcu_read_unlock();
 	return -1;
 }
 
-- 
2.39.2