net_sched: get rid of tcfa_rcu
gen estimator has been rewritten in commit 1c0d32fde5bd
("net_sched: gen_estimator: complete rewrite of rate estimators"),
the caller is no longer needed to wait for a grace period.
So this patch gets rid of it.
This also completely closes a race condition between action free
path and filter chain add/remove path for the following patch.
Because otherwise the nested RCU callback can't be caught by
rcu_barrier().
Please see also the comments in code.
Cc: Jiri Pirko <jiri@mellanox.com>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: Eric Dumazet <edumazet@google.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sched/act_api.c b/net/sched/act_api.c
index a306974..fcd7dc7 100644
--- a/net/sched/act_api.c
+++ b/net/sched/act_api.c
@@ -53,10 +53,13 @@ static void tcf_action_goto_chain_exec(const struct tc_action *a,
res->goto_tp = rcu_dereference_bh(chain->filter_chain);
}
-static void free_tcf(struct rcu_head *head)
+/* XXX: For standalone actions, we don't need a RCU grace period either, because
+ * actions are always connected to filters and filters are already destroyed in
+ * RCU callbacks, so after a RCU grace period actions are already disconnected
+ * from filters. Readers later can not find us.
+ */
+static void free_tcf(struct tc_action *p)
{
- struct tc_action *p = container_of(head, struct tc_action, tcfa_rcu);
-
free_percpu(p->cpu_bstats);
free_percpu(p->cpu_qstats);
@@ -76,11 +79,7 @@ static void tcf_idr_remove(struct tcf_idrinfo *idrinfo, struct tc_action *p)
idr_remove_ext(&idrinfo->action_idr, p->tcfa_index);
spin_unlock_bh(&idrinfo->lock);
gen_kill_estimator(&p->tcfa_rate_est);
- /*
- * gen_estimator est_timer() might access p->tcfa_lock
- * or bstats, wait a RCU grace period before freeing p
- */
- call_rcu(&p->tcfa_rcu, free_tcf);
+ free_tcf(p);
}
int __tcf_idr_release(struct tc_action *p, bool bind, bool strict)
@@ -259,7 +258,7 @@ void tcf_idr_cleanup(struct tc_action *a, struct nlattr *est)
{
if (est)
gen_kill_estimator(&a->tcfa_rate_est);
- call_rcu(&a->tcfa_rcu, free_tcf);
+ free_tcf(a);
}
EXPORT_SYMBOL(tcf_idr_cleanup);