net: rcu-ify tcf_proto
rcu'ify tcf_proto this allows calling tc_classify() without holding
any locks. Updaters are protected by RTNL.
This patch prepares the core net_sched infrastracture for running
the classifier/action chains without holding the qdisc lock however
it does nothing to ensure cls_xxx and act_xxx types also work without
locking. Additional patches are required to address the fall out.
Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
index c28b0d3..e547efd 100644
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -117,7 +117,6 @@
{
struct net *net = sock_net(skb->sk);
struct nlattr *tca[TCA_MAX + 1];
- spinlock_t *root_lock;
struct tcmsg *t;
u32 protocol;
u32 prio;
@@ -125,7 +124,8 @@
u32 parent;
struct net_device *dev;
struct Qdisc *q;
- struct tcf_proto **back, **chain;
+ struct tcf_proto __rcu **back;
+ struct tcf_proto __rcu **chain;
struct tcf_proto *tp;
const struct tcf_proto_ops *tp_ops;
const struct Qdisc_class_ops *cops;
@@ -197,7 +197,9 @@
goto errout;
/* Check the chain for existence of proto-tcf with this priority */
- for (back = chain; (tp = *back) != NULL; back = &tp->next) {
+ for (back = chain;
+ (tp = rtnl_dereference(*back)) != NULL;
+ back = &tp->next) {
if (tp->prio >= prio) {
if (tp->prio == prio) {
if (!nprio ||
@@ -209,8 +211,6 @@
}
}
- root_lock = qdisc_root_sleeping_lock(q);
-
if (tp == NULL) {
/* Proto-tcf does not exist, create new one */
@@ -259,7 +259,8 @@
}
tp->ops = tp_ops;
tp->protocol = protocol;
- tp->prio = nprio ? : TC_H_MAJ(tcf_auto_prio(*back));
+ tp->prio = nprio ? :
+ TC_H_MAJ(tcf_auto_prio(rtnl_dereference(*back)));
tp->q = q;
tp->classify = tp_ops->classify;
tp->classid = parent;
@@ -280,9 +281,9 @@
if (fh == 0) {
if (n->nlmsg_type == RTM_DELTFILTER && t->tcm_handle == 0) {
- spin_lock_bh(root_lock);
- *back = tp->next;
- spin_unlock_bh(root_lock);
+ struct tcf_proto *next = rtnl_dereference(tp->next);
+
+ RCU_INIT_POINTER(*back, next);
tfilter_notify(net, skb, n, tp, fh, RTM_DELTFILTER);
tcf_destroy(tp);
@@ -322,10 +323,8 @@
n->nlmsg_flags & NLM_F_CREATE ? TCA_ACT_NOREPLACE : TCA_ACT_REPLACE);
if (err == 0) {
if (tp_created) {
- spin_lock_bh(root_lock);
- tp->next = *back;
- *back = tp;
- spin_unlock_bh(root_lock);
+ RCU_INIT_POINTER(tp->next, rtnl_dereference(*back));
+ rcu_assign_pointer(*back, tp);
}
tfilter_notify(net, skb, n, tp, fh, RTM_NEWTFILTER);
} else {
@@ -420,7 +419,7 @@
int s_t;
struct net_device *dev;
struct Qdisc *q;
- struct tcf_proto *tp, **chain;
+ struct tcf_proto *tp, __rcu **chain;
struct tcmsg *tcm = nlmsg_data(cb->nlh);
unsigned long cl = 0;
const struct Qdisc_class_ops *cops;
@@ -454,7 +453,8 @@
s_t = cb->args[0];
- for (tp = *chain, t = 0; tp; tp = tp->next, t++) {
+ for (tp = rtnl_dereference(*chain), t = 0;
+ tp; tp = rtnl_dereference(tp->next), t++) {
if (t < s_t)
continue;
if (TC_H_MAJ(tcm->tcm_info) &&