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Message-ID: <20140910155050.2036.26320.stgit@nitbit.x32>
Date: Wed, 10 Sep 2014 08:50:52 -0700
From: John Fastabend <john.fastabend@...il.com>
To: xiyou.wangcong@...il.com, davem@...emloft.net,
eric.dumazet@...il.com, jhs@...atatu.com
Cc: netdev@...r.kernel.org, paulmck@...ux.vnet.ibm.com,
brouer@...hat.com
Subject: [net-next PATCH v4 10/16] net: sched: make cls_u32 lockless
Make cls_u32 classifier safe to run without holding lock. This patch
converts statistics that are kept in read section u32_classify into
per cpu counters.
This patch was tested with a tight u32 filter add/delete loop while
generating traffic with pktgen. By running pktgen on vlan devices
created on top of a physical device we can hit the qdisc layer
correctly. For ingress qdisc's a loopback cable was used.
for i in {1..100}; do
q=`echo $i%8|bc`;
echo -n "u32 tos: iteration $i on queue $q";
tc filter add dev p3p2 parent $p prio $i u32 match ip tos 0x10 0xff \
action skbedit queue_mapping $q;
sleep 1;
tc filter del dev p3p2 prio $i;
echo -n "u32 tos hash table: iteration $i on queue $q";
tc filter add dev p3p2 parent $p protocol ip prio $i handle 628: u32 divisor 1
tc filter add dev p3p2 parent $p protocol ip prio $i u32 \
match ip protocol 17 0xff link 628: offset at 0 mask 0xf00 shift 6 plus 0
tc filter add dev p3p2 parent $p protocol ip prio $i u32 \
ht 628:0 match ip tos 0x10 0xff action skbedit queue_mapping $q
sleep 2;
tc filter del dev p3p2 prio $i
sleep 1;
done
Signed-off-by: John Fastabend <john.r.fastabend@...el.com>
---
net/sched/cls_u32.c | 183 +++++++++++++++++++++++++++++++--------------------
1 file changed, 110 insertions(+), 73 deletions(-)
diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c
index f3227d7..5ed5ac4 100644
--- a/net/sched/cls_u32.c
+++ b/net/sched/cls_u32.c
@@ -36,6 +36,7 @@
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/errno.h>
+#include <linux/percpu.h>
#include <linux/rtnetlink.h>
#include <linux/skbuff.h>
#include <linux/bitmap.h>
@@ -44,16 +45,16 @@
#include <net/pkt_cls.h>
struct tc_u_knode {
- struct tc_u_knode *next;
+ struct tc_u_knode __rcu *next;
u32 handle;
- struct tc_u_hnode *ht_up;
+ struct tc_u_hnode __rcu *ht_up;
struct tcf_exts exts;
#ifdef CONFIG_NET_CLS_IND
int ifindex;
#endif
u8 fshift;
struct tcf_result res;
- struct tc_u_hnode *ht_down;
+ struct tc_u_hnode __rcu *ht_down;
#ifdef CONFIG_CLS_U32_PERF
struct tc_u32_pcnt __percpu *pf;
#endif
@@ -62,24 +63,28 @@ struct tc_u_knode {
u32 mask;
u32 __percpu *pcpu_success;
#endif
+ struct tcf_proto *tp;
struct tc_u32_sel sel;
+ struct rcu_head rcu;
};
struct tc_u_hnode {
- struct tc_u_hnode *next;
+ struct tc_u_hnode __rcu *next;
u32 handle;
u32 prio;
struct tc_u_common *tp_c;
int refcnt;
unsigned int divisor;
- struct tc_u_knode *ht[1];
+ struct tc_u_knode __rcu *ht[1];
+ struct rcu_head rcu;
};
struct tc_u_common {
- struct tc_u_hnode *hlist;
+ struct tc_u_hnode __rcu *hlist;
struct Qdisc *q;
int refcnt;
u32 hgenerator;
+ struct rcu_head rcu;
};
static inline unsigned int u32_hash_fold(__be32 key,
@@ -98,7 +103,7 @@ static int u32_classify(struct sk_buff *skb, const struct tcf_proto *tp, struct
unsigned int off;
} stack[TC_U32_MAXDEPTH];
- struct tc_u_hnode *ht = tp->root;
+ struct tc_u_hnode *ht = rcu_dereference_bh(tp->root);
unsigned int off = skb_network_offset(skb);
struct tc_u_knode *n;
int sdepth = 0;
@@ -110,7 +115,7 @@ static int u32_classify(struct sk_buff *skb, const struct tcf_proto *tp, struct
int i, r;
next_ht:
- n = ht->ht[sel];
+ n = rcu_dereference_bh(ht->ht[sel]);
next_knode:
if (n) {
@@ -123,7 +128,7 @@ next_knode:
#ifdef CONFIG_CLS_U32_MARK
if ((skb->mark & n->mask) != n->val) {
- n = n->next;
+ n = rcu_dereference_bh(n->next);
goto next_knode;
} else {
__this_cpu_inc(*n->pcpu_success);
@@ -141,7 +146,7 @@ next_knode:
if (!data)
goto out;
if ((*data ^ key->val) & key->mask) {
- n = n->next;
+ n = rcu_dereference_bh(n->next);
goto next_knode;
}
#ifdef CONFIG_CLS_U32_PERF
@@ -149,14 +154,16 @@ next_knode:
j++;
#endif
}
- if (n->ht_down == NULL) {
+
+ ht = rcu_dereference_bh(n->ht_down);
+ if (!ht) {
check_terminal:
if (n->sel.flags & TC_U32_TERMINAL) {
*res = n->res;
#ifdef CONFIG_NET_CLS_IND
if (!tcf_match_indev(skb, n->ifindex)) {
- n = n->next;
+ n = rcu_dereference_bh(n->next);
goto next_knode;
}
#endif
@@ -165,13 +172,13 @@ check_terminal:
#endif
r = tcf_exts_exec(skb, &n->exts, res);
if (r < 0) {
- n = n->next;
+ n = rcu_dereference_bh(n->next);
goto next_knode;
}
return r;
}
- n = n->next;
+ n = rcu_dereference_bh(n->next);
goto next_knode;
}
@@ -182,7 +189,7 @@ check_terminal:
stack[sdepth].off = off;
sdepth++;
- ht = n->ht_down;
+ ht = rcu_dereference_bh(n->ht_down);
sel = 0;
if (ht->divisor) {
__be32 *data, hdata;
@@ -224,7 +231,7 @@ check_terminal:
/* POP */
if (sdepth--) {
n = stack[sdepth].knode;
- ht = n->ht_up;
+ ht = rcu_dereference_bh(n->ht_up);
off = stack[sdepth].off;
goto check_terminal;
}
@@ -241,7 +248,9 @@ u32_lookup_ht(struct tc_u_common *tp_c, u32 handle)
{
struct tc_u_hnode *ht;
- for (ht = tp_c->hlist; ht; ht = ht->next)
+ for (ht = rtnl_dereference(tp_c->hlist);
+ ht;
+ ht = rtnl_dereference(ht->next))
if (ht->handle == handle)
break;
@@ -258,7 +267,9 @@ u32_lookup_key(struct tc_u_hnode *ht, u32 handle)
if (sel > ht->divisor)
goto out;
- for (n = ht->ht[sel]; n; n = n->next)
+ for (n = rtnl_dereference(ht->ht[sel]);
+ n;
+ n = rtnl_dereference(n->next))
if (n->handle == handle)
break;
out:
@@ -272,7 +283,7 @@ static unsigned long u32_get(struct tcf_proto *tp, u32 handle)
struct tc_u_common *tp_c = tp->data;
if (TC_U32_HTID(handle) == TC_U32_ROOT)
- ht = tp->root;
+ ht = rtnl_dereference(tp->root);
else
ht = u32_lookup_ht(tp_c, TC_U32_HTID(handle));
@@ -293,6 +304,9 @@ static u32 gen_new_htid(struct tc_u_common *tp_c)
{
int i = 0x800;
+ /* hgenerator only used inside rtnl lock it is safe to increment
+ * without read _copy_ update semantics
+ */
do {
if (++tp_c->hgenerator == 0x7FF)
tp_c->hgenerator = 1;
@@ -328,11 +342,11 @@ static int u32_init(struct tcf_proto *tp)
}
tp_c->refcnt++;
- root_ht->next = tp_c->hlist;
- tp_c->hlist = root_ht;
+ RCU_INIT_POINTER(root_ht->next, tp_c->hlist);
+ rcu_assign_pointer(tp_c->hlist, root_ht);
root_ht->tp_c = tp_c;
- tp->root = root_ht;
+ rcu_assign_pointer(tp->root, root_ht);
tp->data = tp_c;
return 0;
}
@@ -350,19 +364,27 @@ static int u32_destroy_key(struct tcf_proto *tp, struct tc_u_knode *n)
return 0;
}
+static void u32_delete_key_rcu(struct rcu_head *rcu)
+{
+ struct tc_u_knode *key = container_of(rcu, struct tc_u_knode, rcu);
+
+ u32_destroy_key(key->tp, key);
+}
+
static int u32_delete_key(struct tcf_proto *tp, struct tc_u_knode *key)
{
- struct tc_u_knode **kp;
+ struct tc_u_knode __rcu **kp;
+ struct tc_u_knode *pkp;
struct tc_u_hnode *ht = key->ht_up;
if (ht) {
- for (kp = &ht->ht[TC_U32_HASH(key->handle)]; *kp; kp = &(*kp)->next) {
- if (*kp == key) {
- tcf_tree_lock(tp);
- *kp = key->next;
- tcf_tree_unlock(tp);
+ kp = &ht->ht[TC_U32_HASH(key->handle)];
+ for (pkp = rtnl_dereference(*kp); pkp;
+ kp = &pkp->next, pkp = rtnl_dereference(*kp)) {
+ if (pkp == key) {
+ RCU_INIT_POINTER(*kp, key->next);
- u32_destroy_key(tp, key);
+ call_rcu(&key->rcu, u32_delete_key_rcu);
return 0;
}
}
@@ -371,16 +393,16 @@ static int u32_delete_key(struct tcf_proto *tp, struct tc_u_knode *key)
return 0;
}
-static void u32_clear_hnode(struct tcf_proto *tp, struct tc_u_hnode *ht)
+static void u32_clear_hnode(struct tc_u_hnode *ht)
{
struct tc_u_knode *n;
unsigned int h;
for (h = 0; h <= ht->divisor; h++) {
- while ((n = ht->ht[h]) != NULL) {
- ht->ht[h] = n->next;
-
- u32_destroy_key(tp, n);
+ while ((n = rtnl_dereference(ht->ht[h])) != NULL) {
+ RCU_INIT_POINTER(ht->ht[h],
+ rtnl_dereference(n->next));
+ call_rcu(&n->rcu, u32_delete_key_rcu);
}
}
}
@@ -388,28 +410,31 @@ static void u32_clear_hnode(struct tcf_proto *tp, struct tc_u_hnode *ht)
static int u32_destroy_hnode(struct tcf_proto *tp, struct tc_u_hnode *ht)
{
struct tc_u_common *tp_c = tp->data;
- struct tc_u_hnode **hn;
+ struct tc_u_hnode __rcu **hn;
+ struct tc_u_hnode *phn;
WARN_ON(ht->refcnt);
- u32_clear_hnode(tp, ht);
+ u32_clear_hnode(ht);
- for (hn = &tp_c->hlist; *hn; hn = &(*hn)->next) {
- if (*hn == ht) {
- *hn = ht->next;
- kfree(ht);
+ hn = &tp_c->hlist;
+ for (phn = rtnl_dereference(*hn);
+ phn;
+ hn = &phn->next, phn = rtnl_dereference(*hn)) {
+ if (phn == ht) {
+ RCU_INIT_POINTER(*hn, ht->next);
+ kfree_rcu(ht, rcu);
return 0;
}
}
- WARN_ON(1);
return -ENOENT;
}
static void u32_destroy(struct tcf_proto *tp)
{
struct tc_u_common *tp_c = tp->data;
- struct tc_u_hnode *root_ht = tp->root;
+ struct tc_u_hnode *root_ht = rtnl_dereference(tp->root);
WARN_ON(root_ht == NULL);
@@ -421,17 +446,16 @@ static void u32_destroy(struct tcf_proto *tp)
tp->q->u32_node = NULL;
- for (ht = tp_c->hlist; ht; ht = ht->next) {
+ for (ht = rtnl_dereference(tp_c->hlist);
+ ht;
+ ht = rtnl_dereference(ht->next)) {
ht->refcnt--;
- u32_clear_hnode(tp, ht);
+ u32_clear_hnode(ht);
}
- while ((ht = tp_c->hlist) != NULL) {
- tp_c->hlist = ht->next;
-
- WARN_ON(ht->refcnt != 0);
-
- kfree(ht);
+ while ((ht = rtnl_dereference(tp_c->hlist)) != NULL) {
+ RCU_INIT_POINTER(tp_c->hlist, ht->next);
+ kfree_rcu(ht, rcu);
}
kfree(tp_c);
@@ -443,6 +467,7 @@ static void u32_destroy(struct tcf_proto *tp)
static int u32_delete(struct tcf_proto *tp, unsigned long arg)
{
struct tc_u_hnode *ht = (struct tc_u_hnode *)arg;
+ struct tc_u_hnode *root_ht = rtnl_dereference(tp->root);
if (ht == NULL)
return 0;
@@ -450,7 +475,7 @@ static int u32_delete(struct tcf_proto *tp, unsigned long arg)
if (TC_U32_KEY(ht->handle))
return u32_delete_key(tp, (struct tc_u_knode *)ht);
- if (tp->root == ht)
+ if (root_ht == ht)
return -EINVAL;
if (ht->refcnt == 1) {
@@ -473,7 +498,9 @@ static u32 gen_new_kid(struct tc_u_hnode *ht, u32 handle)
if (!bitmap)
return handle | 0xFFF;
- for (n = ht->ht[TC_U32_HASH(handle)]; n; n = n->next)
+ for (n = rtnl_dereference(ht->ht[TC_U32_HASH(handle)]);
+ n;
+ n = rtnl_dereference(n->next))
set_bit(TC_U32_NODE(n->handle), bitmap);
i = find_next_zero_bit(bitmap, NR_U32_NODE, 0x800);
@@ -523,10 +550,8 @@ static int u32_set_parms(struct net *net, struct tcf_proto *tp,
ht_down->refcnt++;
}
- tcf_tree_lock(tp);
- ht_old = n->ht_down;
- n->ht_down = ht_down;
- tcf_tree_unlock(tp);
+ ht_old = rtnl_dereference(n->ht_down);
+ rcu_assign_pointer(n->ht_down, ht_down);
if (ht_old)
ht_old->refcnt--;
@@ -606,8 +631,8 @@ static int u32_change(struct net *net, struct sk_buff *in_skb,
ht->divisor = divisor;
ht->handle = handle;
ht->prio = tp->prio;
- ht->next = tp_c->hlist;
- tp_c->hlist = ht;
+ RCU_INIT_POINTER(ht->next, tp_c->hlist);
+ rcu_assign_pointer(tp_c->hlist, ht);
*arg = (unsigned long)ht;
return 0;
}
@@ -615,7 +640,7 @@ static int u32_change(struct net *net, struct sk_buff *in_skb,
if (tb[TCA_U32_HASH]) {
htid = nla_get_u32(tb[TCA_U32_HASH]);
if (TC_U32_HTID(htid) == TC_U32_ROOT) {
- ht = tp->root;
+ ht = rtnl_dereference(tp->root);
htid = ht->handle;
} else {
ht = u32_lookup_ht(tp->data, TC_U32_HTID(htid));
@@ -623,7 +648,7 @@ static int u32_change(struct net *net, struct sk_buff *in_skb,
return -EINVAL;
}
} else {
- ht = tp->root;
+ ht = rtnl_dereference(tp->root);
htid = ht->handle;
}
@@ -660,6 +685,7 @@ static int u32_change(struct net *net, struct sk_buff *in_skb,
n->handle = handle;
n->fshift = s->hmask ? ffs(ntohl(s->hmask)) - 1 : 0;
tcf_exts_init(&n->exts, TCA_U32_ACT, TCA_U32_POLICE);
+ n->tp = tp;
#ifdef CONFIG_CLS_U32_MARK
n->pcpu_success = alloc_percpu(u32);
@@ -675,21 +701,23 @@ static int u32_change(struct net *net, struct sk_buff *in_skb,
err = u32_set_parms(net, tp, base, ht, n, tb, tca[TCA_RATE], ovr);
if (err == 0) {
- struct tc_u_knode **ins;
- for (ins = &ht->ht[TC_U32_HASH(handle)]; *ins; ins = &(*ins)->next)
- if (TC_U32_NODE(handle) < TC_U32_NODE((*ins)->handle))
+ struct tc_u_knode __rcu **ins;
+ struct tc_u_knode *pins;
+
+ ins = &ht->ht[TC_U32_HASH(handle)];
+ for (pins = rtnl_dereference(*ins); pins;
+ ins = &pins->next, pins = rtnl_dereference(*ins))
+ if (TC_U32_NODE(handle) < TC_U32_NODE(pins->handle))
break;
- n->next = *ins;
- tcf_tree_lock(tp);
- *ins = n;
- tcf_tree_unlock(tp);
+ RCU_INIT_POINTER(n->next, pins);
+ rcu_assign_pointer(*ins, n);
*arg = (unsigned long)n;
return 0;
}
#ifdef CONFIG_CLS_U32_PERF
- kfree(n->pf);
+ free_percpu(n->pf);
#endif
kfree(n);
return err;
@@ -705,7 +733,9 @@ static void u32_walk(struct tcf_proto *tp, struct tcf_walker *arg)
if (arg->stop)
return;
- for (ht = tp_c->hlist; ht; ht = ht->next) {
+ for (ht = rtnl_dereference(tp_c->hlist);
+ ht;
+ ht = rtnl_dereference(ht->next)) {
if (ht->prio != tp->prio)
continue;
if (arg->count >= arg->skip) {
@@ -716,7 +746,9 @@ static void u32_walk(struct tcf_proto *tp, struct tcf_walker *arg)
}
arg->count++;
for (h = 0; h <= ht->divisor; h++) {
- for (n = ht->ht[h]; n; n = n->next) {
+ for (n = rtnl_dereference(ht->ht[h]);
+ n;
+ n = rtnl_dereference(n->next)) {
if (arg->count < arg->skip) {
arg->count++;
continue;
@@ -735,6 +767,7 @@ static int u32_dump(struct net *net, struct tcf_proto *tp, unsigned long fh,
struct sk_buff *skb, struct tcmsg *t)
{
struct tc_u_knode *n = (struct tc_u_knode *)fh;
+ struct tc_u_hnode *ht_up, *ht_down;
struct nlattr *nest;
if (n == NULL)
@@ -762,7 +795,9 @@ static int u32_dump(struct net *net, struct tcf_proto *tp, unsigned long fh,
sizeof(n->sel) + n->sel.nkeys*sizeof(struct tc_u32_key),
&n->sel))
goto nla_put_failure;
- if (n->ht_up) {
+
+ ht_up = rtnl_dereference(n->ht_up);
+ if (ht_up) {
u32 htid = n->handle & 0xFFFFF000;
if (nla_put_u32(skb, TCA_U32_HASH, htid))
goto nla_put_failure;
@@ -770,8 +805,10 @@ static int u32_dump(struct net *net, struct tcf_proto *tp, unsigned long fh,
if (n->res.classid &&
nla_put_u32(skb, TCA_U32_CLASSID, n->res.classid))
goto nla_put_failure;
- if (n->ht_down &&
- nla_put_u32(skb, TCA_U32_LINK, n->ht_down->handle))
+
+ ht_down = rtnl_dereference(n->ht_down);
+ if (ht_down &&
+ nla_put_u32(skb, TCA_U32_LINK, ht_down->handle))
goto nla_put_failure;
#ifdef CONFIG_CLS_U32_MARK
--
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