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SubjectRe: RCU : Use call_rcu_bh() in route cache [3/5]
Use call_rcu_bh() in route cache. This allows faster grace periods and
avoids dst cache overflows during DoS testing.

Thanks
Dipankar


This patch uses the call_rcu_bh() api in route cache code to
facilitate quicker RCU grace periods. Quicker grace periods
avoid overflow of dst cache in heavily loaded routers as
seen in Robert Olsson's testing.

Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com>


net/decnet/dn_route.c | 28 ++++++++++++++--------------
net/ipv4/route.c | 26 +++++++++++++-------------
2 files changed, 27 insertions(+), 27 deletions(-)
diff -puN net/decnet/dn_route.c~rcu-use-call-rcu-bh net/decnet/dn_route.c
--- linux-2.6.8-rc3-mm1/net/decnet/dn_route.c~rcu-use-call-rcu-bh 2004-08-07 15:29:16.000000000 +0530
+++ linux-2.6.8-rc3-mm1-dipankar/net/decnet/dn_route.c 2004-08-07 15:29:16.000000000 +0530
@@ -146,14 +146,14 @@ static __inline__ unsigned dn_hash(unsig

static inline void dnrt_free(struct dn_route *rt)
{
- call_rcu(&rt->u.dst.rcu_head, dst_rcu_free);
+ call_rcu_bh(&rt->u.dst.rcu_head, dst_rcu_free);
}

static inline void dnrt_drop(struct dn_route *rt)
{
if (rt)
dst_release(&rt->u.dst);
- call_rcu(&rt->u.dst.rcu_head, dst_rcu_free);
+ call_rcu_bh(&rt->u.dst.rcu_head, dst_rcu_free);
}

static void dn_dst_check_expire(unsigned long dummy)
@@ -1174,9 +1174,9 @@ static int __dn_route_output_key(struct
struct dn_route *rt = NULL;

if (!(flags & MSG_TRYHARD)) {
- rcu_read_lock();
+ rcu_read_lock_bh();
for(rt = dn_rt_hash_table[hash].chain; rt; rt = rt->u.rt_next) {
- read_barrier_depends();
+ smp_read_barrier_depends();
if ((flp->fld_dst == rt->fl.fld_dst) &&
(flp->fld_src == rt->fl.fld_src) &&
#ifdef CONFIG_DECNET_ROUTE_FWMARK
@@ -1187,12 +1187,12 @@ static int __dn_route_output_key(struct
rt->u.dst.lastuse = jiffies;
dst_hold(&rt->u.dst);
rt->u.dst.__use++;
- rcu_read_unlock();
+ rcu_read_unlock_bh();
*pprt = &rt->u.dst;
return 0;
}
}
- rcu_read_unlock();
+ rcu_read_unlock_bh();
}

return dn_route_output_slow(pprt, flp, flags);
@@ -1647,21 +1647,21 @@ int dn_cache_dump(struct sk_buff *skb, s
continue;
if (h > s_h)
s_idx = 0;
- rcu_read_lock();
+ rcu_read_lock_bh();
for(rt = dn_rt_hash_table[h].chain, idx = 0; rt; rt = rt->u.rt_next, idx++) {
- read_barrier_depends();
+ smp_read_barrier_depends();
if (idx < s_idx)
continue;
skb->dst = dst_clone(&rt->u.dst);
if (dn_rt_fill_info(skb, NETLINK_CB(cb->skb).pid,
cb->nlh->nlmsg_seq, RTM_NEWROUTE, 1) <= 0) {
dst_release(xchg(&skb->dst, NULL));
- rcu_read_unlock();
+ rcu_read_unlock_bh();
goto done;
}
dst_release(xchg(&skb->dst, NULL));
}
- rcu_read_unlock();
+ rcu_read_unlock_bh();
}

done:
@@ -1681,7 +1681,7 @@ static struct dn_route *dn_rt_cache_get_
struct dn_rt_cache_iter_state *s = seq->private;

for(s->bucket = dn_rt_hash_mask; s->bucket >= 0; --s->bucket) {
- rcu_read_lock();
+ rcu_read_lock_bh();
rt = dn_rt_hash_table[s->bucket].chain;
if (rt)
break;
@@ -1697,10 +1697,10 @@ static struct dn_route *dn_rt_cache_get_
smp_read_barrier_depends();
rt = rt->u.rt_next;
while(!rt) {
- rcu_read_unlock();
+ rcu_read_unlock_bh();
if (--s->bucket < 0)
break;
- rcu_read_lock();
+ rcu_read_lock_bh();
rt = dn_rt_hash_table[s->bucket].chain;
}
return rt;
@@ -1727,7 +1727,7 @@ static void *dn_rt_cache_seq_next(struct
static void dn_rt_cache_seq_stop(struct seq_file *seq, void *v)
{
if (v)
- rcu_read_unlock();
+ rcu_read_unlock_bh();
}

static int dn_rt_cache_seq_show(struct seq_file *seq, void *v)
diff -puN net/ipv4/route.c~rcu-use-call-rcu-bh net/ipv4/route.c
--- linux-2.6.8-rc3-mm1/net/ipv4/route.c~rcu-use-call-rcu-bh 2004-08-07 15:29:16.000000000 +0530
+++ linux-2.6.8-rc3-mm1-dipankar/net/ipv4/route.c 2004-08-07 15:29:16.000000000 +0530
@@ -226,11 +226,11 @@ static struct rtable *rt_cache_get_first
struct rt_cache_iter_state *st = seq->private;

for (st->bucket = rt_hash_mask; st->bucket >= 0; --st->bucket) {
- rcu_read_lock();
+ rcu_read_lock_bh();
r = rt_hash_table[st->bucket].chain;
if (r)
break;
- rcu_read_unlock();
+ rcu_read_unlock_bh();
}
return r;
}
@@ -242,10 +242,10 @@ static struct rtable *rt_cache_get_next(
smp_read_barrier_depends();
r = r->u.rt_next;
while (!r) {
- rcu_read_unlock();
+ rcu_read_unlock_bh();
if (--st->bucket < 0)
break;
- rcu_read_lock();
+ rcu_read_lock_bh();
r = rt_hash_table[st->bucket].chain;
}
return r;
@@ -281,7 +281,7 @@ static void *rt_cache_seq_next(struct se
static void rt_cache_seq_stop(struct seq_file *seq, void *v)
{
if (v && v != SEQ_START_TOKEN)
- rcu_read_unlock();
+ rcu_read_unlock_bh();
}

static int rt_cache_seq_show(struct seq_file *seq, void *v)
@@ -439,13 +439,13 @@ static struct file_operations rt_cpu_seq

static __inline__ void rt_free(struct rtable *rt)
{
- call_rcu(&rt->u.dst.rcu_head, dst_rcu_free);
+ call_rcu_bh(&rt->u.dst.rcu_head, dst_rcu_free);
}

static __inline__ void rt_drop(struct rtable *rt)
{
ip_rt_put(rt);
- call_rcu(&rt->u.dst.rcu_head, dst_rcu_free);
+ call_rcu_bh(&rt->u.dst.rcu_head, dst_rcu_free);
}

static __inline__ int rt_fast_clean(struct rtable *rth)
@@ -2231,7 +2231,7 @@ int __ip_route_output_key(struct rtable

hash = rt_hash_code(flp->fl4_dst, flp->fl4_src ^ (flp->oif << 5), flp->fl4_tos);

- rcu_read_lock();
+ rcu_read_lock_bh();
for (rth = rt_hash_table[hash].chain; rth; rth = rth->u.rt_next) {
smp_read_barrier_depends();
if (rth->fl.fl4_dst == flp->fl4_dst &&
@@ -2247,13 +2247,13 @@ int __ip_route_output_key(struct rtable
dst_hold(&rth->u.dst);
rth->u.dst.__use++;
RT_CACHE_STAT_INC(out_hit);
- rcu_read_unlock();
+ rcu_read_unlock_bh();
*rp = rth;
return 0;
}
RT_CACHE_STAT_INC(out_hlist_search);
}
- rcu_read_unlock();
+ rcu_read_unlock_bh();

return ip_route_output_slow(rp, flp);
}
@@ -2463,7 +2463,7 @@ int ip_rt_dump(struct sk_buff *skb, str
if (h < s_h) continue;
if (h > s_h)
s_idx = 0;
- rcu_read_lock();
+ rcu_read_lock_bh();
for (rt = rt_hash_table[h].chain, idx = 0; rt;
rt = rt->u.rt_next, idx++) {
smp_read_barrier_depends();
@@ -2474,12 +2474,12 @@ int ip_rt_dump(struct sk_buff *skb, str
cb->nlh->nlmsg_seq,
RTM_NEWROUTE, 1) <= 0) {
dst_release(xchg(&skb->dst, NULL));
- rcu_read_unlock();
+ rcu_read_unlock_bh();
goto done;
}
dst_release(xchg(&skb->dst, NULL));
}
- rcu_read_unlock();
+ rcu_read_unlock_bh();
}

done:
_
-
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