From 7f5c6d4f665bb57a19a34ce1fb16cc708c04f219 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Mon, 4 Apr 2011 17:04:03 +0200 Subject: netfilter: get rid of atomic ops in fast path We currently use a percpu spinlock to 'protect' rule bytes/packets counters, after various attempts to use RCU instead. Lately we added a seqlock so that get_counters() can run without blocking BH or 'writers'. But we really only need the seqcount in it. Spinlock itself is only locked by the current/owner cpu, so we can remove it completely. This cleanups api, using correct 'writer' vs 'reader' semantic. At replace time, the get_counters() call makes sure all cpus are done using the old table. Signed-off-by: Eric Dumazet Cc: Jan Engelhardt Signed-off-by: Patrick McHardy --- net/ipv4/netfilter/arp_tables.c | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-) (limited to 'net/ipv4/netfilter/arp_tables.c') diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c index 4b5d457c2d7..2ea74333683 100644 --- a/net/ipv4/netfilter/arp_tables.c +++ b/net/ipv4/netfilter/arp_tables.c @@ -260,6 +260,7 @@ unsigned int arpt_do_table(struct sk_buff *skb, void *table_base; const struct xt_table_info *private; struct xt_action_param acpar; + unsigned int addend; if (!pskb_may_pull(skb, arp_hdr_len(skb->dev))) return NF_DROP; @@ -267,7 +268,8 @@ unsigned int arpt_do_table(struct sk_buff *skb, indev = in ? in->name : nulldevname; outdev = out ? out->name : nulldevname; - xt_info_rdlock_bh(); + local_bh_disable(); + addend = xt_write_recseq_begin(); private = table->private; table_base = private->entries[smp_processor_id()]; @@ -338,7 +340,8 @@ unsigned int arpt_do_table(struct sk_buff *skb, /* Verdict */ break; } while (!acpar.hotdrop); - xt_info_rdunlock_bh(); + xt_write_recseq_end(addend); + local_bh_enable(); if (acpar.hotdrop) return NF_DROP; @@ -712,7 +715,7 @@ static void get_counters(const struct xt_table_info *t, unsigned int i; for_each_possible_cpu(cpu) { - seqlock_t *lock = &per_cpu(xt_info_locks, cpu).lock; + seqcount_t *s = &per_cpu(xt_recseq, cpu); i = 0; xt_entry_foreach(iter, t->entries[cpu], t->size) { @@ -720,10 +723,10 @@ static void get_counters(const struct xt_table_info *t, unsigned int start; do { - start = read_seqbegin(lock); + start = read_seqcount_begin(s); bcnt = iter->counters.bcnt; pcnt = iter->counters.pcnt; - } while (read_seqretry(lock, start)); + } while (read_seqcount_retry(s, start)); ADD_COUNTER(counters[i], bcnt, pcnt); ++i; @@ -1115,6 +1118,7 @@ static int do_add_counters(struct net *net, const void __user *user, int ret = 0; void *loc_cpu_entry; struct arpt_entry *iter; + unsigned int addend; #ifdef CONFIG_COMPAT struct compat_xt_counters_info compat_tmp; @@ -1171,12 +1175,12 @@ static int do_add_counters(struct net *net, const void __user *user, /* Choose the copy that is on our node */ curcpu = smp_processor_id(); loc_cpu_entry = private->entries[curcpu]; - xt_info_wrlock(curcpu); + addend = xt_write_recseq_begin(); xt_entry_foreach(iter, loc_cpu_entry, private->size) { ADD_COUNTER(iter->counters, paddc[i].bcnt, paddc[i].pcnt); ++i; } - xt_info_wrunlock(curcpu); + xt_write_recseq_end(addend); unlock_up_free: local_bh_enable(); xt_table_unlock(t); -- cgit v1.2.3