On Fri, 2016-12-09 at 06:24 -0800, Eric Dumazet wrote:
> It looks that you want a seqcount, even on 64bit arches,
> so that CPU 2 can restart its loop, and more importantly you need
> to not accumulate the values you read, because they might be old/invalid.
Untested patch to give general idea. I can polish it a bit later today.
net/netfilter/nft_counter.c | 59 +++++++++++++---------------------
1 file changed, 23 insertions(+), 36 deletions(-)
diff --git a/net/netfilter/nft_counter.c b/net/netfilter/nft_counter.c
index f6a02c5071c2aeafca7635da3282a809aa04d6ab..57ed95b024473a2aa76298fe5bb5013bf709801b 100644
--- a/net/netfilter/nft_counter.c
+++ b/net/netfilter/nft_counter.c
@@ -31,18 +31,25 @@ struct nft_counter_percpu_priv {
struct nft_counter_percpu __percpu *counter;
};
+static DEFINE_PER_CPU(seqcount_t, nft_counter_seq);
+
static inline void nft_counter_do_eval(struct nft_counter_percpu_priv *priv,
struct nft_regs *regs,
const struct nft_pktinfo *pkt)
{
struct nft_counter_percpu *this_cpu;
+ seqcount_t *myseq;
local_bh_disable();
this_cpu = this_cpu_ptr(priv->counter);
- u64_stats_update_begin(&this_cpu->syncp);
+ myseq = this_cpu_ptr(&nft_counter_seq);
+
+ write_seqcount_begin(myseq);
+
this_cpu->counter.bytes += pkt->skb->len;
this_cpu->counter.packets++;
- u64_stats_update_end(&this_cpu->syncp);
+
+ write_seqcount_end(myseq);
local_bh_enable();
}
@@ -110,52 +117,30 @@ static void nft_counter_fetch(struct nft_counter_percpu __percpu *counter,
memset(total, 0, sizeof(*total));
for_each_possible_cpu(cpu) {
+ seqcount_t *seqp = per_cpu_ptr(&nft_counter_seq, cpu);
+
cpu_stats = per_cpu_ptr(counter, cpu);
do {
- seq = u64_stats_fetch_begin_irq(&cpu_stats->syncp);
+ seq = read_seqcount_begin(seqp);
bytes = cpu_stats->counter.bytes;
packets = cpu_stats->counter.packets;
- } while (u64_stats_fetch_retry_irq(&cpu_stats->syncp, seq));
+ } while (read_seqcount_retry(seqp, seq));
total->packets += packets;
total->bytes += bytes;
}
}
-static u64 __nft_counter_reset(u64 *counter)
-{
- u64 ret, old;
-
- do {
- old = *counter;
- ret = cmpxchg64(counter, old, 0);
- } while (ret != old);
-
- return ret;
-}
-
static void nft_counter_reset(struct nft_counter_percpu __percpu *counter,
struct nft_counter *total)
{
struct nft_counter_percpu *cpu_stats;
- u64 bytes, packets;
- unsigned int seq;
- int cpu;
- memset(total, 0, sizeof(*total));
- for_each_possible_cpu(cpu) {
- bytes = packets = 0;
-
- cpu_stats = per_cpu_ptr(counter, cpu);
- do {
- seq = u64_stats_fetch_begin_irq(&cpu_stats->syncp);
- packets += __nft_counter_reset(&cpu_stats->counter.packets);
- bytes += __nft_counter_reset(&cpu_stats->counter.bytes);
- } while (u64_stats_fetch_retry_irq(&cpu_stats->syncp, seq));
-
- total->packets += packets;
- total->bytes += bytes;
- }
+ local_bh_disable();
+ cpu_stats = this_cpu_ptr(counter);
+ cpu_stats->counter.packets -= total->packets;
+ cpu_stats->counter.bytes -= total->bytes;
+ local_bh_enable();
}
static int nft_counter_do_dump(struct sk_buff *skb,
@@ -164,10 +149,9 @@ static int nft_counter_do_dump(struct sk_buff *skb,
{
struct nft_counter total;
+ nft_counter_fetch(priv->counter, &total);
if (reset)
nft_counter_reset(priv->counter, &total);
- else
- nft_counter_fetch(priv->counter, &total);
if (nla_put_be64(skb, NFTA_COUNTER_BYTES, cpu_to_be64(total.bytes),
NFTA_COUNTER_PAD) ||
@@ -285,7 +269,10 @@ static struct nft_expr_type nft_counter_type __read_mostly = {
static int __init nft_counter_module_init(void)
{
- int err;
+ int err, cpu;
+
+ for_each_possible_cpu(cpu)
+ seqcount_init(per_cpu_ptr(&nft_counter_seq, cpu));
err = nft_register_obj(&nft_counter_obj);
if (err < 0)
--
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