tcp: Combat per-cpu skew in orphan tests.
As reported by Anton Blanchard when we use
percpu_counter_read_positive() to make our orphan socket limit checks,
the check can be off by up to num_cpus_online() * batch (which is 32
by default) which on a 128 cpu machine can be as large as the default
orphan limit itself.
Fix this by doing the full expensive sum check if the optimized check
triggers.
Reported-by: Anton Blanchard <anton@samba.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index 808bb92..c35b469 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -66,18 +66,18 @@
static int tcp_out_of_resources(struct sock *sk, int do_reset)
{
struct tcp_sock *tp = tcp_sk(sk);
- int orphans = percpu_counter_read_positive(&tcp_orphan_count);
+ int shift = 0;
/* If peer does not open window for long time, or did not transmit
* anything for long time, penalize it. */
if ((s32)(tcp_time_stamp - tp->lsndtime) > 2*TCP_RTO_MAX || !do_reset)
- orphans <<= 1;
+ shift++;
/* If some dubious ICMP arrived, penalize even more. */
if (sk->sk_err_soft)
- orphans <<= 1;
+ shift++;
- if (tcp_too_many_orphans(sk, orphans)) {
+ if (tcp_too_many_orphans(sk, shift)) {
if (net_ratelimit())
printk(KERN_INFO "Out of socket memory\n");