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.c b/net/ipv4/tcp.c
index 176e11a..197b9b7 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2011,11 +2011,8 @@
}
}
if (sk->sk_state != TCP_CLOSE) {
- int orphan_count = percpu_counter_read_positive(
- sk->sk_prot->orphan_count);
-
sk_mem_reclaim(sk);
- if (tcp_too_many_orphans(sk, orphan_count)) {
+ if (tcp_too_many_orphans(sk, 0)) {
if (net_ratelimit())
printk(KERN_INFO "TCP: too many of orphaned "
"sockets\n");