inet: cache listen_sock_qlen() and read rskq_defer_accept once

Cache listen_sock_qlen() to limit false sharing, and read
rskq_defer_accept once as it might change under us.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index 844808d..7d011e8 100644 (file)
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -571,8 +571,9 @@ static void reqsk_timer_handler(unsigned long data)
        struct inet_connection_sock *icsk = inet_csk(sk_listener);
        struct request_sock_queue *queue = &icsk->icsk_accept_queue;
        struct listen_sock *lopt = queue->listen_opt;
-       int expire = 0, resend = 0;
+       int qlen, expire = 0, resend = 0;
        int max_retries, thresh;
+       u8 defer_accept;
 
        if (sk_listener->sk_state != TCP_LISTEN || !lopt) {
                reqsk_put(req);
@@ -598,19 +599,21 @@ static void reqsk_timer_handler(unsigned long data)
         * embrions; and abort old ones without pity, if old
         * ones are about to clog our table.
         */
-       if (listen_sock_qlen(lopt) >> (lopt->max_qlen_log - 1)) {
+       qlen = listen_sock_qlen(lopt);
+       if (qlen >> (lopt->max_qlen_log - 1)) {
                int young = listen_sock_young(lopt) << 1;
 
                while (thresh > 2) {
-                       if (listen_sock_qlen(lopt) < young)
+                       if (qlen < young)
                                break;
                        thresh--;
                        young <<= 1;
                }
        }
-       if (queue->rskq_defer_accept)
-               max_retries = queue->rskq_defer_accept;
-       syn_ack_recalc(req, thresh, max_retries, queue->rskq_defer_accept,
+       defer_accept = READ_ONCE(queue->rskq_defer_accept);
+       if (defer_accept)
+               max_retries = defer_accept;
+       syn_ack_recalc(req, thresh, max_retries, defer_accept,
                       &expire, &resend);
        req->rsk_ops->syn_ack_timeout(sk_listener, req);
        if (!expire &&