synflood_warned had to be u32 for xchg(), but ensuring atomicity is not really needed. Signed-off-by: Eric Dumazet --- include/net/request_sock.h | 2 +- net/ipv4/tcp_input.c | 4 ++-- 2 files changed, 3 insertions(+), 3 deletions(-) diff --git a/include/net/request_sock.h b/include/net/request_sock.h index 6a5ec1418e8552b4aa9d25d61afa5376187b569d..cd4d4cf71d0d22bdb980f6e1cbe10e8307965b0e 100644 --- a/include/net/request_sock.h +++ b/include/net/request_sock.h @@ -185,8 +185,8 @@ struct fastopen_queue { struct request_sock_queue { spinlock_t rskq_lock; u8 rskq_defer_accept; + u8 synflood_warned; - u32 synflood_warned; atomic_t qlen; atomic_t young; diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index f93d48d98d5dacf2ee868cd6b2d65a396443d106..79d5252ed6cc1a24ec898f4168d47c39c6e92fe1 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -7282,8 +7282,8 @@ static bool tcp_syn_flood_action(struct sock *sk, const char *proto) #endif __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPREQQFULLDROP); - if (!READ_ONCE(queue->synflood_warned) && syncookies != 2 && - xchg(&queue->synflood_warned, 1) == 0) { + if (syncookies != 2 && !READ_ONCE(queue->synflood_warned)) { + WRITE_ONCE(queue->synflood_warned, 1); if (IS_ENABLED(CONFIG_IPV6) && sk->sk_family == AF_INET6) { net_info_ratelimited("%s: Possible SYN flooding on port [%pI6c]:%u. %s.\n", proto, inet6_rcv_saddr(sk), -- 2.51.0.384.g4c02a37b29-goog