From a4fcf8a242c6c89002aa9a406a83d370833f4a58 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Mon, 13 Mar 2023 20:17:32 +0000 Subject: [PATCH] ipv6: remove one read_lock()/read_unlock() pair in rt6_check_neigh() commit c486640aa710ddd06c13a7f7162126e1552e8842 upstream. rt6_check_neigh() uses read_lock() to protect n->nud_state reading. This seems overkill and causes false sharing. Signed-off-by: Eric Dumazet Reviewed-by: David Ahern Reviewed-by: Martin KaFai Lau Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- net/ipv6/route.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/net/ipv6/route.c b/net/ipv6/route.c index 0a9f854bfa50c..0bcdb675ba2c1 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -690,16 +690,16 @@ static enum rt6_nud_state rt6_check_neigh(const struct fib6_nh *fib6_nh) neigh = __ipv6_neigh_lookup_noref(fib6_nh->fib_nh_dev, &fib6_nh->fib_nh_gw6); if (neigh) { - read_lock(&neigh->lock); - if (neigh->nud_state & NUD_VALID) + u8 nud_state = READ_ONCE(neigh->nud_state); + + if (nud_state & NUD_VALID) ret = RT6_NUD_SUCCEED; #ifdef CONFIG_IPV6_ROUTER_PREF - else if (!(neigh->nud_state & NUD_FAILED)) + else if (!(nud_state & NUD_FAILED)) ret = RT6_NUD_SUCCEED; else ret = RT6_NUD_FAIL_PROBE; #endif - read_unlock(&neigh->lock); } else { ret = IS_ENABLED(CONFIG_IPV6_ROUTER_PREF) ? RT6_NUD_SUCCEED : RT6_NUD_FAIL_DO_RR; -- 2.39.5