Re: [PATCH net-next v2 11/14] net: bridge: mcast: track active state, prepare for outside lock reads
From: Ido Schimmel <idosch@nvidia.com>
Date: 2026-02-08 16:11:37
Also in:
bridge, lkml
On Fri, Feb 06, 2026 at 03:52:17AM +0100, Linus Lüssing wrote:
quoted hunk ↗ jump to hunk
@@ -1095,23 +1095,25 @@ static void br_ip6_multicast_update_active(struct net_bridge_mcast *brmctx, { #if IS_ENABLED(CONFIG_IPV6) if (force_inactive) - brmctx->ip6_active = false; + WRITE_ONCE(brmctx->ip6_active, false); else - brmctx->ip6_active = br_ip6_multicast_querier_exists(brmctx); + WRITE_ONCE(brmctx->ip6_active, br_ip6_multicast_querier_exists(brmctx)); #endif } static void br_multicast_notify_active(struct net_bridge_mcast *brmctx, bool ip4_active_old, bool ip6_active_old) { - if (brmctx->ip4_active == ip4_active_old && - brmctx->ip6_active == ip6_active_old) + int ip4_active = READ_ONCE(brmctx->ip4_active); + int ip6_active = READ_ONCE(brmctx->ip6_active);
I believe that this is unnecessary since we are holding the lock and it will confuse people reading the code. We only need the READ_ONCE() later on in the data path
quoted hunk ↗ jump to hunk
+ + if (ip4_active == ip4_active_old && + ip6_active == ip6_active_old) return; br_info(brmctx->br, "mc_active changed, vid: %i: v4: %i->%i, v6: %i->%i\n", brmctx->vlan ? brmctx->vlan->vid : -1, - ip4_active_old, brmctx->ip4_active, - ip6_active_old, brmctx->ip6_active); + ip4_active_old, ip4_active, ip6_active_old, ip6_active); } /**@@ -1136,7 +1138,8 @@ static void br_multicast_notify_active(struct net_bridge_mcast *brmctx, */ static void br_multicast_update_active(struct net_bridge_mcast *brmctx) { - bool ip4_active_old = brmctx->ip4_active, ip6_active_old = brmctx->ip6_active; + bool ip4_active_old = READ_ONCE(brmctx->ip4_active); + bool ip6_active_old = READ_ONCE(brmctx->ip6_active);
Same
quoted hunk ↗ jump to hunk
bool force_inactive = false; lockdep_assert_held_once(&brmctx->br->multicast_lock);@@ -4266,13 +4269,13 @@ void br_multicast_ctx_init(struct net_bridge *br, brmctx->multicast_membership_interval = 260 * HZ; brmctx->ip4_querier.port_ifidx = 0; - brmctx->ip4_active = 0; + WRITE_ONCE(brmctx->ip4_active, 0); seqcount_spinlock_init(&brmctx->ip4_querier.seq, &br->multicast_lock); brmctx->multicast_igmp_version = 2; #if IS_ENABLED(CONFIG_IPV6) brmctx->multicast_mld_version = 1; brmctx->ip6_querier.port_ifidx = 0; - brmctx->ip6_active = 0; + WRITE_ONCE(brmctx->ip6_active, 0); seqcount_spinlock_init(&brmctx->ip6_querier.seq, &br->multicast_lock); #endif-- 2.51.0