[PATCH net-next v2 11/14] net: bridge: mcast: track active state, prepare for outside lock reads
From: Linus Lüssing <hidden>
Date: 2026-02-06 03:01:50
Also in:
bridge, lkml
Subsystem:
ethernet bridge, networking [general], the rest · Maintainers:
Nikolay Aleksandrov, Ido Schimmel, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
We are updating ip{4,6}_active and check all variables their state relies
on while holding the bridge multicast spinlock. However we are going to
read it without this lock in a follow-up commit on fast/data path, too.
As these variables are only booleans this shouldn't be a problem,
ip{4,6}_active will be loaded and stored atomically. And those
read sides should converge eventually. But to allow tooling to verify
this use the READ_ONCE() and WRITE_ONCE macros.
Signed-off-by: Linus Lüssing <redacted>
---
net/bridge/br_multicast.c | 25 ++++++++++++++-----------
1 file changed, 14 insertions(+), 11 deletions(-)
diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index 7a32c6bed111..48552720bcea 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c@@ -1085,9 +1085,9 @@ static void br_ip4_multicast_update_active(struct net_bridge_mcast *brmctx, bool force_inactive) { if (force_inactive) - brmctx->ip4_active = false; + WRITE_ONCE(brmctx->ip4_active, false); else - brmctx->ip4_active = br_ip4_multicast_querier_exists(brmctx); + WRITE_ONCE(brmctx->ip4_active, br_ip4_multicast_querier_exists(brmctx)); } static void br_ip6_multicast_update_active(struct net_bridge_mcast *brmctx,
@@ -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); + + 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); 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