From: Eric Dumazet <edumazet@google.com>
To: "David S . Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
Paolo Abeni <pabeni@redhat.com>
Cc: Simon Horman <horms@kernel.org>,
netdev@vger.kernel.org, Ido Schimmel <idosch@nvidia.com>,
Nikolay Aleksandrov <razor@blackwall.org>,
eric.dumazet@gmail.com, Eric Dumazet <edumazet@google.com>
Subject: [PATCH net-next 06/11] bridge: provide lockless access to p->designated_cost
Date: Thu, 21 May 2026 13:19:11 +0000 [thread overview]
Message-ID: <20260521131916.3627204-7-edumazet@google.com> (raw)
In-Reply-To: <20260521131916.3627204-1-edumazet@google.com>
Add READ_ONCE()/WRITE_ONCE() annotations around p->designated_cost
This is needed at least for sysfs show_designated_cost(), BRCTL_GET_PORT_INFO
and upcoming RTNL avoidance in "ip link" dumps (cf br_port_fill_attrs()).
Signed-off-by: Eric Dumazet <edumazet@google.com>
---
net/bridge/br_ioctl.c | 2 +-
net/bridge/br_netlink.c | 3 ++-
net/bridge/br_stp.c | 20 +++++++++++---------
net/bridge/br_sysfs_if.c | 2 +-
4 files changed, 15 insertions(+), 12 deletions(-)
diff --git a/net/bridge/br_ioctl.c b/net/bridge/br_ioctl.c
index 07cfcb821e27ebcb72901a365a3f06491f8b0bc3..a507c7b369ac49803019cdca7836c7fb9ef4459e 100644
--- a/net/bridge/br_ioctl.c
+++ b/net/bridge/br_ioctl.c
@@ -260,7 +260,7 @@ int br_dev_siocdevprivate(struct net_device *dev, struct ifreq *rq,
p.port_id = pt->port_id;
p.designated_port = pt->designated_port;
p.path_cost = READ_ONCE(pt->path_cost);
- p.designated_cost = pt->designated_cost;
+ p.designated_cost = READ_ONCE(pt->designated_cost);
p.state = pt->state;
p.top_change_ack = pt->topology_change_ack;
p.config_pending = pt->config_pending;
diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
index 1b2fbb3a8f9b18ef6479bd3a0c63fe1e761df9a7..153e1cb0fbb6ea9f65933d884b9a78f5446d0de6 100644
--- a/net/bridge/br_netlink.c
+++ b/net/bridge/br_netlink.c
@@ -264,7 +264,8 @@ static int br_port_fill_attrs(struct sk_buff *skb,
nla_put(skb, IFLA_BRPORT_BRIDGE_ID, sizeof(struct ifla_bridge_id),
&p->designated_bridge) ||
nla_put_u16(skb, IFLA_BRPORT_DESIGNATED_PORT, p->designated_port) ||
- nla_put_u16(skb, IFLA_BRPORT_DESIGNATED_COST, p->designated_cost) ||
+ nla_put_u16(skb, IFLA_BRPORT_DESIGNATED_COST,
+ READ_ONCE(p->designated_cost)) ||
nla_put_u16(skb, IFLA_BRPORT_ID, p->port_id) ||
nla_put_u16(skb, IFLA_BRPORT_NO, p->port_no) ||
nla_put_u8(skb, IFLA_BRPORT_TOPOLOGY_CHANGE_ACK,
diff --git a/net/bridge/br_stp.c b/net/bridge/br_stp.c
index 1367cd3ac4dd6a587d4a6471184453a14af6879c..62dcac1a181c829e2736d7ab8679c870ee676a71 100644
--- a/net/bridge/br_stp.c
+++ b/net/bridge/br_stp.c
@@ -125,8 +125,8 @@ static int br_should_become_root_port(const struct net_bridge_port *p,
else if (t > 0)
return 0;
- t = p->designated_cost + READ_ONCE(p->path_cost) -
- (rp->designated_cost + READ_ONCE(rp->path_cost));
+ t = READ_ONCE(p->designated_cost) + READ_ONCE(p->path_cost) -
+ (READ_ONCE(rp->designated_cost) + READ_ONCE(rp->path_cost));
if (t < 0)
return 1;
@@ -188,7 +188,7 @@ static void br_root_selection(struct net_bridge *br)
} else {
p = br_get_port(br, root_port);
br->designated_root = p->designated_root;
- br->root_path_cost = p->designated_cost +
+ br->root_path_cost = READ_ONCE(p->designated_cost) +
READ_ONCE(p->path_cost);
}
}
@@ -254,7 +254,7 @@ static void br_record_config_information(struct net_bridge_port *p,
const struct br_config_bpdu *bpdu)
{
p->designated_root = bpdu->root;
- p->designated_cost = bpdu->root_path_cost;
+ WRITE_ONCE(p->designated_cost, bpdu->root_path_cost);
p->designated_bridge = bpdu->bridge_id;
p->designated_port = bpdu->port_id;
p->designated_age = jiffies - bpdu->message_age;
@@ -299,9 +299,10 @@ static int br_should_become_designated_port(const struct net_bridge_port *p)
if (memcmp(&p->designated_root, &br->designated_root, 8))
return 1;
- if (br->root_path_cost < p->designated_cost)
+ t = br->root_path_cost - READ_ONCE(p->designated_cost);
+ if (t < 0)
return 1;
- else if (br->root_path_cost > p->designated_cost)
+ else if (t > 0)
return 0;
t = memcmp(&br->bridge_id, &p->designated_bridge, 8);
@@ -341,9 +342,10 @@ static int br_supersedes_port_info(const struct net_bridge_port *p,
else if (t > 0)
return 0;
- if (bpdu->root_path_cost < p->designated_cost)
+ t = bpdu->root_path_cost < READ_ONCE(p->designated_cost);
+ if (t < 0)
return 1;
- else if (bpdu->root_path_cost > p->designated_cost)
+ else if (t > 0)
return 0;
t = memcmp(&bpdu->bridge_id, &p->designated_bridge, 8);
@@ -423,7 +425,7 @@ void br_become_designated_port(struct net_bridge_port *p)
br = p->br;
p->designated_root = br->designated_root;
- p->designated_cost = br->root_path_cost;
+ WRITE_ONCE(p->designated_cost, br->root_path_cost);
p->designated_bridge = br->bridge_id;
p->designated_port = p->port_id;
}
diff --git a/net/bridge/br_sysfs_if.c b/net/bridge/br_sysfs_if.c
index 0616036a3ce45d45ba817555362f1613f5f9d6cf..9d560482e558aa1ef4d2f583373f15ae5db8a0f0 100644
--- a/net/bridge/br_sysfs_if.c
+++ b/net/bridge/br_sysfs_if.c
@@ -117,7 +117,7 @@ static BRPORT_ATTR(designated_port, 0444, show_designated_port, NULL);
static ssize_t show_designated_cost(struct net_bridge_port *p, char *buf)
{
- return sysfs_emit(buf, "%d\n", p->designated_cost);
+ return sysfs_emit(buf, "%d\n", READ_ONCE(p->designated_cost));
}
static BRPORT_ATTR(designated_cost, 0444, show_designated_cost, NULL);
--
2.54.0.669.g59709faab0-goog
next prev parent reply other threads:[~2026-05-21 13:19 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-21 13:19 [PATCH net-next 00/11] bridge: prepare lockless br_port_fill_attrs() (I) Eric Dumazet
2026-05-21 13:19 ` [PATCH net-next 01/11] bridge: add a READ_ONCE() in br_timer_value() Eric Dumazet
2026-05-21 13:19 ` [PATCH net-next 02/11] bridge: add bridge_flags_bit enum Eric Dumazet
2026-05-21 13:19 ` [PATCH net-next 03/11] bridge: use BR_PROMISC_BIT Eric Dumazet
2026-05-21 13:19 ` [PATCH net-next 04/11] bridge: use BR_ADMIN_COST_BIT Eric Dumazet
2026-05-21 13:19 ` [PATCH net-next 05/11] bridge: provide lockless access to p->path_cost Eric Dumazet
2026-05-21 13:19 ` Eric Dumazet [this message]
2026-05-21 13:19 ` [PATCH net-next 07/11] bridge: provide lockless access to p->designated_port Eric Dumazet
2026-05-21 13:19 ` [PATCH net-next 08/11] bridge: provide lockless access to p->priority Eric Dumazet
2026-05-21 13:19 ` [PATCH net-next 09/11] bridge: provide lockless access to p->port_id Eric Dumazet
2026-05-21 13:19 ` [PATCH net-next 10/11] bridge: provide lockless access to p->config_pending Eric Dumazet
2026-05-21 13:19 ` [PATCH net-next 11/11] bridge: read p->flags once in br_port_fill_attrs() Eric Dumazet
2026-05-22 8:45 ` [PATCH net-next 00/11] bridge: prepare lockless br_port_fill_attrs() (I) Ido Schimmel
2026-05-22 9:31 ` Eric Dumazet
2026-05-22 9:32 ` Nikolay Aleksandrov
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