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>,
Nikolay Aleksandrov <razor@blackwall.org>,
Ido Schimmel <idosch@nvidia.com>,
netdev@vger.kernel.org, eric.dumazet@gmail.com,
Eric Dumazet <edumazet@google.com>
Subject: [PATCH v3 net-next 06/11] bridge: provide lockless access to p->designated_cost
Date: Thu, 4 Jun 2026 14:13:38 +0000 [thread overview]
Message-ID: <20260604141343.2124500-7-edumazet@google.com> (raw)
In-Reply-To: <20260604141343.2124500-1-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>
Acked-by: Nikolay Aleksandrov <razor@blackwall.org>
---
net/bridge/br_ioctl.c | 2 +-
net/bridge/br_netlink.c | 3 ++-
net/bridge/br_stp.c | 30 ++++++++++++++++++------------
net/bridge/br_sysfs_if.c | 2 +-
4 files changed, 22 insertions(+), 15 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 08718ebe282aa1d089a127cdc7c24fda5a0a38a5..296f62ebdd4a6f3d404b5902fe661995bd1ca0f5 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 2d9d0823aa56b63a62ed51c49df54055294e82ad..ced8d23f05d1ee262d1760c768e5c88868f13178 100644
--- a/net/bridge/br_stp.c
+++ b/net/bridge/br_stp.c
@@ -102,7 +102,7 @@ struct net_bridge_port *br_get_port(struct net_bridge *br, u16 port_no)
static int br_should_become_root_port(const struct net_bridge_port *p,
u16 root_port)
{
- u32 p_path_cost, rp_path_cost;
+ u32 p_path_cost, rp_path_cost, p_designated_cost, rp_designated_cost;
struct net_bridge_port *rp;
struct net_bridge *br;
int t;
@@ -128,12 +128,14 @@ static int br_should_become_root_port(const struct net_bridge_port *p,
p_path_cost = READ_ONCE(p->path_cost);
rp_path_cost = READ_ONCE(rp->path_cost);
+ p_designated_cost = READ_ONCE(p->designated_cost);
+ rp_designated_cost = READ_ONCE(rp->designated_cost);
- if (p->designated_cost + p_path_cost <
- rp->designated_cost + rp_path_cost)
+ if (p_designated_cost + p_path_cost <
+ rp_designated_cost + rp_path_cost)
return 1;
- else if (p->designated_cost + p_path_cost >
- rp->designated_cost + rp_path_cost)
+ else if (p_designated_cost + p_path_cost >
+ rp_designated_cost + rp_path_cost)
return 0;
t = memcmp(&p->designated_bridge, &rp->designated_bridge, 8);
@@ -191,7 +193,7 @@ 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);
}
}
@@ -257,7 +259,7 @@ 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;
@@ -293,6 +295,7 @@ void br_transmit_tcn(struct net_bridge *br)
static int br_should_become_designated_port(const struct net_bridge_port *p)
{
struct net_bridge *br;
+ u32 p_designated_cost;
int t;
br = p->br;
@@ -302,9 +305,10 @@ 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)
+ p_designated_cost = READ_ONCE(p->designated_cost);
+ if (br->root_path_cost < p_designated_cost)
return 1;
- else if (br->root_path_cost > p->designated_cost)
+ else if (br->root_path_cost > p_designated_cost)
return 0;
t = memcmp(&br->bridge_id, &p->designated_bridge, 8);
@@ -336,6 +340,7 @@ static void br_designated_port_selection(struct net_bridge *br)
static int br_supersedes_port_info(const struct net_bridge_port *p,
const struct br_config_bpdu *bpdu)
{
+ u32 p_designated_cost;
int t;
t = memcmp(&bpdu->root, &p->designated_root, 8);
@@ -344,9 +349,10 @@ 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)
+ p_designated_cost = READ_ONCE(p->designated_cost);
+ if (bpdu->root_path_cost < p_designated_cost)
return 1;
- else if (bpdu->root_path_cost > p->designated_cost)
+ else if (bpdu->root_path_cost > p_designated_cost)
return 0;
t = memcmp(&bpdu->bridge_id, &p->designated_bridge, 8);
@@ -426,7 +432,7 @@ 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 23574476d7f701080452777ab2c23a42b4defba4..36b832902d33a492e91d53a4248778b3ee2322ca 100644
--- a/net/bridge/br_sysfs_if.c
+++ b/net/bridge/br_sysfs_if.c
@@ -135,7 +135,7 @@ 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);
--
2.54.0.1032.g2f8565e1d1-goog
next prev parent reply other threads:[~2026-06-04 14:13 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-04 14:13 [PATCH v3 net-next 00/11] bridge: prepare lockless br_port_fill_attrs() (I) Eric Dumazet
2026-06-04 14:13 ` [PATCH v3 net-next 01/11] bridge: add a READ_ONCE() in br_timer_value() Eric Dumazet
2026-06-04 14:13 ` [PATCH v3 net-next 02/11] bridge: add bridge_flags_bit enum Eric Dumazet
2026-06-04 14:13 ` [PATCH v3 net-next 03/11] bridge: use BR_PROMISC_BIT Eric Dumazet
2026-06-04 14:13 ` [PATCH v3 net-next 04/11] bridge: use BR_ADMIN_COST_BIT Eric Dumazet
2026-06-04 14:13 ` [PATCH v3 net-next 05/11] bridge: provide lockless access to p->path_cost Eric Dumazet
2026-06-04 14:13 ` Eric Dumazet [this message]
2026-06-04 18:43 ` [PATCH v3 net-next 06/11] bridge: provide lockless access to p->designated_cost Ido Schimmel
2026-06-04 14:13 ` [PATCH v3 net-next 07/11] bridge: provide lockless access to p->designated_port Eric Dumazet
2026-06-04 14:13 ` [PATCH v3 net-next 08/11] bridge: provide lockless access to p->priority Eric Dumazet
2026-06-04 14:13 ` [PATCH v3 net-next 09/11] bridge: provide lockless access to p->port_id Eric Dumazet
2026-06-04 14:13 ` [PATCH v3 net-next 10/11] bridge: provide lockless access to p->config_pending Eric Dumazet
2026-06-04 14:13 ` [PATCH v3 net-next 11/11] bridge: read p->flags once in br_port_fill_attrs() Eric Dumazet
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