[net-next RFC PATCH v4 03/15] net: dsa: hold rtnl_mutex when calling dsa_master_{setup,teardown}

Ansuel Smith
2021-12-11T19:58:27Z

From: Vladimir Oltean <vladimir.oltean@nxp.com>

DSA needs to simulate master tracking events when a binding is first
with a DSA master established and torn down, in order to give drivers
the simplifying guarantee that ->master_state_change calls are made
only when the master's readiness state to pass traffic changes.
master_state_change() provide a operational bool that DSA driver can use
to understand if DSA master is operational or not.
To avoid races, we need to block the reception of
NETDEV_UP/NETDEV_CHANGE/NETDEV_GOING_DOWN events in the netdev notifier
chain while we are changing the master's dev->dsa_ptr (this changes what
netdev_uses_dsa(dev) reports).

The dsa_master_setup() and dsa_master_teardown() functions optionally
require the rtnl_mutex to be held, if the tagger needs the master to be
promiscuous, these functions call dev_set_promiscuity(). Move the
rtnl_lock() from that function and make it top-level.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
---
net/dsa/dsa2.c | 8 ++++++++
net/dsa/master.c | 4 ++--
2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/net/dsa/dsa2.c b/net/dsa/dsa2.c
index 86b1e2f11469..90e29dd42d3d 100644
--- a/net/dsa/dsa2.c
+++ b/net/dsa/dsa2.c
@@ -1030,6 +1030,8 @@ static int dsa_tree_setup_master(struct dsa_switch_tree *dst)
struct dsa_port *dp;
int err;

+ rtnl_lock();
+
list_for_each_entry(dp, &dst->ports, list) {
if (dsa_port_is_cpu(dp)) {
err = dsa_master_setup(dp->master, dp);
@@ -1038,6 +1040,8 @@ static int dsa_tree_setup_master(struct dsa_switch_tree *dst)
}
}

+ rtnl_unlock();
+
return 0;
}

@@ -1045,9 +1049,13 @@ static void dsa_tree_teardown_master(struct dsa_switch_tree *dst)
{
struct dsa_port *dp;

+ rtnl_lock();
+
list_for_each_entry(dp, &dst->ports, list)
if (dsa_port_is_cpu(dp))
dsa_master_teardown(dp->master);
+
+ rtnl_unlock();
}

static int dsa_tree_setup_lags(struct dsa_switch_tree *dst)
diff --git a/net/dsa/master.c b/net/dsa/master.c
index f4efb244f91d..2199104ca7df 100644
--- a/net/dsa/master.c
+++ b/net/dsa/master.c
@@ -267,9 +267,9 @@ static void dsa_master_set_promiscuity(struct net_device *dev, int inc)
if (!ops->promisc_on_master)
return;

- rtnl_lock();
+ ASSERT_RTNL();
+
dev_set_promiscuity(dev, inc);
- rtnl_unlock();
}

static ssize_t tagging_show(struct device *d, struct device_attribute *attr,
--
2.32.0