mlxsw: spectrum_ptp: Protect PTP configuration with a mutex

Currently the functions mlxsw_sp2_ptp_{configure, deconfigure}_port()
assume that they are called when RTNL is locked and they warn otherwise.

The deconfigure function can be called when port is removed, for example
as part of device reload, then there is no locked RTNL and the function
warns [1].

To avoid such case, do not assume that RTNL protects this code, add a
dedicated mutex instead. The mutex protects 'ptp_state->config' which
stores the existing global configuration in hardware. Use this mutex also
to protect the code which configures the hardware. Then, there will be
only one configuration in any time, which will be updated in 'ptp_state'
and a race will be avoided.

[1]:
RTNL: assertion failed at drivers/net/ethernet/mellanox/mlxsw/spectrum_ptp.c (1600)
WARNING: CPU: 1 PID: 1583493 at drivers/net/ethernet/mellanox/mlxsw/spectrum_ptp.c:1600 mlxsw_sp2_ptp_hwtstamp_set+0x2d3/0x300 [mlxsw_spectrum]
[...]
CPU: 1 PID: 1583493 Comm: devlink Not tainted5.19.0-rc8-custom-127022-gb371dffda095 #789
Hardware name: Mellanox Technologies Ltd.MSN3420/VMOD0005, BIOS 5.11 01/06/2019
RIP: 0010:mlxsw_sp2_ptp_hwtstamp_set+0x2d3/0x300[mlxsw_spectrum]
[...]
Call Trace:
 <TASK>
 mlxsw_sp_port_remove+0x7e/0x190 [mlxsw_spectrum]
 mlxsw_sp_fini+0xd1/0x270 [mlxsw_spectrum]
 mlxsw_core_bus_device_unregister+0x55/0x280 [mlxsw_core]
 mlxsw_devlink_core_bus_device_reload_down+0x1c/0x30[mlxsw_core]
 devlink_reload+0x1ee/0x230
 devlink_nl_cmd_reload+0x4de/0x580
 genl_family_rcv_msg_doit+0xdc/0x140
 genl_rcv_msg+0xd7/0x1d0
 netlink_rcv_skb+0x49/0xf0
 genl_rcv+0x1f/0x30
 netlink_unicast+0x22f/0x350
 netlink_sendmsg+0x208/0x440
 __sys_sendto+0xf0/0x140
 __x64_sys_sendto+0x1b/0x20
 do_syscall_64+0x35/0x80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

Fixes: 08ef8bc8 ("mlxsw: spectrum_ptp: Support SIOCGHWTSTAMP, SIOCSHWTSTAMP ioctls")
Reported-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Amit Cohen <amcohen@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlxsw/spectrum_ptp.c

@@ -46,6 +46,7 @@ struct mlxsw_sp2_ptp_state {
 					  * enabled.
 					  */
 	struct hwtstamp_config config;
+	struct mutex lock; /* Protects 'config' and HW configuration. */
 };
 
 struct mlxsw_sp1_ptp_key {
@@ -1374,6 +1375,7 @@ struct mlxsw_sp_ptp_state *mlxsw_sp2_ptp_init(struct mlxsw_sp *mlxsw_sp)
 		goto err_ptp_traps_set;
 
 	refcount_set(&ptp_state->ptp_port_enabled_ref, 0);
+	mutex_init(&ptp_state->lock);
 	return &ptp_state->common;
 
 err_ptp_traps_set:
@@ -1388,6 +1390,7 @@ void mlxsw_sp2_ptp_fini(struct mlxsw_sp_ptp_state *ptp_state_common)
 
 	ptp_state = mlxsw_sp2_ptp_state(mlxsw_sp);
 
+	mutex_destroy(&ptp_state->lock);
 	mlxsw_sp_ptp_traps_unset(mlxsw_sp);
 	kfree(ptp_state);
 }
@@ -1461,7 +1464,10 @@ int mlxsw_sp2_ptp_hwtstamp_get(struct mlxsw_sp_port *mlxsw_sp_port,
 
 	ptp_state = mlxsw_sp2_ptp_state(mlxsw_sp_port->mlxsw_sp);
 
+	mutex_lock(&ptp_state->lock);
 	*config = ptp_state->config;
+	mutex_unlock(&ptp_state->lock);
+
 	return 0;
 }
 
@@ -1574,8 +1580,6 @@ static int mlxsw_sp2_ptp_configure_port(struct mlxsw_sp_port *mlxsw_sp_port,
 	struct mlxsw_sp2_ptp_state *ptp_state;
 	int err;
 
-	ASSERT_RTNL();
-
 	ptp_state = mlxsw_sp2_ptp_state(mlxsw_sp_port->mlxsw_sp);
 
 	if (refcount_inc_not_zero(&ptp_state->ptp_port_enabled_ref))
@@ -1597,8 +1601,6 @@ static int mlxsw_sp2_ptp_deconfigure_port(struct mlxsw_sp_port *mlxsw_sp_port,
 	struct mlxsw_sp2_ptp_state *ptp_state;
 	int err;
 
-	ASSERT_RTNL();
-
 	ptp_state = mlxsw_sp2_ptp_state(mlxsw_sp_port->mlxsw_sp);
 
 	if (!refcount_dec_and_test(&ptp_state->ptp_port_enabled_ref))
@@ -1618,16 +1620,20 @@ static int mlxsw_sp2_ptp_deconfigure_port(struct mlxsw_sp_port *mlxsw_sp_port,
 int mlxsw_sp2_ptp_hwtstamp_set(struct mlxsw_sp_port *mlxsw_sp_port,
 			       struct hwtstamp_config *config)
 {
+	struct mlxsw_sp2_ptp_state *ptp_state;
 	enum hwtstamp_rx_filters rx_filter;
 	struct hwtstamp_config new_config;
 	u16 new_ing_types, new_egr_types;
 	bool ptp_enabled;
 	int err;
 
+	ptp_state = mlxsw_sp2_ptp_state(mlxsw_sp_port->mlxsw_sp);
+	mutex_lock(&ptp_state->lock);
+
 	err = mlxsw_sp2_ptp_get_message_types(config, &new_ing_types,
 					      &new_egr_types, &rx_filter);
 	if (err)
-		return err;
+		goto err_get_message_types;
 
 	new_config.flags = config->flags;
 	new_config.tx_type = config->tx_type;
@@ -1640,11 +1646,11 @@ int mlxsw_sp2_ptp_hwtstamp_set(struct mlxsw_sp_port *mlxsw_sp_port,
 		err = mlxsw_sp2_ptp_configure_port(mlxsw_sp_port, new_ing_types,
 						   new_egr_types, new_config);
 		if (err)
-			return err;
+			goto err_configure_port;
 	} else if (!new_ing_types && !new_egr_types && ptp_enabled) {
 		err = mlxsw_sp2_ptp_deconfigure_port(mlxsw_sp_port, new_config);
 		if (err)
-			return err;
+			goto err_deconfigure_port;
 	}
 
 	mlxsw_sp_port->ptp.ing_types = new_ing_types;
@@ -1652,8 +1658,15 @@ int mlxsw_sp2_ptp_hwtstamp_set(struct mlxsw_sp_port *mlxsw_sp_port,
 
 	/* Notify the ioctl caller what we are actually timestamping. */
 	config->rx_filter = rx_filter;
+	mutex_unlock(&ptp_state->lock);
 
 	return 0;
+
+err_deconfigure_port:
+err_configure_port:
+err_get_message_types:
+	mutex_unlock(&ptp_state->lock);
+	return err;
 }
 
 int mlxsw_sp2_ptp_get_ts_info(struct mlxsw_sp *mlxsw_sp,