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author | Vladimir Oltean <vladimir.oltean@nxp.com> | 2022-01-06 02:11:17 +0300 |
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committer | David S. Miller <davem@davemloft.net> | 2022-01-06 14:59:10 +0300 |
commit | 11fd667dac315ea3f2469961f6d2869271a46cae (patch) | |
tree | 5cd6968ce4e769dd00f10ed556941125d72b977c /init | |
parent | 1e3f407f3cacc5dcfe27166c412ed9bc263d82bf (diff) | |
download | linux-11fd667dac315ea3f2469961f6d2869271a46cae.tar.xz |
net: dsa: setup master before ports
It is said that as soon as a network interface is registered, all its
resources should have already been prepared, so that it is available for
sending and receiving traffic. One of the resources needed by a DSA
slave interface is the master.
dsa_tree_setup
-> dsa_tree_setup_ports
-> dsa_port_setup
-> dsa_slave_create
-> register_netdevice
-> dsa_tree_setup_master
-> dsa_master_setup
-> sets up master->dsa_ptr, which enables reception
Therefore, there is a short period of time after register_netdevice()
during which the master isn't prepared to pass traffic to the DSA layer
(master->dsa_ptr is checked by eth_type_trans). Same thing during
unregistration, there is a time frame in which packets might be missed.
Note that this change opens us to another race: dsa_master_find_slave()
will get invoked potentially earlier than the slave creation, and later
than the slave deletion. Since dp->slave starts off as a NULL pointer,
the earlier calls aren't a problem, but the later calls are. To avoid
use-after-free, we should zeroize dp->slave before calling
dsa_slave_destroy().
In practice I cannot really test real life improvements brought by this
change, since in my systems, netdevice creation races with PHY autoneg
which takes a few seconds to complete, and that masks quite a few races.
Effects might be noticeable in a setup with fixed links all the way to
an external system.
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'init')
0 files changed, 0 insertions, 0 deletions