On Tue, Dec 18, 2018 at 02:16:01PM +0200, Leon Romanovsky wrote:
> +static __net_init int rdma_dev_init_net(struct net *net)
> +{
> + struct rdma_dev_net *rdma_net = net_generic(net, rdma_dev_net_id);
> + struct ib_device *device;
> +
> + INIT_LIST_HEAD(&rdma_net->compatdev_list);
> + init_rwsem(&rdma_net->compat_rwsem);
> +
> + /* No need to create any compat devices in init_net. */
> + if (net_eq(net, &init_net))
> + return 0;
> +
> + /* Hold device mutex to synchronize with ib_register_device()
> + * which also tries to add compat devices.
> + */
> + mutex_lock(&ib_device_mutex);
> + /* Hold ib_lists_rwsem read lock; thereby not assume that
> + * ib_device_mutex is always locked while accessing ib_device_list.
> + */
> + down_read(&ib_lists_rwsem);
> + list_for_each_entry(device, &ib_device_list, core_list)
> + rdma_compatdev_create(device, net);
> + up_read(&ib_lists_rwsem);
> + mutex_unlock(&ib_device_mutex);
This is racey
CPU 0 CPU 1
setup_net()
rdma_dev_init_net()
ib_device_register()
list_add_tail_rcu(&net->list..)
Only thing I can think of it is to have our own list of current nets,
with our own locking and do not use for_each_net()
Again, ib_device_mutex is not intended as a registration lock, and
should not be used as such.
Jason
