tasklist_lock, tasklist_unlock are not exported by the kernel any more

If you are running a kernel module that was written before the kernel 2.6.17 was released, you might see code using the tasklist
rcu(tasklist_lock) , rcu(tasklist_unlock).

The codes that do use there symbols will not compile in the kernels after 2.6.17 cause, tasklist is not longer exported by the kernel . So  the modules do not have access to the symbols tasklist_lock and tasklist_unlock