linux kernel C function “need_resched:”

need_resched:
preempt_disable();
cpu = smp_processor_id();
rq = cpu_rq(cpu);
rcu_note_context_switch(cpu);
prev = rq->curr;
switch_count = &prev->nivcsw;

release_kernel_lock(prev);

I would like to ask is: "need_resched:" What is the role.

In detail，The linux kernel version is 2.6.35.3.

http://stackoverflow.com/questions/18578947/what-does-tif-need-resched-do