while(true) vs wait+condition synchronism

Question

Is it a bad practice to put a thread in a while(true) loop and test if a condition is ok to start a treatment?

void run()
{
    for(;;)
    {
        if(dataReady)
        {
            processData();
        }
    }
}

is it preferable to use wait/condition mechanism :

void run()
{
    for(;;)
    {
        if(dataReady)
        {
            processData();
        }
        lock_guard lock(mutex);
        condition_.wait(lock);
    }
}

Another thread of course calls condition_.notify_one()

EDIT:

I expect to almost never wait.

Answer 1

while true is a bad way because it just eats processing cycles.
Second approach is better, where in the thread gets intimated only when it has to perform some work.

Answer 2

It depends on the amount of time you expect to be waiting.

For very short periods a busy-wait can be preferable because it wouldn't involve a context switch as the other technique. The overhead of the context switch may sometimes overweigh the whole busy-wait loop.