Do I need to make both variables volatile in reader/writer scenario?

We have 2 threads. One is a reader. The other is a writer thread who share these 2 variables:

Object data
boolean ready

Do I need to make both volatile? Is it sufficient to make 'ready' volatile?

write() {
    data = <some data>
    ready = true;
}

read() {
    if (ready) {
        consume(data);
        ready = false;
    } 
}

Do I need to make both variables volatile?

Based on my limited understnding of the java memory model, I think I only have to make 'ready' volatile as all the code before reading/writing 'ready' happens-before the code after the reading/writing of 'ready' variable?

Update: For the purposes of this question, assume that atomicity is not an issue. The production and consumption of data is atomic.