Possible interference in the timer?

I do not understand the working of the timer. In init_clock() of
clock.c, timer0 is started to keep track of ticks, and later on in
beep() of console.c, timer2 is started for an alarm clock. Neither
timer is stopped later. Now that these two timers share the same irq
line, won't this result in interference? I mean, for example, maybe
clock handler will count too many ticks as a result?

It seems that I have asked a stupid question. Again. Please just ignore
this question.