newbie question on threading

[Gonçalo Rodrigues]

Hi,

I have another, very naive, question on the threading model. It is about
the condition object and the wait method. I have read the code, and the
main loop is commented thus (in part):

#Balancing act: We can't afford a pure busy loop, so we
#have to sleep; but if we sleep the whole timeout time,
#we'll be unresponsive.

My question is: why is a busy loop not affordable (without a sleep
call), e.g. something like (in pseudo-code description)

while 1:
    <acquire lock>
    if <acquire sucessfull>:
        break
    if <timedout?>:
        break
    <calculate endtime>

Thanks in advance,
Gonçalo Rodrigues