1s delay in delivery of os signals (between python threads)?

Question

I have encountered a 1 second delay in signal delivery, when I send a signal to a thread in python.

Sending thread snippet (import both signal and os (and time)):

print "Signal sent at:", time.time()
os.kill(other_thread_id, signal.SIGALRM)

Receiving thread snippet:

def receive_alarm(signum, stack):
    print "Signal received at:", time.time()
signal.signal(signal.SIGALRM, receive_alarm)

Running both simultaneously gives:

Signal sent at 1423141616.02
Signal received at: 1423141617.02

So delivery of the alarm signal takes a full second. It's always exactly 1 second. This delay makes it unusable for my purpose. Does anyone know more about this? Is it a setting somewhere? Or am I doing something else wrong? I've tried other signals as well.

OS: Debian 7

UPDATE after comments below:

strace python main.py

DOESN'T give this delay.

python main.py

DOES :-). This might get us closer to what's wrong.