为什么我的python SIGPROF不起作用？

Question

I am installing the SIGPROF signal and execute the handler every 2 seconds. Is there any problem?

  1 #!/usr/bin/env python
  2 #-*-coding: utf-8 -*-
  3 #pylint: disable=W0141,W0613,W0603
  4 
  5 import os
  6 import sys
  7 import signal
  8 import time
  9 
 10 def myhandler(signum, frame):
 11     print "myhandler"
 12     sys.stdout.flush()
 13 
 14 signal.signal(signal.SIGPROF, myhandler)
 15 signal.setitimer(signal.ITIMER_PROF, 2, 2)
 16 print signal.getitimer(signal.ITIMER_PROF)
 17 
 18 while True:
 19     print "sleeping 1..."
 20     sys.stdout.flush()
 21     time.sleep(1)

Answer 1

Those timers only decrement when the process is executing, since it's mostly sleeping it takes very long for the timer to expire, if you remove the sleep it should work fine, from the docs :

signal.ITIMER_PROF Decrements interval timer both when the process executes and when the system is executing on behalf of the process. Coupled

Try:

while True:
    for i in xrange(100000):
        pass

Answer 2

No, it works as expected. As stated by the documentation , ITIMER_PROF

decrements interval timer both when the process executes and when the system is executing on behalf of the process. Coupled with ITIMER_VIRTUAL, this timer is usually used to profile the time spent by the application in user and kernel space. SIGPROF is delivered upon expiration.

Since the sleep call causes the process to do nothing, the timer is decremented very slowly. Get rid of the sleep:

#!/usr/bin/env python
#-*-coding: utf-8 -*-
#pylint: disable=W0141,W0613,W0603

import os
import sys
import signal
import time

def myhandler(signum, frame):
    print "myhandler"
    sys.stdout.flush()

signal.signal(signal.SIGPROF, myhandler)
signal.setitimer(signal.ITIMER_PROF, 2, 2)
print signal.getitimer(signal.ITIMER_PROF)

while True:
    continue

And then when it is run you can see the signal working:

$ python prof.py 
(2.004125, 2.000125)
myhandler
myhandler

If you want to time it in 'real' time (its not clear from the question what you're aiming to do) rather than processor time, use ITIMER_REAL and catch the SIGALRM signal instead.