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#1
June 23rd, 2004, 09:06 AM
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Zombi process
Arg! Help! My process table is full of undead zombi threads!
Seems my script doesn't take care of his serious child problem! How can you clean a child thread to prevent it from becoming a zombi thread ? (how can you use the os.kill command, if it is the solution...) Thanks, (BTW when i said full of zombies it looks more like 1 to 2 thousand zombies... so i'd prefer taking care of the problem)
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#2
June 23rd, 2004, 02:11 PM
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Maybe import the os module, run loop through every process you want to kill and run a command os.system('kill -9', x)? I'm new at all this so don't kill me if that is totally irrelevant.
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#3
June 23rd, 2004, 03:33 PM
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Are these threads created through the Python thread/threading modules, or are they child processes created with os.fork?
Either way the thread or process should terminate naturally unless they are stuck in an infinite loop or blocked waiting for some resource to be released. Dave - The Developers' Coach
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#4
June 24th, 2004, 02:17 AM
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Well the thing is that the kill -9 command does not work, I tried it... once the processes are written with the "defunct" mention next to them they are unkillable because they don't really exist any more i think....
Theses processes were created with the thread module, but they should end, there is no infinit loops in them, and they don't seem to take computing time either, so it looks as if they are not running. Well in fact it is a little more complicated, I start a thread and in the thread i use an os.spawnv (this does an automatic fork I think?) to start another script, and it is that script that zombifies. (Should there be a return None at the end of all functions? because i tried to put a sys.exit() to be sure it exited but it still stays there as a zombi, so i'm thinking that the parent process -the thread- has to clean up by its self...)
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#5
June 24th, 2004, 03:07 AM
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My understanding of sys.exit is that if called in the main thread it will kill all the other threads, but if called in a child thread it will only kill off that thread. I may be wrong though. I don't know if that is related to the problem you are having.
Some more questions: * are the spawned programs also written in Python? * is there any way to debug them, e.g. by putting in trace statements so that you can see what they are blocking on? Dave - The Developers' Coach
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#6
June 24th, 2004, 05:44 AM
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I did a few experiments and I think you have two options:
1. Only spawn the child processes in the main thread (why do you need to spawn them in a child thread, perhaps you only need threads for monitoring if at all?). This will allow the child processes to respond to the os.kill. 2. If you must use threads then you need to signal the child process program to terminate somehow and then os.wait() for the child process to finish. But os.kill is ignored! Perhaps you can signal the child app using sockets or pipes. This code starts two processes and then kills them: Code:
import os
import signal
import time
procs = []
for n in range(2):
procs.append(os.spawnvp(os.P_NOWAIT, "ping", ["ping", "127.0.0.1"]))
print procs
time.sleep(5)
for n in procs:
print n
os.kill(n, signal.SIGINT)
This code tries to do the same thing but fails. The kill signal is ignored. Code:
import threading
import os
import signal
import time
procs = []
class Worker(threading.Thread):
def run(self):
procs.append(os.spawnvp(os.P_NOWAIT, "ping", ["ping", "127.0.0.1"]))
for n in range(2):
a = Worker()
a.start()
print procs
time.sleep(5)
for n in procs:
print n
os.kill(n, signal.SIGINT)
When the shell process from which the python program was run is killed the child processes are stopped but you are left with two do nothing zombies. grim 
__________________
*** Experimental Python Markup CGI V2 ***
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#7
June 24th, 2004, 05:53 AM
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Actually, the processes I generarted are reported as Sleeping and not Zombified.
Not sure if this will help.  These processes can be killed with kill -9 PID. Last edited by Grim Archon : June 24th, 2004 at 06:01 AM. Reason: update on kill
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#8
June 24th, 2004, 06:16 AM
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Minor changes...
Code:
procs.append(os.spawnvp(os.P_NOWAIT,"ping",["ping","127.0.0.1"])) os.waitpid(procs[-1],0) Code:
for n in procs:
print n
os.system("kill -9 %s"%n)
print "waiting for the threads to finish"
for n in range(2):
wt[n].join(5.0)
Worked.
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