Sombie Process

[Jose Luis]

Hello everybody:
(HP-UX 11.0)
I have a zombie process and I try kill it with kill -9, kill -2, etc. but those proccess don?t die. Probably being held open by a tcp connection, i'm afraid. I use lsof to see which IP it is:

lsof -i | grep 10257

How can I use the ndd command to close the tcp connection?
Thanks in advance!
PD: Sorry for my poor English

[John Poff]

Hello,

What is the parent process of the zombie?

The 'ndd' command is for viewing and setting network tuneable parameters. It won't help you terminate a TCP connection. Have you been able to do a 'netstat -a' command and see the state of the connection? Maybe it will timeout after while.

Your English is fine!

JP

[Abel Berger]

Hi Jose,

Have a look at Knowledge Base document #S1100002433B. If you adjust the 'tcp_keepalive_interval' and others parameters (with 'ndd') you should be able to automatically close the hung connections in a shorter time.

I hope this help !

Regards,

Abel Berger

[Jose Luis]

Hi John and Abel, thank's for your responses.
The parent process of the zombie is "1", and With "ps -el" the state of this process is "T", but when I do a "ps -fea" there are many iqual procees in the output command with different PID, and don?t die whith the kill command.
Moreover, with the:
tusc -p PID
the message is:
"tusc:retrying attach to process 29349 (process name): Interrupted system call"
What can I do for kill this process?
Thank's Masters

[John Poff]

If the parent process ID is one (init), there probably isn't much hope of killing the zombie process. It will take a reboot to get rid of it. What is the name of the zombie process? Is it part of an application or is it a Unix system process? If the zombie is taking little or no CPU time you will probably be fine with it until your next reboot.

JP

[Magdi KAMAL · Accepted solution]

Hi Jose,

Look, Zombie process are those ones that when they finish working ( normal or abnormal exit ) they didn't find their parents executing a wait() function( waiting ) for them.

That's mean, consider a process P0 is doing a fork ( creates a copy of himeself ). The copy process is P1 called the child process ( and P0 is the parent process of P1).

If P1 finish his work ( normal or abnormal exit ) and P0 is still live and not listening to him with a wait() function. So , P1 became a ZOMBIE process.

Booting is the only manner by which we can kill Zombies. Zombies are "Neither live nor Died process!!! "

If you need any help to avoid this miss programming, I have the solution just append your request .


Have a look in the following book :

Advanced Programming in the UNIX Environment.
Addison-Wesley
W. Richard Stevens.
Pages 195 and 196

The manner by which the Unix model avoid that is :

P0 forks twice ,

P0 fork and gives P1
P1 fork and gives P2

1.The first instruction of P2 is to loop till getppid() returns 1 (getppid means GetParentProcessIdentification, P1 executes an exit() to allow that P2 be inhereted by init process "PID 1").
2. The first instruction of P1 is exit() function.
3. P2 became ORPHAN.
4. init process become the actual parent of P2.
5. The function getppid() returns 1 now for P2 process.
6. The P2 process executes its task.
7. P2 terminates normally or abnormally.
8. init process executes an immediate wait() function.
9. P2 died without being ZAMBIE.

If you follow this protocol, your application will never have zombies processes.

Hope this explain the issue.
Wainting for any discussion.


Magdi

[Magdi KAMAL]

Hi again Jose,

Zombies appear when developpers miss program applications.

You have to have a site with them to explain the steps by which a good programming must be to avoid ZOMBIES, and you key sentence is :

"In a client/server model under unix, what developpers do to avoid ZOMBIES ?".

Whatever the response is, map it on the previous steps to fetch out at which moment they(developpers) generate ZOMBIES .

Magdi

[Mark van Hassel]

Hi,

Just some more info: zombies do not decrease performance, theu do noy use CPU time or memory. They do however take up a process slot so when there are many the proces table (maximum number of processes) will fill up.

[Jose Luis]

Thanks everybody for your help!!!