topic Re: C process zombies managment in Operating System - Linux

C process zombies managment

Fedele Giuseppe — Wed, 07 May 2008 09:41:50 GMT

Hello,

I have the following problem on hp-ux 11i platform.

In a C process I trap the SIGCHLD signals and manage them in a dedicaded routine through waitpid function:

signal(SIGCHLD, SigExit);

...

void SigExit(int sig)
{
int status;
int local_pid;

....

switch(sig)
{
...

case SIGCHLD:
while ((local_pid = waitpid(-1, &status, WNOHANG)) > 0)
{
...
}
signal(sig, SigExit);
return;
break;
}
}

The children processes terminations are correclty trapped, but randomically some zombies processes are generated.

Could someone help me?

Many thanks.

Giuseppe Fedele

Re: C process zombies managment

Dennis Handly — Thu, 08 May 2008 04:29:57 GMT

You may have to use sigaction(2) instead of signal(2). sigaction allows you to block the signal so you don't have multiple signals coming at the same time.

Also, the waitpid(2) says that waitpid(...,, WNOHANG) sometimes returns 0.
If it returns -1, you might want to check errno is ECHILD.

Re: C process zombies managment

Fedele Giuseppe — Thu, 08 May 2008 09:30:50 GMT

Ok, thanks.

A further question: does signal function have problems in multithread environment?
Because this is my case.

Giuseppe

Re: C process zombies managment

Dennis Handly — Thu, 08 May 2008 16:39:36 GMT

>Does signal function have problems in multithread environment?

That may explain why sigaction and blocking will fix it.