I am reframing my question:
Sub-task 1: Until now, parent process cannot control the pid of the forked child. A pid gets assigned as a sequential number by the kernel at the time the process is forked . I want to modify kernel in such a way that parent process can control the pid of the forked child.

Sub-task 2: On Linux, you can find the maximum PID value for your system with the following command:

$ cat /proc/sys/kernel/pid_max

Suppose pid_max=2000 for a system. I want that the parent process should be able to assign a pid which is greater that 2000 to the forked child.

On Mon, Mar 21, 2016 at 12:03 AM, <Valdis.Kletnieks@vt.edu> wrote:

On Sun, 20 Mar 2016 02:07:29 -0700, Nitin Varyani said:

> The linux kernel attaches a pid to newly forked process. I want to
> create a facility by which a process has the option of attaching a new pid
> to its child which is not in the pid space.

Not at all sure what you mean by "not in the pid space", or what you're
trying to achieve by doing it.

But "pid namespaces" may be what you're looking for.