pid_t range question

[linux-os (Dick Johnson)]

On Linux, type pid_t is defined as an int if you look
through all the intermediate definitions such as S32_T,
etc. However, it wraps at 32767, the next value being 300.

Does anybody know why it doesn't go to 0x7fffffff and
then wrap to the first unused pid value? I know the
code "reserves" the first 300 pids. That's not the
question. I wonder why. Also I see the code setting
the upper limit as well. I want to know why it is
set within the range of a short and is not allowed
to use the full range of an int. Nothing I see in
the kernel, related to the pid, ever uses a short
and no 'C' runtime interface limits this either!

Also, attempts to change /proc/sys/kernel/pid_max fail
if I attempt to increase it, but I can decrease it
to where I don't have enough pids available to fork()
the next command! Is this the correct behavior?

Cheers,
Dick Johnson
Penguin : Linux version 2.6.13.4 on an i686 machine (5589.66 BogoMips).
Warning : 98.36% of all statistics are fiction.
_


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