PIDs limited to 15 significant bits

From: Bernhard Bender (Bernhard.Bender@ELSA.com)
Date: Wed Sep 27 2000 - 08:32:17 EST


Hi,

looking at my process list after a week or so of uptime I discoverd that PIDs
seem to wrap arround at 32767 (aka. 2^15 - 1).

I found the relevant code doing this in kernel/fork.c:get_pid() where a mask
(0xffff8000) is used to limit the PID of a new process to 15 significant bits.
(I am running 2.4.0-test6 currently)

I find this "feature" annoying, since I like to view my process list sorted by
PID, which gives a nice overview about recently started processes vs. age-old
daemons.

So, I would like to ask if someone could please explain the reason for this. If
there is no compelling reason I would like to propose to remove this limit. I
recall this was not present in 2.2.x

After all, UIDs have just been changes to 32bits, why limit PIDs?

thanks
Bernhard

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