[Bugfix] Set more than 32K pid_max (reformatted)

[Zhu, Yi]

Hi Andrew and Ingo,

Would any of you review the below patch? I think it is a bug and the fix
is obvious. The bug can be reproduced as follow:

$ echo 40000 > /proc/sys/kernel/pid_max
$ # suppose current latest pid is 2198
$ for((i=2199;i<32768;i++));do ps; done
$ ps
  PID TTY          TIME CMD
 2274 pts/0    00:00:00 bash
 65536 pts/0    00:00:00 ps
$ ps
  PID TTY          TIME CMD
 2274 pts/0    00:00:00 bash
 300 pts/0    00:00:00 ps


Thanks Petri Koistinen reformatted the patch as follow.

--- linux-2.5/kernel/pid.c.orig 2004-01-05 17:54:46.000000000 +0200
+++ linux-2.5/kernel/pid.c      2004-01-05 17:55:35.000000000 +0200
@@ -122,6 +122,8 @@
        }

        if (!offset || !atomic_read(&map->nr_free)) {
+               if (!offser)
+                       map--;
 next_map:
                map = next_free_map(map, &max_steps);
                if (!map)


On Mon, 5 Jan 2004, Zhu, Yi wrote:
> 
> I found this is a bug in alloc_pidmap(). If one sets
> /proc/sys/kernel/pid_max more than 32768, "map" will
> increases 1 at (pid from 32767 to 32768)
> 
> 110: map = pidmap_array + pid / BITS_PER_PAGE;
> 
> But at
> 
> 126: map = next_free_map(map, &max_steps);
> 
> "map" will increase 1 again, because offset == 0.
> 
> This is not correct, but only happens when pid_max > 32k.

-- 
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Intel Corp.

Zhu Yi (Chuyee)

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