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Subject: Re: Fwd: [Lse-tech] get_pid() performance fix
To: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: linux-kernel@vger.kernel.org, lse-tech@lists.sourceforge.net
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From: "Rajan Ravindran" <rajancr@us.ibm.com>
Date: Tue, 5 Mar 2002 11:43:24 -0500
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Yes, pid's are guaranteed to be unique.
Here the problem we focused is the time taken in finding the next
available free pid.
I really don't mean by your task->xxx.

-Rajan



Hubertus Franke <frankeh@watson.ibm.com> writes:

> @@ -153,13 +155,18 @@
>                               if(last_pid & 0xffff8000)
>                                     last_pid = 300;
>                               next_safe = PID_MAX;
> +                             goto repeat;
>                         }
> -                       goto repeat;
> +                       if(unlikely(last_pid == beginpid))
> +                             goto nomorepids;
> +                       continue;

It isn't guaranteed that pid is unique.

In the case:
             task->pid = 300, task->xxx = 301
             pid 301 is free

             This get_pid() returns 301.

Regards.
--
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>

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