Re: [LAU] realtime problem on 2.6.25

On Fri, 2008-04-25 at 07:27 -0700, Ben Tartsa wrote:
> Hi guys, perhaps I'm missing the point here but the kernels linked in
> a later post here:
> http://packages.ubuntu.com/gutsy/linux-image-2.6.22-14-rt
> http://packages.ubuntu.com/hardy/linux-image-2.6.24-16-rt
>
> are both patched w/ the rt patchset allowing full preemption. I am
> aware you can get realltime as root though its a _bad_ idea. patches
> are not available for the 25 series yet. Can someone sort this out?

it is time to once again make clear some fundamentals.

  * the ability to obtain SCHED_FIFO scheduling and use mlock(2) are
     *COMPLETELY* separate from whether or not a kernel has been
     built with Ingo's RT patches

and the corollary:

  * a kernel built with Ingo's RT patches is not required to and does
     not by itself ensure that a non-root user can use SCHED_FIFO
     and mlock(2)

Ingo's RT patches simply make the performance of a system using
SCHED_FIFO-scheduled threads *better*. They have *absolutely nothing* to
do with whether or not a normal user can successfully execute a program
that wants to use SCHED_FIFO. that is determined by other non-kernel
elements of your system (which parts varies by distro, but primarily PAM
on most current distros).

--p

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Received on Fri Apr 25 20:15:04 2008