Re: [PATCH] [5/6] scheduler: Protect important kernel threads against normalize_rt

Andi Kleen
2007-10-08T12:34:32Z

On Monday 08 October 2007 13:51:42 Ingo Molnar wrote:
>
> * Andi Kleen <ak@suse.de> wrote:
>
> > Not only the migration thread, but also softlockup and stop machine
> > need to be protected against normalize_rt(). Instead of checking for
> > them all I added a new process flag for this.
>
> hm, i dont really like this. The migration thread is an absolute
> exception because it's needed for a correct scheduler. SysRq-N is like
> SysRq-U or SysRq-B - last-minute resort in case something Goes Foul.
> Results are not guaranteed.

softlockup is the same. Just think about it.

If you ever renormalize it and then run a fifo thread it will
starve and then eventually kill the box.

And starving CPU unplug is also equally bad.

-Andi