Re: can I bring Linux down by running "renice -20 cpu_intensive_process"?

[Mike Galbraith <efault@gmx.de>]

On Thu, 2006-03-16 at 22:51 +0000, Måns Rullgård wrote:
> Bill Davidsen <davidsen@tmr.com> writes:
> 
> > Måns Rullgård wrote:
> >> Maybe extending sysrq+n to lower the priority of -20 tasks would be a
> >> good idea.
> >>
> > If it runs before the keyboard thread it doesn't matter...
> 
> Of course not, but that's not generally the case.
> 
> > But why should this hang anything, when there should be enough i/o
> > to get out of the user process. There's a good fix for this, don't
> > give this guy root any more ;-)
> 
> Ever heard of bugs?  Anyone developing a program can make a mistake.
> If the program runs with realtime scheduling a bug that makes it enter
> an infinite loop (or do something else that hogs the CPU) can be
> difficult to find since it rather efficiently locks you out.

Given that someone has already determined that installing a safety valve
for RT tasks was worth while, and given that there is practically no
difference between a nice -20 and the lowest RT priority, seems to me
that extending that safety valve to cover reniced tasks is the
obviously-correct thing to do.  I think you should submit a patch.

	-Mike