Re: CPU scheduler weirdness?

[Marton Balint]

On Wed, 19 Aug 2009, Peter Zijlstra wrote:

> On Wed, 2009-08-19 at 14:01 +0200, Marton Balint wrote:
> > On Wed, 19 Aug 2009, Peter Zijlstra wrote:
> > > On Tue, 2009-08-18 at 21:49 +0200, Marton Balint wrote:
> > >
> > > > In the meantime, I was able to create a tiny C program which always
> > > > succesfully reproduces the bug. It's basically an endless loop which does
> > > > not stop while the process is running on the last CPU core. The program
> > > > creates multiple instances of itself, to be able to keep all of the CPU
> > > > cores busy. After 1 second, the processes running on other than the last
> > > > CPU core die, the processes running on the last CPU core remain stuck
> > > > there...
> > > >
> > > > I tested it on my dual core system, if someone could test it on a quad
> > > > core and report back that would probably be useful.
> > > >
> > > > Usage: ./schedtest <number of CPU cores>
> > > >
> > > > And don't forget to kill the stuck processes after using the program! :)
> > >
> > > So what's the bug? Sure one task will stay on the cpu, and because there
> > > is no contention it doesn't get migrated, and therefore won't quit,
> > > how's that a problem?
> >
> > Problem is that more than one processes remain on that CPU core, and none
> > of them get migrated to other (idle) cores. I tested it with my E8400
> > processor and 2.6.31-rc5-git3 kernel.
>
> Only one remains here.. on a c2q running 2.6.31-rc6-tip
>
> Do you have a .config handy?

Yes it's in my original post:

http://marc.info/?l=linux-kernel&m=125012584709800&w=2

Regards,
  Marton
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