Re: [PATCH] 2.6.16-rt17 on IA64

[Ingo Molnar <mingo@elte.hu>]

* Simon Derr <Simon.Derr@bull.net> wrote:

> Hi,
> 
> This is a first version of my port of Ingo's -rt kernel to the IA64 
> arch.

nice! I've added this to the -rt tree and have released -rt18.

> So far the kernel boots with PREEMPT_RT enabled (on a 4-cpu tiger), 
> and that's about it. I've not done extensive tests (only 
> scripts/rt-tester), nor any measurements of any kind.
> 
> There's very probably many bugs I'm not aware of.
> 
> But there is already one thing I know should be fixed : I've changed 
> the declaration of (struct zone).lock (in include/linux/mmzone.h) from 
> spinlock_t to raw_spinlock_t.
> 
> I did this because on IA64, cpu_idle(), which is not allowed to call 
> schedule(), calls check_pgt_cache(). I guess this could be fixed by 
> moving this call to another kernel thread... ideas are welcome.

this should definitely be cleaned up. There are a couple of periodic VM 
threads you could do this from - but none is really per-CPU. So my 
suggestion would be to do the check_pgt_cache() from desched_thread() - 
which is an rt-specific cleanup thread. You dont even have to make it 
ia64-specific i think.

	Ingo