Re: sched domains bringup race?

[Keshavamurthy Anil S <anil.s.keshavamurthy@intel.com>]

On Thu, Jul 15, 2004 at 07:13:46PM -0700, Dave Hansen wrote:
> I keep getting oopses for the non-boot CPU in find_busiest_group(). 
> This occurs the first time that the CPU goes idle.  Those groups are set
> up in sched_init_smp(), which is called after smp_init():
> 
> static int init(void * unused)
> {
> 	...
>         fixup_cpu_present_map();
>         smp_init();
>         sched_init_smp();
> 
> But, the idle threads for the secondary CPUs are initialized in
> smp_init().  So, what happens when a CPU tries to schedule (using sched
> domains) before sched_init_smp() completes?  I think it goes boom! :)
> 
> Anyway, I was thinking that we should just hold the runqueue lock on the
> non-boot CPUs until the sched domain init code is done.  Does that sound
> feasible?

Even on my system which is Intel 865 chipset (P4 with HT enabled system) 
I see a bug check somewhere in the schedular_tick during boot.
However if I move the sched_init_smp() after do_basic_setup() the
kernel boots without any problem. Any clue here?

 static int init(void * unused)
 {
 	...
         fixup_cpu_present_map();
         smp_init();
	 populate_rootfs();
	 do_basic_setup();
 
         sched_init_smp();
-Anil