Re: sched domains bringup race?

From: Keshavamurthy Anil S
Date: Sun Jul 18 2004 - 15:50:36 EST

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)

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