Re: [discuss] [patch 3/3] x86_64: Node local pda take 2 -- node local pda allocation

[Ravikiran G Thirumalai <kiran@scalex86.org>]

On Fri, Dec 16, 2005 at 01:19:34AM +0100, Andi Kleen wrote:
> 
> And for the APs you allocate the PDA in smpboot.c before actually sending
> the startup IPI to the AP. 

You mean wakeup_secondary_via_INIT, called by do_boot_cpu?
That is too late. sched_init happens much earlier, and the per-cpu offset
table for all AP cpus not present is referenced, and I hit an early exception.
sched_init is executed on the BP very early and sched_init does this:

        for (i = 0; i < NR_CPUS; i++) {
                prio_array_t *array;

                rq = cpu_rq(i); 

The cpu_rq macro ends up needing per-cpu offset table stored in cpu_pda of
the AP cpus, even before we hit the code to send startup IPIs.
(#define __per_cpu_offset(cpu) (cpu_pda[cpu].data_offset))
This is way before slab is ready.  So I either use alloc_bootmem before
sched_init in setup_arch, or keep the static boot_cpu_pda.

Am I missing something?

Thanks,
Kiran