Hello.

Andrew Morton wrote:
> umm, actually it's wrong.  i386's smp_prepare_boot_cpu() diddles with
> per-cpu memory, and that's not initialised at that stage.  See the call to
> setup_per_cpu_areas() a few lines later.
> So I'll drop that hunk.  How important is it in practice?
It was important because it used to fix both the printk and
(completely accidentally!) the boot problem itself.

> #ifdef CONFIG_SMP
> 	cpu_set(smp_processor_id(), cpu_online_map);	/* comment */
> #endif
I don't even think #ifdef is needed. Having that for the UP
case may be useless, yet looks consistent to me.

> right there in start_kernel()?
This is enough for printk but not for the boot lockup.
The attached patch is however enough. And it should be
correct, as it is consistent with an UP case.

> (That assumes that smp_processor_id() works at that stage.  Surely that's
> true).
Looking into the arch-specific code, I can see that some
arches evaluate the boot-cpu number by some other means,
not by the smp_processor_id(). Still I am pretty sure the
patch won't hurt them.

With this patch and with the hotfixes, I've got the -mm
kernel working, thanks.

----

Register the boot-cpu in the cpu maps earlier to allow the
early printk to work, and to fix an obscure deadlock at boot.

Signed-off-by: Stas Sergeev <stsp@aknet.ru>