Stas Sergeev <[email protected]> wrote:
>
> main.c: moved smp_prepare_boot_cpu() call earlier. This
> was necessary because otherwise printk() can't print
> It checks cpu_online(), which returns false. This change
> is consistent with the UP case, where's the boot CPU is
> "online" from the very beginning, AFAICS. But again, I am
> not entirely sure whether this is safe.
>
Yeah, this is scary. Early boot is fragile and complex and architectures
might not expect to run smp_prepare_boot_cpu() before setup_arch().
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?
If it's purely to make printk print something then perhaps we can do
something expedient like:
#ifdef CONFIG_SMP
cpu_set(smp_processor_id(), cpu_online_map); /* comment */
#endif
right there in start_kernel()?
(That assumes that smp_processor_id() works at that stage. Surely that's
true).
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