* Thomas Gleixner <[email protected]> wrote:
> On Fri, 10 Jul 2015, Dave Jones wrote:
> > I bought a Haswell Xeon E3-1225 v3 box, and found that
> > my self-built kernel would instantly reboot the machine once
> > grub had loaded it.
> >
> > Through trial and error I found the following options matter..
> >
> > if I _enable_ DEBUG_PAGEALLOC, it boots fine.
> > disabling it again, instant death.
> >
> > further narrowing down revealed that if I have DEBUG_PAGEALLOC off,
> > I also _must_ also have CONFIG_DEBUG_VIRTUAL turned off.
> > With both disabled, it also boots fine.
> >
> > I tried earlyprintk, but this happens so soon I don't think
> > we're even at the point of initializing that code.
> >
> > Any ideas how I can further narrow this down ?
>
> I assume that VIRTUAL_BUG_ON() triggers very early. Changing it to
> WARN_ON() should keep the machine alive and give you a hint which of
> those checks explodes.
I suspect an early console might be useful as well, in case the kernel doesn't
manage to boot.
> --- a/include/linux/mmdebug.h
> +++ b/include/linux/mmdebug.h
> @@ -50,7 +50,7 @@ void dump_mm(const struct mm_struct *mm);
> #endif
>
> #ifdef CONFIG_DEBUG_VIRTUAL
> -#define VIRTUAL_BUG_ON(cond) BUG_ON(cond)
> +#define VIRTUAL_BUG_ON(cond) WARN_ON(cond)
I'd make this WARN_ON_ONCE(), to see the first instance and to cross fingers
afterwards and maybe boot up.
Thanks,
Ingo
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