Re: frequent lockups in 3.18rc4

[Steven Rostedt]

On Fri, 21 Nov 2014 11:06:41 -0800
Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
 
>   static noinline int vmalloc_fault(unsigned long address)
>   {
>         pgd_t *pgd_dst;
>         pgdval_t pgd_entry;
>         unsigned index = pgd_index(address);
> 
>         if (index < KERNEL_PGD_BOUNDARY)
>                 return -1;
> 
>         pgd_entry = init_mm.pgd[index].pgd;
>         if (!pgd_entry)
>                 return -1;

Should we at least check to see if it is present?

	if (!(pgd_entry & 1))
		return -1;

?

-- Steve

> 
>         pgd_dst = __va(PAGE_MASK & read_cr3());
>         pgd_dst += index;
> 
>         if (pgd_dst->pgd)
>                 return -1;
> 
>         ACCESS_ONCE(pgd_dst->pgd) = pgd_entry;
>         return 0;
>   }
>   NOKPROBE_SYMBOL(vmalloc_fault);
> 
> Hmm? Does anybody see anything fundamentally wrong with this?
> 
>                      Linus

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