Re: frequent lockups in 3.18rc4

[Linus Torvalds]

On Fri, Nov 21, 2014 at 12:16 PM, Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
>
> I don't think that works on 32bit. See the magic in
> vmalloc_sync_one().

Heh. I guess we could just add a wrapper around this crap, and make it
very clear that the paravirt case is a horrible horrible hack.

Something like

   #define set_one_pgd_entry(entry,pgdp) (pgdp)->pgd = (entry)

for the regular case, and then for paravirt we do something very
explicitly horrid, like

   #ifdef CONFIG_PARAVIRT
   #ifdef CONFIG_X86_32
   // The pmd is the top-level page directory on non-PAE x86, nested
inside pgd/pud
   #define set_one_pgd_entry(entry,pgdp) set_pmd((pmd_t *)(pgdp),
(pmd_t) { entry } )
   #else
   #define set_one_pgd_entry(entry, pgdp) do { set_pgd(pgdp, (pgd_t) {
entry });  arch_flush_lazy_mmu_mode(); } while (0)
   #endif

because on x86-64, there seems to be that whole lazy_mode pv_ops
craziness (which I'm not at all convinced is needed here, but that's
what the current code does).

                Linus
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