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SubjectRe: frequent lockups in 3.18rc4
On Fri, 21 Nov 2014, Linus Torvalds wrote:
> On Fri, Nov 21, 2014 at 12:16 PM, Thomas Gleixner <tglx@linutronix.de> 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).

I'm fine with that. I just think it's not horrid enough, but that can
be fixed easily :)

Thanks,

tglx




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