On Tue, 7 Feb 2012 16:00:46 -0800 (PST)
Hugh Dickins <hughd@xxxxxxxxxx> wrote:
> Fix CONFIG_TRANSPARENT_HUGEPAGE=y CONFIG_SMP=n CONFIG_DEBUG_VM=y
> CONFIG_DEBUG_SPINLOCK=n kernel: spin_is_locked() is then always false,
> and so triggers some BUGs in Transparent HugePage codepaths.
>
> asm-generic/bug.h mentions this problem, and provides a WARN_ON_SMP(x);
> but being too lazy to add VM_BUG_ON_SMP, BUG_ON_SMP, WARN_ON_SMP_ONCE,
> VM_WARN_ON_SMP_ONCE, just test NR_CPUS != 1 in the existing VM_BUG_ONs.
>
> Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
> ---
>
> mm/huge_memory.c | 4 ++--
> mm/swap.c | 2 +-
> 2 files changed, 3 insertions(+), 3 deletions(-)
>
> --- 3.3-rc2/mm/huge_memory.c 2012-01-20 08:42:35.304020840 -0800
> +++ linux/mm/huge_memory.c 2012-02-07 15:37:18.581666053 -0800
> @@ -2083,7 +2083,7 @@ static void collect_mm_slot(struct mm_sl
> {
> struct mm_struct *mm = mm_slot->mm;
>
> - VM_BUG_ON(!spin_is_locked(&khugepaged_mm_lock));
> + VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
We do have assert_spin_locked(), but I couldn't see any way of using it
while observing these laziness constraints ;)
Should we patch -stable too?
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