On Fri, Apr 20, 2018 at 10:25:14AM -0500, Christopher Lameter wrote:
> On Wed, 18 Apr 2018, Matthew Wilcox wrote:
> > + union {
> > + unsigned long private;
> > +#if USE_SPLIT_PTE_PTLOCKS
> > +#if ALLOC_SPLIT_PTLOCKS
> > + spinlock_t *ptl;
> > +#else
> > + spinlock_t ptl;
>
> ^^^^ This used to be defined at the end of the struct so that you could
> have larger structs for spinlocks here (debugging and some such thing).
>
> Could this not misalign the rest?
Nope:
include/linux/mm_types_task.h:#define ALLOC_SPLIT_PTLOCKS (SPINLOCK_SIZE > BITS_PER_LONG/8)
So we'll only store a spinlock here if it's <= sizeof(long); otherwise
we'll store a pointer here.
