On Wed, Apr 29, 2015 at 02:19:01PM -0700, Andrew Morton wrote:
> On Tue, 28 Apr 2015 15:37:04 +0100 Mel Gorman <mgorman@xxxxxxx> wrote:
>
> > +/*
> > + * Deferred struct page initialisation requires some early init functions that
> > + * are removed before kswapd is up and running. The feature depends on memory
> > + * hotplug so put the data and code required by deferred initialisation into
> > + * the __meminit section where they are preserved.
> > + */
> > +#ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
> > +#define __defermem_init __meminit
> > +#define __defer_init __meminit
> > +#else
> > +#define __defermem_init
> > +#define __defer_init __init
> > +#endif
>
> I still don't get it :(
>
This version was sent out at roughly the same minute you asked the time
before so the comment was not updated. I suggested this as a possible
alternative.
/*
* Deferred struct page initialisation requires init functions that are freed
* before kswapd is available. Reuse the memory hotplug section annotation
* to mark the required code.
*
* __defermem_init is code that always exists but is annotated __meminit * to
* avoid section warnings.
* __defer_init code gets marked __meminit when deferring struct page
* initialistion but is otherwise in the init section.
*/
Suggestions on better names are welcome.
> __defermem_init:
>
> if (CONFIG_DEFERRED_STRUCT_PAGE_INIT) {
> if (CONFIG_MEMORY_HOTPLUG)
> retain
> } else {
> retain
> }
>
> but CONFIG_DEFERRED_STRUCT_PAGE_INIT depends on
> CONFIG_MEMORY_HOTPLUG, so this becomes
>
> if (CONFIG_DEFERRED_STRUCT_PAGE_INIT) {
> retain
> } else {
> retain
> }
>
> which becomes
>
> retain
>
> so why does __defermem_init exist?
>
It suppresses section warnings. Another possibility is that I get rid of
it entirely and use __refok but I feared that it might hide a real problem
in the future.
--
Mel Gorman
SUSE Labs
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