On 10/11/21 19:08, Marco Elver wrote: > On Mon, 11 Oct 2021 at 19:02, Vlastimil Babka <vbabka@xxxxxxx> wrote: > [...] >> > On the other hand, the lazy initialization mode you're introducing >> > requires an explicit stack_depot_init() call somewhere and isn't as >> > straightforward as before. >> > >> > Not sure what is best. My intuition tells me STACKDEPOT_LAZY_INIT would >> > be safer as it's a deliberate opt-in to the lazy initialization >> > behaviour. >> >> I think it should be fine with ALWAYS_INIT. There are not many stackdepot >> users being added, and anyone developing a new one will very quickly find >> out if they forget to call stack_depot_init()? > > I think that's fine. > >> > Preferences? >> > >> > [...] >> >> --- a/drivers/gpu/drm/drm_mm.c >> >> +++ b/drivers/gpu/drm/drm_mm.c >> >> @@ -980,6 +980,10 @@ void drm_mm_init(struct drm_mm *mm, u64 start, u64 size) >> >> add_hole(&mm->head_node); >> >> >> >> mm->scan_active = 0; >> >> + >> >> +#ifdef CONFIG_DRM_DEBUG_MM >> >> + stack_depot_init(); >> >> +#endif >> > >> > DRM_DEBUG_MM implies STACKDEPOT. Not sure what is more readable to drm >> > maintainers, but perhaps it'd be nicer to avoid the #ifdef here, and >> > instead just keep the no-op version of stack_depot_init() in >> > <linux/stackdepot.h>. I don't have a strong preference. >> >> Hm, but in case STACKDEPOT is also selected by something else (e.g. >> CONFIG_PAGE_OWNER) which uses lazy init but isn't enabled on boot, then >> without #ifdef CONFIG_DRM_DEBUG_MM above, this code would call a >> stack_depot_init() (that's not a no-op) even in case it's not going to be >> using it, so not what we want to achieve. >> But it could be changed to use IS_ENABLED() if that's preferred by DRM folks. > > You're right -- but I'll leave this to DRM folks. Ah, the file only includes stackdepot.h in a #ifdef CONFIG_DRM_DEBUG_MM section so I will keep the #ifdef here for a minimal change, unless requested otherwise.
