On Mon, 11 Oct 2021 at 19:02, Vlastimil Babka vbabka@suse.cz 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.
BTW it's possible that there won't be any DRM review because this failed to apply: https://patchwork.freedesktop.org/series/95549/ DRM folks, any hint how to indicate that the base was next-20211001?
[...]
+#ifdef CONFIG_STACKDEPOT_ALWAYS_INIT +static inline int stack_depot_early_init(void) { return stack_depot_init(); } +#else +static inline int stack_depot_early_init(void) { return 0; } +#endif /* CONFIG_STACKDEPOT_ALWAYS_INIT */
We could, but it's a wrapper made for only a single caller...
#endif diff --git a/init/main.c b/init/main.c index ee4d3e1b3eb9..b6a5833d98f5 100644 --- a/init/main.c +++ b/init/main.c @@ -844,7 +844,8 @@ static void __init mm_init(void) init_mem_debugging_and_hardening(); kfence_alloc_pool(); report_meminit();
- stack_depot_init();
- if (IS_ENABLED(CONFIG_STACKDEPOT_ALWAYS_INIT))
stack_depot_init();I'd push the decision of when to call this into <linux/stackdepot.h> via wrapper stack_depot_early_init().
No strong preferrences, if you think it's worth it.
All the other *init() functions seem to follow the same idiom as there are barely any IS_ENABLED() in init/main.c. So I think it's just about being consistent with the rest.
Thanks, -- Marco