On 10/7/21 13:01, Marco Elver wrote: > On Thu, Oct 07, 2021 at 11:58AM +0200, Vlastimil Babka wrote: > [...] >> - Add a CONFIG_STACKDEPOT_ALWAYS_INIT flag to keep using the current >> well-defined point of allocation as part of mem_init(). Make CONFIG_KASAN >> select this flag. >> - Other users have to call stack_depot_init() as part of their own init when >> it's determined that stack depot will actually be used. This may depend on >> both config and runtime conditions. Convert current users which are >> page_owner and several in the DRM subsystem. Same will be done for SLUB >> later. >> - Because the init might now be called after the boot-time memblock allocation >> has given all memory to the buddy allocator, change stack_depot_init() to >> allocate stack_table with kvmalloc() when memblock is no longer available. >> Also handle allocation failure by disabling stackdepot (could have >> theoretically happened even with memblock allocation previously), and don't >> unnecessarily align the memblock allocation to its own size anymore. > ... >> Hi, I'd appreciate review of the DRM parts - namely that I've got correctly >> that stack_depot_init() is called from the proper init functions and iff >> stack_depot_save() is going to be used later. Thanks! > > For ease of review between stackdepot and DRM changes, I thought it'd be > nice to split into 2 patches, but not sure it'll work, because you're > changing the semantics of the normal STACKDEPOT. Yeah, that's why it's a single patch. As the DRM parts are clearly separated to their files, I think review should be fine. > One option would be to flip it around, and instead have > STACKDEPOT_LAZY_INIT, but that seems counter-intuitive if the majority > of STACKDEPOT users are LAZY_INIT users. Agree. > 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()? > 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. 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? >> @@ -30,13 +40,4 @@ int stack_depot_snprint(depot_stack_handle_t handle, char *buf, size_t size, >> >> void stack_depot_print(depot_stack_handle_t stack); >> >> -#ifdef CONFIG_STACKDEPOT >> -int stack_depot_init(void); >> -#else >> -static inline int stack_depot_init(void) >> -{ >> - return 0; >> -} >> -#endif /* CONFIG_STACKDEPOT */ >> - > > Could we avoid the IS_ENABLED() in init/main.c by adding a wrapper here: > > +#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. >> mem_init(); >> mem_init_print_info(); >> /* page_owner must be initialized after buddy is ready */ >> diff --git a/lib/Kconfig b/lib/Kconfig >> index 5e7165e6a346..df6bcf0a4cc3 100644 >> --- a/lib/Kconfig >> +++ b/lib/Kconfig >> @@ -671,6 +671,9 @@ config STACKDEPOT >> bool >> select STACKTRACE >> >> +config STACKDEPOT_ALWAYS_INIT >> + bool > > It looks like every users of STACKDEPOT_ALWAYS_INIT will also select > STACKDEPOT, so we could just make this: > > +config STACKDEPOT_ALWAYS_INIT > + bool > + select STACKDEPOT > > And remove the redundant 'select STACKDEPOT' in Kconfig.kasan. Right, will do, if KConfig resolver doesn't bite me. >> config STACK_HASH_ORDER >> int "stack depot hash size (12 => 4KB, 20 => 1024KB)" >> range 12 20 >> diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan >> index cdc842d090db..695deb603c66 100644 >> --- a/lib/Kconfig.kasan >> +++ b/lib/Kconfig.kasan >> @@ -39,6 +39,7 @@ menuconfig KASAN >> HAVE_ARCH_KASAN_HW_TAGS >> depends on (SLUB && SYSFS) || (SLAB && !DEBUG_SLAB) >> select STACKDEPOT >> + select STACKDEPOT_ALWAYS_INIT > > [...] >> >> -int __init stack_depot_init(void) >> +/* >> + * __ref because of memblock_alloc(), which will not be actually called after >> + * the __init code is gone > > The reason is that after __init code is gone, slab_is_available() will > be true (might be worth adding to the comment). OK Thanks for the review!
