On 6/25/24 7:12 PM, Alexei Starovoitov wrote: > On Tue, Jun 25, 2024 at 7:24 AM Vlastimil Babka <vbabka@xxxxxxx> wrote: >> >> On 6/20/24 12:49 AM, Vlastimil Babka wrote: >> > --- a/mm/slub.c >> > +++ b/mm/slub.c >> > @@ -3874,13 +3874,37 @@ static __always_inline void maybe_wipe_obj_freeptr(struct kmem_cache *s, >> > 0, sizeof(void *)); >> > } >> > >> > -noinline int should_failslab(struct kmem_cache *s, gfp_t gfpflags) >> > +#if defined(CONFIG_FUNCTION_ERROR_INJECTION) || defined(CONFIG_FAILSLAB) >> > +DEFINE_STATIC_KEY_FALSE(should_failslab_active); >> > + >> > +#ifdef CONFIG_FUNCTION_ERROR_INJECTION >> > +noinline >> > +#else >> > +static inline >> > +#endif >> > +int should_failslab(struct kmem_cache *s, gfp_t gfpflags) >> >> Note that it has been found that (regardless of this series) gcc may clone >> this to a should_failslab.constprop.0 in case the function is empty because >> __should_failslab is compiled out (CONFIG_FAILSLAB=n). The "noinline" >> doesn't help - the original function stays but only the clone is actually >> being called, thus overriding the original function achieves nothing, see: >> https://github.com/bpftrace/bpftrace/issues/3258 >> >> So we could use __noclone to prevent that, and I was thinking by adding >> something this to error-injection.h: >> >> #ifdef CONFIG_FUNCTION_ERROR_INJECTION >> #define __error_injectable(alternative) noinline __noclone > > To prevent such compiler transformations we typically use > __used noinline > > We didn't have a need for __noclone yet. If __used is enough I'd stick to that. __used made no difference here (gcc 13.3), __noclone did
