Re: [PATCH 8/8] membarrier: Rewrite sync_core_before_usermode() and improve documentation

Andy Lutomirski
2021-06-16T23:51:05Z

On Wed, Jun 16, 2021, at 11:52 AM, Andy Lutomirski wrote:
> On 6/15/21 9:45 PM, Nicholas Piggin wrote:
> > Excerpts from Andy Lutomirski's message of June 16, 2021 1:21 pm:
> >> The old sync_core_before_usermode() comments suggested that a non-icache-syncing
> >> return-to-usermode instruction is x86-specific and that all other
> >> architectures automatically notice cross-modified code on return to
> >> userspace.
>
> >> +/*
> >> + * XXX: can a powerpc person put an appropriate comment here?
> >> + */
> >> +static inline void membarrier_sync_core_before_usermode(void)
> >> +{
> >> +}
> >> +
> >> +#endif /* _ASM_POWERPC_SYNC_CORE_H */
> >
> > powerpc's can just go in asm/membarrier.h
>
> $ ls arch/powerpc/include/asm/membarrier.h
> ls: cannot access 'arch/powerpc/include/asm/membarrier.h': No such file
> or directory

Which is because I deleted it. Duh. I'll clean this up.

>
>
> >
> > /*
> > * The RFI family of instructions are context synchronising, and
> > * that is how we return to userspace, so nothing is required here.
> > */
>
> Thanks!