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

Andy Lutomirski
2021-06-16T18:54:39Z

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

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

Thanks!