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

Christophe Leroy
2021-06-18T15:29:06Z

Le 16/06/2021 à 20:52, Andy Lutomirski a écrit :
> 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

https://github.com/torvalds/linux/blob/master/arch/powerpc/include/asm/membarrier.h

Was added by https://github.com/torvalds/linux/commit/3ccfebedd8cf54e291c809c838d8ad5cc00f5688

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