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Re: [PATCH] [AArch64] support -mfentry feature for arm64


On 04/19/2016 03:37 PM, Pedro Alves wrote:
> On 04/19/2016 02:25 PM, Andrew Haley wrote:
>> On 04/19/2016 02:19 PM, Michael Matz wrote:
>>
>>> Well, yeah, that's traditional insn caches on multiple cores.  From
>>> user space you need kernel help for this, doing interprocess
>>> interrupts to flush all such buffers on all cores (or at least those
>>> potentially fetching stuff in the patched region, if such
>>> granularity is possible).  An implementation providing such is
>>> non-broken :)
>>
>> Sure.  If you know of any such facility in Linux userspace, please let
>> me know.  :-)
> 
> Sounds like a job for the sys_membarrier system call:
> 
>  https://lkml.org/lkml/2015/3/18/531
>  https://lwn.net/Articles/369567/
> 
> I think it's available in Linux 4.3+.

So it is, thanks.  I'm guessing that might be good enough for full
instruction synchronization barriers, but from looking at the kernel
source I can't really tell.

Andrew.



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