On Wednesday 13 April 2016 19:15:17 Pan Xinhui wrote:
> Hello Peter,
>
> On 2016年04月12日 22:30, Peter Zijlstra wrote:
> > On Sun, Apr 10, 2016 at 10:17:28PM +0800, Pan Xinhui wrote:
> >>
> >> On 2016年04月08日 15:47, Peter Zijlstra wrote:
> >>> On Fri, Apr 08, 2016 at 02:41:46PM +0800, Pan Xinhui wrote:
> >>>> From: pan xinhui <xinhui....@linux.vnet.ibm.com>
> >>>>
> >>>> Implement xchg{u8,u16}{local,relaxed}, and
> >>>> cmpxchg{u8,u16}{,local,acquire,relaxed}.
> >>>>
> >>>> Atomic operation on 8-bit and 16-bit data type is supported from power7
> >>>
> >>> And yes I see nothing P7 specific here, this implementation is for
> >>> everything PPC64 afaict, no?
> >>>
> >> Hello Peter,
> >> No, it's not for every ppc. So yes, I need add #ifdef here. Thanks for
> >> pointing it out.
> >> We might need a new config option and let it depend on POWER7/POWER8_CPU
> >> or even POWER9...
> >
> > Right, I'm not sure if PPC has alternatives, but you could of course
> > runtime patch the code from emulated with 32bit ll/sc to native 8/16bit
> > ll/sc if present on the current CPU if you have infrastructure for these
> > things.
> >
> seems interesting. I have no idea about how to runtime patch the code. I will
> try to learn that.
> If so, we need change {cmp}xchg into uninline functions?
I think you don't need to, see do_feature_fixups()/patch_feature_section()
Note that an #ifdef by itself has to worry about any combination of
architectures, so in a kernel that has both POWER6 and POWER7 enabled,
you cannot call the POWER7-only function.
Arnd
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