2014/1/10 Chen Gang F T <[email protected]>: > On 01/10/2014 02:42 AM, Will Deacon wrote: >> On Thu, Jan 09, 2014 at 12:47:24PM +0000, Stefano Stabellini wrote: >>> On Thu, 9 Jan 2014, Arnd Bergmann wrote: >>>> On Thursday 09 January 2014, Will Deacon wrote: >>>>> On Wed, Jan 08, 2014 at 06:00:23PM +0000, Stefano Stabellini wrote: >>>>>> Remove !GENERIC_ATOMIC64 build dependency: >>>>>> - rename atomic64_xchg to armv7_atomic64_xchg and define it even ifdef >>>>>> GENERIC_ATOMIC64; >>>>>> - call armv7_atomic64_xchg directly from xen/events.h. >>>>>> >>>>>> Remove !CPU_V6 build dependency: >>>>>> - introduce __cmpxchg8 and __cmpxchg16, compiled even ifdef >>>>>> CONFIG_CPU_V6; >>>>>> - implement sync_cmpxchg using __cmpxchg8 and __cmpxchg16. >>>>>> >>>>>> Signed-off-by: Stefano Stabellini <[email protected]> >>>>>> CC: [email protected] >>>>>> CC: [email protected] >>>>>> CC: [email protected] >>>>>> CC: [email protected] >>>>>> CC: [email protected] >>>>>> CC: [email protected] >>>>>> CC: [email protected] >>>>>> CC: [email protected] >>>>>> >>>>> >>>>> I'm confused here. It looks like you want to call armv7 code in a v6 >>>>> kernel. >>>>> What am I missing? >>>> >>>> This is about being able to build a kernel that runs on ARMv6 and ARMv7 >>>> and also includes Xen. Because of obvious hardware limitations, Xen >>>> will only run on v7, but currently you cannot even build it once you >>>> enable (pre-v6K) ARMv6 support, since the combined v6+v7 kernel can't >>>> do atomic accesses in a generic way on non-32bit variables. >>> >>> Yep, that's right. >> >> Ok, thanks for the explanation. Looking at the patch, I wonder whether it's >> not cleaner just to implement xchg code separately for Xen? The Linux code >> isn't always sufficient (due to the GENERIC_ATOMIC64 stuff) and most of the >> churn coming out of this patch is an attempt to provide some small code >> reuse at the cost of code readability. >> >> What do others think? >> > > What Will said sounds reasonable to me. > > > Thanks. > -- > Chen Gang
I agree with Will, Regards, Jaccon -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
