On Thu, 9 Jan 2014, 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 <stefano.stabell...@eu.citrix.com> > > > > > CC: a...@arndb.de > > > > > CC: li...@arm.linux.org.uk > > > > > CC: will.dea...@arm.com > > > > > CC: gang.c...@asianux.com > > > > > CC: catalin.mari...@arm.com > > > > > CC: jaccon.bastiaan...@gmail.com > > > > > CC: linux-arm-ker...@lists.infradead.org > > > > > CC: linux-kernel@vger.kernel.org > > > > > > > > > > > > > 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?
I am OK with that, in fact my first version of the patch did just that: http://marc.info/?l=linux-arm-kernel&m=138436406724990&w=2 Is that what you had in mind? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
