[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v2 15/32] powerpc: define __smp_xxx
On Tue, Jan 05, 2016 at 09:36:55AM +0800, Boqun Feng wrote: > Hi Michael, > > On Thu, Dec 31, 2015 at 09:07:42PM +0200, Michael S. Tsirkin wrote: > > This defines __smp_xxx barriers for powerpc > > for use by virtualization. > > > > smp_xxx barriers are removed as they are > > defined correctly by asm-generic/barriers.h I think this is the part that was missed in review. > > This reduces the amount of arch-specific boiler-plate code. > > > > Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx> > > Acked-by: Arnd Bergmann <arnd@xxxxxxxx> > > --- > > arch/powerpc/include/asm/barrier.h | 24 ++++++++---------------- > > 1 file changed, 8 insertions(+), 16 deletions(-) > > > > diff --git a/arch/powerpc/include/asm/barrier.h > > b/arch/powerpc/include/asm/barrier.h > > index 980ad0c..c0deafc 100644 > > --- a/arch/powerpc/include/asm/barrier.h > > +++ b/arch/powerpc/include/asm/barrier.h > > @@ -44,19 +44,11 @@ > > #define dma_rmb() __lwsync() > > #define dma_wmb() __asm__ __volatile__ (stringify_in_c(SMPWMB) : : > > :"memory") > > > > -#ifdef CONFIG_SMP > > -#define smp_lwsync() __lwsync() > > +#define __smp_lwsync() __lwsync() > > > > so __smp_lwsync() is always mapped to lwsync, right? Yes. > > -#define smp_mb() mb() > > -#define smp_rmb() __lwsync() > > -#define smp_wmb() __asm__ __volatile__ (stringify_in_c(SMPWMB) : : > > :"memory") > > -#else > > -#define smp_lwsync() barrier() > > - > > -#define smp_mb() barrier() > > -#define smp_rmb() barrier() > > -#define smp_wmb() barrier() > > -#endif /* CONFIG_SMP */ > > +#define __smp_mb() mb() > > +#define __smp_rmb() __lwsync() > > +#define __smp_wmb() __asm__ __volatile__ (stringify_in_c(SMPWMB) : > > : :"memory") > > > > /* > > * This is a barrier which prevents following instructions from being > > @@ -67,18 +59,18 @@ > > #define data_barrier(x) \ > > asm volatile("twi 0,%0,0; isync" : : "r" (x) : "memory"); > > > > -#define smp_store_release(p, v) > > \ > > +#define __smp_store_release(p, v) > > \ > > do { > > \ > > compiletime_assert_atomic_type(*p); \ > > - smp_lwsync(); \ > > + __smp_lwsync(); \ > > , therefore this will emit an lwsync no matter SMP or UP. Absolutely. But smp_store_release (without __) will not. Please note I did test this: for ppc code before and after this patch generates exactly the same binary on SMP and UP. > Another thing is that smp_lwsync() may have a third user(other than > smp_load_acquire() and smp_store_release()): > > http://article.gmane.org/gmane.linux.ports.ppc.embedded/89877 > > I'm OK to change my patch accordingly, but do we really want > smp_lwsync() get involved in this cleanup? If I understand you > correctly, this cleanup focuses on external API like smp_{r,w,}mb(), > while smp_lwsync() is internal to PPC. > > Regards, > Boqun I think you missed the leading ___ :) smp_store_release is external and it needs __smp_lwsync as defined here. I can duplicate some code and have smp_lwsync *not* call __smp_lwsync but why do this? Still, if you prefer it this way, please let me know. > > WRITE_ONCE(*p, v); \ > > } while (0) > > > > -#define smp_load_acquire(p) > > \ > > +#define __smp_load_acquire(p) > > \ > > ({ \ > > typeof(*p) ___p1 = READ_ONCE(*p); \ > > compiletime_assert_atomic_type(*p); \ > > - smp_lwsync(); \ > > + __smp_lwsync(); \ > > ___p1; \ > > }) > > > > -- > > MST > > > > -- > > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > > the body of a message to majordomo@xxxxxxxxxxxxxxx > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > Please read the FAQ at http://www.tux.org/lkml/ _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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