[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 10:51:17AM +0200, Michael S. Tsirkin wrote: > 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. > Yes, I realized my mistake after reread the series. But smp_lwsync() is not defined in asm-generic/barriers.h, right? > > > 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. > Yes, you're right, sorry for my mistake... > > > 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 ___ :) > What I mean here was smp_lwsync() was originally internal to PPC, but never mind ;-) > 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 You mean bringing smp_lwsync() back? because I haven't seen you defining in asm-generic/barriers.h in previous patches and you just delete it in this patch. > but why do this? Still, if you prefer it this way, > please let me know. > I think deleting smp_lwsync() is fine, though I need to change atomic variants patches on PPC because of it ;-/ Regards, Boqun > > > 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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