Hi Andrea, I know this is in mainline now, but I think the way you've got the barriers here: On Fri, Feb 23, 2018 at 12:27:54AM -0800, tip-bot for Andrea Parri wrote: > diff --git a/arch/alpha/include/asm/cmpxchg.h b/arch/alpha/include/asm/cmpxchg.h > index 46ebf14aed4e..8a2b331e43fe 100644 > --- a/arch/alpha/include/asm/cmpxchg.h > +++ b/arch/alpha/include/asm/cmpxchg.h > @@ -6,7 +6,6 @@ > * Atomic exchange routines. > */ > > -#define __ASM__MB > #define ____xchg(type, args...) __xchg ## type ## _local(args) > #define ____cmpxchg(type, args...) __cmpxchg ## type ## _local(args) > #include <asm/xchg.h> > @@ -33,10 +32,6 @@ > cmpxchg_local((ptr), (o), (n)); \ > }) > > -#ifdef CONFIG_SMP > -#undef __ASM__MB > -#define __ASM__MB "\tmb\n" > -#endif > #undef ____xchg > #undef ____cmpxchg > #define ____xchg(type, args...) __xchg ##type(args) > @@ -64,7 +59,6 @@ > cmpxchg((ptr), (o), (n)); \ > }) > > -#undef __ASM__MB > #undef ____cmpxchg > > #endif /* _ALPHA_CMPXCHG_H */ > diff --git a/arch/alpha/include/asm/xchg.h b/arch/alpha/include/asm/xchg.h > index e2660866ce97..e1facf6fc244 100644 > --- a/arch/alpha/include/asm/xchg.h > +++ b/arch/alpha/include/asm/xchg.h > @@ -28,12 +28,12 @@ ____xchg(_u8, volatile char *m, unsigned long val) > " or %1,%2,%2\n" > " stq_c %2,0(%3)\n" > " beq %2,2f\n" > - __ASM__MB > ".subsection 2\n" > "2: br 1b\n" > ".previous" > : "=&r" (ret), "=&r" (val), "=&r" (tmp), "=&r" (addr64) > : "r" ((long)m), "1" (val) : "memory"); > + smp_mb(); > > return ret; ends up adding unnecessary barriers to the _local variants, which the previous code took care to avoid. That's why I suggesting adding the smp_mb() into the cmpxchg macro rather than the ____cmpxchg variants. I think it's worth spinning another patch to fix this properly. Will -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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