* Paul E. McKenney <paul...@linux.vnet.ibm.com> wrote: > diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h > index 357b32aaea48..5fdfe874229e 100644 > --- a/include/linux/rcupdate.h > +++ b/include/linux/rcupdate.h > @@ -1175,11 +1175,11 @@ do { \ > * if the UNLOCK and LOCK are executed by the same CPU or if the > * UNLOCK and LOCK operate on the same lock variable. > */ > -#ifdef CONFIG_PPC > +#ifdef CONFIG_ARCH_WEAK_RELACQ > #define smp_mb__after_unlock_lock() smp_mb() /* Full ordering for lock. */ > -#else /* #ifdef CONFIG_PPC */ > +#else /* #ifdef CONFIG_ARCH_WEAK_RELACQ */ > #define smp_mb__after_unlock_lock() do { } while (0) > -#endif /* #else #ifdef CONFIG_PPC */ > +#endif /* #else #ifdef CONFIG_ARCH_WEAK_RELACQ */ > >
So at the risk of sounding totally pedantic, why not structure it like the existing smp_mb__before/after*() primitives in barrier.h? That allows asm-generic/barrier.h to pick up the definition - for example in the case of smp_acquire__after_ctrl_dep() we do: #ifndef smp_acquire__after_ctrl_dep #define smp_acquire__after_ctrl_dep() smp_rmb() #endif Which allows Tile to relax it: arch/tile/include/asm/barrier.h:#define smp_acquire__after_ctrl_dep() barrier() I.e. I'd move the API definition out of rcupdate.h and into barrier.h - even though tree-RCU is the only user of this barrier type. Thanks, Ingo