Re: [PATCH tip/core/rcu 2/3] srcu: Force full grace-period ordering
From: Ingo Molnar <mingo@kernel.org>
Date: 2017-01-15 07:11:35
Also in:
lkml
* Paul E. McKenney [off-list ref] wrote:
quoted hunk ↗ jump to hunk
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