1/* 2 * Generic barrier definitions, originally based on MN10300 definitions. 3 * 4 * It should be possible to use these on really simple architectures, 5 * but it serves more as a starting point for new ports. 6 * 7 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved. 8 * Written by David Howells (dhowells@redhat.com) 9 * 10 * This program is free software; you can redistribute it and/or 11 * modify it under the terms of the GNU General Public Licence 12 * as published by the Free Software Foundation; either version 13 * 2 of the Licence, or (at your option) any later version. 14 */ 15#ifndef __ASM_GENERIC_BARRIER_H 16#define __ASM_GENERIC_BARRIER_H 17 18#ifndef __ASSEMBLY__ 19 20#include <linux/compiler.h> 21 22#ifndef nop 23#define nop() asm volatile ("nop") 24#endif 25 26/* 27 * Force strict CPU ordering. And yes, this is required on UP too when we're 28 * talking to devices. 29 * 30 * Fall back to compiler barriers if nothing better is provided. 31 */ 32 33#ifndef mb 34#define mb() barrier() 35#endif 36 37#ifndef rmb 38#define rmb() mb() 39#endif 40 41#ifndef wmb 42#define wmb() mb() 43#endif 44 45#ifndef read_barrier_depends 46#define read_barrier_depends() do { } while (0) 47#endif 48 49#ifdef CONFIG_SMP 50#define smp_mb() mb() 51#define smp_rmb() rmb() 52#define smp_wmb() wmb() 53#define smp_read_barrier_depends() read_barrier_depends() 54#else 55#define smp_mb() barrier() 56#define smp_rmb() barrier() 57#define smp_wmb() barrier() 58#define smp_read_barrier_depends() do { } while (0) 59#endif 60 61#ifndef set_mb 62#define set_mb(var, value) do { (var) = (value); mb(); } while (0) 63#endif 64 65#define smp_store_release(p, v) \ 66do { \ 67 compiletime_assert_atomic_type(*p); \ 68 smp_mb(); \ 69 ACCESS_ONCE(*p) = (v); \ 70} while (0) 71 72#define smp_load_acquire(p) \ 73({ \ 74 typeof(*p) ___p1 = ACCESS_ONCE(*p); \ 75 compiletime_assert_atomic_type(*p); \ 76 smp_mb(); \ 77 ___p1; \ 78}) 79 80#endif /* !__ASSEMBLY__ */ 81#endif /* __ASM_GENERIC_BARRIER_H */ 82