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 dma_rmb 46 #define dma_rmb() rmb() 47 #endif 48 49 #ifndef dma_wmb 50 #define dma_wmb() wmb() 51 #endif 52 53 #ifndef read_barrier_depends 54 #define read_barrier_depends() do { } while (0) 55 #endif 56 57 #ifdef CONFIG_SMP 58 59 #ifndef smp_mb 60 #define smp_mb() mb() 61 #endif 62 63 #ifndef smp_rmb 64 #define smp_rmb() rmb() 65 #endif 66 67 #ifndef smp_wmb 68 #define smp_wmb() wmb() 69 #endif 70 71 #ifndef smp_read_barrier_depends 72 #define smp_read_barrier_depends() read_barrier_depends() 73 #endif 74 75 #else 76 #ifndef smp_mb 77 #define smp_mb() barrier() 78 #endif 79 80 #ifndef smp_rmb 81 #define smp_rmb() barrier() 82 #endif 83 84 #ifndef smp_wmb 85 #define smp_wmb() barrier() 86 #endif 87 88 #ifndef smp_read_barrier_depends 89 #define smp_read_barrier_depends() do { } while (0) 90 #endif 91 92 #endif 93 94 #ifndef set_mb 95 #define set_mb(var, value) do { (var) = (value); mb(); } while (0) 96 #endif 97 98 #ifndef smp_mb__before_atomic 99 #define smp_mb__before_atomic() smp_mb() 100 #endif 101 102 #ifndef smp_mb__after_atomic 103 #define smp_mb__after_atomic() smp_mb() 104 #endif 105 106 #define smp_store_release(p, v) \ 107 do { \ 108 compiletime_assert_atomic_type(*p); \ 109 smp_mb(); \ 110 ACCESS_ONCE(*p) = (v); \ 111 } while (0) 112 113 #define smp_load_acquire(p) \ 114 ({ \ 115 typeof(*p) ___p1 = ACCESS_ONCE(*p); \ 116 compiletime_assert_atomic_type(*p); \ 117 smp_mb(); \ 118 ___p1; \ 119 }) 120 121 #endif /* !__ASSEMBLY__ */ 122 #endif /* __ASM_GENERIC_BARRIER_H */ 123