1/* SPDX-License-Identifier: GPL-2.0 */ 2/* Atomic operations usable in machine independent code */ 3#ifndef _LINUX_ATOMIC_H 4#define _LINUX_ATOMIC_H 5#include <linux/types.h> 6 7#include <asm/atomic.h> 8#include <asm/barrier.h> 9 10/* 11 * Relaxed variants of xchg, cmpxchg and some atomic operations. 12 * 13 * We support four variants: 14 * 15 * - Fully ordered: The default implementation, no suffix required. 16 * - Acquire: Provides ACQUIRE semantics, _acquire suffix. 17 * - Release: Provides RELEASE semantics, _release suffix. 18 * - Relaxed: No ordering guarantees, _relaxed suffix. 19 * 20 * For compound atomics performing both a load and a store, ACQUIRE 21 * semantics apply only to the load and RELEASE semantics only to the 22 * store portion of the operation. Note that a failed cmpxchg_acquire 23 * does -not- imply any memory ordering constraints. 24 * 25 * See Documentation/memory-barriers.txt for ACQUIRE/RELEASE definitions. 26 */ 27 28/* 29 * The idea here is to build acquire/release variants by adding explicit 30 * barriers on top of the relaxed variant. In the case where the relaxed 31 * variant is already fully ordered, no additional barriers are needed. 32 * 33 * If an architecture overrides __atomic_acquire_fence() it will probably 34 * want to define smp_mb__after_spinlock(). 35 */ 36#ifndef __atomic_acquire_fence 37#define __atomic_acquire_fence smp_mb__after_atomic 38#endif 39 40#ifndef __atomic_release_fence 41#define __atomic_release_fence smp_mb__before_atomic 42#endif 43 44#ifndef __atomic_pre_full_fence 45#define __atomic_pre_full_fence smp_mb__before_atomic 46#endif 47 48#ifndef __atomic_post_full_fence 49#define __atomic_post_full_fence smp_mb__after_atomic 50#endif 51 52#define __atomic_op_acquire(op, args...) \ 53({ \ 54 typeof(op##_relaxed(args)) __ret = op##_relaxed(args); \ 55 __atomic_acquire_fence(); \ 56 __ret; \ 57}) 58 59#define __atomic_op_release(op, args...) \ 60({ \ 61 __atomic_release_fence(); \ 62 op##_relaxed(args); \ 63}) 64 65#define __atomic_op_fence(op, args...) \ 66({ \ 67 typeof(op##_relaxed(args)) __ret; \ 68 __atomic_pre_full_fence(); \ 69 __ret = op##_relaxed(args); \ 70 __atomic_post_full_fence(); \ 71 __ret; \ 72}) 73 74#include <linux/atomic-fallback.h> 75 76#include <asm-generic/atomic-long.h> 77 78#endif /* _LINUX_ATOMIC_H */ 79