atomic.h (2644B)
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#define atomic_cond_read_acquire(v, c) smp_cond_load_acquire(&(v)->counter, (c)) 29#define atomic_cond_read_relaxed(v, c) smp_cond_load_relaxed(&(v)->counter, (c)) 30 31#define atomic64_cond_read_acquire(v, c) smp_cond_load_acquire(&(v)->counter, (c)) 32#define atomic64_cond_read_relaxed(v, c) smp_cond_load_relaxed(&(v)->counter, (c)) 33 34/* 35 * The idea here is to build acquire/release variants by adding explicit 36 * barriers on top of the relaxed variant. In the case where the relaxed 37 * variant is already fully ordered, no additional barriers are needed. 38 * 39 * If an architecture overrides __atomic_acquire_fence() it will probably 40 * want to define smp_mb__after_spinlock(). 41 */ 42#ifndef __atomic_acquire_fence 43#define __atomic_acquire_fence smp_mb__after_atomic 44#endif 45 46#ifndef __atomic_release_fence 47#define __atomic_release_fence smp_mb__before_atomic 48#endif 49 50#ifndef __atomic_pre_full_fence 51#define __atomic_pre_full_fence smp_mb__before_atomic 52#endif 53 54#ifndef __atomic_post_full_fence 55#define __atomic_post_full_fence smp_mb__after_atomic 56#endif 57 58#define __atomic_op_acquire(op, args...) \ 59({ \ 60 typeof(op##_relaxed(args)) __ret = op##_relaxed(args); \ 61 __atomic_acquire_fence(); \ 62 __ret; \ 63}) 64 65#define __atomic_op_release(op, args...) \ 66({ \ 67 __atomic_release_fence(); \ 68 op##_relaxed(args); \ 69}) 70 71#define __atomic_op_fence(op, args...) \ 72({ \ 73 typeof(op##_relaxed(args)) __ret; \ 74 __atomic_pre_full_fence(); \ 75 __ret = op##_relaxed(args); \ 76 __atomic_post_full_fence(); \ 77 __ret; \ 78}) 79 80#include <linux/atomic/atomic-arch-fallback.h> 81#include <linux/atomic/atomic-long.h> 82#include <linux/atomic/atomic-instrumented.h> 83 84#endif /* _LINUX_ATOMIC_H */