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 #ifdef ARCH_ATOMIC 81 #include <linux/atomic-arch-fallback.h> 82 #include <asm-generic/atomic-instrumented.h> 83 #else 84 #include <linux/atomic-fallback.h> 85 #endif 86 87 #include <asm-generic/atomic-long.h> 88 89 #endif /* _LINUX_ATOMIC_H */ 90