LXR linux/include/linux/atomic.h

   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-arch-fallback.h>
  81#include <asm-generic/atomic-instrumented.h>
  82
  83#include <asm-generic/atomic-long.h>
  84
  85#endif /* _LINUX_ATOMIC_H */
  86