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/*
  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