1 files changed, 84 insertions, 0 deletions
diff --git a/include/linux/atomic.h b/include/linux/atomic.h
new file mode 100644
index 000000000..8dd57c3a9
--- /dev/null
+++ b/include/linux/atomic.h
@@ -0,0 +1,84 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Atomic operations usable in machine independent code */
+#ifndef _LINUX_ATOMIC_H
+#define _LINUX_ATOMIC_H
+#include <linux/types.h>
+
+#include <asm/atomic.h>
+#include <asm/barrier.h>
+
+/*
+ * Relaxed variants of xchg, cmpxchg and some atomic operations.
+ *
+ * We support four variants:
+ *
+ * - Fully ordered: The default implementation, no suffix required.
+ * - Acquire: Provides ACQUIRE semantics, _acquire suffix.
+ * - Release: Provides RELEASE semantics, _release suffix.
+ * - Relaxed: No ordering guarantees, _relaxed suffix.
+ *
+ * For compound atomics performing both a load and a store, ACQUIRE
+ * semantics apply only to the load and RELEASE semantics only to the
+ * store portion of the operation. Note that a failed cmpxchg_acquire
+ * does -not- imply any memory ordering constraints.
+ *
+ * See Documentation/memory-barriers.txt for ACQUIRE/RELEASE definitions.
+ */
+
+#define atomic_cond_read_acquire(v, c) smp_cond_load_acquire(&(v)->counter, (c))
+#define atomic_cond_read_relaxed(v, c) smp_cond_load_relaxed(&(v)->counter, (c))
+
+#define atomic64_cond_read_acquire(v, c) smp_cond_load_acquire(&(v)->counter, (c))
+#define atomic64_cond_read_relaxed(v, c) smp_cond_load_relaxed(&(v)->counter, (c))
+
+/*
+ * The idea here is to build acquire/release variants by adding explicit
+ * barriers on top of the relaxed variant. In the case where the relaxed
+ * variant is already fully ordered, no additional barriers are needed.
+ *
+ * If an architecture overrides __atomic_acquire_fence() it will probably
+ * want to define smp_mb__after_spinlock().
+ */
+#ifndef __atomic_acquire_fence
+#define __atomic_acquire_fence		smp_mb__after_atomic
+#endif
+
+#ifndef __atomic_release_fence
+#define __atomic_release_fence		smp_mb__before_atomic
+#endif
+
+#ifndef __atomic_pre_full_fence
+#define __atomic_pre_full_fence		smp_mb__before_atomic
+#endif
+
+#ifndef __atomic_post_full_fence
+#define __atomic_post_full_fence	smp_mb__after_atomic
+#endif
+
+#define __atomic_op_acquire(op, args...)				\
+({									\
+	typeof(op##_relaxed(args)) __ret  = op##_relaxed(args);		\
+	__atomic_acquire_fence();					\
+	__ret;								\
+})
+
+#define __atomic_op_release(op, args...)				\
+({									\
+	__atomic_release_fence();					\
+	op##_relaxed(args);						\
+})
+
+#define __atomic_op_fence(op, args...)					\
+({									\
+	typeof(op##_relaxed(args)) __ret;				\
+	__atomic_pre_full_fence();					\
+	__ret = op##_relaxed(args);					\
+	__atomic_post_full_fence();					\
+	__ret;								\
+})
+
+#include <linux/atomic/atomic-arch-fallback.h>
+#include <linux/atomic/atomic-long.h>
+#include <linux/atomic/atomic-instrumented.h>
+
+#endif /* _LINUX_ATOMIC_H */