1 files changed, 79 insertions, 0 deletions
diff --git a/backport-include/linux/atomic.h b/backport-include/linux/atomic.h
new file mode 100644
index 0000000..7baa2f5
--- /dev/null
+++ b/backport-include/linux/atomic.h
@@ -0,0 +1,79 @@
+#ifndef __BP_ATOMIC_H
+#define __BP_ATOMIC_H
+#include_next <linux/atomic.h>
+
+/* atomic_cmpxchg_relaxed */
+#ifndef atomic_cmpxchg_relaxed
+#define  atomic_cmpxchg_relaxed		atomic_cmpxchg
+#define  atomic_cmpxchg_acquire		atomic_cmpxchg
+#define  atomic_cmpxchg_release		atomic_cmpxchg
+
+#else /* atomic_cmpxchg_relaxed */
+
+#ifndef atomic_cmpxchg_acquire
+#define  atomic_cmpxchg_acquire(...)					\
+	__atomic_op_acquire(atomic_cmpxchg, __VA_ARGS__)
+#endif
+
+#ifndef atomic_cmpxchg_release
+#define  atomic_cmpxchg_release(...)					\
+	__atomic_op_release(atomic_cmpxchg, __VA_ARGS__)
+#endif
+
+#ifndef atomic_cmpxchg
+#define  atomic_cmpxchg(...)						\
+	__atomic_op_fence(atomic_cmpxchg, __VA_ARGS__)
+#endif
+#endif /* atomic_cmpxchg_relaxed */
+
+/* these were introduced together, so just a single check is enough */
+#ifndef atomic_try_cmpxchg_acquire
+#ifndef atomic_try_cmpxchg
+#define __atomic_try_cmpxchg(type, _p, _po, _n)				\
+({									\
+	typeof(_po) __po = (_po);					\
+	typeof(*(_po)) __r, __o = *__po;				\
+	__r = atomic_cmpxchg##type((_p), __o, (_n));			\
+	if (unlikely(__r != __o))					\
+		*__po = __r;						\
+	likely(__r == __o);						\
+})
+
+#define atomic_try_cmpxchg(_p, _po, _n)		__atomic_try_cmpxchg(, _p, _po, _n)
+#define atomic_try_cmpxchg_relaxed(_p, _po, _n)	__atomic_try_cmpxchg(_relaxed, _p, _po, _n)
+#define atomic_try_cmpxchg_acquire(_p, _po, _n)	__atomic_try_cmpxchg(_acquire, _p, _po, _n)
+#define atomic_try_cmpxchg_release(_p, _po, _n)	__atomic_try_cmpxchg(_release, _p, _po, _n)
+#else /* atomic_try_cmpxchg */
+#define atomic_try_cmpxchg_relaxed	atomic_try_cmpxchg
+#define atomic_try_cmpxchg_acquire	atomic_try_cmpxchg
+#define atomic_try_cmpxchg_release	atomic_try_cmpxchg
+#endif /* atomic_try_cmpxchg */
+
+#endif /* atomic_try_cmpxchg_acquire */
+
+#if LINUX_VERSION_IS_LESS(3,7,0)
+/*
+ * atomic_dec_if_positive - decrement by 1 if old value positive
+ * @v: pointer of type atomic_t
+ *
+ * The function returns the old value of *v minus 1, even if
+ * the atomic variable, v, was not decremented.
+ */
+static inline int atomic_dec_if_positive(atomic_t *v)
+{
+	int c, old, dec;
+	c = atomic_read(v);
+	for (;;) {
+		dec = c - 1;
+		if (unlikely(dec < 0))
+			break;
+		old = atomic_cmpxchg((v), c, dec);
+		if (likely(old == c))
+			break;
+		c = old;
+	}
+	return dec;
+}
+#endif
+
+#endif /* __BP_ATOMIC_H */