1 files changed, 25 insertions, 0 deletions

diff --git a/include/linux/atomic.h b/include/linux/atomic.h
index 70cfcb2d63c4..5b08a8540ecf 100644
--- a/include/linux/atomic.h
+++ b/include/linux/atomic.h
@@ -86,6 +86,31 @@ static inline int atomic_dec_unless_positive(atomic_t *p)
 }
 #endif
 
+/*
+ * 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.
+ */
+#ifndef atomic_dec_if_positive
+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
+
 #ifndef CONFIG_ARCH_HAS_ATOMIC_OR
 static inline void atomic_or(int i, atomic_t *v)
 {