1 files changed, 23 insertions, 0 deletions

diff --git a/arch/x86/include/asm/atomic.h b/arch/x86/include/asm/atomic.h
index 8f8217b9bdac..706c69492c14 100644
--- a/arch/x86/include/asm/atomic.h
+++ b/arch/x86/include/asm/atomic.h
@@ -246,6 +246,29 @@ static inline int atomic_add_unless(atomic_t *v, int a, int u)
 
 #define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 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;
+}
+
 /**
  * atomic_inc_short - increment of a short integer
  * @v: pointer to type int