Merge branch 'x86-atomic-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...

[sfrench/cifs-2.6.git] / arch / x86 / include / asm / atomic64_64.h

diff --git a/arch/x86/include/asm/atomic64_64.h b/arch/x86/include/asm/atomic64_64.h
index 51c5b405692952bf9ed7e342ee724bfc202f4017..49fd1ea229511632ac849b17f55543e6782da9ae 100644 (file)
--- a/arch/x86/include/asm/atomic64_64.h
+++ b/arch/x86/include/asm/atomic64_64.h
@@ -18,7 +18,7 @@
  */
 static inline long atomic64_read(const atomic64_t *v)
 {
-       return v->counter;
+       return (*(volatile long *)&(v)->counter);
 }
 
 /**
@@ -221,4 +221,27 @@ static inline int atomic64_add_unless(atomic64_t *v, long a, long u)
 
 #define atomic64_inc_not_zero(v) atomic64_add_unless((v), 1, 0)
 
+/*
+ * atomic64_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 long atomic64_dec_if_positive(atomic64_t *v)
+{
+       long c, old, dec;
+       c = atomic64_read(v);
+       for (;;) {
+               dec = c - 1;
+               if (unlikely(dec < 0))
+                       break;
+               old = atomic64_cmpxchg((v), c, dec);
+               if (likely(old == c))
+                       break;
+               c = old;
+       }
+       return dec;
+}
+
 #endif /* _ASM_X86_ATOMIC64_64_H */