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

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

diff --git a/arch/x86/include/asm/atomic.h b/arch/x86/include/asm/atomic.h
index 8f8217b9bdac67a7312959cad211232f60fbb8ce..952a826ac4e55bf605a05ddad11ae1fb9c315ae9 100644 (file)
--- a/arch/x86/include/asm/atomic.h
+++ b/arch/x86/include/asm/atomic.h
@@ -22,7 +22,7 @@
  */
 static inline int atomic_read(const atomic_t *v)
 {
-       return v->counter;
+       return (*(volatile int *)&(v)->counter);
 }
 
 /**
@@ -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