Return futex value from futex atomic operations

Update the futex atomic operations to return the value of the futex
after the operation (with the exception of cmpxchg which returns the old
value). Update futex_cmpxchg() to return u_int32_t instead of futex_t to
avoid compiler warnings regarding the volatile keyword with gcc 4.2 (but
not 4.1 or 4.4 oddly enough).

Signed-off-by: Darren Hart <dvhltc@us.ibm.com>

1 files changed, 15 insertions, 6 deletions

diff --git a/include/futextest.h b/include/futextest.h
index 7fce3db..048500a 100644
--- a/include/futextest.h
+++ b/include/futextest.h
@@ -228,8 +228,10 @@ futex_cmp_requeue_pi(futex_t *uaddr, futex_t val, futex_t *uaddr2, int nr_wake,
  *
  * Implement cmpxchg using gcc atomic builtins.
  * http://gcc.gnu.org/onlinedocs/gcc-4.1.0/gcc/Atomic-Builtins.html
+ *
+ * Return the old futex value.
  */
-static inline futex_t
+static inline u_int32_t
 futex_cmpxchg(futex_t *uaddr, u_int32_t oldval, u_int32_t newval)
 {
 	return __sync_val_compare_and_swap(uaddr, oldval, newval);
@@ -238,32 +240,39 @@ futex_cmpxchg(futex_t *uaddr, u_int32_t oldval, u_int32_t newval)
 /**
  * futex_dec() - atomic decrement of the futex value
  * @uaddr:	The address of the futex to be modified
+ *
+ * Return the new futex value.
  */
-static inline void
+static inline u_int32_t
 futex_dec(futex_t *uaddr)
 {
-	__sync_sub_and_fetch(uaddr, 1);
+	return __sync_sub_and_fetch(uaddr, 1);
 }
 
 /**
  * futex_inc() - atomic increment of the futex value
  * @uaddr:	the address of the futex to be modified
+ *
+ * Return the new futex value.
  */
-static inline void
+static inline u_int32_t
 futex_inc(futex_t *uaddr)
 {
-	__sync_add_and_fetch(uaddr, 1);
+	return __sync_add_and_fetch(uaddr, 1);
 }
 
 /**
  * futex_set() - atomic decrement of the futex value
  * @uaddr:	the address of the futex to be modified
  * @newval:	New value for the atomic_t
+ *
+ * Return the new futex value.
  */
-static inline void
+static inline u_int32_t
 futex_set(futex_t *uaddr, u_int32_t newval)
 {
 	*uaddr = newval;
+	return newval;
 }
 
 #endif