Merge pull request open-mpi#468 from hjelmn/v2.x_fifo_lifo_fixes

V2.x fifo lifo fixes

Author: jsquyres

opal/class/opal_fifo.h

@@ -189,6 +189,8 @@ static inline opal_list_item_t *opal_fifo_push_atomic (opal_fifo_t *fifo,
 
     item->opal_list_next = &fifo->opal_fifo_ghost;
 
+    opal_atomic_wmb ();
+
     /* try to get the tail */
     tail_item = opal_atomic_swap_ptr (&fifo->opal_fifo_tail.data.item, item);
 

opal/class/opal_lifo.h

@@ -187,20 +187,22 @@ static inline opal_list_item_t *opal_lifo_pop_atomic (opal_lifo_t* lifo)
 {
     opal_list_item_t *item;
     while ((item = (opal_list_item_t *) lifo->opal_lifo_head.data.item) != &lifo->opal_lifo_ghost) {
-        opal_atomic_rmb();
-
         /* ensure it is safe to pop the head */
         if (opal_atomic_swap_32((volatile int32_t *) &item->item_free, 1)) {
             continue;
         }
 
+        opal_atomic_wmb ();
+
         /* try to swap out the head pointer */
         if (opal_atomic_cmpset_ptr (&lifo->opal_lifo_head.data.item, item,
                                    (void *) item->opal_list_next)) {
             break;
         }
+
         /* NTH: don't need another atomic here */
         item->item_free = 0;
+
         /* Do some kind of pause to release the bus */
     }