lib: annotate versioned functions

[dpdk.git] / lib / librte_ring / rte_ring_c11_mem.h

diff --git a/lib/librte_ring/rte_ring_c11_mem.h b/lib/librte_ring/rte_ring_c11_mem.h
index 52da95a..0fb73a3 100644 (file)
--- a/lib/librte_ring/rte_ring_c11_mem.h
+++ b/lib/librte_ring/rte_ring_c11_mem.h
@@ -61,12 +61,13 @@ __rte_ring_move_prod_head(struct rte_ring *r, unsigned int is_sp,
        unsigned int max = n;
        int success;
 
+       *old_head = __atomic_load_n(&r->prod.head, __ATOMIC_RELAXED);
        do {
                /* Reset n to the initial burst count */
                n = max;
 
-               *old_head = __atomic_load_n(&r->prod.head,
-                                       __ATOMIC_ACQUIRE);
+               /* Ensure the head is read before tail */
+               __atomic_thread_fence(__ATOMIC_ACQUIRE);
 
                /* load-acquire synchronize with store-release of ht->tail
                 * in update_tail.
@@ -93,9 +94,10 @@ __rte_ring_move_prod_head(struct rte_ring *r, unsigned int is_sp,
                if (is_sp)
                        r->prod.head = *new_head, success = 1;
                else
+                       /* on failure, *old_head is updated */
                        success = __atomic_compare_exchange_n(&r->prod.head,
                                        old_head, *new_head,
-                                       0, __ATOMIC_ACQUIRE,
+                                       0, __ATOMIC_RELAXED,
                                        __ATOMIC_RELAXED);
        } while (unlikely(success == 0));
        return n;
@@ -135,12 +137,13 @@ __rte_ring_move_cons_head(struct rte_ring *r, int is_sc,
        int success;
 
        /* move cons.head atomically */
+       *old_head = __atomic_load_n(&r->cons.head, __ATOMIC_RELAXED);
        do {
                /* Restore n as it may change every loop */
                n = max;
 
-               *old_head = __atomic_load_n(&r->cons.head,
-                                       __ATOMIC_ACQUIRE);
+               /* Ensure the head is read before tail */
+               __atomic_thread_fence(__ATOMIC_ACQUIRE);
 
                /* this load-acquire synchronize with store-release of ht->tail
                 * in update_tail.
@@ -166,9 +169,10 @@ __rte_ring_move_cons_head(struct rte_ring *r, int is_sc,
                if (is_sc)
                        r->cons.head = *new_head, success = 1;
                else
+                       /* on failure, *old_head will be updated */
                        success = __atomic_compare_exchange_n(&r->cons.head,
                                                        old_head, *new_head,
-                                                       0, __ATOMIC_ACQUIRE,
+                                                       0, __ATOMIC_RELAXED,
                                                        __ATOMIC_RELAXED);
        } while (unlikely(success == 0));
        return n;