New upstream version 18.11-rc3

[deb_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 08825ea..0fb73a3 100644 (file)
--- a/lib/librte_ring/rte_ring_c11_mem.h
+++ b/lib/librte_ring/rte_ring_c11_mem.h
@@ -51,24 +51,31 @@ update_tail(struct rte_ring_headtail *ht, uint32_t old_val, uint32_t new_val,
  *   If behavior == RTE_RING_QUEUE_FIXED, this will be 0 or n only.
  */
 static __rte_always_inline unsigned int
-__rte_ring_move_prod_head(struct rte_ring *r, int is_sp,
+__rte_ring_move_prod_head(struct rte_ring *r, unsigned int is_sp,
                unsigned int n, enum rte_ring_queue_behavior behavior,
                uint32_t *old_head, uint32_t *new_head,
                uint32_t *free_entries)
 {
        const uint32_t capacity = r->capacity;
+       uint32_t cons_tail;
        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,
+               /* Ensure the head is read before tail */
+               __atomic_thread_fence(__ATOMIC_ACQUIRE);
+
+               /* load-acquire synchronize with store-release of ht->tail
+                * in update_tail.
+                */
+               cons_tail = __atomic_load_n(&r->cons.tail,
                                        __ATOMIC_ACQUIRE);
-               const uint32_t cons_tail = r->cons.tail;
-               /*
-                *  The subtraction is done between two unsigned 32bits value
+
+               /* The subtraction is done between two unsigned 32bits value
                 * (the result is always modulo 32 bits even if we have
                 * *old_head > cons_tail). So 'free_entries' is always between 0
                 * and capacity (which is < size).
@@ -87,9 +94,10 @@ __rte_ring_move_prod_head(struct rte_ring *r, 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;
@@ -125,15 +133,24 @@ __rte_ring_move_cons_head(struct rte_ring *r, int is_sc,
                uint32_t *entries)
 {
        unsigned int max = n;
+       uint32_t prod_tail;
        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,
+
+               /* 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.
+                */
+               prod_tail = __atomic_load_n(&r->prod.tail,
                                        __ATOMIC_ACQUIRE);
-               const uint32_t prod_tail = r->prod.tail;
+
                /* The subtraction is done between two unsigned 32bits value
                 * (the result is always modulo 32 bits even if we have
                 * cons_head > prod_tail). So 'entries' is always between 0
@@ -152,9 +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;