rte_smp_rmb() is deprecated. The acquire fence generates the same code everywhere the gcc implementation is used: a compiler barrier on x86 and dmb ishld on ThunderX.
The gcc implementation itself is kept: unlike the lock-free stack, the in-tree comment records a 10% x86 performance drop with the C11 version, which needs re-measuring with current compilers before RTE_USE_C11_MEM_MODEL can be removed. Signed-off-by: Stephen Hemminger <[email protected]> --- lib/ring/rte_ring_gcc_pvt.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/lib/ring/rte_ring_gcc_pvt.h b/lib/ring/rte_ring_gcc_pvt.h index 340ece28c7..9c2c58824d 100644 --- a/lib/ring/rte_ring_gcc_pvt.h +++ b/lib/ring/rte_ring_gcc_pvt.h @@ -55,10 +55,10 @@ __rte_ring_headtail_move_head_st(struct rte_ring_headtail *d, *old_head = d->head; - /* add rmb barrier to avoid load/load reorder in weak - * memory model. It is noop on x86 + /* Acquire fence to avoid load/load reorder in weak + * memory model. It is noop on x86. */ - rte_smp_rmb(); + rte_atomic_thread_fence(rte_memory_order_acquire); /* * The subtraction is done between two unsigned 32bits value -- 2.53.0
