[dpdk-dev] [PATCH 1/5] lib/stack: fix inconsistent weak / strong cas

[Steven Lariau]

Fix cmpexchange usage of weak / strong.
The generated code is the same on x86 and ARM (there is no weak
cmpexchange), but the old usage was inconsistent.
For push and pop update size, weak is used because cmpexchange is inside
a loop.
For pop update root, strong is used even though cmpexchange is inside a
loop, because there may be a lot of operations to do in a loop iteration
(locate the new head).

Signed-off-by: Steven Lariau <steven.lariau at arm.com>
Reviewed-by: Dharmik Thakkar <dharmik.thakkar at arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang at arm.com>
---
 lib/librte_stack/rte_stack_lf_c11.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/librte_stack/rte_stack_lf_c11.h b/lib/librte_stack/rte_stack_lf_c11.h
index 999359f08..1e0ea0bef 100644
--- a/lib/librte_stack/rte_stack_lf_c11.h
+++ b/lib/librte_stack/rte_stack_lf_c11.h
@@ -96,7 +96,7 @@ __rte_stack_lf_pop_elems(struct rte_stack_lf_list *list,
 		/* len is updated on failure */
 		if (__atomic_compare_exchange_n(&list->len,
 						&len, len - num,
-						0, __ATOMIC_ACQUIRE,
+						1, __ATOMIC_ACQUIRE,
 						__ATOMIC_ACQUIRE))
 			break;
 	}
@@ -149,7 +149,7 @@ __rte_stack_lf_pop_elems(struct rte_stack_lf_list *list,
 				(rte_int128_t *)&list->head,
 				(rte_int128_t *)&old_head,
 				(rte_int128_t *)&new_head,
-				1, __ATOMIC_RELEASE,
+				0, __ATOMIC_RELEASE,
 				__ATOMIC_RELAXED);
 	} while (success == 0);
 
-- 
2.17.1