[PATCH v3 20/39] rcu: use C11 alignas

[Tyler Retzlaff <roretzla@linux.microsoft.com>]

* Move __rte_aligned from the end of {struct,union} definitions to
  be between {struct,union} and tag.

  The placement between {struct,union} and the tag allows the desired
  alignment to be imparted on the type regardless of the toolchain being
  used for all of GCC, LLVM, MSVC compilers building both C and C++.

* Replace use of __rte_aligned(a) on variables/fields with alignas(a).

Signed-off-by: Tyler Retzlaff <roretzla@linux.microsoft.com>
---
 lib/rcu/rte_rcu_qsbr.h | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/lib/rcu/rte_rcu_qsbr.h b/lib/rcu/rte_rcu_qsbr.h
index 23c9f89..f6e6ab3 100644
--- a/lib/rcu/rte_rcu_qsbr.h
+++ b/lib/rcu/rte_rcu_qsbr.h
@@ -21,6 +21,8 @@
  * entered quiescent state.
  */
 
+#include <stdalign.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -69,7 +71,7 @@
 #define RTE_QSBR_THRID_INVALID 0xffffffff
 
 /* Worker thread counter */
-struct rte_rcu_qsbr_cnt {
+struct __rte_cache_aligned rte_rcu_qsbr_cnt {
 	RTE_ATOMIC(uint64_t) cnt;
 	/**< Quiescent state counter. Value 0 indicates the thread is offline
 	 *   64b counter is used to avoid adding more code to address
@@ -78,7 +80,7 @@ struct rte_rcu_qsbr_cnt {
 	 */
 	RTE_ATOMIC(uint32_t) lock_cnt;
 	/**< Lock counter. Used when RTE_LIBRTE_RCU_DEBUG is enabled */
-} __rte_cache_aligned;
+};
 
 #define __RTE_QSBR_CNT_THR_OFFLINE 0
 #define __RTE_QSBR_CNT_INIT 1
@@ -91,28 +93,28 @@ struct rte_rcu_qsbr_cnt {
  * 1) Quiescent state counter array
  * 2) Register thread ID array
  */
-struct rte_rcu_qsbr {
-	RTE_ATOMIC(uint64_t) token __rte_cache_aligned;
+struct __rte_cache_aligned rte_rcu_qsbr {
+	alignas(RTE_CACHE_LINE_SIZE) RTE_ATOMIC(uint64_t) token;
 	/**< Counter to allow for multiple concurrent quiescent state queries */
 	RTE_ATOMIC(uint64_t) acked_token;
 	/**< Least token acked by all the threads in the last call to
 	 *   rte_rcu_qsbr_check API.
 	 */
 
-	uint32_t num_elems __rte_cache_aligned;
+	alignas(RTE_CACHE_LINE_SIZE) uint32_t num_elems;
 	/**< Number of elements in the thread ID array */
 	RTE_ATOMIC(uint32_t) num_threads;
 	/**< Number of threads currently using this QS variable */
 	uint32_t max_threads;
 	/**< Maximum number of threads using this QS variable */
 
-	struct rte_rcu_qsbr_cnt qsbr_cnt[0] __rte_cache_aligned;
+	alignas(RTE_CACHE_LINE_SIZE) struct rte_rcu_qsbr_cnt qsbr_cnt[0];
 	/**< Quiescent state counter array of 'max_threads' elements */
 
 	/**< Registered thread IDs are stored in a bitmap array,
 	 *   after the quiescent state counter array.
 	 */
-} __rte_cache_aligned;
+};
 
 /**
  * Call back function called to free the resources.
-- 
1.8.3.1