[v5,03/39] stack: use C11 alignas

Message ID 1708715054-22386-4-git-send-email-roretzla@linux.microsoft.com (mailing list archive)
State Superseded, archived
Delegated to: Thomas Monjalon
Series use C11 alignas |


Context Check Description
ci/checkpatch success coding style OK

Commit Message

Tyler Retzlaff Feb. 23, 2024, 7:03 p.m. UTC
  The current location used for __rte_aligned(a) for alignment of types
and variables is not compatible with MSVC. There is only a single
location accepted by both toolchains.

For variables standard C11 offers alignas(a) supported by conformant
compilers i.e. both MSVC and GCC.

For types the standard offers no alignment facility that compatibly
interoperates with C and C++ but may be achieved by relocating the
placement of __rte_aligned(a) to the aforementioned location accepted
by all currently supported toolchains.

To allow alignment for both compilers do the following:

* 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>
Acked-by: Morten Brørup <mb@smartsharesystems.com>
 lib/stack/rte_stack.h | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)


diff --git a/lib/stack/rte_stack.h b/lib/stack/rte_stack.h
index a379300..8ff0659 100644
--- a/lib/stack/rte_stack.h
+++ b/lib/stack/rte_stack.h
@@ -15,6 +15,8 @@ 
 #ifndef _RTE_STACK_H_
 #define _RTE_STACK_H_
+#include <stdalign.h>
 #ifdef __cplusplus
 extern "C" {
@@ -42,7 +44,7 @@  struct rte_stack_lf_head {
 struct rte_stack_lf_list {
 	/** List head */
-	struct rte_stack_lf_head head __rte_aligned(16);
+	alignas(16) struct rte_stack_lf_head head;
 	/** List len */
 	RTE_ATOMIC(uint64_t) len;
@@ -52,11 +54,11 @@  struct rte_stack_lf_list {
 struct rte_stack_lf {
 	/** LIFO list of elements */
-	struct rte_stack_lf_list used __rte_cache_aligned;
+	alignas(RTE_CACHE_LINE_SIZE) struct rte_stack_lf_list used;
 	/** LIFO list of free elements */
-	struct rte_stack_lf_list free __rte_cache_aligned;
+	alignas(RTE_CACHE_LINE_SIZE) struct rte_stack_lf_list free;
 	/** LIFO elements */
-	struct rte_stack_lf_elem elems[] __rte_cache_aligned;
+	alignas(RTE_CACHE_LINE_SIZE) struct rte_stack_lf_elem elems[];
 /* Structure containing the LIFO, its current length, and a lock for mutual
@@ -71,9 +73,9 @@  struct rte_stack_std {
 /* The RTE stack structure contains the LIFO structure itself, plus metadata
  * such as its name and memzone pointer.
-struct rte_stack {
+struct __rte_cache_aligned rte_stack {
 	/** Name of the stack. */
-	char name[RTE_STACK_NAMESIZE] __rte_cache_aligned;
 	/** Memzone containing the rte_stack structure. */
 	const struct rte_memzone *memzone;
 	uint32_t capacity; /**< Usable size of the stack. */
@@ -82,7 +84,7 @@  struct rte_stack {
 		struct rte_stack_lf stack_lf; /**< Lock-free LIFO structure. */
 		struct rte_stack_std stack_std;	/**< LIFO structure. */
-} __rte_cache_aligned;
  * The stack uses lock-free push and pop functions. This flag is only