[v5,32/39] bpf: use C11 alignas

Message ID 1708715054-22386-33-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State Superseded, archived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, 7:04 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/bpf/bpf_pkt.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)


diff --git a/lib/bpf/bpf_pkt.c b/lib/bpf/bpf_pkt.c
index 793a75d..aaca935 100644
--- a/lib/bpf/bpf_pkt.c
+++ b/lib/bpf/bpf_pkt.c
@@ -23,7 +23,7 @@ 
  * information about installed BPF rx/tx callback
-struct bpf_eth_cbi {
+struct __rte_cache_aligned bpf_eth_cbi {
 	/* used by both data & control path */
 	RTE_ATOMIC(uint32_t) use;    /*usage counter */
 	const struct rte_eth_rxtx_callback *cb;  /* callback handle */
@@ -33,7 +33,7 @@  struct bpf_eth_cbi {
 	LIST_ENTRY(bpf_eth_cbi) link;
 	uint16_t port;
 	uint16_t queue;
-} __rte_cache_aligned;
  * Odd number means that callback is used by datapath.