Re: [PATCH 1/3] lib/eal: add rte_atomic128_cmp_exchange compatible with MSVC

[David Marchand <david.marchand@redhat.com>]

On Tue, Dec 10, 2024 at 5:33 PM Andre Muezerie
<andremue@linux.microsoft.com> wrote:
>
> MSVC does not support inline assembly, which is used by the
> implementation of rte_atomic128_cmp_exchange and is needed
> by lib/stack.
>
> Error printed by MSVC:
>
> stack_rte_stack_lf.c.obj : error LNK2019:
>     unresolved external symbol rte_atomic128_cmp_exchange referenced
>     in function __rte_stack_lf_push_elems
>
> Fix is to provide an implementation for rte_atomic128_cmp_exchange
> which uses an intrinsic function, which is used when compiling with
> MSVC. For other compilers the existing implementation continues to
> be used.
>
> Signed-off-by: Andre Muezerie <andremue@linux.microsoft.com>
> ---
>  lib/eal/x86/include/rte_atomic.h    |  4 ++--
>  lib/eal/x86/include/rte_atomic_64.h | 18 ++++++++++++++++++
>  2 files changed, 20 insertions(+), 2 deletions(-)
>
> diff --git a/lib/eal/x86/include/rte_atomic.h b/lib/eal/x86/include/rte_atomic.h
> index c72c47c83e..e8e0e4c33c 100644
> --- a/lib/eal/x86/include/rte_atomic.h
> +++ b/lib/eal/x86/include/rte_atomic.h
> @@ -288,12 +288,12 @@ static inline int rte_atomic32_dec_and_test(rte_atomic32_t *v)
>
>  #endif
>
> +#endif /* RTE_TOOLCHAIN_MSVC */
> +
>  #ifdef RTE_ARCH_I686
>  #include "rte_atomic_32.h"
>  #else
>  #include "rte_atomic_64.h"
>  #endif
>
> -#endif
> -

This partially reverts 27da6a123414 ("eal: hide legacy atomics API for MSVC").
It would be better to implement an equivalent to
rte_atomic128_cmp_exchange in the DPDK "new" stdatomic API
(rte_stdatomic.h).


-- 
David Marchand