[PATCH 1/6] eal: provide rte stdatomics optional atomics API

[Morten Brørup]

> From: Tyler Retzlaff [mailto:roretzla at linux.microsoft.com]
> Sent: Friday, 11 August 2023 03.32
> 
> Provide API for atomic operations in the rte namespace that may
> optionally be configured to use C11 atomics with meson
> option enable_stdatomics=true
> 
> Signed-off-by: Tyler Retzlaff <roretzla at linux.microsoft.com>
> ---
>  config/meson.build              |   1 +
>  config/rte_config.h             |   1 +
>  lib/eal/include/meson.build     |   1 +
>  lib/eal/include/rte_stdatomic.h | 162
> ++++++++++++++++++++++++++++++++++++++++
>  meson_options.txt               |   1 +
>  5 files changed, 166 insertions(+)
>  create mode 100644 lib/eal/include/rte_stdatomic.h
> 
> diff --git a/config/meson.build b/config/meson.build
> index d822371..ec49964 100644
> --- a/config/meson.build
> +++ b/config/meson.build
> @@ -303,6 +303,7 @@ endforeach
>  # set other values pulled from the build options
>  dpdk_conf.set('RTE_MAX_ETHPORTS', get_option('max_ethports'))
>  dpdk_conf.set('RTE_LIBEAL_USE_HPET', get_option('use_hpet'))
> +dpdk_conf.set('RTE_ENABLE_STDATOMIC', get_option('enable_stdatomic'))
>  dpdk_conf.set('RTE_ENABLE_TRACE_FP', get_option('enable_trace_fp'))
>  # values which have defaults which may be overridden
>  dpdk_conf.set('RTE_MAX_VFIO_GROUPS', 64)
> diff --git a/config/rte_config.h b/config/rte_config.h
> index 400e44e..f17b6ae 100644
> --- a/config/rte_config.h
> +++ b/config/rte_config.h
> @@ -13,6 +13,7 @@
>  #define _RTE_CONFIG_H_
> 
>  #include <rte_build_config.h>
> +#include <rte_stdatomic.h>
> 
>  /* legacy defines */
>  #ifdef RTE_EXEC_ENV_LINUX
> diff --git a/lib/eal/include/meson.build b/lib/eal/include/meson.build
> index b0db9b3..f8a47b3 100644
> --- a/lib/eal/include/meson.build
> +++ b/lib/eal/include/meson.build
> @@ -43,6 +43,7 @@ headers += files(
>          'rte_seqlock.h',
>          'rte_service.h',
>          'rte_service_component.h',
> +        'rte_stdatomic.h',
>          'rte_string_fns.h',
>          'rte_tailq.h',
>          'rte_thread.h',
> diff --git a/lib/eal/include/rte_stdatomic.h
> b/lib/eal/include/rte_stdatomic.h
> new file mode 100644
> index 0000000..832fd07
> --- /dev/null
> +++ b/lib/eal/include/rte_stdatomic.h
> @@ -0,0 +1,162 @@
> +/* SPDX-License-Identifier: BSD-3-Clause
> + * Copyright(c) 2023 Microsoft Corporation
> + */
> +
> +#ifndef _RTE_STDATOMIC_H_
> +#define _RTE_STDATOMIC_H_
> +
> +#ifdef __cplusplus
> +extern "C" {
> +#endif
> +
> +typedef int rte_memory_order;

In C11 memory_order is an enumerated type, and in GCC built-ins it is an int. If possible, rte_memory_order should be too; i.e. remove the typedef here, and make two variants of it instead.

> +
> +#ifdef RTE_ENABLE_STDATOMIC
> +#ifdef __STDC_NO_ATOMICS__
> +#error enable_stdatomics=true but atomics not supported by toolchain
> +#endif
> +
> +#include <stdatomic.h>
> +
> +#define __rte_atomic _Atomic

Move the (changed) C11 memory order type definition here:

/* The memory order is an enumerated type in C11. */
#define memory_order rte_memory_order

> +
> +#define rte_memory_order_relaxed memory_order_relaxed
> +#ifdef __ATOMIC_RELAXED
> +_Static_assert(rte_memory_order_relaxed == __ATOMIC_RELAXED,
> +	"rte_memory_order_relaxed == __ATOMIC_RELAXED");
> +#endif
> +
> +#define rte_memory_order_consume memory_order_consume
> +#ifdef __ATOMIC_CONSUME
> +_Static_assert(rte_memory_order_consume == __ATOMIC_CONSUME,
> +	"rte_memory_order_consume == __ATOMIC_CONSUME");
> +#endif
> +
> +#define rte_memory_order_acquire memory_order_acquire
> +#ifdef __ATOMIC_ACQUIRE
> +_Static_assert(rte_memory_order_acquire == __ATOMIC_ACQUIRE,
> +	"rte_memory_order_acquire == __ATOMIC_ACQUIRE");
> +#endif
> +
> +#define rte_memory_order_release memory_order_release
> +#ifdef __ATOMIC_RELEASE
> +_Static_assert(rte_memory_order_release == __ATOMIC_RELEASE,
> +	"rte_memory_order_release == __ATOMIC_RELEASE");
> +#endif
> +
> +#define rte_memory_order_acq_rel memory_order_acq_rel
> +#ifdef __ATOMIC_ACQ_REL
> +_Static_assert(rte_memory_order_acq_rel == __ATOMIC_ACQ_REL,
> +	"rte_memory_order_acq_rel == __ATOMIC_ACQ_REL");
> +#endif
> +
> +#define rte_memory_order_seq_cst memory_order_seq_cst
> +#ifdef __ATOMIC_SEQ_CST
> +_Static_assert(rte_memory_order_seq_cst == __ATOMIC_SEQ_CST,
> +	"rte_memory_order_seq_cst == __ATOMIC_SEQ_CST");
> +#endif

Excellent idea adding these _Static_asserts!

Have you tested (with the toolchain you are targeting with this _Static_assert) that e.g. __ATOMIC_RELAXED is actually #defined, so the preprocessor can see it? (I guess that being a built-it, it might not be a #define, it might be a magic value known by the compiler only.)

> +
> +#define rte_atomic_load_explicit(ptr, memorder) \
> +	atomic_load_explicit(ptr, memorder)
> +
> +#define rte_atomic_store_explicit(ptr, val, memorder) \
> +	atomic_store_explicit(ptr, val, memorder)
> +
> +#define rte_atomic_exchange_explicit(ptr, val, memorder) \
> +	atomic_exchange_explicit(ptr, val, memorder)
> +
> +#define rte_atomic_compare_exchange_strong_explicit( \
> +	    ptr, expected, desired, succ_memorder, fail_memorder) \
> +	atomic_compare_exchange_strong_explicit( \
> +	    ptr, expected, desired, succ_memorder, fail_memorder)
> +
> +#define rte_atomic_compare_exchange_weak_explicit( \
> +	    ptr, expected, desired, succ_memorder, fail_memorder) \
> +	atomic_compare_exchange_strong_explicit( \
> +	    ptr, expected, desired, succ_memorder, fail_memorder)
> +
> +#define rte_atomic_fetch_add_explicit(ptr, val, memorder) \
> +	atomic_fetch_add_explicit(ptr, val, memorder)
> +
> +#define rte_atomic_fetch_sub_explicit(ptr, val, memorder) \
> +	atomic_fetch_sub_explicit(ptr, val, memorder)
> +
> +#define rte_atomic_fetch_and_explicit(ptr, val, memorder) \
> +	atomic_fetch_and_explicit(ptr, val, memorder)
> +
> +#define rte_atomic_fetch_xor_explicit(ptr, val, memorder) \
> +	atomic_fetch_xor_explicit(ptr, val, memorder)
> +
> +#define rte_atomic_fetch_or_explicit(ptr, val, memorder) \
> +	atomic_fetch_or_explicit(ptr, val, memorder)
> +
> +#define rte_atomic_fetch_nand_explicit(ptr, val, memorder) \
> +	atomic_fetch_nand_explicit(ptr, val, memorder)
> +
> +#define rte_atomic_flag_test_and_set_explict(ptr, memorder) \
> +	atomic_flag_test_and_set_explicit(ptr, memorder)
> +
> +#define rte_atomic_flag_clear_explicit(ptr, memorder) \
> +	atomic_flag_clear(ptr, memorder)
> +
> +#else
> +
> +#define __rte_atomic

Move the built-ins memory order type definition here:

/* The memory order is an integer type in GCC built-ins,
 * not an enumerated type like in C11.
 */
typedef int rte_memory_order;

> +
> +#define rte_memory_order_relaxed __ATOMIC_RELAXED
> +#define rte_memory_order_consume __ATOMIC_CONSUME
> +#define rte_memory_order_acquire __ATOMIC_ACQUIRE
> +#define rte_memory_order_release __ATOMIC_RELEASE
> +#define rte_memory_order_acq_rel __ATOMIC_ACQ_REL
> +#define rte_memory_order_seq_cst __ATOMIC_SEQ_CST

Agree; the memorder type is int, so no enum here.

> +
> +#define rte_atomic_load_explicit(ptr, memorder) \
> +	__atomic_load_n(ptr, memorder)
> +
> +#define rte_atomic_store_explicit(ptr, val, memorder) \
> +	__atomic_store_n(ptr, val, memorder)
> +
> +#define rte_atomic_exchange_explicit(ptr, val, memorder) \
> +	__atomic_exchange_n(ptr, val, memorder)
> +
> +#define rte_atomic_compare_exchange_strong_explicit( \
> +	    ptr, expected, desired, succ_memorder, fail_memorder) \
> +	__atomic_compare_exchange_n( \
> +	    ptr, expected, desired, 0, succ_memorder, fail_memorder)
> +
> +#define rte_atomic_compare_exchange_weak_explicit( \
> +	    ptr, expected, desired, succ_memorder, fail_memorder) \
> +	__atomic_compare_exchange_n( \
> +	    ptr, expected, desired, 1, succ_memorder, fail_memorder)
> +
> +#define rte_atomic_fetch_add_explicit(ptr, val, memorder) \
> +	__atomic_fetch_add(ptr, val, memorder)
> +
> +#define rte_atomic_fetch_sub_explicit(ptr, val, memorder) \
> +	__atomic_fetch_sub(ptr, val, memorder)
> +
> +#define rte_atomic_fetch_and_explicit(ptr, val, memorder) \
> +	__atomic_fetch_and(ptr, val, memorder)
> +
> +#define rte_atomic_fetch_xor_explicit(ptr, val, memorder) \
> +	__atomic_fetch_xor(ptr, val, memorder)
> +
> +#define rte_atomic_fetch_or_explicit(ptr, val, memorder) \
> +	__atomic_fetch_or(ptr, val, memorder)
> +
> +#define rte_atomic_fetch_nand_explicit(ptr, val, memorder) \
> +	__atomic_fetch_nand(ptr, val, memorder)
> +
> +#define rte_atomic_flag_test_and_set_explicit(ptr, memorder) \
> +	__atomic_test_and_set(ptr, memorder)
> +
> +#define rte_atomic_flag_clear_explicit(ptr, memorder) \
> +	__atomic_clear(ptr, memorder)
> +
> +#endif
> +
> +#ifdef __cplusplus
> +}
> +#endif
> +
> +#endif /* _RTE_STDATOMIC_H_ */
> diff --git a/meson_options.txt b/meson_options.txt
> index 621e1ca..7d6784d 100644
> --- a/meson_options.txt
> +++ b/meson_options.txt
> @@ -46,6 +46,7 @@ option('mbuf_refcnt_atomic', type: 'boolean', value:
> true, description:
>         'Atomically access the mbuf refcnt.')
>  option('platform', type: 'string', value: 'native', description:
>         'Platform to build, either "native", "generic" or a SoC. Please
> refer to the Linux build guide for more information.')
> +option('enable_stdatomic', type: 'boolean', value: false, description:
> 'enable use of C11 stdatomic')
>  option('enable_trace_fp', type: 'boolean', value: false, description:
>         'enable fast path trace points.')
>  option('tests', type: 'boolean', value: true, description:
> --
> 1.8.3.1