Re: [PATCH v6 1/6] eal: provide rte stdatomics optional atomics API

[Thomas Monjalon <thomas@monjalon.net>]

22/08/2023 23:00, Tyler Retzlaff:
> --- a/lib/eal/include/generic/rte_rwlock.h
> +++ b/lib/eal/include/generic/rte_rwlock.h
> @@ -32,6 +32,7 @@
>  #include <rte_common.h>
>  #include <rte_lock_annotations.h>
>  #include <rte_pause.h>
> +#include <rte_stdatomic.h>

I'm not sure about adding the include in patch 1 if it is not used here.


> --- /dev/null
> +++ b/lib/eal/include/rte_stdatomic.h
> @@ -0,0 +1,198 @@
> +/* SPDX-License-Identifier: BSD-3-Clause
> + * Copyright(c) 2023 Microsoft Corporation
> + */
> +
> +#ifndef _RTE_STDATOMIC_H_
> +#define _RTE_STDATOMIC_H_
> +
> +#include <assert.h>
> +
> +#ifdef __cplusplus
> +extern "C" {
> +#endif
> +
> +#ifdef RTE_ENABLE_STDATOMIC
> +#ifdef __STDC_NO_ATOMICS__
> +#error enable_stdatomics=true but atomics not supported by toolchain
> +#endif
> +
> +#include <stdatomic.h>
> +
> +/* RTE_ATOMIC(type) is provided for use as a type specifier
> + * permitting designation of an rte atomic type.
> + */
> +#define RTE_ATOMIC(type) _Atomic(type)
> +
> +/* __rte_atomic is provided for type qualification permitting
> + * designation of an rte atomic qualified type-name.

Sorry I don't understand this comment.

> + */
> +#define __rte_atomic _Atomic
> +
> +/* The memory order is an enumerated type in C11. */
> +typedef 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");

Not sure about using static_assert or RTE_BUILD_BUG_ON

> +#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
> +
> +#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_weak_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_explicit(ptr, memorder) \
> +	atomic_flag_test_and_set_explicit(ptr, memorder)
> +
> +#define rte_atomic_flag_clear_explicit(ptr, memorder) \
> +	atomic_flag_clear_explicit(ptr, memorder)
> +
> +/* We provide internal macro here to allow conditional expansion
> + * in the body of the per-arch rte_atomic_thread_fence inline functions.
> + */
> +#define __rte_atomic_thread_fence(memorder) \
> +	atomic_thread_fence(memorder)
> +
> +#else

Better to add some context in comment of this "else": /* !RTE_ENABLE_STDATOMIC */

> +
> +/* RTE_ATOMIC(type) is provided for use as a type specifier
> + * permitting designation of an rte atomic type.
> + */

The comment should say it has no effect.
Or no comment at all for this part.

> +#define RTE_ATOMIC(type) type
> +
> +/* __rte_atomic is provided for type qualification permitting
> + * designation of an rte atomic qualified type-name.
> + */
> +#define __rte_atomic
> +
> +/* 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
> +
> +#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)
> +
> +/* We provide internal macro here to allow conditional expansion
> + * in the body of the per-arch rte_atomic_thread_fence inline functions.
> + */
> +#define __rte_atomic_thread_fence(memorder) \
> +	__atomic_thread_fence(memorder)
> +
> +#endif
> +
> +#ifdef __cplusplus
> +}
> +#endif
> +
> +#endif /* _RTE_STDATOMIC_H_ */