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

[Tyler Retzlaff]

On Fri, Aug 11, 2023 at 11:42:12AM +0200, Morten Brørup wrote:
> > 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.

will be in v2

> 
> > +
> > +#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.)

* llvm and gcc both expose it as a built-in #define for test builds i
  have run. worst case the assert is lost if it isn't.
* since i have to handle non-{clang,gcc} too i still guard with ifdef
* i do need to switch to using assert.h static_assert macro to
  inter-operate with c++ in v2

> 
> > +
> > +#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
>