[PATCH v5 0/6] optional rte optional stdatomics API

[Konstantin Ananyev]

> This series introduces API additions prefixed in the rte namespace that allow
> the optional use of stdatomics.h from C11 using enable_stdatomics=true for
> targets where enable_stdatomics=false no functional change is intended.
> 
> Be aware this does not contain all changes to use stdatomics across the DPDK
> tree it only introduces the minimum to allow the option to be used which is
> a pre-requisite for a clean CI (probably using clang) that can be run
> with enable_stdatomics=true enabled.
> 
> It is planned that subsequent series will be introduced per lib/driver as
> appropriate to further enable stdatomics use when enable_stdatomics=true.
> 
> Notes:
> 
> * Additional libraries beyond EAL make visible atomics use across the
>    API/ABI surface they will be converted in the subsequent series.
> 
> * The eal: add rte atomic qualifier with casts patch needs some discussion
>    as to whether or not the legacy rte_atomic APIs should be converted to
>    work with enable_stdatomic=true right now some implementation dependent
>    casts are used to prevent cascading / having to convert too much in
>    the intial series.
> 
> * Windows will obviously need complete conversion of libraries including
>    atomics that are not crossing API/ABI boundaries. those conversions will
>    introduced in separate series as new along side the existing msvc series.
> 
> Please keep in mind we would like to prioritize the review / acceptance of
> this patch since it needs to be completed in the 23.11 merge window.
> 
> Thank you all for the discussion that lead to the formation of this series.
> 
> v5:
>    * Add RTE_ATOMIC to doxygen configuration PREDEFINED macros list to
>      fix documentation generation failure
>    * Fix two typos in expansion of C11 atomics macros strong -> weak and
>      add missing _explicit
>    * Adjust devtools/checkpatches messages based on feedback. i have chosen
>      not to try and catch use of C11 atomics or _Atomic since using those
>      directly will be picked up by existing CI passes where by compilation
>      error where enable_stdatomic=false (the default for most platforms)
> 
> v4:
>    * Move the definition of #define RTE_ATOMIC(type) to patch 1 where it
>      belongs (a mistake in v3)
>    * Provide comments for both RTE_ATOMIC and __rte_atomic macros indicating
>      their use as specified or qualified contexts.
> 
> v3:
>    * Remove comments from APIs mentioning the mapping to C++ memory model
>      memory orders
>    * Introduce and use new macro RTE_ATOMIC(type) to be used in contexts
>      where _Atomic is used as a type specifier to declare variables. The
>      macro allows more clarity about what the atomic type being specified
>      is. e.g. _Atomic(T *) vs _Atomic(T) it is easier to understand that
>      the former is an atomic pointer type and the latter is an atomic
>      type. it also has the benefit of (in the future) being interoperable
>      with c++23 syntactically
>      note: Morten i have retained your 'reviewed-by' tags if you disagree
>      given the changes in the above version please indicate as such but
>      i believe the changes are in the spirit of the feedback you provided
> 
> v2:
>    * Wrap meson_options.txt option description to newline and indent to
>      be consistent with other options.
>    * Provide separate typedef of rte_memory_order for enable_stdatomic=true
>      VS enable_stdatomic=false instead of a single typedef to int
>      note: slight tweak to reviewers feedback i've chosen to use a typedef
>            for both enable_stdatomic={true,false} (just seemed more consistent)
>    * Bring in assert.h and use static_assert macro instead of _Static_assert
>      keyword to better interoperate with c/c++
>    * Directly include rte_stdatomic.h where into other places it is consumed
>      instead of hacking it globally into rte_config.h
>    * Provide and use __rte_atomic_thread_fence to allow conditional expansion
>      within the body of existing rte_atomic_thread_fence inline function to
>      maintain per-arch optimizations when enable_stdatomic=false
> 
> Tyler Retzlaff (6):
>    eal: provide rte stdatomics optional atomics API
>    eal: adapt EAL to present rte optional atomics API
>    eal: add rte atomic qualifier with casts
>    distributor: adapt for EAL optional atomics API changes
>    bpf: adapt for EAL optional atomics API changes
>    devtools: forbid new direct use of GCC atomic builtins
> 
>   app/test/test_mcslock.c                  |   6 +-
>   config/meson.build                       |   1 +
>   devtools/checkpatches.sh                 |   8 +-
>   doc/api/doxy-api.conf.in                 |   1 +
>   lib/bpf/bpf_pkt.c                        |   6 +-
>   lib/distributor/distributor_private.h    |   2 +-
>   lib/distributor/rte_distributor_single.c |  44 +++----
>   lib/eal/arm/include/rte_atomic_32.h      |   4 +-
>   lib/eal/arm/include/rte_atomic_64.h      |  36 +++---
>   lib/eal/arm/include/rte_pause_64.h       |  26 ++--
>   lib/eal/arm/rte_power_intrinsics.c       |   8 +-
>   lib/eal/common/eal_common_trace.c        |  16 +--
>   lib/eal/include/generic/rte_atomic.h     |  67 +++++++----
>   lib/eal/include/generic/rte_pause.h      |  50 ++++----
>   lib/eal/include/generic/rte_rwlock.h     |  48 ++++----
>   lib/eal/include/generic/rte_spinlock.h   |  20 ++--
>   lib/eal/include/meson.build              |   1 +
>   lib/eal/include/rte_mcslock.h            |  51 ++++----
>   lib/eal/include/rte_pflock.h             |  25 ++--
>   lib/eal/include/rte_seqcount.h           |  19 +--
>   lib/eal/include/rte_stdatomic.h          | 198 +++++++++++++++++++++++++++++++
>   lib/eal/include/rte_ticketlock.h         |  43 +++----
>   lib/eal/include/rte_trace_point.h        |   5 +-
>   lib/eal/loongarch/include/rte_atomic.h   |   4 +-
>   lib/eal/ppc/include/rte_atomic.h         |  54 ++++-----
>   lib/eal/riscv/include/rte_atomic.h       |   4 +-
>   lib/eal/x86/include/rte_atomic.h         |   8 +-
>   lib/eal/x86/include/rte_spinlock.h       |   2 +-
>   lib/eal/x86/rte_power_intrinsics.c       |   7 +-
>   meson_options.txt                        |   2 +
>   30 files changed, 499 insertions(+), 267 deletions(-)
>   create mode 100644 lib/eal/include/rte_stdatomic.h
> 

Series-acked-by: Konstantin Ananyev <konstantin.v.ananyev at yandex.ru>