zhangyu-duck opened a new pull request, #19802:
URL: https://github.com/apache/nuttx/pull/19802
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Summary
This PR reworks the atomic operation implementation in <nuttx/atomic.h> to
provide a unified, portable, and standard-conflict-free atomic interface.
Key changes:
1. Use toolchain builtin atomic functions instead of
<atomic>/<stdatomic.h>. The original implementation relied on
__has_include(<atomic>) and C11 version checks, which is not portable (e.g.,
Tasking compiler doesn't support __has_include). It
also conflicts with third-party C++ libraries that include <atomic> — the
standard library expects template types while NuttX atomic_t is int32_t,
causing compile errors. The new implementation calls compiler builtins
(__atomic_* / __c11_atomic_*
/ _Interlocked*) directly, similar to Zephyr.
2. Rename atomic_fetch_xxx to atomic_xxx (e.g., atomic_fetch_add →
atomic_add). The atomic_fetch_xxx naming is reserved by the C/C++ standard.
Since source files may directly or indirectly include <nuttx/atomic.h>, keeping
the standard name
causes function name conflicts and compile errors. Other non-standard API
names (e.g., atomic_read, atomic_set, atomic_xchg) remain unchanged.
3. Add four selectable atomic backends via Kconfig:
- LIBC_ATOMIC_TOOLCHAIN — compiler builtins (default, lock-free)
- LIBC_ATOMIC_ARCH — arch-native atomic instructions (lock-free)
- LIBC_ATOMIC_HWSPINLOCK — hardware spinlock wrapping critical section
(cross-core, for chips without atomic instructions but with hwspinlock
peripheral)
- LIBC_ATOMIC_IRQ — IRQ disable wrapping critical section (single-core
only, fallback for ARMv6-M / ARM7TDMI / ARM926EJS etc.)
4. Add hwspinlock-based atomic for cxd56, rp2040, and lc823450 (multi-core
capable chips).
5. Use _Atomic qualifier for atomic_t typedef when the compiler supports
it, with a __Atomic(t) wrapper for clang compatibility.
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