atomic: multi-backend framework + builtin + API rename - #19867
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🔗 Cross-repo PR dependenciesThe read-only Build run reported the following dependent PR(s) and fetched head SHA(s): CI run: https://github.com/apache/nuttx/actions/runs/32223697536 |
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The atomic implementation of machine/arch_atomic.c is achieved by switching interrupts. This version does not support SMP. Signed-off-by: zhangyu117 <zhangyu117@xiaomi.com>
Tricore gcc does not support atomic interface but some users need to use atomic operations, so support atomic function using tricore arch instructions (__cmpAndSwap/__swap/__ld32). Signed-off-by: zhangyu117 <zhangyu117@xiaomi.com>
Refine the atomic Kconfig to support multiple backends: LIBC_ATOMIC_TOOLCHAIN (compiler builtins), LIBC_ATOMIC_ARCH (arch instructions), and LIBC_ATOMIC_IRQ (interrupt disable). Rename arch_atomic.c to arch_atomic_irq.c since it supports the IRQ backend. Signed-off-by: zhangyu117 <zhangyu117@xiaomi.com>
Select LIBC_ATOMIC_IRQ at the architecture level (ARM7TDMI, ARM926EJS, ARMv6M) for chips that do not support atomic operations natively. This covers all ARM7TDMI, ARM926EJS, and Cortex-M0 based chips automatically. Also select LIBC_ATOMIC_IRQ for specific non-ARM architectures (AVR, RISC-V, SPARC, Xtensa) that lack atomic instruction support. Signed-off-by: zhangyu117 <zhangyu117@xiaomi.com>
Replace atomic_load with atomic_read in call sites to use the unified interface defined in <nuttx/atomic.h>. Signed-off-by: zhangyu117 <zhangyu117@xiaomi.com>
1. for tasking, map __c11_atomic_xxx as tasking_atomic_xxx 2. for msvc, map _Interlocked_xxx as msvc_atomic_xxx 3. if no special map, use gcc/clang as default as they are most widely used. Signed-off-by: zhangyu117 <zhangyu117@xiaomi.com>
The reason for using builtin atomic is that in C++, when include <atomic> in <nuttx/atomic.h> easily conflicts with third-party function libraries. We wanted to completely separate the implementation of <nuttx/atomic.h>. There are two points: 1. use builtin function directly. 2. Without the standard library implementation, need implement "atomic_fetch_xxx", leading conflicts with the standard library used by third-party programs, introducing redefinition issues and requiring name changes. Signed-off-by: zhangyu117 <zhangyu117@xiaomi.com>
Rename atomic_fetch_add/sub/or/and/xor to atomic_add/sub/or/and/xor to avoid conflicts with the C/C++ standard library naming. The atomic_fetch_xxx naming is reserved by the standard; keeping it causes function name conflicts when source files indirectly include both <nuttx/atomic.h> and <atomic>/<stdatomic.h>. Signed-off-by: zhangyu117 <zhangyu117@xiaomi.com>
1. use _atomic as wrapper because if _Atomic empty, may affects the compilation of other files: 2. for clang builtin function, it donot accept param with keyword "_Atomic" Signed-off-by: zhangyu117 <zhangyu117@xiaomi.com>
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🔗 Cross-repo PR dependenciesThe read-only Build run reported the following dependent PR(s) and fetched head SHA(s): CI run: https://github.com/apache/nuttx/actions/runs/32266949770 |
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Summary
Rework the atomic implementation to support multiple selectable 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)LIBC_ATOMIC_IRQ- IRQ disable wrapping critical section (single-core fallback)Switch
<nuttx/atomic.h>to call toolchain builtin atomic functions directly (__atomic_*/__c11_atomic_*/_Interlocked*), avoiding conflicts with third-party C/C++ standard libraries.Rename
atomic_fetch_xxx->atomic_xxx(e.g.,atomic_fetch_add->atomic_add) because theatomic_fetch_xxxnaming is reserved by the C/C++ standard and conflicts with standard library declarations.Use
_Atomicqualifier foratomic_ttypedef when supported, with a__Atomic(t)wrapper for clang/C++ compatibility.Breaking change
This is a breaking API change. A companion PR in the apps tree renames call sites (
atomic_fetch_add->atomic_add, etc.).depends-on: apache/nuttx-apps/pull/3733
Stacked PR chain
Depends on #19866. This is PR 2 of 3:
Test
CI testbuild across ARM/RISC-V/SIM targets.