| /* |
| * Copyright (c) 2025 Google LLC |
| * |
| * SPDX-License-Identifier: Apache-2.0 |
| */ |
| |
| /** |
| * @file |
| * @brief C-based implementation of GCC __atomic built-ins. |
| * |
| * This file provides a fallback implementation for the C++ atomic functions |
| * required by the compiler on architectures that do not have native atomic |
| * instructions and are using the generic C implementation of atomics. |
| * All operations are made atomic by using a global interrupt lock. |
| */ |
| |
| #include <zephyr/kernel.h> |
| #include <stdint.h> |
| |
| /* |
| * Note on memory ordering: |
| * The `memorder` parameters are ignored because the irq_lock() provides |
| * a full memory barrier, which is equivalent to the strongest memory order, |
| * __ATOMIC_SEQ_CST. This is always safe. |
| */ |
| |
| /* === compare_exchange ======================================================= */ |
| |
| #define DEFINE_ATOMIC_COMPARE_EXCHANGE(n, type) \ |
| bool __atomic_compare_exchange_##n(volatile void *ptr, void *expected, type desired, \ |
| bool weak, int success, int failure) \ |
| { \ |
| bool ret = false; \ |
| unsigned int key = irq_lock(); \ |
| volatile type *p = ptr; \ |
| type *e = expected; \ |
| \ |
| if (*p == *e) { \ |
| *p = desired; \ |
| ret = true; \ |
| } else { \ |
| *e = *p; \ |
| ret = false; \ |
| } \ |
| irq_unlock(key); \ |
| return ret; \ |
| } |
| |
| DEFINE_ATOMIC_COMPARE_EXCHANGE(1, uint8_t) |
| DEFINE_ATOMIC_COMPARE_EXCHANGE(2, uint16_t) |
| DEFINE_ATOMIC_COMPARE_EXCHANGE(4, uint32_t) |
