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https://gitee.com/mirrors_PX4/PX4-Autopilot.git
synced 2026-04-14 10:07:39 +08:00
f300ec1da2
fetch_add/sub were really inc/dec for the __atomic_always_lock_free == true branch. This fixes them so that the arg "num" is actually used.
297 lines
7.5 KiB
C++
297 lines
7.5 KiB
C++
/****************************************************************************
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*
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* Copyright (c) 2019 PX4 Development Team. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name PX4 nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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/**
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* @file atomic.h
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*
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* Provides atomic integers and counters. Each method is executed atomically and thus
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* can be used to prevent data races and add memory synchronization between threads.
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*
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* In addition to the atomicity, each method serves as a memory barrier (sequential
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* consistent ordering). This means all operations that happen before and could
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* potentially have visible side-effects in other threads will happen before
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* the method is executed.
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*
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* The implementation uses the built-in methods from GCC (supported by Clang as well).
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* @see https://gcc.gnu.org/onlinedocs/gcc/_005f_005fatomic-Builtins.html.
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*
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* @note: on ARM, the instructions LDREX and STREX might be emitted. To ensure correct
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* behavior, the exclusive monitor needs to be cleared on a task switch (via CLREX).
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* This happens automatically e.g. on ARMv7-M as part of an exception entry or exit
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* sequence.
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*/
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#pragma once
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#ifdef __cplusplus
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#include <stdbool.h>
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#include <stdint.h>
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#if defined(__PX4_NUTTX)
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# include <nuttx/irq.h>
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#endif // __PX4_NUTTX
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namespace px4
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{
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template <typename T>
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class atomic
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{
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public:
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#if defined(__PX4_POSIX)
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// Ensure that all operations are lock-free, so that 'atomic' can be used from
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// IRQ handlers. This might not be required everywhere though.
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static_assert(__atomic_always_lock_free(sizeof(T), 0), "atomic is not lock-free for the given type T");
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#endif // __PX4_POSIX
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atomic() = default;
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explicit atomic(T value) : _value(value) {}
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/**
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* Atomically read the current value
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*/
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inline T load() const
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{
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#if defined(__PX4_NUTTX)
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if (!__atomic_always_lock_free(sizeof(T), 0)) {
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irqstate_t flags = enter_critical_section();
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T val = _value;
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leave_critical_section(flags);
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return val;
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} else
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#endif // __PX4_NUTTX
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{
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return __atomic_load_n(&_value, __ATOMIC_SEQ_CST);
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}
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}
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/**
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* Atomically store a value
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*/
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inline void store(T value)
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{
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#if defined(__PX4_NUTTX)
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if (!__atomic_always_lock_free(sizeof(T), 0)) {
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irqstate_t flags = enter_critical_section();
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_value = value;
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leave_critical_section(flags);
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} else
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#endif // __PX4_NUTTX
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{
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__atomic_store(&_value, &value, __ATOMIC_SEQ_CST);
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}
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}
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/**
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* Atomically add a number and return the previous value.
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* @return value prior to the addition
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*/
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inline T fetch_add(T num)
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{
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#if defined(__PX4_NUTTX)
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if (!__atomic_always_lock_free(sizeof(T), 0)) {
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irqstate_t flags = enter_critical_section();
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T ret = _value;
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_value += num;
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leave_critical_section(flags);
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return ret;
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} else
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#endif // __PX4_NUTTX
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{
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return __atomic_fetch_add(&_value, num, __ATOMIC_SEQ_CST);
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}
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}
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/**
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* Atomically substract a number and return the previous value.
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* @return value prior to the substraction
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*/
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inline T fetch_sub(T num)
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{
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#if defined(__PX4_NUTTX)
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if (!__atomic_always_lock_free(sizeof(T), 0)) {
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irqstate_t flags = enter_critical_section();
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T ret = _value;
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_value -= num;
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leave_critical_section(flags);
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return ret;
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} else
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#endif // __PX4_NUTTX
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{
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return __atomic_fetch_sub(&_value, num, __ATOMIC_SEQ_CST);
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}
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}
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/**
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* Atomic AND with a number
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* @return value prior to the operation
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*/
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inline T fetch_and(T num)
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{
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#if defined(__PX4_NUTTX)
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if (!__atomic_always_lock_free(sizeof(T), 0)) {
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irqstate_t flags = enter_critical_section();
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T val = _value;
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_value &= num;
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leave_critical_section(flags);
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return val;
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} else
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#endif // __PX4_NUTTX
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{
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return __atomic_fetch_and(&_value, num, __ATOMIC_SEQ_CST);
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}
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}
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/**
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* Atomic XOR with a number
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* @return value prior to the operation
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*/
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inline T fetch_xor(T num)
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{
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#if defined(__PX4_NUTTX)
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if (!__atomic_always_lock_free(sizeof(T), 0)) {
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irqstate_t flags = enter_critical_section();
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T val = _value;
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_value ^= num;
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leave_critical_section(flags);
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return val;
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} else
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#endif // __PX4_NUTTX
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{
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return __atomic_fetch_xor(&_value, num, __ATOMIC_SEQ_CST);
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}
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}
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/**
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* Atomic OR with a number
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* @return value prior to the operation
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*/
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inline T fetch_or(T num)
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{
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#if defined(__PX4_NUTTX)
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if (!__atomic_always_lock_free(sizeof(T), 0)) {
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irqstate_t flags = enter_critical_section();
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T val = _value;
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_value |= num;
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leave_critical_section(flags);
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return val;
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} else
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#endif // __PX4_NUTTX
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{
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return __atomic_fetch_or(&_value, num, __ATOMIC_SEQ_CST);
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}
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}
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/**
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* Atomic NAND (~(_value & num)) with a number
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* @return value prior to the operation
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*/
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inline T fetch_nand(T num)
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{
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#if defined(__PX4_NUTTX)
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if (!__atomic_always_lock_free(sizeof(T), 0)) {
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irqstate_t flags = enter_critical_section();
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T ret = _value;
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_value = ~(_value & num);
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leave_critical_section(flags);
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return ret;
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} else
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#endif // __PX4_NUTTX
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{
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return __atomic_fetch_nand(&_value, num, __ATOMIC_SEQ_CST);
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}
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}
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/**
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* Atomic compare and exchange operation.
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* This compares the contents of _value with the contents of *expected. If
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* equal, the operation is a read-modify-write operation that writes desired
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* into _value. If they are not equal, the operation is a read and the current
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* contents of _value are written into *expected.
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* @return If desired is written into _value then true is returned
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*/
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inline bool compare_exchange(T *expected, T desired)
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{
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#if defined(__PX4_NUTTX)
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if (!__atomic_always_lock_free(sizeof(T), 0)) {
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irqstate_t flags = enter_critical_section();
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if (_value == *expected) {
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_value = desired;
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leave_critical_section(flags);
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return true;
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} else {
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*expected = _value;
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leave_critical_section(flags);
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return false;
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}
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} else
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#endif // __PX4_NUTTX
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{
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return __atomic_compare_exchange(&_value, expected, &desired, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST);
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}
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}
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private:
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T _value {};
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};
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using atomic_int = atomic<int>;
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using atomic_int32_t = atomic<int32_t>;
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using atomic_bool = atomic<bool>;
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} /* namespace px4 */
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#endif /* __cplusplus */
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