Hi3861 OpenHarmony嵌入式应用入门--LiteOS semaphore作为锁

news2024/11/16 3:09:00

CMSIS 2.0 接口中的 Semaphore（信号量）是用于嵌入式系统中多线程或中断服务例程（ISR）之间同步和共享资源保护的重要机制。Semaphore 是一种用于控制对多个共享资源访问的同步机制。它可以被看作是一个计数器，用于跟踪可用资源的数量。

特性

计数信号量：Semaphore 可以作为计数信号量使用，管理多个相同类型的资源。例如，如果有多个 DMA 通道，可以使用 Semaphore 来限制同时访问这些通道的数量。

生产者/消费者信号量：Semaphore 也可以用于实现生产者和消费者之间的同步，确保在消费者准备好之前，生产者不会覆盖数据。

Semaphore在并发编程中确实可以作为一种锁来使用，用于控制多个线程对共享资源的访问。首先，你需要确定在任意时刻能够同时访问共享资源的最大线程数，并将这个数作为初始值来创建一个Semaphore对象。这个初始值通常表示许可的数量，每个许可允许一个线程访问共享资源。当线程想要访问共享资源时，它应该首先调用Semaphore对象的osSemaphoreAcquire()方法。这个方法会尝试从Semaphore中获取一个许可。如果Semaphore中有可用的许可（即计数器的值大于0），那么线程会立即获取一个许可并继续执行。如果没有可用的许可（即计数器的值为0），那么线程将被阻塞，直到有可用的许可。一旦线程成功获取到许可，它就可以安全地访问共享资源了。在访问期间，线程可以执行任何需要的操作。当线程完成对共享资源的访问后，它应该调用Semaphore对象的osSemaphoreRelease()方法来释放之前获取的许可。这个方法会将Semaphore的计数器加1，表示有一个新的许可可用。其他等待的线程（如果有的话）现在可能会获取到这个许可并继续执行。

Semaphore API

API名称	说明
osSemaphoreNew	创建并初始化一个信号量
osSemaphoreGetName	获取一个信号量的名字
osSemaphoreAcquire	获取一个信号量的令牌，若获取不到，则会超时返回
osSemaphoreRelease	释放一个信号量的令牌，但是令牌的数量不超过初始定义的的令牌数
osSemaphoreGetCount	获取当前的信号量令牌数
osSemaphoreDelete	删除一个信号量

代码编写

修改D:\DevEcoProjects\test\src\vendor\rtplay\rt_hi3861\demo\BUILD.gn文件

# Copyright (c) 2023 Beijing HuaQing YuanJian Education Technology Co., Ltd
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
# 
#    http://www.apache.org/licenses/LICENSE-2.0
# 
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License. 

import("//build/lite/config/component/lite_component.gni")

lite_component("demo") {
  features = [
    #"base_00_helloworld:base_helloworld_example",
    #"base_01_led:base_led_example",
    #"base_02_loopkey:base_loopkey_example",
    #"base_03_irqkey:base_irqkey_example",
    #"base_04_adc:base_adc_example",
    #"base_05_pwm:base_pwm_example",
    #"base_06_ssd1306:base_ssd1306_example",
    #"kernel_01_task:kernel_task_example",
    #"kernel_02_timer:kernel_timer_example",
    #"kernel_03_event:kernel_event_example",
    #"kernel_04_mutex:kernel_mutex_example",
    "kernel_05_semaphore_as_mutex:kernel_semaphore_as_mutex_example",
  ]
}

创建D:\DevEcoProjects\test\src\vendor\rtplay\rt_hi3861\demo\kernel_05_semaphore_as_mutex文件夹

文件夹中创建D:\DevEcoProjects\test\src\vendor\rtplay\rt_hi3861\demo\kernel_05_semaphore_as_mutex\kernel_semaphore_as_mutex_example.c文件D:\DevEcoProjects\test\src\vendor\rtplay\rt_hi3861\demo\kernel_05_semaphore_as_mutex\BUILD.gn文件

# Copyright (c) 2023 Beijing HuaQing YuanJian Education Technology Co., Ltd
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
# 
#    http://www.apache.org/licenses/LICENSE-2.0
# 
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License. 

static_library("kernel_semaphore_as_mutex_example") {
    sources = [
        "kernel_semaphore_as_mutex_example.c"
    ]

    include_dirs = [
        "//utils/native/lite/include",
        "//kernel/liteos_m/kal/cmsis",
    ]
}

/*
 * Copyright (c) 2023 Beijing HuaQing YuanJian Education Technology Co., Ltd
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <stdio.h>
#include <unistd.h>

#include "ohos_init.h"
#include "cmsis_os2.h"

osThreadId_t Task1_ID;        //  任务1 ID
osThreadId_t Task2_ID;        //  任务2 ID
osSemaphoreId_t Semaphore_ID; // 信号量ID
uint8_t buff[20] = {0};       // 定义一个共享资源
#define TASK_STACK_SIZE 1024
#define TASK_DELAY_TIME 1 // s

/**
 * @description: 任务1
 * @param {*}
 * @return {*}
 */
void Task1(void)
{
    int i = 0;
    while (1) {
        printf("[info] enter Task 1.......\n");
        osSemaphoreAcquire(Semaphore_ID, osWaitForever); // 请求信号量 -1

        // 操作共享数据 写数据
        printf("[info] write Buff Data: \n");
        for (i = 0; i < sizeof(buff); i++) {
            buff[i] = i;
        }
        printf("\n");
        osSemaphoreRelease(Semaphore_ID); // 释放信号量 +1
        sleep(TASK_DELAY_TIME);
    }
}
/**
 * @description: 任务2
 * @param {*}
 * @return {*}
 */
void Task2(void)
{
    int i = 0;
    while (1) {
        printf("enter Task 2.......\n");
        osSemaphoreAcquire(Semaphore_ID, osWaitForever); // 请求信号量 -1
        // 操作共享数据 读数据
        printf("[info] read Buff Data: \n");
        for (i = 0; i < sizeof(buff); i++) {
            printf("%d \n", buff[i]);
        }
        printf("\n");
        osSemaphoreRelease(Semaphore_ID); // 释放信号量 +1

        sleep(TASK_DELAY_TIME);
    }
}
/**
 * @description: 初始化并创建任务
 * @param {*}
 * @return {*}
 */
static void kernel_mutex_semaphore_example(void)
{
    printf("Enter kernel_mutex_semaphore_example()!\n");

    // 创建信号量
    Semaphore_ID = osSemaphoreNew(1, 1, NULL); // 参数: 最大计数值，初始计数值，参数配置
    if (Semaphore_ID != NULL) {
        printf("ID = %d, Create Semaphore_ID is OK!\n", Semaphore_ID);
    }

    osThreadAttr_t taskOptions;
    taskOptions.name = "Task1";              // 任务的名字
    taskOptions.attr_bits = 0;               // 属性位
    taskOptions.cb_mem = NULL;               // 堆空间地址
    taskOptions.cb_size = 0;                 // 堆空间大小
    taskOptions.stack_mem = NULL;            // 栈空间地址
    taskOptions.stack_size = TASK_STACK_SIZE;           // 栈空间大小 单位:字节
    taskOptions.priority = osPriorityNormal; // 任务的优先级

    Task1_ID = osThreadNew((osThreadFunc_t)Task1, NULL, &taskOptions); // 创建任务1
    if (Task1_ID != NULL) {
        printf("ID = %d, Create Task1_ID is OK!\n", Task1_ID);
    }

    taskOptions.name = "Task2";                                        // 任务的名字
    taskOptions.priority = osPriorityNormal;                           // 任务的优先级
    Task2_ID = osThreadNew((osThreadFunc_t)Task2, NULL, &taskOptions); // 创建任务2
    if (Task2_ID != NULL) {
        printf("ID = %d, Create Task2_ID is OK!\n", Task2_ID);
    }
}
SYS_RUN(kernel_mutex_semaphore_example);

使用build，编译成功后，使用upload进行烧录。