一、任務間通信
- 信號量
概述
信號量是一種實現任務間同步的機制，一般用於多個任務間有限資源競爭訪問。
通常來說，一個信號量中持有一個整形數值，用以表示可用資源的數量。當一個信號量的可用資源數量大於0時，任務嘗試獲取該信號量成功，信號量的可用資源數減一；當一個信號量的可用資源數等於0時，任務嘗試獲取該信號量失敗或進入阻塞狀態。信號量的這一模式，當可用資源數爲1時，可將其用於資源的互斥訪問；或者解決生產者-消費者問題中的資源生產-消費問題。編程實例章節會演示生產者-消費者問題的解決範式。
API講解
編程實例
1、在tos_config.h中，配置信號量組件開關TOS_CFG_SEM_EN：
#define TOS_CFG_SEM_EN 1u
2、編寫main.c示例代碼：
/* USER CODE END Header */
/* Includes ------------------------------------------------------------------*/
#include "main.h"
#include "usart.h"
#include "gpio.h"
/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
#include "cmsis_os.h"
#include "stdio.h"
#include "tos_k.h"
/* USER CODE END Includes */
/* Private typedef -----------------------------------------------------------*/
/* USER CODE BEGIN PTD */
#define STK_SIZE_TASK_PRODUCER 512
#define STK_SIZE_TASK_CONSUMER 512
/* USER CODE END PTD */
/* Private define ------------------------------------------------------------*/
/* USER CODE BEGIN PD */
k_stack_t stack_task_producer[STK_SIZE_TASK_PRODUCER];
k_stack_t stack_task_consumer[STK_SIZE_TASK_CONSUMER];
k_task_t task_producer;
k_task_t task_consumer;
extern void entry_task_producer(void *arg);
extern void entry_task_consumer(void *arg);
k_mutex_t buffer_locker;
k_sem_t full;
k_sem_t empty;
#define RESOURCE_COUNT_MAX 3
struct resource_st {
int cursor;
uint32_t buffer[RESOURCE_COUNT_MAX];
} resource = { 0, {0} };
/* USER CODE END PD */
/* Private macro -------------------------------------------------------------*/
/* USER CODE BEGIN PM */
static void produce_item(int salt)
{
printf("produce item:\n");
printf("%d", salt);
resource.buffer[resource.cursor++] = salt;
printf("\n");
}
void entry_task_producer(void *arg)
{
size_t salt = 0;
k_err_t err;
while (K_TRUE) {
err = tos_sem_pend(&empty, TOS_TIME_FOREVER);
if (err != K_ERR_NONE) {
continue;
}
err = tos_mutex_pend(&buffer_locker);
if (err != K_ERR_NONE) {
continue;
}
produce_item(salt);
tos_mutex_post(&buffer_locker);
tos_sem_post(&full);
tos_task_delay(1000);
++salt;
}
}
static void consume_item(void)
{
printf("cosume item:\n");
printf("%d\t", resource.buffer[--resource.cursor]);
printf("\n");
}
void entry_task_consumer(void *arg)
{
k_err_t err;
while (K_TRUE) {
err = tos_sem_pend(&full, TOS_TIME_FOREVER);
if (err != K_ERR_NONE) {
continue;
}
tos_mutex_pend(&buffer_locker);
if (err != K_ERR_NONE) {
continue;
}
consume_item();
tos_mutex_post(&buffer_locker);
tos_sem_post(&empty);
tos_task_delay(2000);
}
}
/* USER CODE END PM */
/* Private variables ---------------------------------------------------------*/
/* USER CODE BEGIN PV */
/* USER CODE END PV */
/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
/* USER CODE BEGIN PFP */
/* USER CODE END PFP */
/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */
/* USER CODE END 0 */
/**
* @brief The application entry point.
* @retval int
*/
int main(void)
{
/* USER CODE BEGIN 1 */
/* USER CODE END 1 */
/* MCU Configuration--------------------------------------------------------*/
/* Reset of all peripherals, Initializes the Flash interface and the Systick. */
HAL_Init();
/* USER CODE BEGIN Init */
/* USER CODE END Init */
/* Configure the system clock */
SystemClock_Config();
/* USER CODE BEGIN SysInit */
/* USER CODE END SysInit */
/* Initialize all configured peripherals */
MX_GPIO_Init();
MX_USART1_UART_Init();
/* USER CODE BEGIN 2 */
tos_knl_init();
tos_mutex_create(&buffer_locker);
tos_sem_create(&full, 0);
tos_sem_create(&empty, RESOURCE_COUNT_MAX);
(void)tos_task_create(&task_producer, "producer", entry_task_producer, NULL,
4, stack_task_producer, STK_SIZE_TASK_PRODUCER, 0);
(void)tos_task_create(&task_consumer, "consumer", entry_task_consumer, NULL,
4, stack_task_consumer, STK_SIZE_TASK_CONSUMER, 0);
tos_knl_start();
/* USER CODE END 2 */
/* Infinite loop */
/* USER CODE BEGIN WHILE */
while (1)
{
/* USER CODE END WHILE */
/* USER CODE BEGIN 3 */
}
/* USER CODE END 3 */
}
3、運行效果：
源碼鏈接：Git