Simulate event set in RTOS in linux

insert image description here

how to deal with event sets in linux

In Linux, there is no concept directly corresponding to the event set (Event Set) in the real-time operating system (RTOS). Real-time operating systems usually provide a mechanism that allows tasks or threads to wait and wake up according to the occurrence status of events. This is usually achieved through mechanisms such as semaphores, message queues, and event flags.

In Linux, there are some similar mechanisms that can be used to achieve synchronization and communication between tasks or threads. Here are some common mechanisms:

Semaphores (Semaphores): Linux provides a semaphore mechanism that can be used to control access to shared resources. By using a semaphore, a task or thread can wait for the semaphore to be released in order to continue execution.
Mutex: A mutex is used to protect a shared resource, ensuring that only one task or thread can access the resource at any given time. A task or thread can try to acquire a mutex, and if the mutex is already taken, it will be blocked until the mutex becomes available.
Condition Variables (Condition Variables): Condition variables are used to implement the waiting and notification mechanism between tasks or threads. A task or thread can wait for a certain condition variable to be satisfied and be woken up when the condition is met.
Event Flags (Event Flags): Although Linux itself does not have a specific concept of event sets, other mechanisms can be used to achieve similar functions. For example, you can use a mutex and a condition variable to implement the function of an event flag, and a task or thread waits for an event to occur and is woken up when the event occurs.

These mechanisms can be used to implement synchronization and communication between tasks or threads in Linux, and realize functions similar to event sets in RTOS. Which mechanism to choose depends on the needs and design of the application.

Simulate a simple set of events

The following is a sample program that simulates waiting for multiple events in an RTOS in Linux, using mutexes and condition variables:

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>

pthread_mutex_t mutex;
pthread_cond_t cond;
int event1_flag = 0;
int event2_flag = 0;

void* task1(void* arg) {
    
    
    // 等待事件1发生
    pthread_mutex_lock(&mutex);
    while (event1_flag == 0) {
    
    
        pthread_cond_wait(&cond, &mutex);
    }
    pthread_mutex_unlock(&mutex);

    // 执行任务1
    printf("Task 1: Event 1 occurred!\n");

    pthread_exit(NULL);
}

void* task2(void* arg) {
    
    
    // 等待事件2发生
    pthread_mutex_lock(&mutex);
    while (event2_flag == 0) {
    
    
        pthread_cond_wait(&cond, &mutex);
    }
    pthread_mutex_unlock(&mutex);

    // 执行任务2
    printf("Task 2: Event 2 occurred!\n");

    pthread_exit(NULL);
}

void set_event(int event_num) {
    
    
    pthread_mutex_lock(&mutex);
    if (event_num == 1) {
    
    
        event1_flag = 1;
    } else if (event_num == 2) {
    
    
        event2_flag = 1;
    }
    pthread_cond_broadcast(&cond);
    pthread_mutex_unlock(&mutex);
}

int main() {
    
    
    pthread_t thread1, thread2;

    // 初始化互斥锁和条件变量
    pthread_mutex_init(&mutex, NULL);
    pthread_cond_init(&cond, NULL);

    // 创建线程
    pthread_create(&thread1, NULL, task1, NULL);
    pthread_create(&thread2, NULL, task2, NULL);

    // 模拟事件的发生
    sleep(2);
    printf("Events occurred!\n");
    set_event(1);
    set_event(2);

    // 等待线程结束
    pthread_join(thread1, NULL);
    pthread_join(thread2, NULL);

    // 销毁互斥锁和条件变量
    pthread_mutex_destroy(&mutex);
    pthread_cond_destroy(&cond);

    return 0;
}

In this sample program, there are two tasks (threads): task1 and task2. Each task waits for a different event to occur. The set_event() function is used to set the corresponding event flag and notify all waiting threads through pthread_cond_broadcast().

In the main function, first initialize the mutex and condition variable. Then create two threads to execute task1 and task2 respectively. After a certain delay, simulate the occurrence of an event, and call the set_event() function to set the event flag. After setting the event flag, the waiting thread will be woken up and perform the corresponding task. Finally, wait for the thread to end, and destroy the mutex and condition variable when finished.

Note that this is just a simple example program to demonstrate how to use mutexes and condition variables to simulate the functionality of waiting for multiple events. In actual applications, more threads, more complex event processing logic, and finer synchronization mechanisms may be required to handle more events and tasks.

insert image description here