IMX6:pthread_cond_t条件变量测试

news2024/9/28 23:34:02

简介

pthread_cond_t是一个条件变量的数据类型，用于线程间的同步和通信。它通常与互斥锁（pthread_mutex_t）一起使用，以实现线程的等待和唤醒操作。

以下是两个与pthread_cond_t相关的函数的介绍：

pthread_cond_init：用于初始化条件变量。它接受两个参数，第一个参数是指向条件变量的指针，第二个参数是指向条件变量属性的指针。如果不需要特殊属性，可以将第二个参数设置为NULL。该函数在成功时返回0，否则返回错误代码。

pthread_cond_destroy：用于销毁条件变量。它接受一个参数，即指向条件变量的指针。该函数在成功时返回0，否则返回错误代码。

条件变量相关函数

int pthread_cond_init(pthread_cond_t *cv, const pthread_condattr_t *a);

int pthread_cond_destroy(pthread_cond_t *cv);

int pthread_cond_signal (pthread_cond_t *cv);

int pthread_cond_broadcast (pthread_cond_t *cv);

int pthread_cond_wait (pthread_cond_t *cv, pthread_mutex_t *external_mutex);

int pthread_cond_timedwait(pthread_cond_t *cv, pthread_mutex_t *external_mutex, const struct timespec *t);

int pthread_cond_timedwait_relative_np(pthread_cond_t *cv, pthread_mutex_t *external_mutex, const struct timespec *t);

互斥锁相关函数

int pthread_mutex_lock(pthread_mutex_t *m);

int pthread_mutex_timedlock(pthread_mutex_t *m, const struct timespec *ts);

int pthread_mutex_unlock(pthread_mutex_t *m);

int pthread_mutex_trylock(pthread_mutex_t *m);

int pthread_mutex_init(pthread_mutex_t *m, const pthread_mutexattr_t *a);

int pthread_mutex_destroy(pthread_mutex_t *m);

测试源码：

#include <sys/epoll.h>
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <fcntl.h>
#include <errno.h>
#include <pthread.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#define _DEBUG_INFO
#ifdef _DEBUG_INFO
#define DEBUG_INFO(format, ...) printf("%s:%s:%d -- "format"\n" \
,__FILE__,__func__,__LINE__ \
, ##__VA_ARGS__)
#else
#define DEBUG_INFO(format, ...)
#endif

struct my_struct {
    pthread_cond_t cond;
    pthread_mutex_t mutex;
    int run;
};

void * my_func1(void * arg){
    struct my_struct *p = (struct my_struct *)arg;
    pthread_mutex_lock(&p->mutex);
    DEBUG_INFO("Main thread waking up the other thread...\n");
    pthread_cond_signal(&p->cond);
    DEBUG_INFO("I want to sleep");
    sleep(1);
    DEBUG_INFO("Are you waiting me?Yes,You must wait");
    pthread_mutex_unlock(&p->mutex);
    DEBUG_INFO("task 1 exit");
    return NULL;
}

void * my_func2(void * arg){
    struct my_struct *p = (struct my_struct *)arg;
    pthread_mutex_lock(&p->mutex);
    DEBUG_INFO("Thread waiting...\n");
    pthread_cond_wait(&p->cond, &p->mutex);
    DEBUG_INFO("Thread woken up!\n");
    pthread_mutex_unlock(&p->mutex);
    p->run = 0;
    return NULL;
}

int main(int argc, char *argv[]){
    pthread_t p1,p2;
    int ret;
    struct my_struct *p = malloc(sizeof(struct my_struct));    
    if(p == NULL){
        return NULL;
    }
    pthread_cond_init(&p->cond,NULL);
    pthread_mutex_init(&p->mutex,NULL);
    p->run = 1;
    ret = pthread_create(&p1,NULL,my_func1,p);
    if(ret < 0){
        perror("pthread_create");
        DEBUG_INFO("pthread_create");
        return -1;
    }
    pthread_detach(p1);

    ret = pthread_create(&p2,NULL,my_func2,p);
    if(ret < 0){
        perror("pthread_create");
        DEBUG_INFO("pthread_create");
        return -1;
    }
    pthread_detach(p2);

    while (p->run)
    {
        sleep(1);
    }
    
    DEBUG_INFO("bye bye");
    return 0;
}

CMakeLists.txt

project(libevent_project)
cmake_minimum_required(VERSION 3.8)
message(STATUS "lkmao:CMAKE_SOURCE_DIR -- ${CMAKE_SOURCE_DIR}")

SET(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -pthread -g -Wall")
SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -pthread -lstdc++")

# add_executable(app epoll.c)
# add_executable(app epoll2.c)
add_executable(app cond.c)

编译脚本：

#!/bin/bash
set -e
rm -rf _build_
mkdir _build_ -p
cmake -S ./ -B _build_
make -C _build_
# ./_build_/main_01
# ./_build_/app
echo ""
file ./_build_/app
echo ""
./_build_/app hello.txt