int pthread_mutex_destroy(pthread_mutex_t *mutex)；

互斥量加锁和解锁

int pthread_mutex_lock(pthread_mutex_t *mutex);
int pthread_mutex_unlock(pthread_mutex_t *mutex);
返回值:成功返回0,失败返回错误号

调用 pthread_lock是，可能会遇到以下情况

互斥量处于未上锁状态，该函数会讲把互斥量锁定返回成功

如何发起函数调用时，其他线程已锁定互斥量，没有竞争到互斥量资源，此时pthread_lock调用会陷入阻塞，直到互斥量解锁

修该上面的售票代码

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <pthread.h>
#include <sched.h>
int ticket = 100;
pthread_mutex_t mutex;
void *route(void *arg)
{
char *id = (char*)arg;
while ( 1 ) {
pthread_mutex_lock(&mutex);if ( ticket > 0 ) {
usleep(1000);
printf("%s sells ticket:%d\n", id, ticket);
ticket--;
pthread_mutex_unlock(&mutex);
// sched_yield(); 放弃CPU
} 
else {
pthread_mutex_unlock(&mutex);
break;
}}}int main( void )
{
pthread_t t1, t2, t3, t4;
pthread_mutex_init(&mutex, NULL);
pthread_create(&t1, NULL, route, "thread 1");
pthread_create(&t2, NULL, route, "thread 2");
pthread_create(&t3, NULL, route, "thread 3");
pthread_create(&t4, NULL, route, "thread 4");
pthread_join(t1, NULL);
pthread_join(t2, NULL);
pthread_join(t3, NULL);
pthread_join(t4, NULL);
pthread_mutex_destroy(&mutex);
}

1-3 互斥量的封装

test_4_22_httpserve/Mutex.h · liu xi peng/linux---ubuntu系统 - 码云 - 开源中国

大家有兴趣的可以点进去看一下

2.线程同步

2-1 条件变量

当一个线程互斥地访问某个变量时，他可能发现在其他线程状态改变之前他什么也做不了

例如⼀个线程访问队列时，发现队列为空，它只能等待，只到其它线程将⼀个节点添加到队列

2-2 同步概念与竞态条件

#include <iostream>
#include <string.h>
#include <unistd.h>
#include <pthread.h>
pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
void *active( void *arg )
{
std::string name = static_cast<const char*>(arg);
while (true){
pthread_mutex_lock(&mutex);
pthread_cond_wait(&cond, &mutex);
std::cout << name << " 活动..." << std::endl;
pthread_mutex_unlock(&mutex);
}
}
int main( void )
{
pthread_t t1, t2;
pthread_create(&t1, NULL, active, (void*)"thread-1");
pthread_create(&t2, NULL, active, (void*)"thread-2");
sleep(3); // 可有可⽆，这⾥确保两个线程已经在运⾏
while(true)
{
// 对⽐测试
// pthread_cond_signal(&cond); // 唤醒⼀个线程
pthread_cond_broadcast(&cond); // 唤醒所有线程
sleep(1);
}pthread_join(t1, NULL);
pthread_join(t2, NULL);
}