【回眸】Linux 内核 (十五) 之多线程编程上

前言

进程和线程区别

线程API

1.创建线程

2.线程退出

3.线程等待

4.线程脱离

5. 线程ID获取及比较

6.创建及销毁互斥锁

7.创建及销毁条件变量

8. 等待

9.触发

多线程编程

后记

前言

高产的几天。

进程和线程区别

进程——资源分配的最小单位，线程——程序执行的最小单位

进程有独立的地址空间，线程没有单独的地址空间（同一进程内的线程共享进程的地址空间）。

线程API

多线程开发在 Linux 平台上已经有成熟的 pthread 库支持。其涉及的多线程开发的最基本概念主要包含三点：线程，互斥锁，条件。其中，线程操作又分线程的创建，退出，等待 3 种。互斥锁则包括 4 种操作，分别是创建，销毁，加锁和解锁。条件操作有 5 种操作：创建，销毁，触发，广播和等待。

1.创建线程

#include <pthread.h>
int pthread_create(pthread_t *restrict tidp, const pthread_attr_t *restrict attr, void *(*start_rtn)(void *), void *restrict arg);
// 返回：若成功返回0，否则返回错误编号

2.线程退出

#include <pthread.h>
int pthread_exit(void *rval_ptr);

3.线程等待

#include <pthread.h>
int pthread_join(pthread_t thread, void **rval_ptr);
// 返回：若成功返回0，否则返回错误编号

4.线程脱离

#include <pthread.h>
int pthread_detach(pthread_t thread);
// 返回：若成功返回0，否则返回错误编号

5. 线程ID获取及比较

#include <pthread.h>
pthread_t pthread_self(void);
// 返回：调用线程的ID

#include <pthread.h>
int pthread_equal(pthread_t tid1, pthread_t tid2);
// 返回：若相等则返回非0值，否则返回0

6.创建及销毁互斥锁

#include <pthread.h>
int pthread_mutex_init(pthread_mutex_t *restrict mutex, const pthread_mutexattr_t *restrict attr);
int pthread_mutex_destroy(pthread_mutex_t mutex);
// 返回：若成功返回0，否则返回错误编号

#include <pthread.h>
int pthread_mutex_lock(pthread_mutex_t *mutex)
int pthread_mutex_trylock(pthread_mutex_t *mutex);
int pthread_mutex_unlock(pthread_mutex_t *mutex);
// 返回：若成功返回0，否则返回错误编号

7.创建及销毁条件变量

#include <pthread.h>
int pthread_cond_init(pthread_cond_t *restrict cond, const pthread_condattr_t *restrict attr);
int pthread_cond_destroy(pthread_cond_t cond);
// 返回：若成功返回0，否则返回错误编号

8. 等待

#include <pthread.h>
int pthread_cond_wait(pthread_cond_t *restrict cond, pthread_mutex_t *restrict mutex);
int pthread_cond_timedwait(pthread_cond_t *restrict cond, pthread_mutex_t *restrict mutex, cond struct timespec *restrict timeout);
// 返回：若成功返回0，否则返回错误编号

9.触发

#include <pthread.h>
int pthread_cond_signal(pthread_cond_t cond);
int pthread_cond_broadcast(pthread_cond_t cond);
// 返回：若成功返回0，否则返回错误编号

多线程编程

thread1.c(线程创建)

#include <stdio.h>
#include <pthread.h>void *func1(void *arg){printf("t1:%ld thread is created.\n",(unsigned long)pthread_self());
printf("t1:param is %d\n",*((int *)arg));}int main(){
int ret;
int param =100;
pthread_t t1;
ret = pthread_create(&t1,NULL,func1,(void *)&param);
if(ret == 0){
printf("main:Create t1 sucess.\n");
}
printf("mainID:%ld .\n",(unsigned long)pthread_self());
while(1);return 0;
}

thread2.c（等待和退出，传整数）

#include <stdio.h>
#include <pthread.h>void *func1(void *arg){
static int ret = 10;
printf("t1:%ld thread is created.\n",(unsigned long)pthread_self());
printf("t1:param is %d\n",*((int *)arg));
pthread_exit((void *)&ret);}int main(){
int ret;
int param =100;
int *pret;
pthread_t t1;
ret = pthread_create(&t1,NULL,func1,(void *)&param);
if(ret == 0){
printf("main:Create t1 sucess.\n");
}
printf("mainID:%ld .\n",(unsigned long)pthread_self());
//while(1);
pthread_join(t1,(void **)&pret);
printf("main:t1 exit. ret = %d\n", *pret);
return 0;
}

thread3.c（等待和退出传字符串）

#include <stdio.h>
#include <pthread.h>void *func1(void *arg){
static char *p = "t1 pijiuya1 is runing.\n";
printf("t1:%ld thread is created.\n",(unsigned long)pthread_self());
printf("t1:param is %d\n",*((int *)arg));
pthread_exit((void *)p);//退出}int main(){
int ret;
int param =100;
char *pret = NULL;
pthread_t t1;
ret = pthread_create(&t1,NULL,func1,(void *)&param);
if(ret == 0){
printf("main:Create t1 sucess.\n");
}
printf("mainID:%ld .\n",(unsigned long)pthread_self());
//while(1);
pthread_join(t1,(void **)&pret);//等待
printf("main:t1 exit. ret = %s\n", pret);
return 0;
}

thread4.c（创建2个）

#include <stdio.h>
#include <pthread.h>void *func1(void *arg){
static int ret = 10;
printf("t1:%ld thread is created.\n",(unsigned long)pthread_self());
printf("t1:param is %d\n",*((int *)arg));
pthread_exit((void *)&ret);}int main(){
int ret;
int param =100;
int *pret;
pthread_t t1;
ret = pthread_create(&t1,NULL,func1,(void *)&param);
if(ret == 0){
printf("main:Create t1 sucess.\n");
}
printf("mainID:%ld .\n",(unsigned long)pthread_self());
//while(1);
pthread_join(t1,(void **)&pret);
printf("main:t1 exit. ret = %d\n", *pret);
return 0;
}

thread5.c（创建2个且打印顺序发现多线程共享同一段内存【顺序没有重复】）

#include <stdio.h>
#include <pthread.h>
#include <unistd.h>int g_data = 0;
void *func1(void *arg){printf("t1:%ld thread is created.\n",(unsigned long)pthread_self());
printf("t1:param is %d\n",*((int *)arg));
while(1){
printf("t1:%d\n",g_data++);
sleep(1);
};}
void *func2(void *arg){
printf("t2:%ld thread is created.\n",(unsigned long)pthread_self());
printf("t2:param is %d\n",*((int *)arg));
while(1){
printf("t2:%d\n",g_data++);
sleep(1);
};}
int main(){
int ret;
int param =100;
pthread_t t1;
pthread_t t2;
ret = pthread_create(&t1,NULL,func1,(void *)&param);
if(ret == 0){
printf("main:Create t1 sucess.\n");
}
printf("mainID:%ld .\n",(unsigned long)pthread_self());
ret = pthread_create(&t2,NULL,func2,(void *)&param);
if(ret == 0){
printf("main:Create t2 sucess.\n");
}
printf("mainID:%ld .\n",(unsigned long)pthread_self());
while(1){
printf("main:%d\n",g_data++);
sleep(1);
};
pthread_join(t1,NULL);//等待
pthread_join(t2,NULL);//等待
return 0;
}

抢占资源是随机的，每次运行的结果不尽相同。

thread6.c(创建3个线程并且加锁，让t1优先运行且不被t2 t3 打断，t1 释放锁后，t3和t2竞争资源)

#include <stdio.h>
#include <pthread.h>
#include <unistd.h>pthread_mutex_t mutex;
pthread_attr_t attr;
void *func1(void *arg){
int i ;
pthread_mutex_lock(&mutex);//保证t1优先
for(i = 0;i<5;i++){
printf("t1:%ld thread is created.\n",(unsigned long)pthread_self());
printf("t1:param is %d\n",*((int *)arg));
}
pthread_mutex_unlock(&mutex);}
void *func2(void *arg){
pthread_mutex_lock(&mutex);
printf("t2:%ld thread is created.\n",(unsigned long)pthread_self());
printf("t2:param is %d\n",*((int *)arg));
pthread_mutex_unlock(&mutex);
}
void *func3(void *arg){
pthread_mutex_lock(&mutex);
printf("t3:%ld thread is created.\n",(unsigned long)pthread_self());
printf("t3:param is %d\n",*((int *)arg));
pthread_mutex_unlock(&mutex);
}
int main(){
int ret;
int param =100;
pthread_t t1;
pthread_t t2;
pthread_t t3;
pthread_mutex_init(&mutex,NULL);
ret = pthread_create(&t1,NULL,func1,(void *)&param);
if(ret == 0){
printf("main:Create t1 sucess.\n");
}
ret = pthread_create(&t2,NULL,func2,(void *)&param);
if(ret == 0){
printf("main:Create t2 sucess.\n");
}
ret = pthread_create(&t3,NULL,func3,(void *)&param);
if(ret == 0){
printf("main:Create t3 sucess.\n");
}
printf("mainID:%ld .\n",(unsigned long)pthread_self());pthread_join(t1,NULL);//等待
pthread_join(t2,NULL);//等待
pthread_join(t3,NULL);//等待
pthread_attr_destroy(&attr);
return 0;
}

thread7.c（fun1先运行到10退出锁，func2后运行不退出）

#include <stdio.h>
#include <pthread.h>
#include <unistd.h>pthread_mutex_t mutex;
pthread_attr_t attr;
int g_data = 0;
void *func1(void *arg){
pthread_mutex_lock(&mutex);//保证t1优先
while(1){
printf("t1:%d\n",g_data++);
sleep(1);
if (g_data == 10){
pthread_mutex_unlock(&mutex);
pthread_exit(NULL);
}
}}
void *func2(void *arg){printf("t2:%ld thread is created.\n",(unsigned long)pthread_self());
printf("t2:param is %d\n",*((int *)arg));
while(1){
pthread_mutex_lock(&mutex);
printf("t2:%d\n",g_data);
g_data++;
pthread_mutex_unlock(&mutex);
sleep(1); 
}
}
int main(){
int ret;
int param =100;
pthread_t t1;
pthread_t t2;
pthread_mutex_init(&mutex,NULL);
ret = pthread_create(&t1,NULL,func1,(void *)&param);
if(ret == 0){
printf("main:Create t1 sucess.\n");
}
ret = pthread_create(&t2,NULL,func2,(void *)&param);
if(ret == 0){
printf("main:Create t2 sucess.\n");
}
printf("mainID:%ld .\n",(unsigned long)pthread_self());
printf("main:g_data = %d.\n",g_data);
pthread_join(t1,NULL);//等待
pthread_join(t2,NULL);//等待
pthread_attr_destroy(&attr);
return 0;
}