有什么做兼职的网站比较好,企业门户网站的设计 流程图,北京百姓网,常州网站建设优化在 Linux 系统中#xff0c;进程和线程是两种重要的并发执行单元。本文将详细介绍它们的区别、使用场景、以及多线程编程中的关键API和示例代码。
进程与线程的区别
进程
进程是程序运行的一个实例#xff0c;承担分配系统资源的基本单位。每个进程都有独立的地址空间进程和线程是两种重要的并发执行单元。本文将详细介绍它们的区别、使用场景、以及多线程编程中的关键API和示例代码。
进程与线程的区别
进程
进程是程序运行的一个实例承担分配系统资源的基本单位。每个进程都有独立的地址空间一个进程崩溃不会影响其他进程。进程的创建和切换消耗较多资源。
线程
线程是进程中的一个执行路径是CPU调度的基本单位。线程共享进程的地址空间但每个线程有自己的堆栈和局部变量。线程的创建和切换开销较小。如果一个线程崩溃会导致整个进程崩溃。
使用线程的理由
节省资源创建进程需要分配独立的地址空间建立多个数据表来维护其代码段、数据段和堆栈段这种方式十分昂贵。线程共享同一进程的地址空间和大部分数据启动一个线程比启动一个进程要快很多。一个进程的开销大约是一个线程的30倍。方便的通信机制不同进程之间的数据传递需要通过通信机制如管道、信号等这种方式耗时且复杂。而线程共享进程的数据空间数据共享非常方便和快捷但需要注意数据同步的问题。
多线程开发及API
多线程开发主要包含三点线程、互斥锁、条件变量。以下是具体的操作和API介绍
线程操作
线程的创建
#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否则返回错误编号线程的获取和比较
#include pthread.h
pthread_t pthread_self(void);线程的等待
#include pthread.h
int pthread_join(pthread_t thread, void **rval_ptr);
// 参数
// pthread_t thread等待的线程
// void **rval线程退出状态的收回NULL表示不收回线程的退出
#include pthread.h
int pthread_exit(void *rval_ptr);线程的创建、退出、等待示例
#include stdio.h
#include pthread.hvoid *func1(void *arg)
{static int ret 10;printf(t1:%ld thread is created\n, (unsigned long)pthread_self());printf(t1: parameter is %d\n, *((int *)arg));pthread_exit((void*)ret); // 线程退出
}int main()
{int ret;int param 100;int *pret NULL;pthread_t t1;ret pthread_create(t1, NULL, func1, (void*)param); // 创建线程if(ret 0){printf(main: create t1 success\n);}printf(main: %ld\n, (unsigned long)pthread_self()); // 获取线程IDpthread_join(t1, (void**)pret); // 等待线程退出printf(main: t1 quit with %d\n, *pret);return 0;
}传入一个结构体的线程创建示例
#include stdio.h
#include pthread.h
#include stdlib.hstruct data
{int a;char *s;
};void *func1(void *arg)
{static char *x t1 run out;struct data *temp;temp (struct data*)arg;printf(t1:%ld pthread is created\n, (unsigned long)pthread_self());printf(t1: %d\n, temp-a);printf(t1: %s\n, temp-s);pthread_exit((void*)x);
}int main()
{int ret;pthread_t t1;char *pret NULL;struct data *p (struct data*)malloc(sizeof(struct data));p-a 1;p-s xiancheng;ret pthread_create(t1, NULL, func1, (void*)p);if(ret 0){printf(main: create t1 success\n);}printf(main: %ld\n, (unsigned long)pthread_self());pthread_join(t1, (void**)pret);printf(main: t1 quit with %s\n, pret);free(p);return 0;
}线程共享空间验证示例
#include stdio.h
#include pthread.h
#include unistd.hint g_data 10;void *func1(void *arg)
{printf(t1:%ld thread is created\n, (unsigned long)pthread_self());printf(t1: parameter is %d\n, *((int*)arg));while(1){printf(%d\n, g_data);sleep(1);if(g_data 3){pthread_exit(NULL);}}
}void *func2(void *arg)
{printf(t2:%ld thread is created\n, (unsigned long)pthread_self());printf(t2: parameter is %d\n, *((int*)arg));while(1){printf(%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 success\n);}ret pthread_create(t2, NULL, func2, (void*)param);if(ret 0){printf(main: create t2 success\n);}printf(main: %ld\n, (unsigned long)pthread_self());while(1){printf(%d\n, g_data);sleep(1);} pthread_join(t1, NULL);pthread_join(t2, NULL);return 0;
}互斥锁Mutex
互斥锁API
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 *restrict mutex);加锁及解锁
#include pthread.h
int pthread_mutex_lock(pthread_mutex_t *restrict mutex);
int pthread_mutex_trylock(pthread_mutex_t *restrict mutex);
int pthread_mutex_unlock(pthread_mutex_t *restrict mutex);使用互斥锁的示例
#include stdio.h
#include pthread.h
#include unistd.hint g_data 0;
pthread_mutex_t mutex; // 定义锁void *func1(void *arg)
{pthread_mutex_lock(mutex); // 加锁for(int i 0; i 5; i){printf(t1: %ld thread is created\n, (unsigned long)pthread_self());printf(t1: parameter is %d\n, *((int*)arg));sleep(1);}pthread_mutex_unlock(mutex); // 解锁
}void *func2(void *arg)
{pthread_mutex_lock(mutex);for(int i 0; i 5; i){printf(t2: %ld thread is created\n, (unsigned long)pthread_self());printf(t2: parameter is %d\n, *((int*)arg));sleep(1);}pthread_mutex_unlock(mutex);
}void *func3(void *arg)
{pthread_mutex_lock(mutex);for(int i 0; i 5; i){printf(t3: %ld thread is created\n, (unsigned long)pthread_self());printf(t3: parameter is %d\n, *((int*)arg));sleep(1);}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); // 初始化锁ret pthread_create(t1, NULL, func1, (void*)param);if(ret 0){printf(main: create t1 success\n);}ret pthread_create(t2, NULL, func2, (void*)param);if(ret 0){printf(main: create t2 success\n);}ret pthread_create(t3, NULL, func3, (void*)param);if(ret 0){printf(main: create t3 success\n);}printf(main: %ld\n, (unsigned long)pthread_self());pthread_join(t1, NULL);pthread_join(t2, NULL);pthread_join(t3, NULL);pthread_mutex_destroy(mutex); // 收回锁return 0;
}互斥锁限制共享资源的访问示例
#include stdio.h
#include pthread.h
#include unistd.hint g_data 0;
pthread_mutex_t mutex;void *func1(void *arg)
{printf(t1: %ld pthread is created\n, (unsigned long)pthread_self());printf(t1: parameter is %d\n, *((int*)arg));while(1){pthread_mutex_lock(mutex);printf(%d\n, g_data);sleep(1);if(g_data 3){pthread_mutex_unlock(mutex);pthread_exit(NULL);}}
}void *func2(void *arg)
{printf(t2: %ld pthread is created\n, (unsigned long)pthread_self());printf(t2: parameter is %d\n, *((int*)arg));while(1){printf(%d\n, g_data);pthread_mutex_lock(mutex);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 success\n);}ret pthread_create(t2, NULL, func2, (void*)param);if(ret 0){printf(main: create t2 success\n);}printf(main: %ld\n, (unsigned long)pthread_self());pthread_join(t1, NULL);pthread_join(t2, NULL);pthread_mutex_destroy(mutex);return 0;
}死锁示例
#include stdio.h
#include pthread.h
#include unistd.hpthread_mutex_t mutex;
pthread_mutex_t mutex2;void *func1(void *arg)
{pthread_mutex_lock(mutex);sleep(1);pthread_mutex_lock(mutex2);for(int i 0; i 5; i){printf(t1: %ld\n, (unsigned long)pthread_self());printf(t1: parameter is %d\n, *((int *)arg));sleep(1);}pthread_mutex_unlock(mutex);pthread_mutex_unlock(mutex2);
}void *func2(void *arg)
{pthread_mutex_lock(mutex2);sleep(1);pthread_mutex_lock(mutex);for(int i 0; i 5; i){printf(t2: %ld\n, (unsigned long)pthread_self());printf(t2: parameter is %d\n, *((int *)arg));sleep(1);}pthread_mutex_unlock(mutex2);pthread_mutex_unlock(mutex);
}void *func3(void *arg)
{pthread_mutex_lock(mutex);for(int i 0; i 5; i){printf(t3: %ld\n, (unsigned long)pthread_self());printf(t3: parameter is %d\n, *((int *)arg));sleep(1);}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);pthread_mutex_init(mutex2, NULL);ret pthread_create(t1, NULL, func1, (void*)param);if(ret 0){printf(main: create t1 success\n);}ret pthread_create(t2, NULL, func2, (void*)param);if(ret 0){printf(main: create t2 success\n);}ret pthread_create(t3, NULL, func3, (void*)param);if(ret 0){printf(main: create t3 success\n);}printf(main: %ld\n, (unsigned long)pthread_self());pthread_join(t1, NULL);pthread_join(t2, NULL);pthread_join(t3, NULL);pthread_mutex_destroy(mutex);pthread_mutex_destroy(mutex2);return 0;
}条件变量实现线程同步
条件变量API
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);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, const struct timespec *restrict timeout);触发
#include pthread.h
int pthread_cond_signal(pthread_cond_t *restrict cond);
int pthread_cond_broadcast(pthread_cond_t cond);使用条件变量的示例
#include stdio.h
#include pthread.h
#include unistd.h
#include stdlib.hint g_data 0;
pthread_mutex_t mutex;
pthread_cond_t cond;void *func1(void *arg)
{static int cnt 10;printf(t1: %ld pthread is created\n, (unsigned long)pthread_self());printf(t1: parameter is %d\n, *((int*)arg));while(1){pthread_cond_wait(cond, mutex); // 等待if(g_data 3){printf(t1 run\n);}printf(t1: %d\n, g_data);g_data 0;sleep(1);if(cnt 10){exit(1);}}
}void *func2(void *arg)
{printf(t2: %ld pthread is created\n, (unsigned long)pthread_self());printf(t2: parameter is %d\n, *((int*)arg));while(1){printf(t2: %d\n, g_data);pthread_mutex_lock(mutex);printf(%d\n, g_data);if(g_data 3){pthread_cond_signal(cond); // 触发}pthread_mutex_unlock(mutex);sleep(1);}
}int main()
{int ret;int param 100;pthread_t t1;pthread_t t2;pthread_cond_init(cond, NULL);pthread_mutex_init(mutex, NULL);ret pthread_create(t1, NULL, func1, (void *)param);if(ret 0){printf(main: create t1 success\n);}ret pthread_create(t2, NULL, func2, (void *)param);if(ret 0){printf(main: create t2 success\n);}pthread_join(t1, NULL);pthread_join(t2, NULL);pthread_mutex_destroy(mutex);pthread_cond_destroy(cond);return 0;
}通过上述示例和API的讲解本文详细介绍了Linux下进程与线程的区别、多线程开发的基本操作以及常见问题和解决方案。希望能够帮助大家更好地理解和使用多线程编程。
