linux系统和网络(三):IO,信号,信号量,线程

本文主要探讨linux的IO,信号,信号量,线程相关知识,详细知识可参考本博客其他文章。

信号（可参考本博客其他文章）
信号是内容受限的异步通信机制,硬件异常后统内核发出信号

alarm产生SIGALARM信号,读端关闭后管道write产生SIGPIPE信号

常见信号
SIGINT             2         Ctrl+C(前台进程组中每个进程)
SIGABRT            6         异常终止
SIGPOLL   SIGIO    8         异步IO
SIGKILL            9         杀死进程
SIGSEGV            11        无效存储访问信号
SIGPIPE            13        管道,socket
SIGALARM           14        alarm
SIGTERM            15        kill命令默认
SIGCHLD            17        子进程终止(父进程接收信号)
SIGUSR1            10        自定义信号
SIGUSR2            12        自定义信号

信号处理

typedef void (*sighandler_t)(int);
sighandler_t signal(int signum, sighandler_t handler);

默认处理SIG_DFL
忽略处理SIG_IGN
捕获处理handler
返回出错为SIG_ERR

int sigaction(int signum, const struct sigaction *act,struct sigaction *oldact);
struct sigaction {
               void     (*sa_handler)(int);
               void     (*sa_sigaction)(int, siginfo_t *, void *);
               sigset_t   sa_mask;
               int        sa_flags;
               void     (*sa_restorer)(void);
           };

sigaction可设置新捕获函数和获取旧的捕获函数,signal须在新捕获函数中获取旧捕获函数

alarm和pause

alarm内核提供闹钟的API

unsigned int alarm(unsigned int seconds);

int pause(void);

内核挂起,进程暂停运行,交出CPU给其他进程(阻塞住),需被信号唤醒

信号量（可参考本博客其他文章）

sem_t sem; 
int sem_init(sem_t *sem, int pshared, unsigned int value);
int sem_destroy(sem_t *sem);
int sem_wait(sem_t *sem);
int sem_post(sem_t *sem);
sem：信号量,pshared：0线程间非0用于进程,value：信号量初值

IO
        阻塞IO：wait、pause、sleep、read、write等
        非阻塞IO访问：添加O_NONBLOCK模式(fd调用fcntl)
        select和poll(多路复用IO):外部阻塞式，内部非阻塞式自动轮询多路阻塞式IO

int poll(struct pollfd *fds, nfds_t nfds, int timeout);
struct pollfd {
               int   fd;         /* 文件描述符*/
               short events;     /* 监控事件 */
               short revents;    /* 监控事件中满足条件的返回事件*/
           };

POLLIN普通或带外优先数据可读,即POLLRDNORM | POLLRDBAND
POLLRDNORM 数据可读
POLLRDBAND 优先级带数据可读
POLLPRI 高优先级可读数据
POLLOUT普通或带外数据可写
POLLWRNORM 数据可写
POLLWRBAND 优先级带数据可写
POLLERR 发生错误
POLLHUP 发生挂起
POLLNVAL 描述字不是一个打开的文件

nfds：监控文件描述符个数

timeout：等待(ms),-1阻塞等,0：不阻塞进程,>0等待指定毫秒数

int select(int nfds, fd_set *readfds, fd_set *writefds,fd_set *exceptfds, struct timeval *timeout);

nfds：监控文件描述符个数

struct timeval {
               long    tv_sec;         /* seconds */
               long    tv_usec;        /* microseconds */
           };

       and

           struct timespec {
               long    tv_sec;         /* seconds */
               long    tv_nsec;        /* nanoseconds */
           };

FD_ZERO(fd_set* fdset)： 将fd_set位初始化为0
FD_SET（int fd, fd_set* fdset）：注册文件描述符fd信息
FD_CLR(int fd, fd_set* fdset)：清除文件描述符fd信息
FD_ISSET(int fd, fd_set* fdset)：fd_set包含文件描述符fd信息返回真

异步IO(操作系统中断)
存储映射IO(mmap):共享内存,提高效率(LCD显示和IPC间共享内存)

线程（可参考本博客其他文章）
进程:CPU时分复用,实现多任务系统需求,进程间切换开销大,通信效率低
线程间通信效率高且可多任务

线程函数
线程创建,退出,回收,分离,id

int pthread_create(pthread_t *thread, const pthread_attr_t *attr,void *(*start_routine) (void *), void *arg);
void pthread_exit(void *retval);
int pthread_join(pthread_t thread, void **retval);
int pthread_detach(pthread_t thread);
pthread_t pthread_self(void);

线程退出后,主线程pthread_join回收子线程,pthread_detach是线程分离,子线程自回收

取消线程

int pthread_cancel(pthread_t thread);

线程取消状态
int pthread_setcancelstate(int state, int *oldstate);
PTHREAD_CANCEL_ENABLE：线程可取消(默认值)
PTHREAD_CANCEL_DISABLE：线程不可取消,取消请求挂起至线程状态为 PTHREAD_CANCEL_ENABLE

线程取消性类型
int pthread_setcanceltype(int type, int *oldtype);
PTHREAD_CANCEL_DEFERRED：取消请求到达,线程继续运行,取消请求挂起,直到线程到达取消点(默认)
PTHREAD_CANCEL_ASYNCHRONOUS：立即取消

线程清理函数中添加和移除清理函数
void pthread_cleanup_push(void (*routine)(void *),void *arg);
void pthread_cleanup_pop(int execute);
routine:清理函数,arg给清理函数传参
execute为0清理函数不调用且清理函数栈中最顶层函数移除,非0还清除清理该函数
线程清理函数中添加(入栈)和清理(出栈)次数相同

互斥量(代码保护)

pthread_mutex_t mutex;
int pthread_mutex_lock(pthread_mutex_t *mutex);
int pthread_mutex_unlock(pthread_mutex_t *mutex);
int pthread_mutex_destroy(pthread_mutex_t *mutex);
int pthread_mutex_init(pthread_mutex_t *restrict mutex,const pthread_mutexattr_t *restrict attr);

线程条件

pthread_cond_t  cond;
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 abstime);
int pthread_cond_broadcast(pthread_cond_t *cond);
int pthread_cond_signal(pthread_cond_t *cond);

demo1:

linux的sleep命令

#include <stdio.h>
#include <unistd.h>
#include <signal.h>

void func(int sig)
{

}

void my_sleep(unsigned int sec)
{
        struct sigaction act = {0};
        act.sa_handler = func;
        sigaction(SIGALRM, &act, NULL);
        alarm(sec);
        pause();
}


int main(int argc,char *argv[])
{
        if(argc != 2)
                printf("ex: ./a.out sec");
        printf("my_sleep start\n");
        my_sleep(atoi(argv[1]));
        printf("my_sleep end\n");

        return 0;
}

结果显示：

demo2：

多路io（poll）监控鼠标和键盘

#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <poll.h>

int main(void)
{
        int fd;
        int ret;
        char buf[256];
        struct pollfd fds[2] = {0};

        fd = open("/dev/input/mouse0", O_RDONLY);
        if (fd < 0)
        {
                perror("open");
                return -1;
        }

        fds[0].fd = 0;
        fds[0].events = POLLIN;

        fds[1].fd = fd;
        fds[1].events = POLLIN;

        ret = poll(fds,2, 10000);
        if (ret < 0)
        {
                perror("poll");
                return -1;
        }
        else if (ret == 0)
        {
                printf("timeout\n");
        }
        else
        {
                if (fds[0].events == fds[0].revents)
                {
                        memset(buf, 0, sizeof(buf));
                        read(0, buf, 5);
                        printf("keyboard:%s\n", buf);
                }

                if (fds[1].events == fds[1].revents)
                {
                        memset(buf, 0, sizeof(buf));
                        read(fd, buf, 50);
                        printf("mouse:%s\n", buf);
                }
        }

        return 0;
}

结果显示:

多路io（select）监控鼠标和键盘

#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/select.h>
#include <sys/time.h>


int main()
{
        int fd;
        int ret;
        char buf[256];
        fd_set set;
        struct timeval tm;

        fd = open("/dev/input/mouse0", O_RDONLY);
        if (fd < 0)
        {
                perror("open:");
                return -1;
        }

        FD_ZERO(&set);
        FD_SET(fd, &set);
        FD_SET(0, &set);

        tm.tv_sec = 10;
        tm.tv_usec = 0;

        ret = select(fd+1, &set, NULL, NULL, &tm);
        if (ret < 0)
        {
                perror("select");
                return -1;
        }
        else if (ret == 0)
        {
                printf("timeout\n");
        }
        else
        {
                if (FD_ISSET(0, &set))
                {
                        memset(buf, 0, sizeof(buf));
                        read(0, buf, 5);
                        printf("keyboard:%s\n", buf);
                }

                if (FD_ISSET(fd, &set))
                {
                        memset(buf, 0, sizeof(buf));
                        read(fd, buf, 50);
                        printf("mouse:%s\n", buf);
                }
        }

        return 0;
}

结果显示：

异步IO监控鼠标和键盘 (可配合poll.selectshi用)

#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <signal.h>

int mouse_fd;

void func(int sig)
{
        char buf[200] = {0};

        if (sig != SIGIO)
                return;

        read(mouse_fd, buf, 50);
        if(strlen(buf))
                printf("mouse:%s\n", buf);
}

int main()
{
        char buf[200];
        int flag = -1;

        mouse_fd = open("/dev/input/mouse0", O_RDONLY);
        if (mouse_fd < 0)
        {
                perror("open:");
                return -1;
        }

        //获取 mouse_fd
        flag = fcntl(mouse_fd, F_GETFL);
        //add O_ASYNC(异步)
        flag |= O_ASYNC;
        //重写 mouse_fd
        fcntl(mouse_fd, F_SETFL, flag);
        //设置 mouse_fd 接收SIGIO/SIGURG信号且与进程绑定
        fcntl(mouse_fd, F_SETOWN, getpid());

        signal(SIGIO, func);

        while (1)
        {
                memset(buf, 0, sizeof(buf));
                read(0, buf, 5);
                if(strlen(buf))
                        printf("keyboard:%s\n", buf);
        }

        return 0;
}

结果显示:

demo3:

字符输入和个数计算（线程+信号量）

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

char buf[256] = {0};
sem_t sem;
unsigned int flag = 0;


void *func(void *arg)
{
        sem_wait(&sem);
        while (flag == 0)
        {
                printf("the num of string :%ld\n", strlen(buf));
                memset(buf, 0, sizeof(buf));
                sem_wait(&sem);
        }

        pthread_exit(NULL);
}


int main(void)
{
        int ret;
        pthread_t th;

        sem_init(&sem, 0, 0);

        ret = pthread_create(&th, NULL, func, NULL);
        if (ret != 0)
        {
                printf("pthread_create error\n");
                exit(-1);
        }

        printf("input string:\n");
        while (scanf("%s", buf))
        {
                if (!strncmp(buf, "end", 3))
                {
                        printf("process end\n");
                        flag = 1;
                        sem_post(&sem);
                        break;
                }

                sem_post(&sem);
        }

        ret = pthread_join(th, NULL);
        if (ret != 0)
        {
                printf("join error\n");
                exit(-1);
        }

        printf("join sucess\n");
        sem_destroy(&sem);

        return 0;
}

结果显示：