- 作業(yè)
- 用代碼實(shí)現(xiàn)汽車(chē)發(fā)動(dòng)以及停車(chē),乘客上車(chē),售票員等功能
#include<stdio.h>
#include<string.h>
#include<unistd.h> //fork
#include<stdlib.h>
#include<sys/types.h>//kill()
#include<signal.h> //signal
pid_t pid=-1;
//司機(jī):到站停車(chē)--->SIGINT Ctrl+c
// 關(guān)門(mén)開(kāi)車(chē)--->SIGUSR1
void handleDrive(int sig)
{
if(SIGINT==sig)
{
printf("到站了...\n");
sleep(1);
printf("司機(jī)開(kāi)始停車(chē)\n");
sleep(1);
int ret = 0;
ret = kill(pid,SIGUSR2);//發(fā)送信號(hào)給子進(jìn)程,發(fā)送信號(hào)給售票員讓她開(kāi)門(mén)
if (-1 == ret)
{
perror("kill");
}
}
else if(SIGUSR1==sig)
{
printf("司機(jī)開(kāi)始開(kāi)車(chē)\n");
sleep(1);
printf("車(chē)正在跑\n");
sleep(1);
}
}
//管理員:開(kāi)門(mén)--->SIGUSR2
void handleConductor(int sig)
{
if(SIGUSR2==sig)
{
printf("售票員開(kāi)門(mén)\n");
sleep(1);
printf("乘客上車(chē)\n");
sleep(1);
printf("售票員關(guān)門(mén)\n");
sleep(1);
kill(getppid(),SIGUSR1);//售票員發(fā)送信號(hào)給司機(jī)開(kāi)車(chē)
}
}
int main()
{
pid=fork();
if(pid>0)//drive
{
signal(SIGINT,handleDrive);//注冊(cè)信號(hào)
signal(SIGUSR1,handleDrive);
printf("司機(jī)等待售票員做好開(kāi)車(chē)準(zhǔn)備\n");
while(1)
{
pause();
}
}
else if(pid==0)//conductor
{
signal(SIGINT,SIG_IGN);
signal(SIGUSR2,handleConductor);
sleep(1);
//發(fā)送和一個(gè)開(kāi)車(chē)信號(hào)，讓其開(kāi)車(chē)
kill(getppid(),SIGUSR1);
while(1)
{
pause();//有信號(hào)則返回，無(wú)信號(hào)就掛起
}
}
else if(pid==-1)//創(chuàng)建進(jìn)程失敗
{
perror("fork");
return -1;
}
return 0;
}
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線(xiàn)程
并發(fā)執(zhí)行
- 同時(shí)存在,同時(shí)運(yùn)行.(并不是同時(shí)運(yùn)行的,分給A10ms,運(yùn)行完之后,則掛起,再給B10ms.由于時(shí)間很短,人為看不出來(lái),以為是同時(shí)運(yùn)行的)
時(shí)間片
創(chuàng)建線(xiàn)程
- 編譯時(shí)一定要加-pthread
- 以下程序:測(cè)試兩個(gè)線(xiàn)程是否同時(shí)運(yùn)行
- 是交替執(zhí)行,不是并發(fā)
#include<pthread.h> //pthread_create()
#include<stdio.h>
#include<string.h>//strerror()
#include<errno.h> //errno
#include<stdlib.h>
void *thread_run(void *arg)
{
while(1)
{
printf("this is thread_run...\n");
sleep(1);
}
return NULL;
}
int main()
{
pthread_t thread;
int ret=0;
ret=pthread_create(&thread,NULL,thread_run,NULL);//現(xiàn)在線(xiàn)程的屬性默認(rèn)為NULL
if(0!=ret)
{
printf("errno:%d,error:%s\n",ret,strerror(ret));
return -1;
}
while(1)
{
printf("this is main...\n");
sleep(1);
}
return 0;
}
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- 5s之后將線(xiàn)程結(jié)束,但是main函數(shù)繼續(xù)執(zhí)行
//使用return,只能結(jié)束當(dāng)前線(xiàn)程,exit會(huì)將該線(xiàn)程所屬的進(jìn)程掛掉,當(dāng)然線(xiàn)程也會(huì)掛斷
- 一個(gè)進(jìn)程創(chuàng)建線(xiàn)程后,創(chuàng)建的線(xiàn)程同屬于該進(jìn)程,不獨(dú)立于進(jìn)程,共享進(jìn)程的所有資源.
- 線(xiàn)程是最小的執(zhí)行單元,若一個(gè)進(jìn)程沒(méi)有創(chuàng)建線(xiàn)程,我們既可以把它看作是進(jìn)程,也可以是相當(dāng)于線(xiàn)程,若一個(gè)進(jìn)程創(chuàng)建線(xiàn)程之后,我們可以將該線(xiàn)程稱(chēng)之為主線(xiàn)程,一個(gè)進(jìn)程可以創(chuàng)建多個(gè)線(xiàn)程,線(xiàn)程之間資源共享
#include<pthread.h> //pthread_create()
#include<stdio.h>
#include<string.h>//strerror()
#include<errno.h> //errno
#include<stdlib.h>
void *thread_run(void *arg)
{
int i=0;//將這個(gè)線(xiàn)程,5s之后結(jié)束
while(1)
{
printf("this is thread_run...\n");
sleep(1);
i++;
if(i==5)
{
return NULL;
}
}
return NULL;
}
int main()
{
pthread_t thread;
int ret=0;
ret=pthread_create(&thread,NULL,thread_run,NULL);//現(xiàn)在線(xiàn)程的屬性默認(rèn)為NULL
if(0!=ret)
{
printf("errno:%d,error:%s\n",ret,strerror(ret));
return -1;
}
while(1)
{
printf("this is main...\n");
sleep(1);
}
return 0;
}
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- 使用exit之后,exit會(huì)將該線(xiàn)程所屬的進(jìn)程掛掉,當(dāng)然線(xiàn)程也會(huì)掛斷
#include<pthread.h> //pthread_create()
#include<stdio.h>
#include<string.h>//strerror()
#include<errno.h> //errno
#include<stdlib.h>
void *thread_run(void *arg)
{
int i=0;//將這個(gè)線(xiàn)程,5s之后結(jié)束
while(1)
{
printf("this is thread_run...\n");
sleep(1);
i++;
if(i==5)
{
//使用return,只能結(jié)束當(dāng)前線(xiàn)程,exit會(huì)將該線(xiàn)程所屬的進(jìn)程掛掉,當(dāng)然線(xiàn)程也會(huì)掛掉
exit(1);
}
}
return NULL;
}
int main()
{
pthread_t thread;
int ret=0;
ret=pthread_create(&thread,NULL,thread_run,NULL);//現(xiàn)在線(xiàn)程的屬性默認(rèn)為NULL
if(0!=ret)
{
printf("errno:%d,error:%s\n",ret,strerror(ret));
return -1;
}
while(1)
{
printf("this is main...\n");
sleep(1);
}
return 0;
}
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- 資源共享
#include<pthread.h> //pthread_create()
#include<stdio.h>
#include<string.h>//strerror()
#include<errno.h> //errno
#include<stdlib.h>
int g_iData=999;
void *thread_run(void *arg)
{
//while(1)
{
printf("this is thread_run...iData=%d\n",g_iData);
g_iData++;
// sleep(1);
}
return NULL;
}
int main()
{
pthread_t thread;
int ret=0;
ret=pthread_create(&thread,NULL,thread_run,NULL);//現(xiàn)在線(xiàn)程的屬性默認(rèn)為NULL
if(0!=ret)
{
printf("errno:%d,error:%s\n",ret,strerror(ret));
return -1;
}
sleep(2);
// while(1)
{
printf("this is main...iData=%d\n",g_iData);
// sleep(1);
}
return 0;
}
- 沒(méi)有將iData拷貝一份,而是資源共享
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參數(shù)的傳遞
- 將地址傳給他
#include<pthread.h> //pthread_create()
#include<stdio.h>
#include<string.h>//strerror()
#include<errno.h> //errno
#include<stdlib.h>
#include<unistd.h>
void *thread_run(void *arg)
{
while(1)
{
printf("this is thread_run...arg=%d\n",*(int *)arg);
printf("this is thread_run...arg=%d\n",(int)arg);
sleep(1);
}
return NULL;
}
int main()
{
pthread_t thread;
int ret=0;
int iArg=1999;
ret=pthread_create(&thread,NULL,thread_run,&iArg);//將參數(shù)的地址傳給他
if(0!=ret)
{
printf("errno:%d,error:%s\n",ret,strerror(ret));
return -1;
}
while(1)
{
printf("this is main...\n");
sleep(1);
}
return 0;
}
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#include<pthread.h> //pthread_create()
#include<stdio.h>
#include<string.h>//strerror()
#include<errno.h> //errno
#include<stdlib.h>
#include<unistd.h>
void *thread_run(void *arg)
{
while(1)
{
printf("this is thread_run...arg=%d\n",(int)arg);
sleep(1);
}
return NULL;
}
int main()
{
pthread_t thread;
int ret=0;
int iArg=1999;
pthread_create(&thread,NULL,thread_run,(void *)iArg);//或者(void *)1888效果如上
if(0!=ret)
{
printf("errno:%d,error:%s\n",ret,strerror(ret));
return -1;
}
while(1)
{
printf("this is main...\n");
sleep(1);
}
return 0;
}
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- 將結(jié)構(gòu)體傳給他
#include<pthread.h> //pthread_create()
#include<stdio.h>
#include<string.h>//strerror()
#include<errno.h> //errno
#include<stdlib.h>
#include<unistd.h>
typedef struct Student
{
int iId;
char caName[32];
float fScore;
}Student;
void *thread_run(void *arg)
{
while(1)
{
Student *pStu=(Student *)arg;
printf("id:%d,name:%s,score:%.2f\n",pStu->iId,pStu->caName,pStu->fScore);
sleep(1);
}
return NULL;
}
int main()
{
pthread_t thread;
int ret=0;
int iArg=1999;
Student stu={1001,"zhangsan",89};
ret=pthread_create(&thread,NULL,thread_run,&stu);
// ret=pthread_create(&thread,NULL,thread_run,(void *)stu);//這種方法不可以
if(0!=ret)
{
printf("errno:%d,error:%s\n",ret,strerror(ret));
return -1;
}
while(1)
{
printf("this is main...\n");
sleep(1);
}
return 0;
}
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pthread cancel(發(fā)送一個(gè)請(qǐng)求)
#include<pthread.h> //pthread_create()
#include<stdio.h>
#include<string.h>//strerror()
#include<errno.h> //errno
#include<stdlib.h>
void *thread_run(void *arg)
{
//在線(xiàn)程函數(shù)中調(diào)用pthread_setcancelstate來(lái)設(shè)置
//不同意結(jié)束線(xiàn)程請(qǐng)求,阻塞線(xiàn)程結(jié)束請(qǐng)求
//直到線(xiàn)程允許接收線(xiàn)程結(jié)束請(qǐng)求
pthread_setcancelstate(PTHREAD_CANCEL_DISABLE,NULL);
while(1)
{
printf("this is thread_run...\n");
sleep(1);
}
return NULL;
}
int main()
{
pthread_t thread;
int ret=0;
ret=pthread_create(&thread,NULL,thread_run,NULL);//現(xiàn)在線(xiàn)程的屬性默認(rèn)為NULL
if(0!=ret)
{
printf("errno:%d,error:%s\n",ret,strerror(ret));
return -1;
}
sleep(3);
//發(fā)送一個(gè)結(jié)束線(xiàn)程請(qǐng)求給指定線(xiàn)程,默認(rèn)情況下,線(xiàn)程會(huì)同意該結(jié)束線(xiàn)程請(qǐng)求,還可以設(shè)置不同意
pthread_cancel(thread);//3秒之后讓線(xiàn)程掛掉
while(1)//測(cè)試是否掛掉,如果掛掉了,則會(huì)打印this is main
{
printf("this is main...\n");
sleep(1);
}
return 0;
}
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pthread_exit
#include<pthread.h> //pthread_create()
#include<stdio.h>
#include<string.h>//strerror()
#include<errno.h> //errno
#include<stdlib.h>
void *thread_run(void *arg)
{
//在線(xiàn)程函數(shù)中調(diào)用pthread_setcancelstate來(lái)設(shè)置
//不同意結(jié)束線(xiàn)程請(qǐng)求,阻塞線(xiàn)程結(jié)束請(qǐng)求
//直到線(xiàn)程允許接收線(xiàn)程結(jié)束請(qǐng)求
pthread_setcancelstate(PTHREAD_CANCEL_DISABLE,NULL);
while(1)
{
printf("this is thread_run...\n");
sleep(1);
}
return NULL;
}
int main()
{
pthread_t thread;
int ret=0;
ret=pthread_create(&thread,NULL,thread_run,NULL);//現(xiàn)在線(xiàn)程的屬性默認(rèn)為NULL
if(0!=ret)
{
printf("errno:%d,error:%s\n",ret,strerror(ret));
return -1;
}
sleep(3);
//若存在主線(xiàn)程中,如果含有其他線(xiàn)程存在,則阻塞等待其他線(xiàn)程結(jié)束明若沒(méi)有其他線(xiàn)程,則結(jié)束
pthread_exit(NULL);
while(1)//測(cè)試是否掛掉,如果掛掉了,則會(huì)打印this is main
{
printf("this is main...\n");
sleep(1);
}
return 0;
}
- 一直等待其他線(xiàn)程的結(jié)束,則退出.如果其他線(xiàn)程結(jié)束,則退出
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#include<pthread.h> //pthread_create()
#include<stdio.h>
#include<string.h>//strerror()
#include<errno.h> //errno
#include<stdlib.h>
void *thread_run(void *arg)
{
//在線(xiàn)程函數(shù)中調(diào)用pthread_setcancelstate來(lái)設(shè)置
//不同意結(jié)束線(xiàn)程請(qǐng)求,阻塞線(xiàn)程結(jié)束請(qǐng)求
//直到線(xiàn)程允許接收線(xiàn)程結(jié)束請(qǐng)求
pthread_setcancelstate(PTHREAD_CANCEL_DISABLE,NULL);
while(1)
{
printf("this is thread_run...\n");
sleep(1);
break;//則執(zhí)行一次,退出程序
}
return NULL;
}
int main()
{
pthread_t thread;
int ret=0;
ret=pthread_create(&thread,NULL,thread_run,NULL);//現(xiàn)在線(xiàn)程的屬性默認(rèn)為NULL
if(0!=ret)
{
printf("errno:%d,error:%s\n",ret,strerror(ret));
return -1;
}
sleep(3);
//若存在主線(xiàn)程中,如果含有其他線(xiàn)程存在,則阻塞等待其他線(xiàn)程結(jié)束,若沒(méi)有其他線(xiàn)程,則結(jié)束
pthread_exit(NULL);
while(1)//測(cè)試是否掛掉,如果掛掉了,則會(huì)打印this is main
{
printf("this is main...\n");
sleep(1);
}
return 0;
}
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#include<pthread.h> //pthread_create()
#include<stdio.h>
#include<string.h>//strerror()
#include<errno.h> //errno
#include<stdlib.h>
void *thread_run(void *arg)
{
//在線(xiàn)程函數(shù)中調(diào)用pthread_setcancelstate來(lái)設(shè)置
//不同意結(jié)束線(xiàn)程請(qǐng)求,阻塞線(xiàn)程結(jié)束請(qǐng)求
//直到線(xiàn)程允許接收線(xiàn)程結(jié)束請(qǐng)求
pthread_setcancelstate(PTHREAD_CANCEL_DISABLE,NULL);
while(1)
{
printf("this is thread_run...\n");
sleep(1);
break;//則執(zhí)行一次,退出程序
pthread_exit(NULL);//如果放在此處,則表示結(jié)束所屬線(xiàn)程
}
return NULL;
}
int main()
{
pthread_t thread;
int ret=0;
ret=pthread_create(&thread,NULL,thread_run,NULL);//現(xiàn)在線(xiàn)程的屬性默認(rèn)為NULL
if(0!=ret)
{
printf("errno:%d,error:%s\n",ret,strerror(ret));
return -1;
}
sleep(3);
while(1)//測(cè)試是否掛掉,如果掛掉了,則會(huì)打印this is main
{
printf("this is main...\n");
sleep(1);
}
return 0;
}
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pthread_join等待線(xiàn)程結(jié)束,若線(xiàn)程在運(yùn)行,則阻塞等待,若線(xiàn)程結(jié)束,立即返回,第一個(gè)參數(shù):要等待的線(xiàn)程,第二個(gè)參數(shù):要來(lái)獲得線(xiàn)程的返回值
#include<pthread.h> //pthread_create()
#include<stdio.h>
#include<string.h>//strerror()
#include<errno.h> //errno
#include<stdlib.h>
void *thread_run(void *arg)
{
while(1)
{
printf("this is thread_run...\n");
sleep(1);
}
return NULL;
}
int main()
{
pthread_t thread;
int ret=0;
ret=pthread_create(&thread,NULL,thread_run,NULL);//現(xiàn)在線(xiàn)程的屬性默認(rèn)為NULL
if(0!=ret)
{
printf("errno:%d,error:%s\n",ret,strerror(ret));
return -1;
}
//等待線(xiàn)程結(jié)束,若線(xiàn)程在運(yùn)行,則阻塞等待,若線(xiàn)程結(jié)束,立即返回,第一個(gè)參數(shù):要等待的線(xiàn)程,第二個(gè)參數(shù):要來(lái)獲得線(xiàn)程的返回值
pthread_join(thread,NULL);
while(1)
{
printf("this is main...\n");
sleep(1);
}
return 0;
}
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#include<pthread.h> //pthread_create()
#include<stdio.h>
#include<string.h>//strerror()
#include<errno.h> //errno
#include<stdlib.h>
void *thread_run(void *arg)
{
while(1)
{
printf("this is thread_run...\n");
sleep(1);
break;
}
return NULL;
}
int main()
{
pthread_t thread;
int ret=0;
ret=pthread_create(&thread,NULL,thread_run,NULL);//現(xiàn)在線(xiàn)程的屬性默認(rèn)為NULL
if(0!=ret)
{
printf("errno:%d,error:%s\n",ret,strerror(ret));
return -1;
}
//等待線(xiàn)程結(jié)束,若線(xiàn)程在運(yùn)行,則阻塞等待,若線(xiàn)程結(jié)束,立即返回,第一個(gè)參數(shù):要等待的線(xiàn)程,第二個(gè)參數(shù):要來(lái)獲得線(xiàn)程的返回值
pthread_join(thread,NULL);
while(1)
{
printf("this is main...\n");
sleep(1);
}
return 0;
}
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pthread_addNum
#include<pthread.h> //pthread_create()
#include<stdio.h>
#include<string.h>//strerror()
#include<errno.h> //errno
#include<stdlib.h>
int g_iData=0;
void *thread_run(void *arg)
{
while(1)
{
++g_iData;
printf("thread :data=%d\n",g_iData);
}
return NULL;
}
int main()
{
pthread_t thread;
int ret=0;
ret=pthread_create(&thread,NULL,thread_run,NULL);//現(xiàn)在線(xiàn)程的屬性默認(rèn)為NULL
if(0!=ret)
{
printf("errno:%d,error:%s\n",ret,strerror(ret));
return -1;
}
while(1)
{
++g_iData;
printf("main :data=%d\n",g_iData);
}
return 0;
}
- g_iData=0;A線(xiàn)程++g_iData,如果線(xiàn)程A時(shí)間足夠的話(huà),則g_iData=1;B線(xiàn)程再執(zhí)行,則變?yōu)?;
- 若A時(shí)間片不夠,雖然++了但++后的值還沒(méi)有返回到g_iData里,所以B線(xiàn)程++后的值仍然為1
- 如下,會(huì)出現(xiàn)中斷的情況
Paste_Image.png
- 解決以上情況,則定義一個(gè)原子鎖
#include<pthread.h> //pthread_create()
#include<stdio.h>
#include<string.h>//strerror()
#include<errno.h> //errno
#include<stdlib.h>
pthread_mutex_t mutex; //互斥量或者稱(chēng)為鎖
int g_iData=0;
void *thread_run(void *arg)
{
while(1)
{
//使用pthread_mutex_lock和pthread_mutex_unlock
//使它們之間的語(yǔ)句合成原子操作
pthread_mutex_lock(&mutex);
++g_iData;
printf("thread :data=%d\n",g_iData);
pthread_mutex_unlock(&mutex);
}
return NULL;
}
int main()
{
//初始化互斥量,NULL表示使用默認(rèn)屬性初始化該互斥量
pthread_mutex_init(&mutex,NULL);//使用他的默認(rèn)屬性進(jìn)行初始化
pthread_t thread;
int ret=0;
ret=pthread_create(&thread,NULL,thread_run,NULL);//現(xiàn)在線(xiàn)程的屬性默認(rèn)為NULL
if(0!=ret)
{
printf("errno:%d,error:%s\n",ret,strerror(ret));
return -1;
}
while(1)
{
pthread_mutex_lock(&mutex);
++g_iData;
printf("main :data=%d\n",g_iData);
pthread_mutex_unlock(&mutex);
}
return 0;
}
- 這樣就不會(huì)出現(xiàn)中斷的情況
一個(gè)線(xiàn)程從文件讀取數(shù)據(jù),另一個(gè)線(xiàn)程打印出來(lái)
- 先通過(guò)以前的代碼,在文件里寫(xiě)入幾個(gè)同學(xué)的信息
#include <stdio.h>
#include <unistd.h> //write() read()
#include <errno.h> //errno
#include <string.h> //strerror()
/*open()*/
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <pthread.h> //pthread_create
pthread_mutex_t mutex;
#define NAME_LEN 32
typedef struct Student
{
int iId;
char caName[NAME_LEN];
char cSex;
float fScore;
}Student;
int myOpen(const char *pathname)
{
int fd = -1;
if (NULL != pathname)
{
fd = open(pathname, O_RDONLY | O_CREAT
, S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
if (-1 == fd)
{
printf("open error: %s\n", strerror(errno));
}
}
return fd;
}
int g_iSign = 0;
void *read_thread(void *arg)
{
int fd = -1;
fd = myOpen("stu.info");
if (-1 != fd)
{
int ret = -1;
Student *pStu = (Student *)arg;
while (1)
{
if (0 == g_iSign)
{
pthread_mutex_lock(&mutex);
memset(pStu, '\0', sizeof(Student));
ret = read(fd, pStu, sizeof(Student));
if (0 == ret)
{
printf("reached the file end\n");
pthread_mutex_unlock(&mutex);
g_iSign = 1;
break;
}
else if (-1 == ret)
{
printf("read error:%s\n", strerror(errno));
pthread_mutex_unlock(&mutex);
g_iSign = 1;
break;
}
pthread_mutex_unlock(&mutex);
g_iSign = 1;
}
}
close(fd);
}
return NULL;
}
void *print_thread(void *arg)
{
Student *pStu = (Student *)arg;
int i = 0;
while (1)
{
if (1 == g_iSign)
{
pthread_mutex_lock(&mutex);
if (0 == pStu->iId)
{
pthread_mutex_unlock(&mutex);
break;
}
printf("id:%d, name:%s, sex:%c, score:%.1f\n"
, pStu->iId, pStu->caName
, pStu->cSex, pStu->fScore);
pthread_mutex_unlock(&mutex);
g_iSign = 0;
}
}
return NULL;
}
int main(void)
{
pthread_mutex_init(&mutex, NULL);
Student stu;
pthread_t pthr_read;
pthread_t pthr_show;
pthread_create(&pthr_read, NULL, read_thread, &stu);
pthread_create(&pthr_show, NULL, print_thread, &stu);
pthread_join(pthr_read, NULL);
pthread_join(pthr_show, NULL);
return 0;
}
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信號(hào)量(sem_wait)
//int sem_init();//pshared
#include <stdio.h>
#include <unistd.h> //write() read()
#include <errno.h> //errno
#include <string.h> //strerror()
/*open()*/
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <pthread.h> //pthread_create
#include <semaphore.h>
pthread_mutex_t mutex;
sem_t read_sem;//讀的信號(hào)量
sem_t print_sem;//顯示的信號(hào)量
#define NAME_LEN 32
typedef struct Student
{
int iId;
char caName[NAME_LEN];
char cSex;
float fScore;
}Student;
int myOpen(const char *pathname)
{
int fd = -1;
if (NULL != pathname)
{
fd = open(pathname, O_RDONLY | O_CREAT
, S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
if (-1 == fd)
{
printf("open error: %s\n", strerror(errno));
}
}
return fd;
}
void *read_thread(void *arg)
{
int fd = -1;
fd = myOpen("stu.info");
if (-1 != fd)
{
int ret = -1;
Student *pStu = (Student *)arg;
while (1)
{
//如果read_sem大于0,接著往下執(zhí)行,并且將該變量減1,如果等于0,則阻塞,直到該值大于0
sem_wait(&read_sem);//此時(shí)read_sem=1
pthread_mutex_lock(&mutex);
memset(pStu, '\0', sizeof(Student));
ret = read(fd, pStu, sizeof(Student));
if (0 == ret)
{
printf("reached the file end\n");
pthread_mutex_unlock(&mutex);
sem_post(&print_sem);//出錯(cuò)了,發(fā)送這個(gè)信號(hào)
break;
}
else if (-1 == ret)
{
printf("read error:%s\n", strerror(errno));
pthread_mutex_unlock(&mutex);
sem_post(&print_sem);//出錯(cuò)了,發(fā)送這個(gè)信號(hào)
break;
}
pthread_mutex_unlock(&mutex);
sem_post(&print_sem);//出錯(cuò)了,發(fā)送這個(gè)信號(hào)
}
close(fd);
}
return NULL;
}
void *print_thread(void *arg)
{
Student *pStu = (Student *)arg;
int i = 0;
while (1)
{
//如果print_sem大于0,接著往下執(zhí)行,并且將該變量減1,如果等于0,則阻塞,直到該值大于0
sem_wait(&print_sem);
pthread_mutex_lock(&mutex);
if (0 == pStu->iId)
{
pthread_mutex_unlock(&mutex);
sem_post(&read_sem);
break;
}
printf("id:%d, name:%s, sex:%c, score:%.1f\n"
, pStu->iId, pStu->caName
, pStu->cSex, pStu->fScore);
pthread_mutex_unlock(&mutex);
//將信號(hào)量的值加1
sem_post(&read_sem);
}
return NULL;
}
int main(void)
{
pthread_mutex_init(&mutex, NULL);
sem_init(&read_sem,0,1);//對(duì)信號(hào)量的初始化,必須先讀才能再顯示,將read_sem的值置為1
sem_init(&print_sem,0,0);//將print_sem的值置為0
Student stu;
pthread_t pthr_read;
pthread_t pthr_show;
pthread_create(&pthr_read, NULL, read_thread, &stu);
pthread_create(&pthr_show, NULL, print_thread, &stu);
pthread_join(pthr_read, NULL);
pthread_join(pthr_show, NULL);
return 0;
}
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用代碼模仿5個(gè)哲學(xué)家進(jìn)餐問(wèn)題
- 創(chuàng)建5根筷子(5個(gè)信號(hào)量創(chuàng)建一組信號(hào)量)
- 創(chuàng)建5科學(xué)家
- 獲得筷子
- 放下筷子
- 繼續(xù)思考
int semop(int semid, struct sembuf *sops, unsigned nsops);
參數(shù)
- semid：信號(hào)集的識(shí)別碼，可通過(guò)semget獲取。
- sops：指向存儲(chǔ)信號(hào)操作結(jié)構(gòu)的數(shù)組指針，信號(hào)操作結(jié)構(gòu)的原型如下
struct sembuf
{
unsigned short sem_num; /* semaphore number */
short sem_op; /* semaphore operation */
short sem_flg; /* operation flags */
};
- 這三個(gè)字段的意義分別為：
- sem_num：操作信號(hào)在信號(hào)集中的編號(hào)，第一個(gè)信號(hào)的編號(hào)是0。
- sem_op：
- 1, 如果其值為正數(shù)，該值會(huì)加到現(xiàn)有的信號(hào)內(nèi)含值中。
通常用于釋放所控資源的使用權(quán)； - 2, 如果sem_op的值為負(fù)數(shù)，而其絕對(duì)值又大于信號(hào)的現(xiàn)值，
操作將會(huì)阻塞，直到信號(hào)值大于或等于sem_op的絕對(duì)值。
通常用于獲取資源的使用權(quán)； - 3, 如果sem_op的值為0，如果沒(méi)有設(shè)置IPC_NOWAIT，
則調(diào)用該操作的進(jìn)程或者線(xiàn)程將暫時(shí)睡眠，直到信號(hào)量的值為0； 否則，進(jìn)程或者線(xiàn)程不會(huì)睡眠，函數(shù)返回錯(cuò)誤EAGAIN。
- sem_flg：信號(hào)操作標(biāo)志，可能的選擇有兩種
- 1, IPC_NOWAIT //對(duì)信號(hào)的操作不能滿(mǎn)足時(shí)，semop()不會(huì)阻塞，
并立即返回，同時(shí)設(shè)定錯(cuò)誤信息。 - 2, SEM_UNDO //程序結(jié)束時(shí)(不論正常或不正常)，
保證信號(hào)值會(huì)被重設(shè)為semop()調(diào)用前的值。
這樣做的目的在于避免程序在異常情況下結(jié)束時(shí)
未將鎖定的資源解鎖，造成該資源永遠(yuǎn)鎖定。
- nsops：信號(hào)操作結(jié)構(gòu)的數(shù)量，恒大于或等于1。
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <string.h>//perror()
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <unistd.h>
#include <stdio.h>
union semun
{
int val;
struct semid_ds *buf;
unsigned short *array;
struct seminfo *__buf;
};
void getChopsticks(int iNum,int *semfd)
{
int iLeft=iNum;
int iRight=(iNum+1)%5;
struct sembuf semope[2]={{iLeft,-1,0},
{iRight,-1,0}};
semop(*semfd,semope,2);//拿筷子,獲得左右兩邊的筷子
}
void putChopsticks(int iNum,int *semfd)
{
int iLeft=iNum;
int iRight=(iNum+1)%5;
struct sembuf semope[2]={{iLeft,1,0},
{iRight,1,0}};
semop(*semfd,semope,2);//拿筷子,獲得左右兩邊的筷子
}
void thinkAndEat(int iNum,int *semfd)
{
while(1)
{
printf("%d say:I am thinking...\n",iNum);
/*拿筷子吃飯*/
getChopsticks(iNum,semfd);
sleep(1);
printf("%d say:I am eatting...\n",iNum);
/*放下筷子*/
putChopsticks(iNum,semfd);
printf("%d say:I am puting chopsticks...\n",iNum);
sleep(1);
}
}
int main(void)
{
int semfd=-1;
//獲得信號(hào)量集的標(biāo)識(shí),若信號(hào)量集不存在則創(chuàng)建
semfd=semget(0x1024,5,IPC_CREAT | 0777);//5,代表5個(gè)信號(hào)量
if(-1==semfd)
{
perror("semget");
return -1;
}
//對(duì)信號(hào)集中的信號(hào)量進(jìn)行賦值
union semun sem;
sem.val=1;
int i=0;
for(;i<5;i++)
{
if(-1==semctl(semfd,i,SETVAL,sem))
{
perror("semctl");
return -1;
}
}
//創(chuàng)建5個(gè)哲學(xué)家進(jìn)程
int iNum=0;//用來(lái)保存表示第幾個(gè)科學(xué)家
pid_t pid=-1;
for(i=0;i<4;i++)
{
pid=fork();
if(pid>0)//parent
{
iNum=4;
}
else if(pid==0)//child
{
iNum=i;
break;//
}
else if(pid==-1)//error
{
return -1;
}
}
thinkAndEat(iNum,&semfd);
return 0;
}
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