linux多线程初学讨论

[fly2sky]

初学linux多线程，基本函数的意思也都理解，想做个程序实现个几个线程同时往一个缓冲区里放数据，几个线程取数据，程序放上来，希望能抛砖引玉，忘高手们给挑挑毛病，讲讲逻辑过程最好，看我理解的是否正确！谢谢！

#include<stdio.h>
#include<pthread.h>
#define SIZE 4
struct product
{
pthread_mutex_t mutex;
pthread_cond_t notfull;
pthread_cond_t notempty;
int pos;
int buf[SIZE];
};

void init(struct product *t)
{
pthread_mutex_init(&t->mutex,NULL);
pthread_cond_init(&t->notfull,NULL);
pthread_cond_init(&t->notempty,NULL);
t->pos =-1;
}

void put(struct product *t,int data)
{
pthread_mutex_lock(&t->mutex);
if((t->pos+1)>(SIZE-1))
pthread_cond_wait(&t->notfull,&t->mutex);
t->pos = t->pos +1;
t->buf[t->pos] = data;
printf("Thread %d put a data:%d to pos%d\n",pthread_self(),data,t->pos);
pthread_cond_broadcast(&t->notempty);
pthread_mutex_unlock(&t->mutex);
}

void get(struct product *t)
{
int rtntemp;
pthread_mutex_lock(&t->mutex);
if(t->pos<0)
pthread_cond_wait(&t->notempty,&t->mutex);
printf("Thread %d get a data:%d from pos%d\n",pthread_self(),t->buf[t->pos],t->pos);
rtntemp = t->buf[t->pos];
t->pos = t->pos -1;
pthread_cond_broadcast(&t->notfull);
pthread_mutex_unlock(&t->mutex);
}

struct product pdt;
void *putter()
{
int n;
for(n=0;n<8;n++)
put(&pdt,n);
}

void *getter()
{
int n;
for(n=0;n<8;n++)
get(&pdt);
}


int main(void)
{
pthread_t pt1,pt2,gt1,gt2;
void *retval;
init(&pdt);
pthread_create(&pt1,NULL,putter,0);
pthread_create(&pt2,NULL,putter,0);
pthread_create(>1,NULL,getter,0);
pthread_create(>2,NULL,getter,0);

pthread_join(pt1,&retval);
pthread_join(pt2,&retval);
pthread_join(gt1,&retval);
pthread_join(gt2,&retval);
return 0;
}

[fly2sky]

现在执行结果是：
Thread -1208501328 put a data:0
Thread -1208501328 put a data:1
Thread -1208501328 put a data:2
Thread -1208501328 put a data:3
Thread -1208501328 put a data:4
Thread -1208501328 put a data:5
Thread -1208501328 put a data:6
Thread -1208501328 put a data:7
Thread -1208501328 put a data:8
Thread -1208501328 put a data:9
Thread -1208501328 put a data:10
Thread -1208501328 put a data:11
Thread -1208501328 put a data:12
Thread -1208501328 put a data:13
Thread -1208501328 put a data:14


然后就没有然后了，我有点想不通，为什么就没然后了呢

[fly2sky]

我擦 一发帖就看到一个低级错误，一个应该是 unlock写成lock了

[fly2sky]

Thread -1208394832 put a data:0 to pos0
Thread -1208394832 put a data:1 to pos1
Thread -1208394832 put a data:2 to pos2
Thread -1208394832 put a data:3 to pos3
Thread -1229374544 get a data:3 from pos3
Thread -1229374544 get a data:2 from pos2
Thread -1229374544 get a data:1 from pos1
Thread -1229374544 get a data:0 from pos0
Thread -1208394832 put a data:4 to pos0
Thread -1208394832 put a data:5 to pos1
Thread -1208394832 put a data:6 to pos2
Thread -1208394832 put a data:7 to pos3
Thread -1218884688 put a data:0 to pos4
Thread -1229374544 get a data:0 from pos4
Thread -1229374544 get a data:7 from pos3
Thread -1229374544 get a data:6 from pos2
Thread -1229374544 get a data:5 from pos1
Thread -1239864400 get a data:4 from pos0
Thread -1218884688 put a data:1 to pos0
Thread -1218884688 put a data:2 to pos1
Thread -1218884688 put a data:3 to pos2
Thread -1218884688 put a data:4 to pos3
Thread -1239864400 get a data:4 from pos3
Thread -1218884688 put a data:5 to pos3
Thread -1239864400 get a data:5 from pos3
Thread -1218884688 put a data:6 to pos3
Thread -1239864400 get a data:6 from pos3
Thread -1218884688 put a data:7 to pos3
Thread -1239864400 get a data:7 from pos3
Thread -1239864400 get a data:3 from pos2
Thread -1239864400 get a data:2 from pos1
Thread -1239864400 get a data:1 from pos0

现在结果是这样的~~~

[qq120848369]

太基础了，还是回去闷头学吧。

[fly2sky]

想明白了，结贴，我认为是这样的，是boradcast这里出了问题，当有两个put同时等待的时候，这个时候pos为3的话，boradcast就会让两个线程都得到释放信好，这两个线程相继往下运行，就会出现pos大于SIZE的情况，同样get的时候也可能导致pos小于0的情况。

[赵4老师]

仅供参考

//循环向a函数每次发送200个字节长度（这个是固定的）的buffer,
//a函数中需要将循环传进来的buffer，组成240字节（也是固定的）的新buffer进行处理，
//在处理的时候每次从新buffer中取两个字节打印
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <windows.h>
#include <process.h>
#include <io.h>
//Log{
#define MAXLOGSIZE 10000000
#define ARRSIZE(x) (sizeof(x)/sizeof(x[0]))
#include <time.h>
#include <sys/timeb.h>
#include <stdarg.h>
char logfilename1[]="MyLog1.log";
char logfilename2[]="MyLog2.log";
char logstr[16000];
char datestr[16];
char timestr[16];
char mss[4];
CRITICAL_SECTION cs_log;
FILE *flog;
void Lock(CRITICAL_SECTION *l) {
    EnterCriticalSection(l);
}
void Unlock(CRITICAL_SECTION *l) {
    LeaveCriticalSection(l);
}
void LogV(const char *pszFmt,va_list argp) {
    struct tm *now;
    struct timeb tb;

    if (NULL==pszFmt||0==pszFmt[0]) return;
    if (-1==_vsnprintf(logstr,ARRSIZE(logstr),pszFmt,argp)) logstr[ARRSIZE(logstr)-1]=0;
    ftime(&tb);
    now=localtime(&tb.time);
    sprintf(datestr,"%04d-%02d-%02d",now->tm_year+1900,now->tm_mon+1,now->tm_mday);
    sprintf(timestr,"%02d:%02d:%02d",now->tm_hour     ,now->tm_min  ,now->tm_sec );
    sprintf(mss,"%03d",tb.millitm);
    printf("%s %s.%s %s",datestr,timestr,mss,logstr);
    flog=fopen(logfilename1,"a");
    if (NULL!=flog) {
        fprintf(flog,"%s %s.%s %s",datestr,timestr,mss,logstr);
        if (ftell(flog)>MAXLOGSIZE) {
            fclose(flog);
            if (rename(logfilename1,logfilename2)) {
                remove(logfilename2);
                rename(logfilename1,logfilename2);
            }
            flog=fopen(logfilename1,"a");
            if (NULL==flog) return;
        }
        fclose(flog);
    }
}
void Log(const char *pszFmt,...) {
    va_list argp;

    Lock(&cs_log);
    va_start(argp,pszFmt);
    LogV(pszFmt,argp);
    va_end(argp);
    Unlock(&cs_log);
}
//Log}
#define ASIZE    200
#define BSIZE    240
#define CSIZE      2
char Abuf[ASIZE];
char Cbuf[CSIZE];
CRITICAL_SECTION cs_HEX ;
CRITICAL_SECTION cs_BBB ;
struct FIFO_BUFFER {
    int  head;
    int  tail;
    int  size;
    char data[BSIZE];
} BBB;
int No_Loop=0;
void HexDump(int cn,char *buf,int len) {
    int i,j,k;
    char binstr[80];

    Lock(&cs_HEX);
    for (i=0;i<len;i++) {
        if (0==(i%16)) {
            sprintf(binstr,"%03d %04x -",cn,i);
            sprintf(binstr,"%s %02x",binstr,(unsigned char)buf[i]);
        } else if (15==(i%16)) {
            sprintf(binstr,"%s %02x",binstr,(unsigned char)buf[i]);
            sprintf(binstr,"%s  ",binstr);
            for (j=i-15;j<=i;j++) {
                sprintf(binstr,"%s%c",binstr,('!'<buf[j]&&buf[j]<='~')?buf[j]:'.');
            }
            Log("%s\n",binstr);
        } else {
            sprintf(binstr,"%s %02x",binstr,(unsigned char)buf[i]);
        }
    }
    if (0!=(i%16)) {
        k=16-(i%16);
        for (j=0;j<k;j++) {
            sprintf(binstr,"%s   ",binstr);
        }
        sprintf(binstr,"%s  ",binstr);
        k=16-k;
        for (j=i-k;j<i;j++) {
            sprintf(binstr,"%s%c",binstr,('!'<buf[j]&&buf[j]<='~')?buf[j]:'.');
        }
        Log("%s\n",binstr);
    }
    Unlock(&cs_HEX);
}
int GetFromRBuf(int cn,CRITICAL_SECTION *cs,FIFO_BUFFER *fbuf,char *buf,int len) {
    int lent,len1,len2;

    lent=0;
    Lock(cs);
    if (fbuf->size>=len) {
        lent=len;
        if (fbuf->head+lent>BSIZE) {
            len1=BSIZE-fbuf->head;
            memcpy(buf     ,fbuf->data+fbuf->head,len1);
            len2=lent-len1;
            memcpy(buf+len1,fbuf->data           ,len2);
            fbuf->head=len2;
        } else {
            memcpy(buf     ,fbuf->data+fbuf->head,lent);
            fbuf->head+=lent;
        }
        fbuf->size-=lent;
    }
    Unlock(cs);
    return lent;
}
void thdB(void *pcn) {
    char        *recv_buf;
    int          recv_nbytes;
    int          cn;
    int          wc;
    int          pb;

    cn=(int)pcn;
    Log("%03d thdB              thread begin...\n",cn);
    while (1) {
        Sleep(10);
        recv_buf=(char *)Cbuf;
        recv_nbytes=CSIZE;
        wc=0;
        while (1) {
            pb=GetFromRBuf(cn,&cs_BBB,&BBB,recv_buf,recv_nbytes);
            if (pb) {
                Log("%03d recv %d bytes\n",cn,pb);
                HexDump(cn,recv_buf,pb);
                Sleep(1);
            } else {
                Sleep(1000);
            }
            if (No_Loop) break;//
            wc++;
            if (wc>3600) Log("%03d %d==wc>3600!\n",cn,wc);
        }
        if (No_Loop) break;//
    }
}
int PutToRBuf(int cn,CRITICAL_SECTION *cs,FIFO_BUFFER *fbuf,char *buf,int len) {
    int lent,len1,len2;

    Lock(cs);
    lent=len;
    if (fbuf->size+lent>BSIZE) {
        lent=BSIZE-fbuf->size;
    }
    if (fbuf->tail+lent>BSIZE) {
        len1=BSIZE-fbuf->tail;
        memcpy(fbuf->data+fbuf->tail,buf     ,len1);
        len2=lent-len1;
        memcpy(fbuf->data           ,buf+len1,len2);
        fbuf->tail=len2;
    } else {
        memcpy(fbuf->data+fbuf->tail,buf     ,lent);
        fbuf->tail+=lent;
    }
    fbuf->size+=lent;
    Unlock(cs);
    return lent;
}
void thdA(void *pcn) {
    char        *send_buf;
    int          send_nbytes;
    int          cn;
    int          wc;
    int           a;
    int          pa;

    cn=(int)pcn;
    Log("%03d thdA              thread begin...\n",cn);
    a=0;
    while (1) {
        Sleep(100);
        memset(Abuf,a,ASIZE);
        a=(a+1)%256;
        if (16==a) {No_Loop=1;break;}//去掉这句可以让程序一直循环直到按Ctrl+C或Ctrl+Break或当前目录下存在文件No_Loop
        send_buf=(char *)Abuf;
        send_nbytes=ASIZE;
        Log("%03d sending %d bytes\n",cn,send_nbytes);
        HexDump(cn,send_buf,send_nbytes);
        wc=0;
        while (1) {
            pa=PutToRBuf(cn,&cs_BBB,&BBB,send_buf,send_nbytes);
            Log("%03d sent %d bytes\n",cn,pa);
            HexDump(cn,send_buf,pa);
            send_buf+=pa;
            send_nbytes-=pa;
            if (send_nbytes<=0) break;//
            Sleep(1000);
            if (No_Loop) break;//
            wc++;
            if (wc>3600) Log("%03d %d==wc>3600!\n",cn,wc);
        }
        if (No_Loop) break;//
    }
}
int main() {
    InitializeCriticalSection(&cs_log );
    Log("Start===========================================================\n");
    InitializeCriticalSection(&cs_HEX );
    InitializeCriticalSection(&cs_BBB );

    BBB.head=0;
    BBB.tail=0;
    BBB.size=0;

    _beginthread((void(__cdecl *)(void *))thdA,0,(void *)1);
    _beginthread((void(__cdecl *)(void *))thdB,0,(void *)2);

    if (!access("No_Loop",0)) {
        remove("No_Loop");
        if (!access("No_Loop",0)) {
            No_Loop=1;
        }
    }
    while (1) {
        Sleep(1000);
        if (No_Loop) break;//
        if (!access("No_Loop",0)) {
            No_Loop=1;
        }
    }
    Sleep(3000);
    DeleteCriticalSection(&cs_BBB );
    DeleteCriticalSection(&cs_HEX );
    Log("End=============================================================\n");
    DeleteCriticalSection(&cs_log );
    return 0;
}