线程从队列中获取其他线程的IPC消息（Linux）

Question

当我在Linux上有两个不同的IPC消息队列时，有时会抓取来自错误队列的消息。

以下玩具程序显示问题，可以在不同的处理器上重复。

任何帮助都非常感谢！

伯特

/*
    To compile;
    gcc MM.c -o mm -fno-stack-protector -pthread

    We want Mickey to send a message to Minnie exclusively.
    We want Donald to send a message to pluto exclusively.

    Problem: Pluto intercepts Minnie's messages.

    Listing gives:

    $ ./mm
    Mickey thread successfully started.
    Minnie thread successfully started.
    Pluto thread successfully started.
    Donald thread successfully started.
    Donald sent a message to Pluto.
    Mickey sent a message to Minnie.
    Pluto received: Sit, Pluto!

    Minnie received: Hello, Minnie!

    Mickey sent a message to Minnie.  (100 times)

    Pluto received: Hello, Minnie!
*/
#include <sys/types.h>
#include <sys/msg.h>
#include <sys/ipc.h>
#include <string.h>
#include <stdio.h>

pthread_t t1,t2,t3,t4;  

// Mickey send
key_t ipcMickey;
int mqMickeyid;
char helloMickeymsg[] = {"Hello, Minnie!"};
struct { long type; char text[100]; } myMickeymsg;

// Minnie get
int mqMinnieid;
struct { long type; char text[100]; } myMinniemsg;

// Donald send
key_t ipcDonald;
int mqDonaldid;
char helloDonaldmsg[] = {"Sit, Pluto!"};
struct { long type; char text[100]; } myDonaldmsg;

// Pluto get
int mqPlutoid;
struct { long type; char text[100]; } myPlutomsg;

static void * DONALDthreadFunc(void *arg)
{
    printf("Donald thread successfully started.\n");
    char *s = (char *) arg;

    while(1)
    {
        //send
        memset(myDonaldmsg.text, 0, 100); 
        strncpy(myDonaldmsg.text, helloDonaldmsg, strlen(helloDonaldmsg));
        myDonaldmsg.type = 1;
        msgsnd(mqDonaldid, &myDonaldmsg, sizeof(myDonaldmsg), 0);
        printf("Donald sent a message to Pluto.\r\n");
        sleep(4);
    }

    /* just a formality */
    return (void *) strlen(s);
}

static void * PLUTOthreadFunc(void *arg)
{
    printf("Pluto thread successfully started.\n");
    char *s = (char *) arg;

    while(1)
    {
        //receive
        mqPlutoid = msgget(ipcDonald, 0);
        msgrcv(mqPlutoid, &myPlutomsg, sizeof(myPlutomsg), 0, 0);
        printf("Pluto received: %s\r\n\r\n", myPlutomsg.text);
        sleep(1);
    }

    /* just a formality */
    return (void *) strlen(s);
}

static void * MICKEYthreadFunc(void *arg)
{
    printf("Mickey thread successfully started.\n");
    char *s = (char *) arg;

    while(1)
    {
        //send
        memset(myMickeymsg.text, 0, 100); 
        strncpy(myMickeymsg.text, helloMickeymsg, strlen(helloMickeymsg));
        myMickeymsg.type = 1;
        msgsnd(mqMickeyid, &myMickeymsg, sizeof(myMickeymsg), 0);
        printf("Mickey sent a message to Minnie.\r\n");
        usleep(10000);
    }

    /* just a formality */
    return (void *) strlen(s);
}

static void * MINNIEthreadFunc(void *arg)
{
    printf("Minnie thread successfully started.\n");
    char *s = (char *) arg;

    while(1)
    {
        //receive
        mqMinnieid = msgget(ipcMickey, 0);
        msgrcv(mqMinnieid, &myMinniemsg, sizeof(myMinniemsg), 0, 0);
        printf("Minnie received: %s\r\n\r\n", myMinniemsg.text);
        sleep(3);
    }

    return (void *) strlen(s);
}

int main (void) 
{
        ipcMickey = ftok("/tmp/mqmickey", 63);
        mqMickeyid = msgget(ipcMickey, IPC_CREAT | 0666);

    ipcDonald = ftok("/tmp/mqdonald", 69);
        mqDonaldid = msgget(ipcDonald, IPC_CREAT | 0666);

    pthread_create(&t1, NULL, MICKEYthreadFunc, "Mickey sends\n");
    pthread_create(&t2, NULL, MINNIEthreadFunc, "Minnie replies\n");
    pthread_create(&t3, NULL, DONALDthreadFunc, "Donald sends\n");
    pthread_create(&t4, NULL, PLUTOthreadFunc, "Pluto replies\n");

    while(1)
    {
        sleep(5);
    }
}

Answer 1

问题是您错过了错误处理。

包含

ipcMickey = ftok("/tmp/mqmickey", 63);
if (-1==ipcMickey)
{
    perror("ipcMickey");
    exit(255);
}
ipcDonald = ftok("/tmp/mqdonald", 69);
if (-1==ipcDonald)
{
    perror("ipcDonald");
    exit(255);
}

你很快就会找到

./mm
ipcDonald: No such file or directory

在这种情况下，ftok的返回值为-1。如果两个文件都丢失，则两个ipc密钥都为-1，表示所有流量共享同一个端口：）

所以

touch /tmp/mqmickey /tmp/mqdonald

修复它。一些统计数据（用usleep(random()%10000)替换睡眠）：

gcc MM.c -o mm -O3 -fno-stack-protector -pthread
time ./mm | { trap "" INT; sort | uniq -c | tee stats; } 
  16047 
      1 Donald sent a 
   8054 Donald sent a message to Pluto.
      1 Donald thread successfully started.
   8040 Mickey sent a message to Minnie.
      1 Mickey thread successfully started.
   8065 Minnie received: Hello, Minnie!
      1 Minnie thread successfully started.
   7982 Pluto received: Sit, Pluto!
      1 Pluto thread successfully started.


real    0m40.814s
user    0m0.168s
sys 0m0.092s

Answer 2

非常感谢你和VJo，

这是该程序的修改版本，考虑到您的所有评论。

希望这对其他人有用。

伯特

/*
    We want Mickey to send a message to Minnie exclusively.
    We want Donald to send a message to pluto exclusively.  

    To compile:
    gcc mm.c -o mm -fno-stack-protector -pthread

    Requires: 
    syslog enabled and started.

    To test:
    time ./mm | { trap "" INT; sort | uniq -c | tee stats; } 

    Results:
    1503373 Donald sent a message to Pluto.
          1 Donald thread successfully started.
    1423964 Mickey sent a message to Minnie.
          1 Mickey thread successfully started.
    1423958  Minnie received: Hello, Minnie!
          1 Minnie thread successfully started.
    1503333 Pluto received: Sit, Pluto!
          1 Pluto thread successfully started.

    real    0m17.133s
    user    0m16.053s
    sys 0m5.248s

*/
#include <sys/types.h>
#include <sys/msg.h>
#include <sys/ipc.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <syslog.h>


#define MQMICKEY "/tmp/MQMickey"
#define MQDONALD "/tmp/MQDonald"

pthread_t t1,t2,t3,t4;
FILE *fMickeypointer;
FILE *fDonaldpointer;

// Mickey send
key_t ipcMickey;
int mqMickeyid;
char helloMickeymsg[] = {"Hello, Minnie!"};
struct { long type; char text[100]; } myMickeymsg;

// Minnie get
int mqMinnieid;
struct { long type; char text[100]; } myMinniemsg;

// Donald send
key_t ipcDonald;
int mqDonaldid;
char helloDonaldmsg[] = {"Sit, Pluto!"};
struct { long type; char text[100]; } myDonaldmsg;

// Pluto get
int mqPlutoid;
struct { long type; char text[100]; } myPlutomsg;

static void * DONALDthreadFunc(void *arg)
{
    printf("Donald thread successfully started.\n");
    char *s = (char *) arg;

    while(1)
    {
        //send
        memset(myDonaldmsg.text, 0, 100);
        strncpy(myDonaldmsg.text, helloDonaldmsg, strlen(helloDonaldmsg));
        myDonaldmsg.type = 1;
        msgsnd(mqDonaldid, &myDonaldmsg, sizeof(myDonaldmsg), 0);
        printf("Donald sent a message to Pluto.\r\n"); 
    }

    /* just a formality */
    return (void *) strlen(s);
}

static void * PLUTOthreadFunc(void *arg)
{
    printf("Pluto thread successfully started.\n");
    char *s = (char *) arg;

    while(1)
    {
        //receive
        mqPlutoid = msgget(ipcDonald, 0);
        msgrcv(mqPlutoid, &myPlutomsg, sizeof(myPlutomsg), 0, 0);
        printf("Pluto received: %s\r\n", myPlutomsg.text);
    }

    /* just a formality */
    return (void *) strlen(s);
}

static void * MICKEYthreadFunc(void *arg)
{
    printf("Mickey thread successfully started.\n");
    char *s = (char *) arg;

    while(1)
    {
        //send
        memset(myMickeymsg.text, 0, 100);
        strncpy(myMickeymsg.text, helloMickeymsg, strlen(helloMickeymsg));
        myMickeymsg.type = 1;
        msgsnd(mqMickeyid, &myMickeymsg, sizeof(myMickeymsg), 0);
        printf("Mickey sent a message to Minnie.\r\n");
    }

    /* just a formality */
    return (void *) strlen(s);
}

static void * MINNIEthreadFunc(void *arg)
{
    printf("Minnie thread successfully started.\n");
    char *s = (char *) arg;

    while(1)
    {
        //receive
        mqMinnieid = msgget(ipcMickey, 0);
        msgrcv(mqMinnieid, &myMinniemsg, sizeof(myMinniemsg), 0, 0);
        printf(" Minnie received: %s\r\n", myMinniemsg.text);
    }

    return (void *) strlen(s);
}

int main (void)
{
    /* 
        MUST create the target files first.

        The return of ftok is -1 if file is missing. If BOTH files are missing, both ipc keys 
        will be -1, meaning all traffic shares the same port. Result: one queue will acquire
        messages not intended for it!
    */
    fMickeypointer = fopen(MQMICKEY, "a");
    if(fMickeypointer == NULL) 
    {
        printf("Failed to create Mickey queue file.\n");

        /* system logging */
        setlogmask (LOG_UPTO (LOG_NOTICE));
        openlog ("MickeyDonald", LOG_CONS | LOG_PID | LOG_NDELAY, LOG_LOCAL1);
        syslog (LOG_NOTICE, "Failed to create Mickey queue file." );
        closelog ();
        exit(91);
    }

    fDonaldpointer = fopen(MQDONALD, "a");
    if(fDonaldpointer == NULL) 
    {
        printf("Failed to create Donald queue file.\r\n");

        /* system logging */
        setlogmask (LOG_UPTO (LOG_NOTICE));
        openlog ("MickeyDonald", LOG_CONS | LOG_PID | LOG_NDELAY, LOG_LOCAL1);
        syslog (LOG_NOTICE, "Failed to create Donald queue file." );
        closelog ();
        exit(92);
    }

    ipcMickey = 0;
    ipcDonald = 0;

    /* make sure we assign DIFFERENT ipc values */  
    while(ipcMickey == ipcDonald)
    {
        ipcMickey = ftok(MQMICKEY, 63);
        if (-1==ipcMickey)
        {
            printf("ipcMickey does not exist.\r\n");

            /* system logging */
            setlogmask (LOG_UPTO (LOG_NOTICE));
            openlog ("MickeyDonald", LOG_CONS | LOG_PID | LOG_NDELAY, LOG_LOCAL1);
            syslog (LOG_NOTICE, "Failed to ftok Mickey file." );
            closelog ();
            exit(93);
        }

        ipcDonald = ftok(MQDONALD, 69);
        if (-1==ipcDonald)
        {
            printf("ipcDonald does not exist.\r\n");

            /* system logging */
            setlogmask (LOG_UPTO (LOG_NOTICE));
            openlog ("MickeyDonald", LOG_CONS | LOG_PID | LOG_NDELAY, LOG_LOCAL1);
            syslog (LOG_NOTICE, "Failed to ftok Donald file." );
            closelog ();
            exit(94);
        }
    }

    mqMickeyid = msgget(ipcMickey, IPC_CREAT | 0666);
    mqDonaldid = msgget(ipcDonald, IPC_CREAT | 0666);

    pthread_create(&t1, NULL, MICKEYthreadFunc, "Mickey sends\n");
    pthread_create(&t2, NULL, MINNIEthreadFunc, "Minnie replies\n");
    pthread_create(&t3, NULL, DONALDthreadFunc, "Donald sends\n");
    pthread_create(&t4, NULL, PLUTOthreadFunc, "Pluto replies\n");

    long exitcounter = 0;
    while(exitcounter < 100000)
    {
        exitcounter +=1;        
        usleep(100);
    }
    exit(0);
}

Answer 3

以下是程序的略微修改版本：

/*
    To compile;
    gcc MM.c -o mm -fno-stack-protector -pthread

    We want Mickey to send a message to Minnie exclusively.
    We want Donald to send a message to pluto exclusively.

    Problem: Pluto intercepts Minnie's messages.

    Listing gives:

    $ ./mm
    Mickey thread successfully started.
    Minnie thread successfully started.
    Pluto thread successfully started.
    Donald thread successfully started.
    Donald sent a message to Pluto.
    Mickey sent a message to Minnie.
    Pluto received: Sit, Pluto!

    Minnie received: Hello, Minnie!

    Mickey sent a message to Minnie.  (100 times)

    Pluto received: Hello, Minnie!
*/
#include <sys/types.h>
#include <sys/msg.h>
#include <sys/ipc.h>
#include <string.h>
#include <stdio.h>

pthread_t t1,t2,t3,t4;

// Mickey send
key_t ipcMickey;
int mqMickeyid;
char helloMickeymsg[] = {"Hello, Minnie!"};
struct { long type; char text[100]; } myMickeymsg;

// Minnie get
int mqMinnieid;
struct { long type; char text[100]; } myMinniemsg;

// Donald send
key_t ipcDonald;
int mqDonaldid;
char helloDonaldmsg[] = {"Sit, Pluto!"};
struct { long type; char text[100]; } myDonaldmsg;

// Pluto get
int mqPlutoid;
struct { long type; char text[100]; } myPlutomsg;

static void * DONALDthreadFunc(void *arg)
{
    printf("Donald thread successfully started.\n");
    char *s = (char *) arg;

    while(1)
    {
        //send
        memset(myDonaldmsg.text, 0, 100);
        strncpy(myDonaldmsg.text, helloDonaldmsg, strlen(helloDonaldmsg));
        myDonaldmsg.type = 1;
        msgsnd(mqDonaldid, &myDonaldmsg, sizeof(myDonaldmsg), 0);
        printf("Donald sent a message to Pluto.\r\n");
        sleep(4);
    }

    /* just a formality */
    return (void *) strlen(s);
}

static void * PLUTOthreadFunc(void *arg)
{
    printf("Pluto thread successfully started.\n");
    char *s = (char *) arg;

    while(1)
    {
        //receive
        mqPlutoid = msgget(ipcDonald, 0);
        msgrcv(mqPlutoid, &myPlutomsg, sizeof(myPlutomsg), 0, 0);
        printf("Pluto received: %s\r\nPluto uses MQ with id = %d\r\n", myPlutomsg.text,mqPlutoid);
        sleep(1);
    }

    /* just a formality */
    return (void *) strlen(s);
}

static void * MICKEYthreadFunc(void *arg)
{
    printf("Mickey thread successfully started.\n");
    char *s = (char *) arg;

    while(1)
    {
        //send
        memset(myMickeymsg.text, 0, 100);
        strncpy(myMickeymsg.text, helloMickeymsg, strlen(helloMickeymsg));
        myMickeymsg.type = 1;
        msgsnd(mqMickeyid, &myMickeymsg, sizeof(myMickeymsg), 0);
        printf("Mickey sent a message to Minnie.\r\n");
        usleep(10000);
    }

    /* just a formality */
    return (void *) strlen(s);
}

static void * MINNIEthreadFunc(void *arg)
{
    printf("Minnie thread successfully started.\n");
    char *s = (char *) arg;

    while(1)
    {
        //receive
        mqMinnieid = msgget(ipcMickey, 0);
        msgrcv(mqMinnieid, &myMinniemsg, sizeof(myMinniemsg), 0, 0);
        printf(" Minnie received: %s\r\nMinnie uses MQ with id = %d\r\n", myMinniemsg.text,mqMinnieid);
        sleep(3);
    }

    return (void *) strlen(s);
}

int main (void)
{
    ipcMickey = ftok("./mqmickey", 63);
    mqMickeyid = msgget(ipcMickey, IPC_CREAT | 0666);
    printf( "mqMickeyid=%d\n",mqMickeyid);

    ipcDonald = ftok("./mqdonald", 69);
    mqDonaldid = msgget(ipcDonald, IPC_CREAT | 0666);
    printf( "mqDonaldid=%d\n",mqDonaldid);

    pthread_create(&t1, NULL, MICKEYthreadFunc, "Mickey sends\n");
    pthread_create(&t2, NULL, MINNIEthreadFunc, "Minnie replies\n");
    pthread_create(&t3, NULL, DONALDthreadFunc, "Donald sends\n");
    pthread_create(&t4, NULL, PLUTOthreadFunc, "Pluto replies\n");

    while(1)
    {
        sleep(5);
    }
}

我发现由于某种原因，msgget失败，并且两个MQ具有相同的id，然后它是一个首先开始攻击的种族。

使用此程序的修改版本，执行以下操作：

touch mqmickey
touch mqdonald

首先创建文件。

你应该看到消息传递给正确的收件人。