问题描述
|
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。
以下玩具程序显示了问题,可以在不同的处理器上重复进行。
任何帮助,不胜感激!
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,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);
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,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);
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,MINNIEthreadFunc,\"Minnie replies\\n\");
pthread_create(&t3,DONALDthreadFunc,\"Donald sends\\n\");
pthread_create(&t4,PLUTOthreadFunc,\"Pluto replies\\n\");
while(1)
{
sleep(5);
}
}
解决方法
问题是您错过了错误处理。
包括
ipcMickey = ftok(\"/tmp/mqmickey\",63);
if (-1==ipcMickey)
{
perror(\"ipcMickey\");
exit(255);
}
ipcDonald = ftok(\"/tmp/mqdonald\",69);
if (-1==ipcDonald)
{
perror(\"ipcDonald\");
exit(255);
}
您很快就会发现
./mm
ipcDonald: No such file or directory
在这种情况下,ftok
的回报为-1。如果两个文件都丢失,则两个ipc密钥都将为-1,这意味着所有流量共享相同的端口:)
所以
touch /tmp/mqmickey /tmp/mqdonald
解决它。一些统计数据(用ѭ5代替睡眠):
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
,非常感谢您和VJo,
这是程序的修改版本,考虑了您的所有注释。
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,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);
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,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);
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\",\"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_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\",\"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,MINNIEthreadFunc,\"Minnie replies\\n\");
pthread_create(&t3,DONALDthreadFunc,\"Donald sends\\n\");
pthread_create(&t4,PLUTOthreadFunc,\"Pluto replies\\n\");
long exitcounter = 0;
while(exitcounter < 100000)
{
exitcounter +=1;
usleep(100);
}
exit(0);
}
,这是您的程序的稍作修改的版本:
/*
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,t4;
// Mickey send
key_t ipcMickey;
int mqMickeyid;
char helloMickeymsg[] = {\"Hello,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);
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);
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);
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,\"Pluto replies\\n\");
while(1)
{
sleep(5);
}
}
我发现由于某种原因,“ 9”失败,并且两个MQ都具有相同的ID,这是线程首先进入的竞赛。
使用此程序的修改版本,请执行以下操作:
touch mqmickey
touch mqdonald
首先创建文件。
并且您应该看到消息发送给正确的收件人。