rosko@runx.ips.oz (Ross McKay) (10/16/88)
Hello,
I have been trying to get message passing to work on my Microport
System (System V.2, uPort version 2.3, a '286 box (yes, I know it's hideous,
but it's also cheap)). I tried using an example programme from Bach's book,
"The Design of the Unix Operating System", shown below. The problem is that
on the first msgget() call, the operating system return ENOENT, which according
to the manual means "A message queue identifier does not exist for key and
(msgflg & IPC_CREAT) is false." msgflg & IPC_CREAT is true, however, but
uPort nicely returns the error anyway.
I am running the kernel with message passing enabled, so I am wondering
just what Microport did to message passing ...
Jan Mikkelsen
c/o rosko@runx.ips.oz.AU
------CUT HERE FOR EXAMPLE CODE---8<-----------------------------------------
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/msg.h>
#define MSGKEY 75
struct msgform
{
long mtype;
char mtext[256];
} msg;
int msgid;
main()
{
int i, pid, *pint;
extern cleanup();
for(i = 0; i < 20; ++i)
signal(i, cleanup);
if((msgid = msgget(MSGKEY, -1)) == -1)
{
perror("msgget"); /* error check added by janm */
exit(1);
}
for(;;)
{
pint = (int *) msg.mtext;
pid = *pint;
printf("server: receive from pid %d\n", pid);
msg.mtype = pid;
*pint = getpid();
msgsnd(msgid, &msg, sizeof(int), 0);
}
}
cleanup()
{
msgctl(msgid, IPC_RMID, 0);
exit();
}gregg@ihlpb.ATT.COM (Wonderly) (10/19/88)
From article <1794@runx.ips.oz>, by rosko@runx.ips.oz (Ross McKay): > > Hello, > I have been trying to get message passing to work on my Microport > System. > ..... > > ------CUT HERE FOR EXAMPLE CODE---8<----------------------------------------- > > for(i = 0; i < 20; ++i) ^^^ PLEASE, PLEASE, PLEASE use NSIG here or something a little more portable. Signal numbers start at 1 besides... > signal(i, cleanup); > > if((msgid = msgget(MSGKEY, -1)) == -1) ^^^ Try using the actual flag here. MAKE IT OBVIOUS WHAT THE HECK YOU ARE DOING. You are also setting IPC_EXCL, IPC_NOWAIT besides IPC_CREATE. If the key already exists, then this will fail with EEXIST. -- Gregg Wonderly AT&T Bell Laboratories DOMAIN: gregg@ihlpb.att.com IH2D217 - (312) 979-2794 UUCP: att!ihlpb!gregg
wietse@wzv.UUCP (Wietse Z. Venema) (10/20/88)
In article <1794@runx.ips.oz> rosko@runx.ips.oz (Ross McKay) writes: > I have been trying to get message passing to work on my Microport >System (System V.2, uPort version 2.3, a '286 box (yes, I know it's hideous, >but it's also cheap)). I tried using an example programme from Bach's book, >[problem description deleted] > I am running the kernel with message passing enabled, so I am wondering >just what Microport did to message passing ... >[example program deleted] Before accusing Microport of anything, it would be a good idea to lint your program first, then flame about the example program. function argument ( number ) used inconsistently msgget( arg 1 ) llib-lc(84) :: example.c(55) msgsnd( arg 2 ) llib-lc(86) :: example.c(68) msgsnd( arg 3 ) llib-lc(86) :: example.c(68) msgctl( arg 3 ) llib-lc(82) :: example.c(74) -- work: wswietse@eutrc3.uucp | Eindhoven University of Technology ditto: wswietse@heitue5.bitnet | Mathematics and Computing Science home: wietse@wzv.uucp | 5600 MB Eindhoven, The Netherlands