topic Re: semop not working in Operating System - HP-UX

semop not working

anup1890 — Thu, 18 Nov 2010 10:23:42 GMT

We were having a semaphore locking implementation to lock semaphore before accessing the shared memory .When this implementation is ported to HP Ux from Digital.

When the code is ported to HP UX, the application is hanging at semop function.

sem_buf.sem_num = 0;
sem_buf.sem_op = LOCK; /* LOCK = -1*/
sem_buf.sem_flg = SEM_UNDO;

/*
** lock
*/
if ( semop(shms.sem_id, &sem_buf, 1) ) {
rc = IPC_ERROR_EXIT;
}

Is there any change in HP UX for semop

Re: semop not working

Dennis Handly — Fri, 19 Nov 2010 12:52:57 GMT

Do know what the value of semval is?
How are you calling semctl(2)? Are you in 64 bit mode?

Re: semop not working

anup1890 — Sat, 20 Nov 2010 08:38:43 GMT

Hi,
Thanks for the response,

Yes, I am compiling in 64bit mode.

Creation of semaphore is done like this
semctl(*sem_id, 0, SETVAL, 1)

Once before calling semop I used "semctl(sem_id, 0, GETVAL, 0);" to get semaphore value
it returned me 0. So this means semaphore value is 0.

One more thing i noted is when i used IPC_NOWAIT for sem_flg the hanging issue was not there
Is it correct to use IPC_NOWAIT instead of SEM_UNDO. Or am i doing something functionally wrong due to which this problem is comming

Thanks

Re: semop not working

Dennis Handly — Sat, 20 Nov 2010 10:50:04 GMT

>semctl(*sem_id, 0, SETVAL, 1)

As I suspected on the 4th parm, that's your problem, this is illegal:
http://forums.itrc.hp.com/service/forums/questionanswer.do?threadId=1137658
http://forums.itrc.hp.com/service/forums/questionanswer.do?threadId=1385188
http://forums.itrc.hp.com/service/forums/questionanswer.do?threadId=472388
http://forums.itrc.hp.com/service/forums/questionanswer.do?threadId=631198
http://forums.itrc.hp.com/service/forums/questionanswer.do?threadId=847096
http://forums.itrc.hp.com/service/forums/questionanswer.do?threadId=1116632

Re: semop not working

anup1890 — Sat, 20 Nov 2010 13:09:22 GMT

It worked!!

Thanks for the solution Dennis.

Re: semop not working

Dennis Handly — Sun, 21 Nov 2010 08:38:06 GMT

>Thanks for the solution Dennis.

If you are happy with the answers you have gotten, please read the following about how to assign points:
http://forums.itrc.hp.com/service/forums/helptips.do?#33