topic shmat() in Operating System - HP-UX

shmat()

Victor.Lin — Thu, 14 Jun 2001 09:16:28 GMT

I remenber that my program worked well the first time, but failed several times later.
I guess that the problem is that only shmget() shmat() and shmdt() are performed, but shmctl() is not. Ultimately the resource runs out.
But how can I remove this memory "garbage" ?
I use "ipcrm -m" to remove these shared memory and reboot the system, but the problem is still there.

Re: shmat()

Ravi_8 — Thu, 14 Jun 2001 11:48:09 GMT

shmctl(free) makes all shared memory free

Re: shmat()

Victor.Lin — Thu, 14 Jun 2001 23:49:33 GMT

ravi:
What did you mean ?
int shmctl(int shmid, int cmd, struct shmid_ds *buf);
There are only IPC_STAT IPC_SET IPC_RMID SHM_LOCK SHM_UNLOCK for cmd. Where is free ?

Re: shmat()

A. Clay Stephenson — Fri, 15 Jun 2001 23:59:49 GMT

No, here's what you want to do:

struct shmis_ds dummy;

int my_shmid; /* I assume you have done a shmget to get the shared memory identifier*/

result = shmctl(my_shmid,IPC_RMID,&dummy);

This will only work if you have the proper permissions (super-user or shm segment owner)

Regards, Clay