[SOLVED] Free shared memory of dead process

parrotfortytwo · 11-01-2010, 06:45 AM

Hello, I have the problem that a process crashes, but does not free up its shared memory after itself. Thus, next time I want to start it, it crashes again this time due for the lack of shared memory (I know it from the error message).
Is there a way to find out which memory the crashed process was occupying, and to somehow free it manually? Otherwise I always have to reboot the machine if I want to start the process again.

EDDY1 · 11-01-2010, 06:53 AM

Maybe you can look in system monitor and find running process, it's under Applications >> System Tools >> System Monitor under processes tab. Dmesg also tells alot. Linux newbie here too.

parrotfortytwo · 11-01-2010, 07:11 AM

I had already done something similar to looking into system monitor*, but the process was not there (since it had crashed). To be sure, I tried now to look into the system monitor as well, but it was not there either.
Now I also tried dmesg, as you suggested, but I do not know what I should look for :S It really tells a lot of things, but they seem to me more hardware related...

* more exactly, I did:

Code:

ps aux | grep <process>

mesiol · 11-01-2010, 11:04 AM

Hi,

shared memory can be viewed with

Code:

ipcs

. You can delete shared memory segments with

Code:

ipcrm

.

parrotfortytwo · 11-01-2010, 02:18 PM

Thanks, mesiol; these were the commands I was looking for -- next time the process crashes I will try them out.
In Google, I kept finding man pages of C functions for managing shared memory...

mesiol · 11-01-2010, 05:42 PM

Hi,

if this is your solution, so please mark the thread as solved.

Valery Reznic · 11-02-2010, 05:11 AM

Quote:

Originally Posted by parrotfortytwo

Hello, I have the problem that a process crashes, but does not free up its shared memory after itself. Thus, next time I want to start it, it crashes again this time due for the lack of shared memory (I know it from the error message).
Is there a way to find out which memory the crashed process was occupying, and to somehow free it manually? Otherwise I always have to reboot the machine if I want to start the process again.

You may change executable to deal with shared memory segment already exist
(Correct thing IMO) This will make it more robust.

parrotfortytwo · 11-02-2010, 01:34 PM

mesiol: did that now
Valery Reznic: could you please give me the name of the command (or a pointer to the documentation) on how to do that?

Valery Reznic · 11-03-2010, 02:56 AM

Quote:

Originally Posted by parrotfortytwo

mesiol: did that now
Valery Reznic: could you please give me the name of the command (or a pointer to the documentation) on how to do that?

See 'man shmget'

I guess that your shared memory created with code like following:

Code:

shmget(key, size, IPC_CREAT | IPC_EXCL);

IPC_CREAT | IPC_EXCL force shmget return error if shared memory already exist.

If you remove IPC_EXCL flag it will work when shared memory already exist and when it not.