topic Semaphore problem in Operating System - HP-UX

Semaphore problem

Bob Manocchia — Thu, 17 Jul 2008 13:10:24 GMT

I have an rp4440 server running hpux 11.11. We are having a problem with left behind semaphores. When I run ipcs -bcopts I can see serveral (about 560) semaphores listed belonging to root: Here is a brief listing.
s 125 0x00000000 ----------- root sys root sys 1 no-entry 17:48:37
s 126 0x00000000 ----------- root sys root sys 1 no-entry 17:48:37
s 4225 0x00000000 ----------- root sys root sys 1 no-entry 17:48:52
s 8324 0x00000000 ----------- root sys root sys 1 no-entry 19:16:37
s 129 0x00000000 ----------- root sys root sys 1 no-entry 17:48:37
s 130 0x00000000 ----------- root sys root sys 1 no-entry 17:48:37
s 4229 0x00000000 ----------- root sys root sys 1 no-entry 19:16:37
s 8328 0x00000000 ----------- root sys root sys 1 no-entry 19:36:36
s 133 0x00000000 ----------- root sys root sys 1 no-entry 17:48:37
s 134 0x00000000 ----------- root sys root sys 1 no-entry 17:48:37
s 8331 0x00000000 ----------- root sys root sys 1 no-entry 19:36:36
s 4234 0x00000000 ----------- root sys root sys 1 no-entry 19:16:37
s 4235 0x00000000 ----------- root sys root sys 1 no-entry 19:16:37

I know the first 20 of so root entries should not be touched and the ones belonging to the SAP user should not be touched as well but these appear after those and look like they aren't owned by anything.

Can we determine what processes these belong to and can we safely remove them using ipcrm.

Thanks

Re: Semaphore problem

Ivan Krastev — Thu, 17 Jul 2008 17:01:06 GMT

Hello Bob,

Look for tool, called shminfo - it will give you detailed information about semaphores <-> processes.

regards,
ivan

Re: Semaphore problem

Dennis Handly — Fri, 18 Jul 2008 07:55:43 GMT

Take a look at my attachment in the following thread. Compile it and that will give the time AND date of each semaphore.
http://forums.itrc.hp.com/service/forums/questionanswer.do?threadId=1144781

Re: Semaphore problem

Bob Manocchia — Fri, 18 Jul 2008 10:56:08 GMT

How do I complie this. In you original email you mention DHP_11.11.

Re: Semaphore problem

Dennis Handly — Fri, 18 Jul 2008 11:27:44 GMT

>In you original email you mention -DHP11_11.

Yes: cc -DHP11_11 291516.c

Re: Semaphore problem

Bob Manocchia — Fri, 18 Jul 2008 12:21:53 GMT

I do not have this compiler and I tried googling it to no avail.

Re: Semaphore problem

Dennis Handly — Fri, 18 Jul 2008 12:34:43 GMT

Yes: cc -DHP11_11 291516.c

>I do not have this compiler

It should be on all systems. Try the absolute path:
/usr/ccs/bin/cc_bundled 291516.c -DHP11_11 -o semaphore_date
And to execute: ./semaphore_date

Re: Semaphore problem

Bob Manocchia — Fri, 18 Jul 2008 12:57:31 GMT

Thanks. Got it. So the semaphores with the NO-ENTRY are not being used and can be removed.

Re: Semaphore problem

Dennis Handly — Fri, 18 Jul 2008 13:17:58 GMT

>So the semaphores with the NO-ENTRY are not being used and can be removed.

Well, you need to use "ipcs -sa" to find the owner. Also, was it created long ago?
I suppose it is possible to create them and never used them, yet? 560 seems like a lot.

Re: Semaphore problem

Bob Manocchia — Fri, 18 Jul 2008 13:20:02 GMT

The owner is root and it looks like they were created sometime back in December of 07.

Re: Semaphore problem

Dennis Handly — Fri, 18 Jul 2008 21:08:26 GMT

>The owner is root and it looks like they were created sometime back in December of 07.

So the system has been up that long?
Can you check syslog or the SD logs to see what happened on that date/time?

Re: Semaphore problem

Bob Manocchia — Mon, 05 Jan 2009 13:53:55 GMT

Thanks for all the help.