Date: Wed, 13 May 1998 14:54:41 -0400 (EDT) From: CyberPeasant <djv@bedford.net> To: jaspal@best.com (Jaspal Kohli) Cc: freebsd-questions@FreeBSD.ORG Subject: Re: leaking shm segments Message-ID: <199805131854.OAA05851@castor.loco.net> In-Reply-To: <3559CC2E.2BAEE281@best.com> from Jaspal Kohli at "May 13, 98 09:37:03 am"
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Jaspal Kohli wrote:
> If a process creates a shared memory segment using shmget() and exits
> without
> deleting it via shmctl(), the segment does not get deleted. Since this
> is a limited
> resource in the kernel, the system will run out of shm segments.
Well, you can run out of inodes, too.
> It was not clear to me from the man pages whether this is the expected
> behavior
> or whether this is a kernel bug (i.e. shm segments should be deleted
> when the
> creating process exits).
>
This is normal behavior. These segments are more like files than
anything else -- global resources that may be accessed by any process
on the system, subject to permissions. [An extension to the semantics
on some OS's allows access from different machines over a network].
Unlike files, they only live from boot to boot.
shmctl can be used to make them have the delete-when-unreferenced
property, if that's what your app. needs, using IPC_RMID.
Similar remarks apply to SysV semaphores and message queues.
Dave
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