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From Jim Jagielski <>
Subject Re: Using semaphore locking
Date Mon, 08 Sep 1997 21:48:55 GMT
Martijn Koster wrote:
> What system is that, Linux? Have you got any code to demonstrate this
> working? It'd be neat, but surprising. Compare:
> FreeBSD 3.0-CURRENT, man semctl():
>      IPC_RMID     Immediately removes the semaphore set from the system.

I notice you didn't note FreeBSD 2.2 which clearly details that the
removal is not done until all attached processes are no longer
accessing the semaphore.

Linux and A/UX both have the above behavior as well. I seem to
recall that HP-UX and AIX has it as well. Most likely this
is old behavior and has since been changed. It seems that most
OSs that lack a command-line command to remove semaphores and
shared-mem segments may be a common thread, as well as those
with mmap().

Note that using shared-memory, Apache currently uses shmctl
to immediately IPC_RMID

      Jim Jagielski            |       jaguNET Access Services           |
            "Look at me! I'm wearing a cardboard belt!"

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