[Fwd: [gp@familiehaase.de: sem_* functions in cygwin]]

Mark Paulus mark.paulus@mci.com
Thu Dec 9 16:50:00 GMT 2004

So, does that mean that if process 1 opens a semaphore,
process 2 also grabs it, then process 1 unlinks it, and then
"reconnects" to it, that process 1 and process 2 do not have
and cannot have the same semaphore anymore, even though
they are using the same IPC_KEY?

(Or am I way confused/off base here)?

  On Thu, 09 Dec 2004 17:44:42 +0100, Corinna Vinschen wrote:

>[Catching up on some older mails]

>> ----- Forwarded message from "Gerrit P. Haase" -----
>> From: "Gerrit P. Haase" 
>> To: cygwin ML
>> Subject: sem_* functions in cygwin
>> Date: Sun, 21 Nov 2004 22:48:20 +0100
>> Hi,
>> nearly all sem_* functions are available, but sem_unlock is missing,
>> was there a problem implementing sem_unlock() or was it just missed
>> by accident?
>> Gerrit
>> ----- End forwarded message -----

>I guess you're asking about sem_unlink().  It's not implemented so far
>since named POSIX semaphores are implemented using named Windows semaphores. 
>The SUSv3 description contains a pretty unfortunate implementation detail:

>  Calls to sem_open() to recreate or reconnect to the semaphore refer
>  to a new semaphore after sem_unlink() is called.

>There's no way I know of, which allows to implement this using named
>Windows semaphores.  At least not without adding a lot of annoying
>bookkeeping overhead, possibly involving cygserver.


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