Hello Chuck!

I am using cygwin 1.3.4-1 at the moment with cygipc 1.10-1.

The problem i have is, that if all processes using shm are
dead (nattch = 0) and the flag SHM_DEST is set in shm_perm.mode,
the shm-entry does not disappear until calling ipcrm, so
i can't start my application again.

My application is already working on many unixes
(HP-UX/AIX/Linux/SunOS/ReliantUNIX), and now i also
tested it successfully on FreeBSD.

So i checked the behaviour of shmctl(IPC_RMID) and shmdt(), in
cooperation with fork() after shmat(), watching the output of
ipcs on HP-UX, Linux and FreeBSD.

In short words my test does this:

*) Some tasks are using the same shm.
*) one of these tasks says shmctl(IPC_RMID)
*) on all systems this shmid is invalidated
*) on HP-UX and Linux another task can create a new shm with same
   key now while the old tasks can continue using their shm.
*) on FreeBSD the shmid does not disappear until the last task using
   it has shmdt()'d, but the key of this shmid is changed to zero
   and a new task cannot create a new shm with this key.

Somewhere on cygwin's homepage i read that cygwin wants to be more
like FreeBSD than Linux, so i tried to modify to FreeBSD-behaviour
(which i like more than the others in this special case) with attached
patch.

Another problem might be that forking with attached shm does not
increment the nattch-counter, but this is not really a problem
for me and i suppose this might not be as simple as this one.

Please can you check this patch, i can't really say if it affect's
other applications using cygipc, especially postgresql (i found
it often together with cygipc in the mailing-lists), since i am
not yet using postgresql.

Maybe you should remove the unneeded function killseg() in shm.c

Thank you very much for reading this quite long mail!

-- haubi
Michael Haubenwallner                       SALOMON Automation GmbH
Forschung & Entwicklung                     A-8114 Friesach bei Graz
T +43 3127 200 308                          T +43 3127 200
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