POSIX shm, sem & aio

POSIX shm, sem & aio

Post by Harold Smit » Fri, 30 Jul 1999 04:00:00



Is there a general way in POSIX to query the shared memory and/or
semaphores created using POSIX services? I'm looking fro something
similar to the System V 'ipcs' command.

As well, when using msync, is there any way of determining when an
asyncronous update has been performed. That is, after doing an
msync with the MS_ASYNC flag, how can I tell if my request has been
completed?

-- Hal

 
 
 

1. Socket/SHM/Sem Ids and child processes

        I have the following situation:  I am responsible for a particular
TLCSC of a software system, which will be composed of several (9, actually)
processes.  There will be one large SHM area, common to all CSCs, and I
intend to have a SHM area local to my own CSC.  There is one process which
controls the others within my CSC, and it is invoked by the highest-level CSC
in the system.

        Okay.  If the main process of my CSC shmgets the id of the global
area, and semgets a semaphore used within my CSC, and then forks/execs to create
the other processes within my CSC, is it safe for me to place those ids within
the local SHM area?  Are these ids the same regardless of which process does
a 'get with a particular key?

        Empirically, I've found this to be true, however I can vaguely recall
reading somewhere (I think it was something on the IBMLink network) to the
effect that this is a Bad Thing.  Anyone know for sure?

        Thanx.

        Mitch



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