Hi Jimmy,

ok, now I understand. Well, I don't see your problem. I just tried with the 
current SVN 
version to start

midas/examples/experiment/frontend
midas/examples/slowcont/scfe

in the same directory (without "-h localhost") and it works just fine (see 
attachemnt). I even started them from the same directory. Yes there are *.SHM 
files and they correspond to shared memory, but both front-ends use this shared 
memory together (that's why it's called 'shared').

Your error message 'Semaphore already present' is strange. The string is not 
contained in any midas program, so it must come from somewhere else. Do you 
maybe try to access the same hardware with the two front-end programs?

I would propose you do the following: Use the two front-ends from the 
distribution (see above). They do not access any hardware. See if you can run 
them with the current SVN version of midas. If not, report back to me.

Best regards,

  Stefan


> Dear Stefan,
> 
> Thanks for the reply. I have tried your patch and it didn't solve my problem. 
Maybe I 
> have not written my question clearly. The two frontends could run on the same 
computer 
> if I use the remote method, i.e. by setting up the mserver and connect to the 
> experiment by specifying "-h localhost", also the frontend programs need to be 
put in 
> different directory. What I want to know is whether I can simply start 
multiple 
> frontends in the same directory without setting up the mserver etc. I noticed 
that 
> there are several *.SHM files, I'm not familiar with semaphore, but I guess 
they are 
> the key to the problem. Please correct me if I misunderstood something.
> 
> Best Regards,
> Jimmy
> 
> 
> > > Dear All,
> > > 
> > > I want to run two frontend programs (one for trigger and one for slow 
control)
> > > concurrently on the same computer, but I failed. The second frontend said: 
> > > 
> > > Semaphore already present
> > >  There is another process using the semaphore.
> > >  Or a process using the semaphore exited abnormally.
> > >  In That case try to manually release the semaphore with:
> > >    ipcrm sem XXX.
> > > 
> > > The two frontends are connected to the same experiment. Is there any way I 
can
> > > overcome this problem?
> > 
> > That might be related to the RPC mutex, which gets created system wide now. 
I 
> > modified this in midas.c rev. 4628, so there will be one mutex per process. 
Can you 
> > try that temporary patch and tell me if it works for you?