Dear Stefan,

I followed your suggestion to try the sample front-ends from the distribution and 
they work fine. They also work fine with any one of my front-ends. Only my two 
front-ends cannot run concurrently in the same directory. I later found that the 
problem is in the CAEN HV wrapper library. The problem arises when the front-ends 
are both linked to that library and it is solved now.

Thanks & Best Regards,
Jimmy


> 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?