> > > some old front-end are not running any more since they do use RO_ALWAYS together with 
> > triggered events.
> > 
> > I confirm, if you have mfe.c frontends that have RO_ALWAYS, after you update MIDAS, 
> > some of these frontends will fail to start.
> > https://bitbucket.org/tmidas/midas/commits/1961af0d657e4f76ab9db17f9b70c0c492172b6d
> > 
> > tmfe c++ frontends do not have this restriction but by default only read data when run 
> > is active (per-equipment fEqConfReadOnlyWhenRunning default is true).
> 
> As of commit 
> https://bitbucket.org/tmidas/midas/commits/28d9c96bd6d4f65346ebcd6a04492ea764c90823 mfe.c 
> frontends will no longer fail to start. an error will still be issued "Equipment \"%s\" 
> contains RO_STOPPED or RO_ALWAYS. This can lead to undesired side-effect and should be 
> removed."
> 
> BTW 1:
> 
> Some of our old frontends use EQ_MULTITHREAD to implement multithreaded periodic equipments. 
> They do not generate any events when there is no run (some of them do not generate any 
> events at all). Now they will start printing this error message, for no reason. (no we will 
> not be rewriting them justy to get rid of this message. life is too short).
> 
> BTW 2:
> 
> the c++ tmfe frontend does not have any protections against these "undersired side-effects".
> 
> What are these undesired side effects and should we add protection against them?
> 
> K.O.

The undesired side-effects are the following: The logger tries to collect all events at the end of 
the run by emptying the SYSTEM buffer. If events keep coming after the run is stopped, this loop in 
the logger might be an endless loop, crashing the whole experiment in the end. 

Another issue (and actually the reason for this change) is the funciton receive_trigger_event() in 
mfe.cxx which will get confused if events are still coming in after a run has been stopped and 
actually enters an infinite loop.

Combining EQ_MULTITHREAD with EQ_PERIODIC or EQ_SLOW is a wrong parameter combination as written in 
the documentation. If one wants to have multi-threaded slow control events, one has to use the 
DF_MULTITHREAD flag in the DEVICE_DRIVER structure.

Having triggered events being sent to the system after a run has been stopped I would consider 
simply wrong. Why should we ever use a run start/stop if events are always flowing? Adding 
protections in all places for this case is certainly much more work than just changing one flag for 
frontends which produce this error message now for a wrong parameter combination.