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Entry  14 Oct 2014, Konstantin Olchanski, Bug Report, Problem with EQ_USER 
    Reply  15 Oct 2014, Stefan Ritt, Bug Report, Problem with EQ_USER 
    Reply  16 Oct 2014, Stefan Ritt, Bug Report, Problem with EQ_USER 
Message ID: 1029     Entry time: 16 Oct 2014     In reply to: 1024
Author: Stefan Ritt 
Topic: Bug Report 
Subject: Problem with EQ_USER 
I restructured the front-end code to enable multiple readout threads for EQ_USER equipment. Last summer I was definitively interrupted during 
that work and left it in an half finished state, sorry for that.

The way it works now is illustrated in mtfe.c. You create N ring buffers and N threads via

   for (int i=0 ; i<N ; i++) {
      ss_thread_create(trigger_thread, (void*)(PTYPE)i);

then each readout thread accesses its own readout buffer

   index = (int)(PTYPE)param;
   signal_readout_thread_active(index, TRUE);
   rbh = get_event_rbh(index);
   while (is_readout_thread_enabled()) {
      ... read event and put it into ring buffer ...

   signal_readout_thread_active(index, FALSE);

The is_readout_thread_enabled() and signal_readout_thread_active() are used by the framework to shut down gracefully threads correct at the end 
of the program. This way each thread can close any hardware correctly.

Note that no other thread management is done by the framework. In the old days with interrupt equipment, the framework disabled interrupts 
when reading out periodic events, since that was necessary when using a single CAMAC crate for ADCs and scalers. This is obsolete now and not 
needed any longer. It is now the responsibility of the user code to resolve hardware access conflicts between different threads (like using a local 
mutex to access the same hardware). There is also no "readout when running" handling. If events should not be read out when the run is stopped, 
the readout thread has to check to run status, or better the EOR routine should disable the hardware trigger and the BOR routine should re-enable 
it. The readout threads will then poll for new events and just go to sleep if nothing is there.

I testes the mtfe.c program with 100 Hz and 1 MHz event rate on a dummy experiment (no hardware access) and it worked without problem.

Let me know if there is any issue left over.

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