Sure, each thread needs its own ring buffer for writing.

So I see that we need back the multiple-ring-buffer-readout-scheme even before MEG will start. So what you need is something like

for (i=0 ; rb[i] != 0 ; i++) {
  read event from rb[i];
}

as it was before. What I do not like is that rb is a global variable, we should better use the encapsulation functions and extend get_event_rb() to 
get_event_rb(i) so you can have n ring buffers.

Give me one day, I will extend the current code to make it work again and to implement N threads.

Cheers,
Stefan