sc_fifo data_read_event

[plafratt]

I had been using the sc_fifo with the assumption that data_read_event would get notified whenever the receiver read from the fifo. However, I am seeing cases where the receiver reads from the fifo, but the data_read_event doesn't get notified. Is this the intended behavior?

[Roman Popov]

Here is how it is specified by standard:

Quote

virtual const sc_event& data_read_event() const;

Member function data_read_event shall return a reference to an event, the data-read event, that is notified in the delta notification phase that occurs at the end of the delta cycle in which a value is read from the fifo.

So it notified after each delta cycle where fifo was read. Can it be that your receiver does nb_read from empty fifo?

[plafratt]

I'm actually using read(), rather than nb_read(). Given the specification you posted, it seems like something unexpected is happening. I can see the fifo is getting read (I put a log statement in after the read() call), but I don't see the thread that is waiting on data_read_event getting woken up (I put a log statement there, too).

The thread that is waiting on data_read_event does eventually get woken up when the last item is read off the fifo.

[plafratt]

I looked at the implementation of sc_fifo, as I'd guessed that in the read() function, it would just notify data_read_event, but the logic surrounding the notify looks a little more complex than that.

[Roman Popov]

Quote

The thread that is waiting on data_read_event does eventually get woken up when the last item is read off the fifo.

Did you probably forget to add wait() into consumer thread to suspend it after first read?

[plafratt]

That is it. Thank you very much.

Regards,

Patrick