On Tue, 23 Sep 2003, [iso-8859-1] emmanuel ALLAUD wrote:
> >
> > I'm assuming futexes are some interprocess mutex
> > mechanism?
> > If so, I don't see how this helps.
> >
>
> Yes it is. Actually I am not familiar with them
> either, but if you had a way to be able to wake up
> your waiting process ASAP when eg DMA is finished,
> instead of waiting that the OS scheduler gives you the
> CPU back (which can be very long), that would be good.
> Problem is that you must in the first place be able to
> have a way (here interrupt I guess) that tells you
> that the work is finished, which means something in
> kernel (in case of DMA do you have an interrupt driven
> way to know if it's completed?).
The "nv" driver is completely in user-space and requires
no kernel support. It should remain so due to portability
concerns. Besides, I don't really want to know when DMA is
finished. I want to know when there's enough free room in
the DMA buffer so the CPU can continue putting data into it
rather than polling for it. Yielding in my poll loop has
been a good solution in other cases.
Mark.
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