3 Dec
2009
3 Dec
'09
9:14 a.m.
Sean Bolton wrote:
On Dec 2, 2009, at 7:33 AM, lieven moors wrote:
Thanks very much for your reply!
I was reluctant to start using atomic pointers,
because I might change the program later to
read longer sequences of Arps. So the ringbuffer approach
might be a good choice after all.
I think your idea is exactly what I was looking for.
Thanks again,
Greetings,
Lieven
P.S.
I would love to see a simple (maybe fake) example of how to use
atomic pointers though, because I only have a vague
idea of how they are used in practice... Anyone?
Paul Davis wrote:
All of that stuff is great to learn about, but on the other
hand, you've already got the hang of the ringbuffer API -- why
not just use that? The way I usually deal with this sort of
thing is to have two ringbuffers, one from the worker thread to
the process thread, and one from the process thread back to the
worker thread. Worker (inotify) thread creates a new Arp, and
passes a pointer to it through the ring buffer to the process
thread. Process thread then reads the new Arp pointer from the
first ringbuffer, begins to use it, and passes a pointer to the
old Arp back through the second ringbuffer to the worker thread.
Worker thread then reads the old Arp pointer from the second
ringbuffer, and frees or reuses it.
Disadvantage to this is it's not quite as efficient as an atomic
pointer exchange, but the advantage is you've already got everything
you need right there in jack, no need for an extra library.
HTH,
-Sean
On Tue, Dec 1, 2009 at 9:51 PM, lieven moors
<lievenmoors(a)gmail.com>
wrote:
Could you give me a hint on how to use atomic pointers?
Should I use __sync_val_compare_and_swap from GCC?
I've been looking around for other libraries, but I'm not sure where to
start.
Also, what did you mean with 'integer exchange'?
Is it yet another way of using CAS? I want to repeat the same Arp, until there is an
update to the text
file.
One arp is allready
loaded in each ringbuffer in main(). When the file is modified, a
second one
is added, and
process skips to the second one. Since I have only space for two
arps in the
buffer, there
should always be exactly one which is readable. I know it is a bit
weird,
but it seems to
work, apart from the problem I described.
sounds as if you might want to look into atomic pointer and/or integer
exchange instead, to get lock-free double buffering.
ringbuffers are generally for passing streaming data/events.