Adam Rosenberg wrote:
> On Fri, Nov 5, 2010 at 3:10 PM, Clemens Ladisch <clemens@xxxxxxxxxx> wrote:
> > And you should use poll() with all eight handles so that you don't
> > eat CPU while waiting.)
>
> I can't use poll because the application has to perform many other
> tasks in a deterministic manner (meaning I can only use threads and
> other processes to notify the main loop to perform some task).
As Mark wrote, this is what poll() was designed for.
> the main loop of my application basically does this:
> while(1)
> {
> processNextAlsaStream();
> processMp3Decoder();
> processLCD();
> processInputs();
> processSerial();
> }
With poll(), it would look somewhat like this:
struct pollfd pollfds[...];
// fill pollfds with all handles
while (1)
{
poll(...);
for (1..8)
if (stream ready for writing)
processAlsaStream(i);
if (input ready for reading)
processInputs();
if (serial ready for whatever)
processSerial();
processMp3Decoder();
}
If you set the PCM device to non-blocking mode, you do not need to call
avail_update before writing; just try to write as much as you currently
have.
If you want to do something regularly, use the timeout of poll(), or
use a timerfd.
You mentioned threads; these are not directly supported with poll()
because they do not have a file handle, but if you want to wake up the
main loop, you can write to an eventfd or to a pipe created with pipe().
Regards,
Clemens
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