Changes to UART ns8250

[Adrian Chadd]

I'd love to see a linux style way of saying "I'd like to sleep from roughly
this time interval to this time interval; feel free to do what you need."

Then yes, it could be implemented as a sleep wakeup from a timer, or as a
call to a hypervisor to do the same, or .. or...


-adrian


On 7 October 2013 13:26, Ian Lepore <ian at freebsd.org> wrote:

> On Mon, 2013-10-07 at 13:15 -0700, Adrian Chadd wrote:
> > Hi,
> >
> > You should add:
> >
> > *[snip]
> > * a DELAY(1) or something.
> >
>
> Why?  Why oh why do people write
>
>  while (!read_some_status_register())
>     DELAY(n);
>
> when DELAY() is implemented as, roughly:
>
>   while (read_some_counter_register() < something)
>      continue;
>
> The whole point of DELAY() is to busy-wait.
>
> What might be nice is some function that we can call in such a loop such
> as cpu_busywait(), so that when running in an emulated or virtualized
> environment the emulator or hypervisor could use that as a hint to do
> something smart.
>
> -- Ian
>
>
>