Re: Is there a delay which yields?

On Thursday 19 March 2009 23:02:49 Barney Cordoba wrote:
> --- On Thu, 3/19/09, John Baldwin <jhb_at_freebsd.org> wrote:
> > From: John Baldwin <jhb_at_freebsd.org>
> > Subject: Re: Is there a delay which yields?
> > To: freebsd-current_at_freebsd.org, barney_cordoba_at_yahoo.com
> > Cc: "Julian Elischer" <julian_at_elischer.org>, current_at_freebsd.org
> > Date: Thursday, March 19, 2009, 11:23 AM
> >
> > On Sunday 15 March 2009 2:43:18 pm Barney Cordoba wrote:
> > > --- On Sun, 3/15/09, Julian Elischer
> >
> > <julian_at_elischer.org> wrote:
> > > > From: Julian Elischer <julian_at_elischer.org>
> > > > Subject: Re: Is there a delay which yields?
> > > > To: barney_cordoba_at_yahoo.com
> > > > Cc: current_at_freebsd.org
> > > > Date: Sunday, March 15, 2009, 1:16 PM
> > > >
> > > > Barney Cordoba wrote:
> > > > > I'd expect DELAY to yield till timeout
> >
> > but a task
> >
> > > > with a delay loop just
> > > >
> > > > > runs to 100% usage. Is there a function
> >
> > which can
> >
> > > > yield exectution for
> > > >
> > > > > a set amount of time (without having to use
> >
> > a timer)?
> >
> > > > DELAY is designe for use early in the boot when
> >
> > thre are no
> >
> > > > timers.
> > > > it is only occasionally used for cases during
> >
> > normal
> >
> > > > operation.
> > > >
> > > > how would a thread know how long it has been away
> >
> > if no
> >
> > > > timer is used?
> > >
> > > I guess I mean a sleep.
> > >
> > > Also, this is a kernel driver. I have a device
> > > which requires a toggle with a 10ms delay between
> >
> > pulses. I hate to
> >
> > > tie up the cpu for 10ms with a delay. Sort of like the
> >
> > following:
> > > write_pulse();
> > > delay(10000);
> > > write_pulse();
> >
> > Use pause(9).
>
> timo is in hz? So 1/1000th of a second by default?

tvtohz() (see time.h) will help you figure out how many ticks you need for a 
given timeval.

> Also, I notice that hz is 1000 but get 2000 ints/second per
> cpu. Why is it twice hz?

That I don't know.

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