On Wed, 7 Mar 2007 13:17:57 +0800 "Sonic Zhang" <[EMAIL PROTECTED]> wrote:
> On 3/6/07, Andrew Morton <[EMAIL PROTECTED]> wrote:
> > On Tue, 06 Mar 2007 14:54:18 +0800 "Wu, Bryan" <[EMAIL PROTECTED]> wrote:
> >
> > > Hi folks,
> > >
> > > [PATCH] Blackfin: blackfin i2c driver
> > >
>
> > > + struct i2c_msg *pmsg;
> > > + int i, ret;
> > > + int rc = 0;
> > > +
> > > + if (!(bfin_read_TWI_CONTROL() & TWI_ENA))
> > > + return -ENXIO;
> > > +
> > > + down(&iface->twi_lock);
> > > +
> > > + while (bfin_read_TWI_MASTER_STAT() & BUSBUSY) {
> > > + up(&iface->twi_lock);
> > > + schedule();
> > > + down(&iface->twi_lock);
> > > + }
> >
> > That's a busy loop until this task's timeslice has expired. It'll work,
> > but it'll suck a bit. (Repeated in several places)
> >
>
> OK, I change it into yield(). So, current process will be move to the
> tail of the run queue. Is that OK with you?
Nope, yield is terribly bad when there are busy processes running: it can
stall for a very long time indeed,
Is this hardware not capable of generating an interrupt when BUSBUSY gets
negated?
I guess not, in which case you're stuck with having to poll it - probably
use a cond_resched() in the loop, and an angry comment.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
